Collapse Mechanism in RCC members can be in the following category: 

Bond Failure: Brittle

Shear Failure: Brittle

Flexural Failure

Brittle: if over-reinforced section (compression failure)

Ductile: if under-reinforced section (tension failure)

Hence, We need to ensure that bond failure does not take place. Shearfailure does not precede flexural yielding. Beam is under-reinforced. IS:13920 code has stipulated this condition. In Clause-6.2.2, it says- the maximum steel ratio on any face of a flexural member should not exceed  row, max=0.025

Failure of RC Section : This may be in the following form: 

Yielding of tension bars- this type of failure is having the following category-

• Ductile
• Tension failure
• Under-reinforced section

Crushing of compression concrete this-type of failure is having the following category- 

• Brittle
• Compression failure
• Over-reinforced section failure

Tension failure more likely if:

• Less tension reinforcement
• Morecompression reinforcement
• Higher grade of concrete
• Lowergrade of steel
• Lower value of axial compression

Section ductility increases as- 

• Grade of concrete improves
• Grade of steel reduces
• Tension steel reduces
• Compression steel increases
• Axial compression  force reduces 

Generally, columns are less ductile than beams.

Capacity Design Concept:

• The chain has both ductile and brittle elements.
• To ensure ductile failure, we must ensure that the ductile link yields before any of the brittle links fails.

For instance, in a RC member:    

 
Shear failure is brittle      
Flexural failure can be made ductile      
Element must yield in flexure and not fail in shear

Capacity Design of Frames:  

We need to consider the following: 

• Choose yield mechanism
• Locate desirable hinge locations
• Estimate reasonable design seismic force on the building
• Design the members at hinge locations (upper bound type)
• Assess the member forces at other locations under the action of “capacity” force
• Design other locations for that force; need not detail these for high ductility

Materials in RC Members:  

Concrete and steel have very different characteristics

Steel ductile: strain capacity: ~12% to 25%

Concrete brittle: strain capacity: ~0.35%

Confinement of concrete:

It considerably improves its strain capacity:

Main Steps:

• Weak Girder – Strong Column Philosophy
• Shear Failure Prevented by Special Calculations (Capacity Design Method)
• Good Development Length
• Regions Likely to have Hinges Confined with Closely-spaced and Closed Stirrups

To ensure ductility: 

• Correct collapse mechanism
• Adequate ductility at locations likely to form hinge in collapse mechanism
• Need sufficient member ductility to ensure adequate structural ductility.
• Prevent brittle failure mechanisms to take place prior to ductile yielding

Storey collapse Mechanism: 

• Columns require too much ductility
• Columns are difficult to make ductile
• Collapse in column may lead to failure of whole structure.

Beam –Hinge Mechanism (Sway Mechanism):

Preferred mechanism

Ensure that beams yield before columns do

Strong Column –Weak Beam Design

The following OpenSTAAD function extracts the load case number (Primary and combination load case) and corresponding combination factors for a combination load case.

Load.GetLoadAndFactorForCombination varLoadCombNo, varLoadNos, varFactors

Where:

varLoadCombNo

A long variable which stores the load combination number.

varLoadNos

A long array which stores the load case numbers present in the load combination.

varFactors

A double array which stores the combination factor corresponding to each load case present in the load combination.

VB Example

Dim varLoadCombNo As Long

Dim varLoadNos As Long

Dim varFactors As Double

objOpenSTAAD.Load.GetLoadAndFactorForCombination varLoadCombNo, varLoadNos, varFactors

The following OpenSTAAD function adds a repeat load case with specified multiplication factor to an existing load case.

Load.AddRepeatLoad varLoadCaseList, varFactorList

Where:

varLoadCaseList

An integer array which stores the load case numbers present in the load combination.

varFactorList

A double array which stores the combination factor corresponding to each load case present in the load combination.

VB Example

Dim varLoadCaseList As Integer

Dim varFactorList As Double

objOpenSTAAD.Load.AddRepeatLoad varLoadCaseList, varFactorList

This page contains a list of new Output functions.

The following OpenSTAAD finds whether a STAAD.Pro model is already analyzed or not.

Output.AreResultsAvailable()

Return Value

Value will return True if the model is already analyzed and False if the model is not analyzed.

VB Example

Dim status As String

status = objOpenSTAAD.Output.AreResultsAvailable()

The following OpenSTAAD function returns the critical steel design ratio for a steel member.

Output.GetMemberSteelDesignRatio nBeamNo, dRatio

Where:

nBeamNo

A Long variable contains the member number.

dRatio

A double variable which stores the critical design ratio.

VB Example

Dim nBeamNo As Long

Dim dRatio As Double

objOpenSTAAD.Output.GetMemberSteelDesignRatio nBeamNo, dRatio

Error or Warning Message

XXXXXXX(Provide the exact message. Do not include user-specific paths--replace with "<path to file>" or similar.)XXXXXXX

Explanation

XXXXXXX(Provide a detailed explanation of the error message.)XXXXXXX

How to Avoid

Option 1 XXXX(Delete this heading if only one option exists.)XXXX

1. XXXXXXX

2. XXXXXXX(add more steps as needed)XXXXXXX

Option 2 XXXX(Delete this section if only one option exists.)XXXX

1. XXXXXXX
2. XXXXXXX(add more steps as needed)XXXXXX

See Also

XXXXXXX(Add links as needed for other relevant Be Communities content.)XXXXXXX

1. Is it possible to quickly find out the total number of nodes & beams in a model ?
2. How do I stop the Auto Save screen from appearing over and over again in Staad.Pro?
3. How can I define a built up section whose cross section shape is not that of any standard rolled section?
4. I am trying to cut a rectangular hole in an arbitrary triangular region in space which has been meshed with plates. Is there a way to orient the construction grid (for the "snap node/plate" feature) to align with three pre-defined nodes (i.e. the corners of the triangle) to simplify removal of the rectangular feature inside? The angle of the triangle is very odd and I am concerned about the nodes defining the rectangle being slightly out of plane if I try to set the construction grid manually based on the coordinates and angle of the triangle.
5. One issue that I have encountered is that if I go into the load function and realize that I have the wrong units specified, I cannot change the units by going back to the geometry menus and selecting the correct units to use. When I enter the loading menus again, the units have not changed. Is there another way to change the units once you enter the loading functions?
6. When using the foundation support, I am required to give the subgrade modulus and supply a direction. I have always used Y as the direction. However, I am interested in knowing what would occur if I choose Y-only. Is there some type of weak spring placed in X & Z directions, is it completely restrained, or is it somewhere in between?
7. The "View - View Selected Objects Only" option requires two clicks to work.Why ?
8. I am using STAAD.Pro 2004 Build 1004.US also known as the second edition. When I try to add plates using the new feature in the Geometry menu called "Create infill plates", I encounter the message "No closed polygon found to fill in with plates, please check beam selection".What am I doing wrong?
9. I have a rather large frame building consisting of several floors. I want to look at individual floors by themselves without the rest of the structure cluttering up the view. Can you tell me how to do that?
10. How do I access online help in STAAD.Pro? The F1 key does not bring up any help screens.
11. How can I convert single line input to multiple line input? The program currently converts my joint coordinate and member incidence data from multiple line to single line input.
12. How do I merge 2 staad models?
13. I am designing a mat foundation supporting a steel structure. I am applying the column loads as NODAL LOAD. I do not think this is the right approach because I have a base plate that distributes the load over the area of the base plate. How to model this ?
14. Can one create a user defined grid system in STAAD.Pro?
15. I get a warning message during analysis saying *WARNING- APPLIED SELFWEIGHT IS MORE THAN TOTAL WEIGHT OF ALL STRUCTURAL ELEMENTS IN LOAD CASE    113 ALONG Z. What does this mean ?
16. I am modeling a steel building with braced frame (OBF). I want the braces to carry lateral loads only and not the gravity loads. How can I do that ?
17. I have to deal with relatively big model with approximately 50000 plates. However processing is very slow. Are there any limitations on number of plates?
18. How to assign offsets to the plate elements?
19. If we have some beams connecting to a perpendicular beam, should that perpendicular beam be split at the junction of the other beams or that beam can be merged into a single beam?
20. There is a property named Ct that I see within the W shape table of the AISC steel section database. What does this stand for ?
21. After I import the model from the Structure Wizard, it will only create 1 node and there would be a pop up saying that the duplicated nodes and beams are ignored. Why is this happening?
22. If a diaphragm is modeled using plates, will it simulate a flexible or a rigid diaphragm ?

1. Is it possible to quickly find out the total number of nodes & beams in a model ?

Yes. On the left side of the screen, click on the Setup page. On the right side of the screen, click on the button called "More".

Another place to get this from is the button that looks like a question mark. It is called Info. See the figure below.

2. How do I stop the Auto Save screen from appearing over and over again in Staad.Pro?

From the File menu of the main program screen, select "Open Backup Manager".

The dialog box that comes up has a facility to turn off the Autosave feature as seen in the next figure.

3. How can I define a built up section whose cross section shape is not that of any standard rolled section?

You have to specify its properties using the User Table-General section. You can find the details in section 5.19 of the Technical Reference Manual as shown next. Refer to the section titled General

 

4. I am trying to cut a rectangular hole in an arbitrary triangular region in space which has been meshed with plates. Is there a way to orient the construction grid (for the "snap node/plate" feature) to align with three pre-defined nodes (i.e. the corners of the triangle) to simplify removal of the rectangular feature inside? The angle of the triangle is very odd and I am concerned about the nodes defining the rectangle being slightly out of plane if I try to set the construction grid manually based on the coordinates and angle of the triangle.  

Using STAAD's graphical tools, it is quite difficult to insert an opening after the plate has been meshed, unless your plate elements are aligned in a manner that exactly matches the boundary of the opening. The process is far less painful if the hole is specified before the meshing process commences. To do that, please have a look at the solution described later in this section under the topic "Generation of a plate element mesh for an irregular slab with holes/openings"

Alternatively, you may use Parametric Models option as described in section 2.3.6.11 titled Geometry | Create Parametric Models

5. One issue that I have encountered is that if I go into the load function and realize that I have the wrong units specified, I cannot change the units by going back to the geometry menus and selecting the correct units to use. When I enter the loading menus again, the units have not changed. Is there another way to change the units once you enter the loading functions?

From the Edit menu, choose Edit Input Command File. Scroll down till you see commands like

LOAD 1

or

LOAD 2

Prior to the load case which has the units error, add the appropriate unit as shown

UNIT POUND FEET

For example

UNIT KIP FEET
LOAD 1
SELF Y -1.0
MEMBER LOAD
1 TO 25 UNI GY -0.2
UNIT POUND
LOAD 2
JOINT LOAD
33 FX 400
UNIT KNS METER
LOAD 3
MEMBER LOAD
45 UNI GY -3.0

6. When using the foundation support, I am required to give the subgrade modulus and supply a direction. I have always used Y as the direction. However, I am interested in knowing what would occur if I choose Y-only. Is there some type of weak spring placed in X & Z directions, is it completely restrained, or is it somewhere in between?

If X or Y or Z is specified for direction, then,

a) a spring support is generated in that direction
b) the other two translational directions are fully restrained
c) the associated rotational degre of freedom is fully restrained
d) the other 2 rotational degrees of freedom are treated as unrestrained

Example :

plate-list PLATE MAT DIR Y SUBGRADE 0.4

FX is fixed
FY gets a spring
FZ is fixed
MX is free
MY is fixed
MZ is free

If XONLY or YONLY or ZONLY is specified, then, a spring support is generated in that direction. All the remaining 5 degrees of freedom are treated as unrestrained.

Example :

plate-list PLATE MAT DIR YONLY SUBGRADE 0.4

FX is free
FY gets a spring
FZ is free
MX is free
MY is free
MZ is free

7. The "View - View Selected Objects Only" option requires two clicks to work.Why ? 

This error was present in the American edition of STAAD.Pro 2004 Build 1004. For finding the Release and build number, go to Help - About STAAD.Pro. It has been corrected in Build 1005.US.REL. In case you still need to use the version that had the problem, you could do the following to get around the problem :

a) Go to the View menu and choose "View Selected Objects Only" again.

b) Click the right mouse button, choose "New View" followed by one of the 2 options it offers.

8. I am using STAAD.Pro 2004 Build 1004.US also known as the second edition. When I try to add plates using the new feature in the Geometry menu called "Create infill plates", I encounter the message "No closed polygon found to fill in with plates, please check beam selection".What am I doing wrong?

This was an in build 1004 and has been rectified in the US Build 1005. If you need to use build 1004, you can use the same facility from its icon which is shown below.

9. I have a rather large frame building consisting of several floors. I want to look at individual floors by themselves without the rest of the structure cluttering up the view. Can you tell me how to do that?

Method 1 :

a) Orient the view of your model in such a way as to make it convenient to extract using a mouse, the portion you want to view separately. This can be done from View | Orientation, or by clicking on the icons available for this.

b) From the select menu, select the Geometry cursor. Then, using your mouse,create a window around the region you wish to view. That region will be highlighted.

c) Click the right mouse button and select New View. Or, from the View menu, select New View. Set the button on "Create a new window for the View", and click on OK.

The region will now be displayed in a separate window. Once in this window, you can change the viewing angles using View | Orientation, or through the orientation icons, or simply by pressing the up, down, left or right arrow keys on the keyboard.

Method 2 :

This method involves cutting a section using the Tools - Cut section option. Details are available in Section 2.3.4 of the STAAD.Pro Graphical Environment Manual, which can be accessed from Help - Contents.

10. How do I access online help in STAAD.Pro? The F1 key does not bring up any help screens.

The F1 key for help is currently not operational in STAAD. We are working on implementing this for one of the forthcoming releases.

To obtain online help in STAAD, you can do one of the following:

From the Help
menu, if you click on Contents, if will bring up all the STAAD manuals. You can search for specific information, or go through the topic list to select the items you want.

From Help, if you click on Multi Media help, it will bring up a set of movies which will explain the procedure for creating a
model.

If you click on the Start button on your Windows desktop, select Programs, choose STAAD.Pro 2001 followed by STAAD.Pro Online
Documentation, it will bring up the same set of information as the one you can access from step (1) above.

11. How can I convert single line input to multiple line input? The program currently converts my joint coordinate and member incidence data from multiple line to single line input.

 Start STAAD.Pro. Select File - Configure.

Click on the tab called Input File Format

If you want Single line format, switch on the check boxes. If you want Multiple line format, keep them "unchecked".

Click on Accept.

Then from the File menu, open your STAAD input file. When you Save the file from the Graphical screen, the data will be saved in the format you chose in the step above.

12. How do I merge 2 staad models?

Start STAAD.Pro. Open the first file. Keep it open.

STAAD another instance of STAAD.Pro. Open the second file. Stay in this file.

Go to the Select menu, and Select All Geometry. From the Edit menu, select Copy.

Go back to the screen of the first file. From the Edit menu, select Paste.

You will be prompted to specify the X, Y and Z distances by which to move the structure of the second file before it gets copied to the first structure. Specify those values and click on OK.

13. I am designing a mat foundation supporting a steel structure. I am applying the column loads as NODAL LOAD. I do not think this is the right approach because I have a base plate that distributes the load over the area of the base plate. How to model this ?

There are a couple of things you can do.

1.Instead of applying the load as a concentrated point load, try applying the load as a pressure loading on the plates.

OR

2.You may define dummy members ( having high E and zero density ) between the point of application of the concentrated load and the neighboring plate nodes which would help in distributing the load over a wider area.

14. Can one create a user defined grid system in STAAD.Pro?

Yes, a user defined grid system can be created. You need to go to Geometry menu and select Snap/Grid Node -> Beam. Snap Node/Beam window will appear:

Click on the Create button and this window will appear:

You will need to provide a Grid name, select Grid type (Linear, Radial or Irregular) and set various other options. Once this is done, click OK and created Grid name will appear in the list. Check the box near it to activate that Grid.

As new grids are added or modified, the information is stored in the STAAD.Pro data folder with a GRD extension that allows other STAAD files to re-use these defined grids.

You can also import Grids from the DXF file or Grids previously defined in another STAAD.Pro model by clicking on the Import button. The latter import option opens a browse dialog box to identify a GRD file created by the Snap Node Grid tool. Note that GRD files are only created by STAAD.Pro 2007 (or later).

More information can be found in the STAAD.Pro Help (go to Help -> Contents) chapter AD.2007-1001.1.2 Enhanced Grid Tool.

15. I get a warning message during analysis saying *WARNING- APPLIED SELFWEIGHT IS MORE THAN TOTAL WEIGHT OF ALL STRUCTURAL ELEMENTS IN LOAD CASE    113 ALONG Z. What does this mean ?

First a bit of a background as to why this message was introduced and then the reason for the message. STAAD now support a LIST assignment for selfweight command which it did not in earlier versions. After this was introduced, it was found that many times selfweight was not being assigned to all members by users or sometimes selfweight for few members were being accounted for multiple times due to erroneous assignment on part of the user. A check was therefore introduced in STAAD to warn the user of such scenarios. So what the software does is,

a. It finds out the total selfweight ( UNFACTORED ) of the structure ( say X )
b. It finds out all instances of selfweight command used in each case and checks the associated LIST of members and adds these weights up for each member to arrive at a value of selfweight (UNFACTORED) for each case ( say Y ). While doing this, it ignores any factor applied to the selfweight.

For example, let us consider the following example load cases

LOAD 1
SELFWEIGHT Y -1
…

LOAD 6
SELFWEIGHT Z -2.015
…

LOAD 10
SELFWEIGHT Z -1
…

LOAD 113
REPEAT LOAD
1 1.603 6 1.5 10 0.003
…

The load case 6 and 10 both has selfweight assigned to all members in Z.

So when it comes to load case 113, the software checks and finds that selfweight command has been applied in Z direction to all members as part of load case 6 ( it ignores the factor 2.015 ) and then the selfweight has been applied in Z direction to all members as part of load case 10. It ignores the 1.5 and 0.003 factors applied to the selfweight as part of the REPEAT LOAD. Hence for load case 113, the total unfactored selfweight is applied twice to all members and so the Y comes out to be more ( twice in this case) than X. Whenever Y does not match X, the software flags these as warnings.

Now it does NOT mean that there is an error in the analysis. It is just that the software is trying to make the user aware of the scenario by providing these warnings. For this case, one may simply ignore these warnings.

16. I am modeling a steel building with braced frame (OBF). I want the braces to carry lateral loads only and not the gravity loads. How can I do that ?

This can be achieved by making the bracing members inactive for the gravity load cases and re-activating them for the lateral load cases. The INACTIVE specification for beam members is available within General > Spec page. You can find more details on inactive specification within section 5.18 of the technical reference manual. There is also an example 4, demonstrating how to use the INACTIVE specification, which can be found within Help > Contents > Application Examples. The corresponding .std file is provided with the software and can be found within the folder X:\SProV8i\STAAD\Examp\US where X represents the drive in which STAAD is installed.

17. I have to deal with relatively big model with approximately 50000 plates. However processing is very slow. Are there any limitations on number of plates?

The limits on the number of entities, loads etc are outlined in section 5.2 of the Technical Reference Manual. From our experience, it is best if you can restrict your model to 30000 nodes and 30000 beams + plates. Although theoretically it is possible to analyze much bigger models ( Number of Members, Plates and Solids = 225000 ), however from a practical standpoint, it is better to restrict the model to the size mentioned above because for larger models, displaying loads or even navigating through the program's GUI can be quite slow and tedious. Also postprocessing can be very slow and sometimes some of the postprocessing results may fail to load in memory, if the data files are too large. So due to these limitations, we recommend keeping the model size smaller whenever possible.

18. How to assign offsets to the plate elements?

The plates can be moved by the offset distance and connectivity with other plates (beams) should be retained through the use of extremely rigid "link" members. These members are specified with a material having very high modulus of elasticity and low density which ensures the members transfer load, but do not contribute any weight to the structure. 

19. If we have some beams connecting to a perpendicular beam, should that perpendicular beam be split at the junction of the other beams or that beam can be merged into a single beam?

Forces between the beams (or other elements) in STAAD.Pro can be transferred only through the common nodes. If some beams do not intersect with other beam members, you need to split those beams in order to have common nodes with other beams, so that the forces could be transferred correctly.

You can quickly intersect members by selecting all members and going to Geometry -> Intersect Selected Members -> Intersect.

20. There is a property named Ct that I see within the W shape table of the AISC steel section database. What does this stand for ?

The Ct parameter is applicable only for T shapes being cut from W shapes. The parameter denotes the distance of the cg of the T section ( cut from the W shape ) from the flange as shown in the diagram below.

21. After I import the model from the Structure Wizard, it will only create 1 node and there would be a pop up saying that the duplicated nodes and beams are ignored. Why is this happening?

2 things should be checked:

1)  Go to the View -> Options menu and select line Tolerance in the opened window. Make sure that the Tolerance value is entered as 0.01 inches (or 0.001 meters). If this value is much higher or entered as 0, change it to 0.01.

2) Open the Structure Wizard and go to File -> Select Units. Make sure that selected units are the same as in the main STAAD.Pro model.

*Note: in order to change the Tolerance value, make sure that you have full read/write privileges to the file StaadPro20070.ini which is located in (for STAAD.Pro SELECTseries 4):

Windows XP OS: C:\Documents and Settings\All Users\Application Data\Bentley\Engineering\STAAD.Pro V8i SS4\

Windows 7/8 OS: C:\ProgramData\Bentley\Engineering\STAAD.Pro V8i SS4\
 

This file can be located in different folder for older STAAD.Pro versions.

22. If a diaphragm is modeled using plates, will it simulate a flexible or a rigid diaphragm ?

When one defines a plate, the actual thickness of the diaphragm is modeled through plate thickness definition. So the true stiffness of the slab is considered in the analysis and diaphragm shears are distributed accordingly. If the thickness is small, the diaphragm would behave more like a flexible diaphragm and similarly as thickness is increased, the slab would tend to behave like a rigid diaphragm.

The software does not idealize the diaphragm as rigid or flexible. However you can always compare the maximum lateral deflection of the diaphragm to the average lateral drift of the adjacent vertical elements and thereby classify it, if you need to.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Link

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

Couple of comments:

Q. How do I stop the Auto Save screen from appearing over and over again in Staad.Pro?

Proposed "solution" is not an answer to the question. The users want to know how to stop the  Auto Save screen popping-up endlessly, not how to turn off auto safe feature.

Q. How do I merge 2 staad models?

First of all - suggested technique does not work - error message "Multiple entities cannot be copied on the clipboard" appears after Edit/Copy. Second - the question is quite clear - "How do I merge 2 staad models", not "How do I merge geometry". Model is much more that just geometry and includes specifications, loads, load combinations, units, groups, etc.

1. In the output file, I see the following message ** WARNING ** A SOFT MATERIAL WITH (1.0 / 1.750E+01) TIMES THE STIFFNESS OF CONCRETE ENTERED. PLEASE CHECK.
2. In STAAD.Pro, you are providing Steel, Concrete and Aluminum as standard materials with built-in default values. Why isn't timber included? I am looking for the Modulus of Elasticity and Density of Douglas Fir.
3. I am analysing a plane frame. I specify a prismatic section with IX. The analysis stops with the error message that I need to specify IZ. What is the need to specify IZ?
4. What is the purpose of the "member release" command? What is the basis for the terms MX, MY and MZ in this command?
5. Can you please explain the concept behind member offsets?
6. Shouldn't there be a way to set the MEMBER TENSION attribute once for the model and have the program always look back on that line for the list of members which have been assigned this property? Obviously, the same goes for MEMBER TRUSS.
7. The STAAD graphical interface is showing a steel column in my model in an incorrect orientation. I have checked my input file (and also by double clicking on the actual member) and all of my columns consistently start at the lower node and go in the +y direction, all have a beta of 0, and all have the same member property. I have the exact same data for this graphically-incorrect column as the one below it that shows up the correct orientation. Yet another column shows a slightly skewed column orientation as if I had assigned it something other than 0 or 90 degrees, and I know for a fact that I haven't done this. 
8. I have a beam member for which I have assigned a single angle from the American steel table. When I look at the member properties output for that member, the values that STAAD reports for moments of inertia Iz and Iy do not match the values I see in the AISC steel publication for that angle section.
9. I understand that one should use the REPEAT LOAD command and not the LOAD COMBINATION command when analysing a model for cases where the MEMBER TENSION or MEMBER COMPRESSION command has been used. Talking about load combinations, in Section 5.35 of the STAAD Technical Reference Manual, notes Item (2) mentions that the LOAD COMBINATION command is inappropriate for a PDELTA analysis, and that one should use REPEAT LOADs instead. This appears to be true for NON-LINEAR analysis also. Why? 
10. How to account for cracked section properties when modeling with concrete in STAAD.Pro ?
11. How can I apply master slave specifications between nodes in non global directions ? For example I have two nodes and I want to apply a rigid connection between the two nodes along a line joining those two nodes. The line is inclined to the global direction

1. In the output file, I see the following message

** WARNING ** A SOFT MATERIAL WITH (1.0 / 1.750E+01) TIMES THE STIFFNESS OF
CONCRETE ENTERED. PLEASE CHECK.

Please explain to me in plain English what StaadPro is trying to tell me.

STAAD checks to see if the E (Modulus of Elasticity) assigned to members and elements is comparable to the values of steel, aluminum, concrete or timber. If it falls below or above the range of these materials, warning messages similar to the one you encountered are displayed. This is done to notify the user in case he/she is not aware of this fact, or if he/she may have specified the value in an incorrect unit system.

If you believe that your E is specified correctly, you may ignore the message. Else, correct the number.

2. In STAAD.Pro, you are providing Steel, Concrete and Aluminum as standard materials with built-in default values. Why isn't timber included? I am looking for the Modulus of Elasticity and Density of Douglas Fir.

Unlike the 3 materials mentioned in your question, timber comes in several varieties, with each variety having its own unique set of material properties. Douglas Fir alone comes in several varieties, as explained below.

The American Wood Council and the American Forest & Paper Association publish a document called the "Supplement NDS for Wood Construction", 1997 edition. It provides design values for structural sawn lumber and glued laminated timber. There is also a category called Visually Graded Decking.

Under each category, Douglas Fir comes in various species or combination of species. Under each species, there are various commercial grades. Each of those grades have a unique value of E, ranging from 1000 ksi to 1900 ksi. If the category, species, and commercial grade is known, the E value can be read from the tables in this document.

The American Wood Council and the American Forest & Paper Association also publish a document called the "ASD Manual for Engineered Wood Construction". In the 1999 edition of this document, Table 8A, page 15 contains the specific gravity of Douglas Fir as ranging from 0.46 to 0.5.

3. I am analysing a plane frame. I specify a prismatic section with IX. The analysis stops with the error message that I need to specify IZ. What is the need to specify IZ?

For plane frames with no beta angle, what is needed is IZ, not IX. IX is the torsion constant. IZ is the moment of inertia about the Z axis. Members of a plane frame with a beta angle of zero will bend about the Z axis, which explains the need for IZ. They are not prone to twisting, and that is why IX is not needed.

Table 1.1 from the Technical Reference manual, which shows the properties required for various types of structures, is reproduced below.

4. What is the purpose of the "member release" command? What is the basis for the terms MX, MY and MZ in this command?

By default, STAAD assumes the connection between any 2 members to be fully capable of transmitting all 3 forces and all 3 moments from one member to the other. This is usually achieved in practice by moment resistant connections, such as between a concrete beam and a concrete column which are monolithically cast.

If you want the connection to be of the type which does not permit one or more forces/moments to be transmitted, use member releases. A shear connection is such an example. The degrees of freedom FX through MZ that you release are based on the local axis of the member at whose end the release is specified.

See section 5.22.1 and the figures in Section 1.19 of the STAAD.Pro Technical Reference manual for additional information.

5. Can you please explain the concept behind member offsets?  

 When creating a model consisting of beams and columns, generally, the START or END face of the member is assumed to be located at the nodal point. In other words, the distance from the respective node to the start or end face of the member is treated as zero. Thus, for example, if member 47 is defined as being connected between nodes 12 and 13, then, the start face of the member is located at node 12, and the end face at node 13.

 This assumption may not always reflect the true physical condition on the structure. For example, when a beam meets a column, the common node between the beam and column is usually defined as being at the shear center (centerline for symmetrically shaped) of the column.

But, physically, the start face of the beam is not at that node, but at half the column depth away from the node. One may choose to ignore this "shift" if the column depth is negligible in comparison to the span of the beam. However, if one wishes to take advantage of the high stiffness that the half-depth region of the column offers, he/she may consider this using the member offset command.

The member offset is a way of declaring that the region, whose length is defined by the offset, is a rigid zone. Hence, if the offset values in X, Y and Z coordinates are a, b and c, the length of that region is d=sqrt(a*a + b*b + c*c). The face of the member is then assumed to be "d" away from the node.

The member end forces that STAAD reports are at the face of the member, not at the node, when an offset is specified. If the offset is applied at the base of a column, then the member end force may not be equal in magnitude to the corresponding support reaction terms. If one is interested in checking static equilibrium based on the free body diagram at that support, the member end forces must be transferred from the member face to the support node taking into consideration the rigid link defined by the offset. 

6. Shouldn't there be a way to set the MEMBER TENSION attribute once for the model and have the program always look back on that line for the list of members which have been assigned this property? Obviously, the same goes for MEMBER TRUSS.

In fact, that is exactly what STAAD is designed to do already. There is no need to keep re-specifying the MEMBER TENSION command, unless you want to specify a different list of such members. So, specify it once for the first analysis, and you don't have to specify it again. Same goes for the MEMBER TRUSS command.

7. The STAAD graphical interface is showing a steel column in my model in an incorrect orientation. I have checked my input file (and also by double clicking on the actual member) and all of my columns consistently start at the lower node and go in the +y direction, all have a beta of 0, and all have the same member property. I have the exact same data for this graphically-incorrect column as the one below it that shows up the correct orientation. Yet another column shows a slightly skewed column orientation as if I had assigned it something other than 0 or 90 degrees, and I know for a fact that I haven't done this.

a - Is the graphical interface a reliable representation of my input?

b - If yes, can you think of some other possible sources of this particular error?

If you look at the coordinates of the columns which appear to be oriented in the wrong way, chances are that you will find the Z coordinate of the 2 ends to be different by a very minute value, such as 0.001. For example, one end may have a Z value of 5.999 while the other end may be at 6.000. If so, you could do the following to correct it. Select the Geometry-Beam page along the left side of the screen, and it will display the node coordinates in the tables on the right hand side. In those tables, make the necessary correction so both ends of the column have the same Z coordinate.

The potential cause of this difference in coordinates is the following. The program has something called a Base Unit system. You can find this by starting the program, and before opening any file, go to the File menu, select Configure, and see if it says "English" or "Metric". If the model you are going to create is in Metres and KNs, you ought to have the base units in Metric. If the model you are going to create is in Feet and Kips, you ought to have the base units in English. Mixing unit systems causes the program to perform internal unit conversions which can result in loss of digits because the built-in conversion factors have only upto 8 digits of accuracy.

In fututure versions of STAAD, there will be a feature which will enable you to select the "offending" column and make the Z coordinate of its 2 ends to be equal so it becomes truly vertical.

8. I have a beam member for which I have assigned a single angle from the American steel table. When I look at the member properties output for that member, the values that STAAD reports for moments of inertia Iz and Iy do not match the values I see in the AISC steel publication for that angle section.

The numbers reported in the STAAD output for Iz and Iy are the moments of inertia about the principal axes of the single angle. The values in the AISC publication that you are comparing them with are most probably the values about the geometric axes. That is very likely the cause of the mis-match.

9. I understand that one should use the REPEAT LOAD command and not the LOAD COMBINATION command when analysing a model for cases where the MEMBER TENSION or MEMBER COMPRESSION command has been used. Talking about load combinations, in Section 5.35 of the STAAD Technical Reference Manual, notes Item (2) mentions that the LOAD COMBINATION command is inappropriate for a PDELTA analysis, and that one should use REPEAT LOADs instead. This appears to be true for NON-LINEAR analysis also. Why?

Before we can explain why, we first need to understand a few facts about loads in STAAD. There are two types of load cases in STAAD : Primary load cases, and Combination load cases.

Primary load cases

A primary load case is one where the load data is directly specified by the user in the form of member loads, joint loads, temperature loads, element pressure loads, etc. It is characterized by the fact that the data generally follow a title which has the syntax

LOAD n

where "n" is the load case number. For example,

LOAD 3

MEMBER LOAD

2 UNI GY -3.4

JOINT LOAD

10 FX 12.5

LOAD 4

ELEMENT LOAD

23 PR GY -1.2

LOAD 5

TEMPERATURE LOAD

15 17 TEMP 40.0 -25.0

Combination load case

Here, the user does not directly specify the load data, but instead asks the program to add up the results of the component cases - which are defined prior to the combination case - after factoring them by the user specified factors. It is characterized by the title which has the syntax

LOAD COMBINATION n

where "n" is the case number of the combination load case.

LOAD COMBINATION 40

3 1.2 4 1.6 5 1.3

What is a REPEAT LOAD type, and Which category does is belong to?

A Repeat Load type is a Primary load case. That is because, when the program runs into this command, it physically creates the load data for this case by assembling together the load information from all the component load cases (after factoring them by the respective load factors) which the user wants to "REPEAT". Thus, when you specify

LOAD 10

REPEAT LOAD

4 1.4 5 1.7

STAAD creates a physical load case called 10 whose contents will include all of the data of load case 4 factored by 1.4, and all of the data of load case 5 factored by 1.7.
If we use the same data used in the definition of the primary load case above, STAAD internally converts the REPEAT LOAD case 10 to the following :

LOAD 10

ELEMENT LOAD

23 PR GY -1.68

TEMPERATURE LOAD

15 17 TEMP 68.0 -42.5

What is the difference between a REPEAT LOAD case and LOAD COMBINATION?

The difference lies in the way STAAD goes about calculating the results - joint displacements, member forces and support reactions. For a load combination case, STAAD simply ALGEBRAICALLY COMBINES THE RESULTS of the component cases after factoring them. In the example shown above, it

gathers the results of load case 3, factors them by 1.2,

gathers the results of load case 4, factors them by 1.6,

gathers the results of load case 5, factors them by 1.3,

and adds them all together. In other words, in order to obtain the results of load 10, it has no need to know what exactly is it that constitues load cases 3, 4 and 5. It just needs to know what the results of those cases are. Thus, the structure is NOT actually analysed for a combination load case. With a REPEAT LOAD case however, the procedure followed is that which occurs for any other primary load case. A load vector {P} is first created, and later, that load vector gets pre-multiplied by the inverted stiffness matrix.

[Kinv] {P}

to obtain the joint displacements. Those displacements are then used to calculate the member forces and support reactions. Thus, the structure IS analysed for that load case {P}.

Why should the difference in the way STAAD treats a REPEAT LOAD case vs. a COMBINATION LOAD case matter?

Normally, if you are doing a linear static analysis - which is what a PERFORM ANALYSIS command does - it should make no difference whether you specify REPEAT or COMBINATION. However, if you are doing a PDELTA analysis, or a NONLINEAR analysis, or cases involving MEMBER TENSION and MEMBER COMPRESSION, etc., it matters. That is because, in those situations, the results of those individual cases acting simultaneously IS NOT the same as the summation of the results of those individual cases acting alone. In other words,

(Results of Load A) + (Results of Load B) is not equal to (Results of Load (A+B))

Take the case of a PDelta analysis. The P-Delta effect comes about from the interaction of the vertical load and the horizontal load. If they do not act simultaneously, there is no P-Delta effect. And the only way to make them act simultaneously is to get the program to compute the displacement with both loads being present in a single load case. A REPEAT LOAD case achieves that. A COMBINATION load case does not.

10. How to account for cracked section properties when modeling with concrete in STAAD.Pro ?

There are two ways. One can directly enter the reduced values for the sections using the PRISMATIC option as shown next

…

UNIT IN KIP

MEMB PROP

11 TO 21 PR YD 21.0 ZD 16.0 IZ 4321 IY 2509

…

The YD and ZD represent the overall dimensions which are used by the software to calculate the properties that are not input directly by the user. The IZ and IY represent the cracked section properties. Using the GUI, one can do the same from within the General > Property page. Click on Define within the Property – Whole Structure window and define the properties using the General option as shown next

Alternately one can define the cracked section property from within the modeling mode, by going to the General > Spec page. From within the Specification - Whole Structure dialog box on the right, click on Beam button and there is the Property Reduction Factors tab in there. Using that one can assign reduction factors to properties like cross sectional area and moment of inertia as shown next

11. How can I apply master slave specifications between nodes in non global directions ? For example I have two nodes and I want to apply a rigid connection between the two nodes along a line joining those two nodes. The line is inclined to the global direction.

The master slave specification is a method to model certain linkages between a control point (called a master joint) and a set of nodes (called slave joints) that are connected in the physical structure to the master joint through those linkages.

Those linkages cause the displacement of certain degrees of freedom at the slave nodes to be patterned after the displacement of those d.o.fs of the master node.

One of the limitations of the master-slave feature is that those degrees of freedom can be defined in the global directions only. Constraining a displacement or rotation along non-global direction is not available.

If you want to apply the constraints along directions which are inclined to the global directions, one way would be to define a dummy beam element connecting the two nodes along the inclination and assign a material having high E and zero density to that dummy member.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!!!

Check out the Structural Analysis and Design TechNotes And FAQs and the Structural Drafting and Detailing TechNotes and FAQs

Structural Analysis and Design products

See Also

• Structural Integration and the Structural Dashboard
• Structural Drafting and Detailing products
• Bridge Design and Engineering products
• Pipe Stress Analysis products
• See all Bentley products

Resources

• Structural Analysis and Design Product TechNotes and FAQs
• Bentley Structural Team Blog
• Structural Analysis & Design product Forums

Recently, Bentley Systems, Incorporated, the global leader dedicated to providing architects, engineers, constructors, and owner-operators with comprehensive architecture and engineering software solutions for sustaining infrastructure, partnered with S-Cube Futuretech Pvt. Ltd. to provide the most comprehensive concrete building design workflow for the Indian market.

This integrated solution is called STAAD.building and it addresses the entire workflow related to the design of reinforced concrete buildings; including conceptual layout and framing, advanced analysis, design and detailing and finally, production of site ready drawings along with bill-of-quantity reports. STAAD.building combines the power of STAAD.Pro’s analytical engine with the purpose-built building modelling, design and drawing solutions from S-Cube.

It extends [[STAAD.Pro]], the world's #1 structural analysis and design software, to accommodate the intricate needs of drawings and design of reinforced concrete structures as per Indian standards. The key differentiator is the workflow. Unlike any other software in the market, it helps engineers to conceptualize the engineering model by suggesting preliminary member sizes based on the framing layout, loading conditions, and geographical location. The model is generated in a physical environment to help you generate an analytical model automatically behind the scenes but also offers you the power of STAAD.Pro’s analytical modeling environment to optimize building configurations. It combines the power of a physical modeling system along with an analytical text editor to offer the best possible tools to address every possible need of a building designer.

This is the only solution in the market which completes the workflow by offering an interactive physical member design environment along with complete detailing and drawing generation. Early adopters indicated that drawings are of very high quality and meet the intricate requirements of site-ready drawings. Another recent addition is Bar Bending Schedule (BBS) creation. After detailing structural members, a detailed BBS can be generated in compliance with the Indian detailing standards.

STAAD.building is a bundle package of four products:

• STAAD.Pro is the leading structural analysis and design program (Learn more here )
• STAAD RCDC is the detail reinforced concrete design and detailing program which design structural components like Beam, column, slab, shear wall etc. and automatically produce drawings and bill of materials
• STAAD Planwin is a building modeling program which provides physical building modeling environment to create structural frames and components
• STAAD Foundation Advanced which provides the foundation design of common and complex types of foundations along with drawings and step by step hand calculation. (Learn more here)

STAAD Planwin

Some of the features of STAAD Planwin are:

• Seamless integration with STAAD.Pro
• Import architectural centre-line (DXF model)
• Detects beams and columns
• Align / locate members
• Add floor loads and wall loads
• View load distribution element-wise
• Check modelling error at plan level
• Size beams and columns for vertical loads
• Define shear walls
• Generate wind loading
• Generate earth quake loading
• Export 2D and 3D CAD drawings
• Generate accurate 3D analysis model with:
  • Member offsets
  • Releases
  • Beta angles
  • Pier definitions
  • Joint and member loads
  • Wind and EQ load, etc.

For more information on STAAD Planwin, please visit

STAAD RCDC

Some of the highlights of STAAD RCDC are:

• General
  • Seamless integration with STAAD.Pro
  • Compliance to latest Indian design standards
  • Auto Detection of design continuum
  • Facility to group members across levels and plan
• Detailing
  • Optimized and practical detailing
  • Interactive detailing interface
  • Control of all detailing parameters
• Drawing: Organized site ready drawings in DXF format
  • Elevations
  • Cross sections
  • In-plan detailing
  • Layout Drawings
  • Text Schedules
• Documentation
  • Detailed design calculation report
  • Design Summary
  • Failure Diagnostics
  • Member properties changed report

For more information on STAAD RCDC, please visit

Create Material Macro

The Create Material macro can quickly create new materials with industry standard property values.

First download and install the Create Material.vbs file and save it to the folder:

C:\SProV8i SS5\STAAD\Plugins\Create Material.vbs

If there is an older version of the file already there, replace it with this one.

To load the macro into STAAD.pro use Tools - Configure User Tools.

And in the Customize User Defined Tools window click New (Insert)

On the new row enter a name, like "Create Material"

and in the file selection box select the Create Material.vbs file.

Then click OK.

Afterwards, to use the tool, go to Tools - User tools, or the Hammer icon at the end of the file toolbar.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

1. How do I display the deflection diagram and the displacement values on that diagram?
2. After running the analysis, I go to the View menu, select Tables | Node Displacements, and select the load cases for which I want to see the values. The values are displayed in inch units. I want them in "cms" units. Changing the units using Tools | Set Current Unit doesn't seem to make a difference.
3. I want to print out a picture which consists of a truss I have modeled with the STAAD. I want the output forces labeled right on each member. This is very similar to what would be put on to a plan sheet. Can STAAD do this or must I print out a report to get these forces?
4. When I annotate beam moments on my diagrams, I can't seem to 1) change the font by adjusting the Beam Labels option and 2) turn off the unit being written on every single number.
5. Why are my annotations for maximum bending moment or shear values not showing up in the post-processing mode?
6. If I have a moment vector along the local positive Z axis does it have a twisting action going to the right along the positive direction of the axis?
7. What are the sign conventions for moments in a 3-D structure?
8. After performing the analysis, I enter the post-processing mode to view the member end force values. I click on the Beam page on the left side of the screen and see the values listed on the tables on the right hand side. Unfortunately, the moment values are in kip-inch units, even though my current units are set to feet and pounds. What do I have to do to get the values to show up in pound-feet units in the tables?
9. What is the purpose of the Beam - Graphs page on the left side of the screen?
10. How do I display the bending moment diagram and the values on that diagram, or shear forces or Axial forces?
11. When I take a picture, it prints on the top half of a 8-1/2 x 11 size page. How can I take pictures that fill the page?
12. How to insert a company logo into STAAD.Pro report?
13. Can I get STAAD.Pro to report the torsion stress ?
14. How can I have STAAD report more than 3 places of decimal in the post processing result tables?
15. How to know the version of the design code which is being used by STAAD.Pro during the analysis?
16. How to see the displacement of only one particular node graphically?
17. What is the difference between the local and global deflection in the member query box?
18. I am analyzing a large 3D structure. I changed the beta angle of one of the members to 90. I expected the MY and MZ for the two scenarios ( beta =0 and beta=90) to get interchanged. However that does not seem to happen. Why ?
19. How to get Member End Forces for a specific selection of beams?
20. How do I change stress output units in the *.ANL output file? They are coming out as kN/m2. I want N/mm2

1. How do I display the deflection diagram and the displacement values on that diagram?

The first step to viewing these results is to perform the analysis of the model successfully. Select Analyze from the Staad.Pro top menu bar followed by the Analysis option.

A dialog box by the name Select Analysis Engine will appear. Click on the Run Analysis button of this dialog box. After the analysis of the file is completed, click on the Done button.

The next step is to go to the Post Processing mode to view the deflection values graphically. To enter into the Post Processing mode, select Mode from the top menu bar and select Post Processing. Remember that if your analysis is not successfully completed (for reasons such as errors in your input data), you will not be able to access the Post Processing mode.

By default, the deflection diagram always opens up in the post processing screen of Staad.Pro.

From the top menu bar, choose Results - View value. Under Ranges, choose All. (The All button means the deflection diagram will be annotated for all nodes.)

Under the Node tab, you will see the options Global X, Global Y, Global Z and Resultant. Make the appropriate choice. Click on the Annotate button. Then click on the close button.

If you would like to see the diagram annotated for a different load case, select that load case from the load selection box.

2. After running the analysis, I go to the View menu, select Tables | Node Displacements, and select the load cases for which I want to see the values. The values are displayed in inch units. I want them in "cms" units. Changing the units using Tools | Set Current Unit doesn't seem to make a difference.

The unit system in which results are displayed on the tables is set using the facilities available under the View - Options menu. These are known as the display units. To set the display units for the node displacements, please do the following :

In the View menu, select Options - Structure units. In the category called Displacement, select the units you desire and click on OK.

3. I want to print out a picture which consists of a truss I have modeled with the STAAD. I want the output forces labeled right on each member. This is very similar to what would be put on to a plan sheet. Can STAAD do this or must I print out a report to get these forces?

First, you have to ask STAAD to Annotate the drawing with the axial forces. For this, please go to the post processing mode after you have analyzed the structure.

Click on the "Beam" tab on the left side and then click on the sub-tab labeled "Forces."

Click the right mouse button on the screen and select "Structure Diagrams."

From the "Loads and Results" tab, click on "Axial" under the "Beam Forces" heading.

Uncheck the "bending zz" box and click "Apply" followed by "OK."

Maximize the screen and then go to the "Results" pull down menu and select "View Value..."

Click on the "Beam Results" tab and then check the box under the "Axial" heading labeled "Ends."

Click "Annotate" and then "Close."

The axial loading values should be displayed on your screen.

4. When I annotate beam moments on my diagrams, I can't seem to 1) change the font by adjusting the Beam Labels option and 2) turn off the unit being written on every single number.

Annotation labels, although applied to beams, nodes, plates and solids, are not altered by the associated options (i.e View | Options | Beam Labels). In order to change the display of the annotations, go to View | Options from the main menu and choose the Annotation tab. To remove the display of the units for each annotation, simply choose the option "123.4" instead of "123.4 kN" under the Style list box in the Annotation tab. This will write the unit in the bottom right-hand corner of the screen for force, length and moment. If the units are not shown, go to View | Structure Diagrams and choose the Labels tab. Check on the option "Show Diagram Info" under the General box.

5. Why are my annotations for maximum bending moment or shear values not showing up in the post-processing mode?

In order to see the annotation (from Results->View Value in the post-processing mode) for a particular force or moment, the corresponding diagram must be on. For example, if one was to select maximum bending under the Beam Results tab, the bending moment diagram must be on (either MX, MY and/or MZ). Also, under the Ranges tab, make sure that the "None" option is not selected. Obviously, this would not annotate anything if it were selected. As a final note, once the annotations are visible, the size and font can be changed from the Annotation tab under View->Options in the main menu.

6. If I have a moment vector along the local positive Z axis does it have a twisting action going to the right along the positive direction of the axis?

If a member is drawn with its longitudinal axis (local-X) from left to right, and the local Z axis coming out of the page towards you, a positive MZ would cause tension on the top fiber, and a negative MZ would cause tension on the bottom fiber.

7. What are the sign conventions for moments in a 3-D structure?

The sign conventions are as follows:

Axial (FX) : Positive = Along local X axis, Negative = Opposite to local X
axis
Shear-Y (FY) : Positive = Along local Y axis, Negative = Opposite to local Y
axis
Shear-Z (FZ) : Positive = Along local Z axis, Negative = Opposite to local Z
axis

Torsion (MX) : Positive = Along local X axis, Negative = Opposite to local X
axis
Moment-Y (MY) : Positive = Along local Y axis, Negative = Opposite to local
Y axis
Moment-Z (MZ) : Positive = Along local Z axis, Negative = Opposite to local
Z axis

For axial forces,

Positive at the start node indicates compression at the start node.
Positive at the end node indicates tension at the end node.

Negative at the start node indicates tension at the start node.
Negative at the end node indicates compression at the end node.

8. After performing the analysis, I enter the post-processing mode to view the member end force values. I click on the Beam page on the left side of the screen and see the values listed on the tables on the right hand side. Unfortunately, the moment values are in kip-inch units, even though my current units are set to feet and pounds. What do I have to do to get the values to show up in pound-feet units in the tables?

The unit system in which results are displayed on the tables is set using the facilities available under the View - Options menu. These are known as the display units. To set the display units for the bending moments and torsional moments, please do the following :

In the View menu, select Options - Force units. In the category called Moment, select the units you desire and click on OK.

9. What is the purpose of the Beam - Graphs page on the left side of the screen?

This is another way to display the bending, shear and axial force diagrams on the screen.

In the post processing mode, select the Beam page from the left side of the screen. Then select graphs.

The right side portion of the screen will display the Bending diagram (MZ), shear diagram (FY) and the axial force diagram (FX) with values. In the drawing area, if you select a member by clicking on it, MZ, FY and FX of
that member will be displayed on the right hand side. To display the diagrams of another member, select that member.

10. How do I display the bending moment diagram and the values on that diagram, or shear forces or Axial forces?

First you must Analyze the file. Select Analyze from the Staad.Pro top menu bar. Select the Analysis option. After this, click on Run Analysis at the bottom of the small window dialog box.

After the analysis of the file is completed, click on the Done button.

Next, we go to the Post Processing mode to view the forces and results graphically.

To enter into the Post Processing mode, select Mode from the top menu bar and select Post Processing. Remember that if your analysis is not complete, you will not be able to access the Post Processing mode.

By default, the deflection diagram always opens up in the post processing screen of Staad.Pro.

To view the Bending Moment Diagrams, select the Beam page from the left side. From the top menu bar, choose Results - View value. Under Ranges, choose All. (The All button means the Bending moment diagram will be displayed for all members.)

Under the Beam Results tab, you will see the options Bending, Shear, Axial, Displacement and Stresses.
Make the appropriate choice.

Click on the Annotate button. Then click on the close button.

11. When I take a picture, it prints on the top half of a 8-1/2 x 11 size page. How can I take pictures that fill the page? 

There is no direct way to change the size of the picture from within STAAD.Pro. However here are a few options that you may find useful

Option 1

1. Before taking a picture, please ensure that the model is
   zoomed in sufficiently so that it fills up the space within the picture border as far as possible.
2. Take the picture and include that as part of the report using the Report Setup.
3. Go to File > Printer Setup and change the orientation to Landscape.
4. Go to File > Print Preview Report to check whether it looks satisfactory or not and if so, print it.

Option 2

1. You may copy the picture by going to the menu option Edit > Copy Picture. You can then paste the picture in MSWord or Excel or Paint.
2. Adjust the size of the picture using the tools available within these applications and take a print from there.

12. How to insert a company logo into STAAD.Pro report?

1. Open the start-up window of STAAD.Pro and go to the Configuration option.

2. Choose “File Options” tab and tick the “Remove Bentley Logo from Report” box. This will remove the Bentley logo    from your reports

3. Open the STAAD.Pro file. Go to the Report setup page and click on “Name and Logo” option.

4. Go to file option and choose the path where you have stored your logo. The logo should be in .bmp format.

5. Write the company name. You can orient the logo and company name by the Alignment option.

Note, Ram Elements, Connection and Ram Structural System have similar options. For Elements or Connection go to the upper left menu - General Configuration - Print tab. For RAM Structural System you just have to replace the logo.bmp file in the program directory with your own logo.bmp or logo.jpg file. it tends to work best when the log has roughly a 1:1 aspect ratio.

13. Can I get STAAD.Pro to report the torsion stress ?

STAAD.Pro does not report stress due to Torsion but here are a couple of items which you may find useful.

The beam end forces table that you can get from Postprocessing mode Beam > Forces page, reports the torsion ( MX ) in a beam member.

STAAD is also able to account for stresses due to torsion during the design phase. In steel design for example, the torsion stresses are converted to normal and shear stresses and added to existing normal/shear stresses following guidelines laid out in AISC Design Guide 9. When it comes to the new AISC 360-10 code, currently the software can account for the torsion for HSS sections only although work is under progress to account for torsion for Non-HSS sections too and this should be available in a couple of months. 

14.How can I have STAAD report more than 3 places of decimal in the post processing result tables?

You need to go to the top menu and click on View > Options > Choose the appropriate item and change the corresponding number of decimal places as desired > Click Apply > OK.

15. How to know the version of the design code which is being used by STAAD.Pro during the analysis?

The design code version which is being used by STAAD.Pro during the design phase is written in the Output file

16. How to see the displacement of only one particular node graphically?

1. Analyze the model and go to the Postprocessing mode, Node -> Displacements page.
2. If needed, turn on the node symbol (click Shift + K on your keyboard) and node numbers (Shift + N).
3. Go to the Results -> View Value menu.
4. In the Ranges tab select Ranges and enter the node number(s) for which you want to see the displacement.

5. Then go to the Node tab and select Nodal Displacement which you want to see. Click Annotate.

Now the displacement of only selected node will be seen on the screen. Similarly, beam force diagram values, beam maximum displacements, beam combined stresses and support reactions can be set.

17. What is the difference between the local and global deflection in the member query box?

Figures (1) and (2) show the local and global deflections of the beam #2 which is a part of the beam joining 2 columns:

Figure (1) 

Figure (2)

Global deflection is the largest distance between (a) and (b) where:

(a) is the line joining the ends of the member in its un-deflected position (named as 'Original shape' in the figure (3));

(b) is the elastic curve of the member representing its deflected shape.

Local deflection is the largest distance between (c) and (d) where:

(c) is the line joining the ends of the member in its deflected position;

(d) is the elastic curve of the member representing its deflected shape.

Figure (3)

18. I am analyzing a large 3D structure. I changed the beta angle of one of the members to 90. I expected the MY and MZ for the two scenarios ( beta =0 and beta=90) to get interchanged. However that does not seem to happen. Why ?

The Mz and My would not simply get interchanged when you apply a beta angle to 90 for every situation. The same would be true if you are analyzing a beam in isolation without considering any effect from the rest of the structure. However when a beam is part of a bigger structure, the beam’s local stiffness in each direction would affect the global stiffness of the structure along each DOF. Depending on that there will be a redistribution of the forces which will result in different moments/shears.

19. How to get Member End Forces for a specific selection of beams?

The procedure of specifying the commands to report the member end forces is described in STAAD.Pro Help manual chapter 1.5.12:



Alternatively, one can use a Report Setup with specified Ranges (by group or simply typing in the member numbers in the Ranges field):

20. How do I change stress output units in the *.ANL output file? They are coming out as kN/m2. I want N/mm2.

The units of items reported in the analysis output file are based on the unit settings in the input command file ( editor ). The unit that is current at the time the relevant command triggering the output is processed, is used for the reporting. One can set the units appropriately using the editor ( Edit > Edit Input Command File ) as explained next. For example to get the support reactions and member forces reported in Newton and mm units one needs to enter the unit command before the print commands as shown next

…

PERFORM ANALYSIS

UNIT MM NEWTON

PRINT SUPPORT REACTIONS

PRINT MEMBER FORCES

…

Any other output printed in the ANL file following the above commands, would also be printed in the currently set units of Newton and mm.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

1. Is it possible to specify a displacement and then have STAAD analyze a frame to give me a corresponding load (the load that would have been required to produce that displacement)?
2. I am applying a UBC seismic load on a bridge. The analysis engine reports an error message which says that:EITHER NA OR NV FACTOR HAS NOT BEEN SPECIFIED WHILE SEISMIC ZONE HAS BEEN SPECIFIED AS 4.
3. I would like to create a REPEAT LOAD case whose constituent load cases are themselves REPEAT LOAD cases. Is this allowed?
4. After determining the lateral loads using Staad UBC seismic analysis in a first file, I note down the lateral loads computed at each joint. In a second separate file with the same frame model, I apply the lateral loads from the first file combining them with the gravity loads and perform the analysis. I consider this procedure of mine very tedious in case of a 3D high rise building most specifically in view of the first file. Is there any shorter procedure for this? Please take note that I am using the Command File Editor.
5. I am trying to analyse a structure which consists of a large dia pipe supported at discrete points. I am unable to get STAAD to analyse this for UBC loads.
6. I am modelling a steel building consisting of columns and beams. The floor slab is a non-structural entity which, though capable of carrying the loads acting on itself, is not meant to be an integral part of the framing system. It merely transmits the load to the beam-column grid.  There are uniform area loads on the floor (think of the load as wooden pallets supporting boxes of paper). Since the slab is not part of the structural model, is there a way to tell the program to transmit the load to the beams without manually figuring out the beam loads on my own?
7. When does one use FLOOR LOAD and when does one use ELEMENT LOAD?
8. What is the difference between the LOAD COMB & REPEAT LOAD commands?
9. I am modelling an elevated silo which will be used for storing grain. The columns which support the structure are modelled as members and the walls of the silo (containment part of the structure) are modelled using plate elements. The silo has vertical and sloping walls. The loads on the structure consist of the weight of the grain contained in the silo. What is the best method for applying the load when the silo is full of grain? As pressure loads on the inside? How should the load be applied on the sloping walls?
10. I modeled a curved beam using cylindrical coordinates and tried to run a moving load over the curved beam. STAAD.Pro is not allowing me to do this. Why?
11. What is the significance of the Rw Value in the UBC code?
12. How is the wind load calculated/generated for a structure in STAAD.Pro ? What is the exposure factor calculated and how is it calculated? In 2002, I hear you can now define your own "panels"? What does this mean?
13. I am using the moving load generation. The truck that I am specifying is so wide (dimension perpendicular to direction of traffic) that within the width of one lane of traffic, there are 3 or more parallel beams along the direction of traffic. How does STAAD determine how the truck load should be converted to beam loads?
14. For moving load generation, does STAAD provide the location of all the moving point loads in terms of member number and distance from the start of the member?
15. How does STAAD consider the moving load over the beams if the load is not applied over a beam exactly?
16. If we have a wind load on a bracing system (perpendicular to the bracing plane), can we apply the wind loading directly to the brace as a uniform load instead of resolving the force into point loads? How does Staad handle this type of loading on members that are declared trusses?
17. I am using the moving load generation facility to generate a set of load cases for a truck moving on a bridge. Can STAAD provide the support reactions for the critical position that produces the maximum effects on the system flooring?
18. I have some distributed loads on some members of the model. I would like to consider the weights due to these loads in the base shear calculation for UBC load generation. Can you explain the process for doing this?
19. What is JOINT WEIGHT? I'm trying to learn how to use the seismic load generator and I don't see anything explaining what JOINT WEIGHT is or what it is used for.
20. How do I get STAAD to automatically combine static load cases with load cases generated using the MOVING LOAD generation facility?
21. How to calculate the temperature parameter f1 and f2  for applying temperature load on the
    structure?
22. I have multiple structures modeled in STAAD with varying heights and I want to use the Automatic Seismic Load Generation in STAAD. Can STAAD still properly distribute the seismic forces even though my structures are disjointed ?
23. I defined dead and live loads as reference load cases and I used these cases for specifying seismic weights as part of my seismic load definition. Do I have to re-define the dead loads and live loads as part of the seismic load case ?
24. Can STAAD automatically calculate the seismic forces both in horizontal and vertical direction required by ASCE as shown next E = (Rho) x QE (+/-) 0.2 x SDS x D
25. I am trying to generate moving loads but keep getting a message "Cannot create Load Generation command".
26. I can define Load Envelopes consisting of groups of loads and find that there are types like STRENGTH, SERVICEABILITY, COLUMN etc that I can choose from. What does these envelope types mean ?
27. I want to exclude some of my members from taking wind loading generated by STAAD. I cannot use the XR and YR to eliminate these members as there are other members within the same range that has to take up wind loading. Is there a way to do that ?

1. Is it possible to specify a displacement and then have STAAD analyze a frame to give me a corresponding load (the load that would have been required to produce that displacement)?

You first need to know the pattern or arrangement of the loading which will eventually cause the displacement you wish to see. This is because, there can be millions of loading arrangements which cause that amount of displacement at that node, so one needs to have an idea of which of those patterns is the one that one wants. By pattern, we are talking of details like, is the load going to consist of concentrated forces at nodes, or distributed and trapezoidal loads on members, or pressures on plates, etc. For example, any of these loads will cause a certain amount of displacement at a node along a certain direction.

So, a unit load analysis would be the best approach for solving this kind of a problem. That means, all the components of the loading pattern would be represented by unit loads. Let us say that by applying a member load of 100 pounds/ft, you get 0.4 inches of displacement along global X at node 43. So, if the final desired displacement at node 43 along X is say, 1.2 inches, the applied load should be simply (1.2/0.4)*100 = 300 pounds/ft.

2. I am applying a UBC seismic load on a bridge. The analysis engine reports an error message which says that:

EITHER NA OR NV FACTOR HAS NOT BEEN SPECIFIED

WHILE SEISMIC ZONE HAS BEEN SPECIFIED AS 4.

This is due to the fact that, for your model, STAAD looks at the data under the DEFINE UBC LOAD command and concludes that you intend to analyse the structure per the UBC 1997 code. It then checks whether all the required parameters have been specified for that code, and detects that NA and NV are missing. You perhaps have an input similar to the one below :

DEFINE UBC LOAD
ZONE 0.4 I 1 RWX 12 RWZ 12 STYP 1.2 PX 0.2626 PZ 0.2626

For Zone 4, Na and Nv are two of the fundamental parameters necessary to calculate the base shear. If you look at Tables 16-Q and 16-R on pages 2-34 & 2-35 of the UBC 1997 code, you will find that for Zone 4, the coefficients Ca and Cv are dependent on Na and Nv.

So, specify the NA and NV parameters, so that the commands look similar to the one below :

DEFINE UBC LOAD
ZONE 0.4 I 1 RWX 12 RWZ 12 STYP 1.2 NA 1.6 NV 1.6 PX 0.2626 PZ 0.2626

3. I would like to create a REPEAT LOAD case whose constituent load cases are themselves REPEAT LOAD cases. Is this allowed?

You can do this if you have STAAD.Pro version 2002 or later. An example of this is shown below.

LOADING 1
SELFWEIGHT Y -1.0

LOAD 2
REPEAT LOAD
1 1.0
JOINT LOAD
4 5 FY -15. ; 11 FY -35.

LOAD 3
REPEAT LOAD
2 1.0
MEMB LOAD
8 TO 13 UNI Y -0.9 ; 6 UNI GY -1.2

LOAD 4
SELFWEIGHT Y -1.0
JOINT LOAD
4 5 FY -15. ; 11 FY -35.
MEMB LOAD
8 TO 13 UNI Y -0.9 ; 6 UNI GY -1.2

PERF ANALY
LOAD LIST 3 4
PRINT *** RES
FINISH

In the above example, load case 3 repeats load case 2, which in turn repeats load case 1.

4. After determining the lateral loads using Staad UBC seismic analysis in a first file, I note down the lateral loads computed at each joint. In a second separate file with the same frame model, I apply the lateral loads from the first file combining them with the gravity loads and perform the analysis. I consider this procedure of mine very tedious in case of a 3D high rise building most specifically in view of the first file. Is there any shorter procedure for this? Please take note that I am using the Command File Editor.

There is absolutely no need for you to take the lateral load data from the output of the first file, and insert it as input into the second file. In STAAD, once the lateral loads due to UBC or IBC are generated, they are automatically available for combining with gravity loads, or any other loads for that matter. Consequently, there are 2 ways in which this combination can be achieved, and each is demonstrated below :

Method 1 :
Generate the lateral load in one load case. Specify the gravity load in another load case. Then, combine the two in a load combination case.

LOAD 1 - GENERATE LATERAL LOADS DUE TO UBC ALONG X
UBC X 1.0

LOAD 2 - SPECIFY GRAVITY LOADS
SELFWEIGHT Y -1.0
MEMBER LOAD
1 TO 25 UNI GY -1.2
JOINT LOAD
10 39 FY -10.0

LOAD COMBINATION 3 - COMBINE THE LATERAL AND GRAVITY LOADS IN ONE CASE
1 1.0 2 1.0

Method 2 :
Create a single load case in which the lateral forces are generated, and gravity loads are specified.

LOAD 1 - LATERAL LOADS + GRAVITY LOADS
UBC X 1.0
SELFWEIGHT Y -1.0
MEMBER LOAD
1 TO 25 UNI GY -1.2
JOINT LOAD
10 39 FY -10.0

5. I am trying to analyse a structure which consists of a large dia pipe supported at discrete points. I am unable to get STAAD to analyse this for UBC loads.

When the UBC committee came up with the recommendations for analysing structures subjected to earthquakes, the type of structures they had in mind were conventional style buildings where the base of the model, namely, the points where the supports are located is at the lowest elevation with respect to the rest of the model.

If you look at the UBC procedure, it involves computation of the base shear, which then has to be distributed over the height of the building, so that one can then calculate the inter-story shears. A certain amount of the weight gets lumped at the highest point of the building, and the rest gets distributed along the height. In other words, the principle is that a mass at any height of the building is subjected to an acceleration and the force caused by the acceleration is represented by a concentrated force where the mass is located. The summation of all such forces at a given floor cause the columns beneath that floor to be subjected to a shear force.

When you talk of a model like a pipe which is defined as line members attached to several collinear nodes, all of which are at the same elevation, the UBC rules become impossible to apply. The fact is, to analyse your structure for seismic effects, you do not even need the elaborate procedure of the UBC code. You can take the selfweight, and any imposed loads on the pipe, and apply them along a horizontal direction like X or Z with a factor, and you will get what is normally expected in a seismic analysis.

So, you just have to have

LOAD 2
SELF X n

where n is a number like 1.5, which represents that there is a net force of 1.5 times the weight of the structure acting along the X direction due to an earthquake. For better handling of the distributed loads, you might want to consider defining several nodes along the length of the pipe, between supports.

6. I am modelling a steel building consisting of columns and beams. The floor slab is a non-structural entity which, though capable of carrying the loads acting on itself, is not meant to be an integral part of the framing system. It merely transmits the load to the beam-column grid.  There are uniform area loads on the floor (think of the load as wooden pallets supporting boxes of paper). Since the slab is not part of the structural model, is there a way to tell the program to transmit the load to the beams without manually figuring out the beam loads on my own?

STAAD's FLOOR LOAD option is ideally suited for such cases. This is a facility where you specify the load as a pressure, and the program converts the pressure to individual beam loads. Thus, the input required from the user is very simple - load intensity in the form of pressure, and the region of the structure in terms of X, Y and Z coordinates in space, of the area over which the pressure acts.

In the process of converting the pressure to beam loads, STAAD will consider the empty space between criss-crossing beams (in plan view) to be panels, similar to the squares of a chess board. The load on each panel is then tranferred to beams surrounding the panel, using a triangular or trapezoidal load distribution method.

Additional information on this facility is available in example problem 15 in the examples manual, and section 5.32.4 in the STAAD.Pro Technical Reference manual.

7. When does one use FLOOR LOAD and when does one use ELEMENT LOAD?

When modelling a grid system made up of horziontal beams and the slabs which span between the beams, we have found that there are 2 approaches that users take :

1) They model the beams only, and do not include the slabs in the model. However, they take into account the large inplane stiffness of the slab by using the master-slave relationship to tie together the nodes of the deck so that a rigid diaphragm effect is simulated for the horizontal plane at the slab level.

2) They model the slabs along with the beams. The slabs are modelled using plate elements.

The question that arises is, how does one account for the distributed loading (load per area of floor) which is present on top of the slab?

If you model the structure using method (1), the load can be assumed to be transferred directly on to the beams. The slab-beam grillage is assumed to be made up of a number of panels, similar to the squares of a chess board. The load on each panel is then tranferred to beams surrounding the panel, using a triangular or trapezoidal load distribution method. You can do this in STAAD by defining the load intensity in the FLOOR LOAD command. In other words, the pressure load on the slabs (which are not included in the model) are converted to individual beam loads by utilizing the FLOOR LOAD facility.

In method (2), the fact that the slab is part of the model makes it very easy to handle the load. The load can be applied on individual elements using the ELEMENT LOAD facility. The connectivity between the beams and elements ensures that the load will flow from the plates to the beams through the columns to the supports.

8. What is the difference between the LOAD COMB & REPEAT LOAD commands?

The difference lies in the way STAAD goes about calculating the results - joint displacements, member forces and support reactions. For a load combination case, STAAD simply ALGEBRAICALLY COMBINES THE RESULTS of the component cases after factoring them. In other words, for example, in order to obtain the results of load 10, it has no need to know what exactly is it that constitutes load cases 3, 4 and 5. It just needs to know what the results of those cases are. Thus, the structure is NOT actually analysed for a combination load case. With a REPEAT LOAD case however, the procedure followed is that which occurs for any other primary load case. A load vector {P} is first created, and later, that load vector gets pre-multiplied by the inverted stiffness matrix.

9. I am modelling an elevated silo which will be used for storing grain. The columns which support the structure are modelled as members and the walls of the silo (containment part of the structure) are modelled using plate elements. The silo has vertical and sloping walls. The loads on the structure consist of the weight of the grain contained in the silo. What is the best method for applying the load when the silo is full of grain? As pressure loads on the inside? How should the load be applied on the sloping walls?

There are 2 segments of the tank which have to be individually considered for application of the load.

The vertical walls
------------------

The material in the tank, especially if it is a fluid, will exert a lateral pressure on the vertical walls of the tank. This pressure load can be applied on the tank using the ELEMENT PRESSURE load facility. You can use one of 2 options to do this.

a) A uniform pressure. If you take any individual element on the wall, if you know the pressure intensity at the top edge, and the pressure intensity at the bottom edge, the average of these 2 intensities can be applied as a constant pressure on the entire surface of the element, as in the following example :

45 PRESSURE -3.5

Since the load is along the local Z axis of the element, you do not have to specify the axis name in the above command since local Z is the default for the axis. The load value must be accompanied by the proper sign (positive or negative) which accounts for whether the load acts along or opposite to the direction of the local Z axis.

b) A trapezoidally varying pressure.

In case (a) above, we decided to take the average of the pressures at the top and bottom edges, and thus obtain a uniform pressure. However, this is not absolutely necessary. The load can be applied as a trapezoidal load, in which case, the TRAP option is used and the intensities at the top and bottom edges must be specified. An example of that is

45 PRESSURE TRAP Y -4.5 -2.5

In this example, it is assumed that the local Y axis of element 45 is along the vertical direction, and thus the trapezoidal variation is along the local Y. The load itself acts perpendicular to the surface of the element, and hence along local Z. If local Y is in the same sense as global Y, -4.5 indicates the intensity at the lower edge, and -2.5 indicates the intensity at the upper edge.

If the vertical wall has many divisions along the vertical direction, there will be several "horizontal rings" of elements. Every element contained in a ring has the same intensity at its top and bottom edge. That means, the top & bottom intensity for each of those rings will have to be manually calculated. There is a facility in the STAAD.Pro GUI to simplify this task. From the top of the screen, select Commands - Loading - Load Commands - Element - Hydrostatic Trapezoidal, and provide the intensities at the top and bottom edges of the vertical wall. The program will use the linear interpolation method to find the intensity at each intermediate division, and then create the individual element TRAPEZOIDAL loads.

The sloping walls
-----------------

The load on the elements which make up these walls is derived from the weight of the column of material directly above these elements, and acts along the global vertical downward direction. Since the element TRAP load facility that is available in STAAD allows a load to be applied only along the local Z axis, and since local Z is not parallel to any of the global directions, the TRAP load option cannot be used here. Hence, one will have to apply these as uniform pressure loads, the value of which has to be calculated for each sloping element as the average of the intensities at the 4 nodes of that element. There is no generation facility currently available in the program to automate this task.

10. I modeled a curved beam using cylindrical coordinates and tried to run a moving load over the curved beam. STAAD.Pro is not allowing me to do this. Why?

Moving load on curved beams is not supported by the DEFINE MOVING LOAD command in STAAD.Pro. The STAAD moving load generator assumes:
1)All loads are acting in the negative global vertical (Y or Z) direction. The user is advised to set up the structure model accordingly.
2)Resultant direction of movement is determined from the X, Y and Z increments of movements as provided by the user.

However, STAAD.beava, an automated bridge load generator, can handle moving loads for curved or custom-defined bridge decks with beams and plates. It also generates a 3D influence surface based on displacements, support reactions, beam forces or plate stresses for any point on the bridge. The critical loading patterns and critical vehicle position will be identified as well. STAAD.beava is an integrated module in the STAAD.Pro environment.

11. What is the significance of the Rw Value in the UBC code?

The UBC 1997 code defines Rw as a Numerical Coefficient representative of the inherent overstrength and global ductility capacity of lateral-force resisting systems.

It is to be used in the equation for computing base shear. Its values are dependent on the type of lateral-force resisting system in the building, such as whether the system is a Light-framed wall with shear panels or Shear wall made of concrete or a special moment resisting frame, etc.

Values of Rw are listed in Tables 16-N and 16-P of the UBC 1994 and 1997 codes.

12. How is the wind load calculated/generated for a structure in STAAD.Pro ? What is the exposure factor calculated and how is it calculated? In 2002, I hear you can now define your own "panels"? What does this mean?

The DEFINE WIND LOAD command may be used to define the parameters for automatic generation of wind loads on the structure. The user needs to define the intensity and corresponding heights along with the exposure factors. If the exposure factor is not defined, the program takes the default value as 1.0.

A value of 1.0 means that the wind force may be applied on the full influence area associated with the joints if they are also exposed to the wind load direction.
All loads and heights are in the current unit system. In the list of intensities, the first value of intensity (p1) acts from the ground level up to the first height. The second intensity (p2) acts in the global vertical direction between the first two heights (h1 and h2) and so on. The program assumes that the ground level has the lowest global vertical coordinate of any joint entered for the structure.

The exposure factor (e) is the fraction of the influence area associated with the joint(s) on which the load may act if it is also exposed to the wind load. Total load on a particular joint is calculated as follows.

JOINT LOAD = (Exposure Factor) x (Influence Area) x (Wind Intensity).

Exposure factor (User specified) = (Fraction of Influence Area) x (influence width for joint).

In STAAD.Pro 2002, the built-in wind load generation facility has been enhanced to allow the user to specify the actual panels of the building which are exposed to the wind. This user-level control will now allow the user to obtain a more accurate distribution of wind forces, especially when the exposed surface of the building lies in several vertical zones, each reset from the one below or the one above, in terms of the direction of wind force. Further, the basic algorithm for detecting the shape of the panels and the amount of load which should be calculated for the panel corners too has undergone significant improvements. The parameters for definition of the wind load types are described in Section 5.31.3 of the STAAD.PRO Technical Reference Manual. The relevant extracts from Section 5.32.12 of the STAAD.Pro Technical Reference Manual, where the method for applying wind loading in the form of a data in load cases has been explained, is provided below. Note that areas bounded by beam members (and ground), and exposed to the wind, are used to define loaded areas (plates and solids are ignored). The loads generated are applied only at the joints at vertices of the bounded areas. For example, in the following set of commands:

DEFINE WIND LOAD
TYPE 1
INTENSITY 0.1 0.12 HEIGHT 100 200
EXP 0.6 JOI 1 TO 25 BY 7 29 TO 37 BY 4 22 23
TYPE 2
INT 0.1 0.12 HEIGHT 100 900
EXP 0.3 YR 0 500
LOAD 1
SELF Y -1.0
LOAD 2
WIND LOAD Z 1.2 TYPE 2 ZR 10 11
LOAD 3
WIND LOAD X TYPE 1 XR 7 8

A minus sign indicates that suction occurs on the other side of the selected structure. If all of the members are selected and X (or Z) is used and the factor is positive, then the exposed surfaces facing in the -x (or -z) direction will be loaded in the positive x (or z) direction (normal wind in positive direction). If X and a negative factor is used, then the exposed surfaces facing in the +x direction will be loaded in the negative x direction (normal wind in negative direction). [If -X is entered and a negative factor, then the exposed surfaces facing in the -x direction will be loaded in the negative x direction (suction). If -X is entered and a positive factor, then the exposed surfaces facing in the +x direction will be loaded in the positive x direction (suction).] A member list or a range of coordinate values (in global system) may be used. All members which have both end coordinates within the range are assumed to be candidates for defining a surface which may be loaded if the surface is exposed to the wind. The loading will be in the form of joint loads (not member loads). 1, 2 or 3 ranges can be entered to form a "layer", "tube" or "box" for selecting members in the combined ranges. Use ranges to speed up the calculations on larger models.

It is advisable not to use the SET Z UP command in a model with wind load. A closed surface is generated by the program based on the members in the ranges above and their end joints. The area within this closed surface is determined and the share of this area (influence area) for each node in the list is then calculated. The individual bounded areas must be planar surfaces, to a close tolerance, or they will not be loaded. Hence, one should make sure that the members/joints that are exposed to the wind make up a closed surface (ground may form an edge of the closed surface). Without a proper closed surface, the area calculated for the region may be indeterminate and the joint force values may be erroneous. Consequently, the number of exposed joints should be at least 3.

13. I am using the moving load generation. The truck that I am specifying is so wide (dimension perpendicular to direction of traffic) that within the width of one lane of traffic, there are 3 or more parallel beams along the direction of traffic. How does STAAD determine how the truck load should be converted to beam loads?

Based on the data you provide under the DEFINE MOVING LOAD command, each truck is treated as a set of axles. If the WIDTH option is NOT specified, each axle is assumed to be comprised of 1 tire. If the WIDTH option is specified, each axle is assumed to be comprised of 2 tires.

The program looks at each tire independently. For any given tire, it looks for one longitudinal beam to the left of the tire, and another longitudinal beam to the right of the tire. Then it distributes the tire weight on those 2 beams as though the tire is located on a simply supported cross beam that spans the two longitudinal members on either side.

Thus, even if a lane spans across 3 longitudinal beams or for that matter several beams, the above approach ensures that the tire weights get properly applied on the correct set of beams as concentrated member loads.

You can get a listing of these concentrated member loads by using the command:
PERFORM ANALYSIS PRINT LOAD DATA

14. For moving load generation, does STAAD provide the location of all the moving point loads in terms of member number and distance from the start of the member?

Yes. Please use the PRINT LOAD DATA option with your PERFORM ANALYSIS command and you will get the information in your output file.

15. How does STAAD consider the moving load over the beams if the load is not applied over a beam exactly?

If a wheel falls inside a panel composed of beams on either side of the wheel running parallel to the direction of movement of the vehicle, the load is distributed on the 2 beams as simply supported reactions. Hence, if the wheel load is 10 kips, and if the distance from the wheel to the beam on the left is 7 ft, and the distance to the beam on the right is 3 ft, the beam on the left gets a 3 kip load, and the beam on the right gets a 7 kip load.

16. If we have a wind load on a bracing system (perpendicular to the bracing plane), can we apply the wind loading directly to the brace as a uniform load instead of resolving the force into point loads? How does Staad handle this type of loading on members that are declared trusses?

If a transverse load such as a uniform distributed load or a concentrated force is applied on a truss member, STAAD converts it to the equivalent concentrated shears at the 2 ends of the member. The member end force output will show them as shears on the member under the output terms SHEAR-Y or SHEAR-Z depending on the local axis direction the load is applied in.

However, if you determine the equivalent end shears and apply them as joint loads instead, and not as a member load, the truss members at that node will not experience any shear force due to that load.

17. I am using the moving load generation facility to generate a set of load cases for a truck moving on a bridge. Can STAAD provide the support reactions for the critical position that produces the maximum effects on the system flooring?

This would require that the support reactions for all generated load cases be produced in a report form sorted in a descending order based upon the specific support reaction criteria we are interested in, such as the FY force, or the MZ moment.

To get this report, first run the analysis. Go to the Post processing mode. Select the support node(s) at which you want the information you are seeking. From the top of the screen, select Report | Support Reactions. In the dialog box that comes up, select the degree of freedom (FY, MZ, etc.) which should be used as the criteria for sorting. Set the sorting order (high to low or low to high). From the loading tab, select the load cases that you want considered. Click on OK. A report of the results will be displayed in tabular form.

18. I have some distributed loads on some members of the model. I would like to consider the weights due to these loads in the base shear calculation for UBC load generation. Can you explain the process for doing this?

When analysing a structure for UBC loads, there 2 stages in the input. The first stage is the one where one defines data such as the various parameters (zone factor, importance factor, soil structure interaction factor, etc.) as well as the weights. In terms of the STAAD command language, it is initiated using the DEFINE UBC LOAD command, and an example for this may be found in Example 14 of the STAAD.Pro Examples manual.

Graphically, one may assign the data in the following manner.

Select the beam or beams you want to assign the distributed weights to. Next, from the top of the screen, select Commands | Loading | Define Load | Seismic Load. In the Parameters tab, select the type, and enter the relevant
values for the parameters. Press the "Save" button. A new tab called "Weights" should come up. Press the "Member Weight" button. For the loading type, choose UNI, enter the distributed weight value, distances to where the load starts and the load ends, and press "OK". Press the "Assign" button to actually assign them to the selected members. Finally, press the "Close" button.

19. What is JOINT WEIGHT? I'm trying to learn how to use the seismic load generator and I don't see anything explaining what JOINT WEIGHT is or what it is used for.

In the block of commands which fall under the DEFINE UBC LOAD heading or any of the other ones like AIJ ,1893, etc., the weight data which goes into the calculation of the total weight consists of :

SELFWEIGHT

MEMBER WEIGHT

JOINT WEIGHT

If at any of the joints of the structure, there are any weights which you want included in the total weight calculation, you specify them using the JOINT WEIGHT option.

20. How do I get STAAD to automatically combine static load cases with load cases generated using the MOVING LOAD generation facility?

You should use the option called ADD LOAD along with the LOAD GENERATION command.

Shown below is an example:

DEFINE MOVING LOAD
TYPE 1 LOAD 20. 20. 10. DISTANCE 10. 5. WIDTH 10.
LOAD 1 STATIC LOAD
SELF Y -1.0

* GENERATE MOVING LOADS AND ADD THE SELFWEIGHT
* LOAD TO EACH GENERATED LOAD CASE

LOAD GENERATION 10 ADD LOAD 1
TYPE 1 7.5 0. 0. ZI 10.
PERFORM ANALYSIS PRINT LOAD DATA

21. How to calculate the temperature parameter f1 and f2  for applying temperature load on the
structure?

You have to know three temperatures :
 
1) the stress-free temperature, which is the temperature that the structure was at when it was constructed or installed.  Call it A.
 
2) The temperature of the top fiber (the fiber that is farthest along the positive direction of the local Z axis of elements and local Y axis for beam). Call it B.
 
3) The temperature of the bottom fiber (the fiber that is farthest along the negative direction of the local Z axis of element and local Y axis for beam). Call it C.
 
When you specify the temperature load, the command is
member-list TEMPERATURE f1 f2
where
 
f1 = (B+C)/2 - A
 
f2 = B-C
 
f1 is the temperature that causes axial elongation / shrinkage along the longitudinal axis (local X of the member, and, local X and Y axes for the plate element).
 
 f2 is the temperature responsible for inducing bending in the member and element.
 
Also, refer to article 5.32.6 of the Technical Reference Manual of Staad.pro

22. I have multiple structures modeled in STAAD with varying heights and I want to use the Automatic Seismic Load Generation in STAAD. Can STAAD still properly distribute the seismic forces even though my structures are disjointed ?

STAAD.Pro Seismic Load Generation should not be used in this case. If the structures are independent of each other, you should have 3 separate models and do seismic load generation on each model separately.

23. I defined dead and live loads as reference load cases and I used these cases for specifying seismic weights as part of my seismic load definition. Do I have to re-define the dead loads and live loads as part of the seismic load case ?

Related question : I defined dead loads, live loads for seismic weight calculation as part of my seismic load definition. Do I again need to specify the dead and live loads as part of the seismic load cases ?

No you do not need to. Once the seismic weight is defined ( either through reference load or through the various seismic weight definition options ) as part of the seismic load definition, the software is able to figure out the total seismic weight. You do not need to redefine. Doing so would apply these as additional loads to the ones already defined. 

24. Can STAAD automatically calculate the seismic forces both in horizontal and vertical direction required by ASCE as shown next 

E = (Rho) x Q_E (+/-) 0.2 x S_DS x D

The seismic load generation in STAAD only calculates the horizontal portion Q_E. The factors like Rho or the vertical effect factors like 0.2SDS has to be calculated manually and applied as factors to the appropriate loads when defining load combinations. 

25. I am trying to generate moving loads but keep getting a message "Cannot create Load Generation command".

Most likely you have LOAD COMBINATIONS already defined as part of the file and there is not enough gap in numbering between the last primary load case and the load combination to accomodate the number of moving load generations that has been asked for. For example if you have 

LOAD 1 DEAD LOAD
SELF Y -1.0
*
LOAD 2 LIVE LOAD
MEMBER LOAD
100 TO 150 UNI GY -1
*
LOAD COMB 3 DEAD + LIVE
1 1.0 2 1.0

then if you try to generate 30 moving load cases as shown next

LOAD GENERATION 30
TYPE 10 12 1 0 ZINC 1

Here are a couple of options to handle this scenario.

Change the LOAD COMBINATION number to anything higher than 32 to accomodate 30 generations after load case 2. Remember these generations are all treated as primary load cases by STAAD and so has to come shead of the combinations.

Alternately you may change the LOAD COMBINATION to REPEAT LOAD as shown next

LOAD 3 DEAD + LIVE
REPEAT LOAD
1 1.0 2 1.0

REPEAT LOADs are considered as primary load case by STAAD.Pro and hence you would be able to generate the moving load generations after that without any problem.

26. I can define Load Envelopes consisting of groups of loads and find that there are types like STRENGTH, SERVICEABILITY, COLUMN etc that I can choose from. What does these envelope types mean ?

The type for the envelopes are supposed to indicate what the envelope ( which is essentially a cluster of loads ) is meant to be used for. For example if the type is specified as Serviceability it would be used for serviceability checks like deflection check. STRENGTH envelope means the component loads would be used for member strength check. However as of now, all design codes in STAAD.Pro are not equipped to honor the envelope types. The latest
AISC 360 10 code check is able to do appropriate code checking based on envelope specifications SERVICEABILITY and STRENGTH. As far as the other envelope types are concerned, COLUMN was developed based on requirement obtained from a particular company who wanted to tag all the load cases for column design separately and type Connection was defined to tag all load cases to be used for connection design.

27. I want to exclude some of my members from taking wind loading generated by STAAD. I cannot use the XR and YR to eliminate these members as there are other members within the same range that has to take up wind loading. Is there a way to do that ?

Often one may need to apply wind loading on a specific set of members in a model. For example one may have cross braces in a vertical plane and may have wind load acting normal to the plane of these braces, which one may not want the braces to take. In such situations, one may define a group consisting of members which are expected to take the wind load and apply the
wind loading on these groups as shown next. As of now the data has to be entered using the editor as there are no options in the GUI for doing this

In the above example, wind loading type 2 and 4 has been applied on two separate member groups _X_AT_WEST and _X_AT_EAST respectively.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

Change Reaction Mark TN

To change the reaction mark so that there are no trailing zeros and a small "k" instead of kips you need to edit the tag family.

• Select a start reaction tag.
   
• Click the Edit Family button.
• In the Family Editor select the label and click the Edit Label button.
• Select a parameter and click the Edit Parameter's Units Format button.
  
• Uncheck Use project settings.
  
  
• Leave units set as Kips.
• Change Rounding to 0 decimal places.
• Set Unit Symbol to None.
• Check Suppress trailing 0's.
• Click OK.
• In the Suffix column enter a lowercase k.
  
• In the Edit Label dialog repeat this for each parameter as needed.
• Click Apply and then  OK.

Back in the Revit model open the Annotation family and reload the Structural Framing Tag-w-Start Reactions. Repeat these steps for the Structural Framing Tag-w-End Reactions label.  

Are the applied surface loads cumulative?

No, in RAM Structural System only the top applied surface load counts. The underlying loads are not deleted however, so if you delete the top load you can see the original load underneath. If too many load layers are applied to a model, a polygon error can occur when processing the loads. For this reason it is always best to remove any existing surface loads before modeling new layers.

Also note, this is different than the behavior in RAM Concept. In that program, overlapping surface loads are cumulative. Consequently, when Direct Gravity loads are imported from RAM SS into Concept, they are converted into equivalent separate polygons that do not overlap.

Is the structure self-weight included in the loads?

That depends on the settings under RAM Manager - Criteria - Self-Weight. Here the user can automatically include beam, column, wall or deck self-weight. Note, open web steel joists self-weight is never included.

For composite beam design, the self weight is always considered part of the Construction Dead Load. Hence, if all the self weight options are turned on, and there is no other load present during construction, the user applied CDL might be zero.

On the right hand side of the dialog box are the settings for self-weight as it applies to the building mass which is used for seismic loads, dynamic analysis and for P-Delta calculations.

In order for the steel gravity beam and column self weight mass to be considered in RAM Frame, it is imperative that those modules be run first, using the design-all process. So long as the RAM Manager indicates a green light next to each of those modules, RAM Frame should have the latest member self weight data available.

Note, in RAM Frame, under Loads - Masses, the program calculated diaphragm mass totals can be overridden with User Specified values, normally using calculated masses is advised. There is a similar dialog box for the total Gravity Loads which is used to determine program generated notional loads.

Is the additional weight of concrete due to beam sag or "ponding" considered?

No, the self-weight of the deck is based on the thickness and weight parameters set in the Modeler - Deck Properties. When beams sag under the weight of the deck it is a common practice for the topping concrete to be leveled off which adds additional weight to the system assuming it's not cambered or shored. This additional weight should be incorporated into the applied construction dead loads (and masses).

How are partition loads handled.

The Partition load is an additional Live Load; it is treated as an unreducible Live Load and will not be reduced. It is in addition to the loads specified as Live Load. Partition loads are defined variously by the Codes, some as Dead Load and some as Live Load. For those codes that define Partition loads as an unreducible Live Load, those should be specified here. For those Codes that define Partition loads as a Dead Load or as part of the regular Live Load, those should be included as part of the Dead Load or Live Load accordingly.

Unlike construction live load, the partition live load is not a portion of the total live load entered. You can apply 0 Live Load and still apply 15 psf Partition Live load, for example.

Partition loads are not automatically included in the seismic mass. The total Mass DL should be increased to account for partition weight as required by the code for seismic loads.

How is the self weight of Concrete Beam determined?

The program calculates rectangular beam unit self-weight based on the area of the beam times the "Unit Weight of Self weight". The other "Unit Weight" parameter is only used in calculating the elastic modulus, E, of the member.
The Concrete slab can independently be included in the self weight, so in cases where there is a concrete slab and rectangular concrete beams the weight of the concrete times the thickness of the slab and the width of the beam is double counted.

 
To alleviate this problem, "T" shaped beam sections are handled differently. With T beams, it's only the area of the stem below the slab that is applied as the beam self weight.

.

Why are my Roof Live loads ignored in the design?

RAM Structural System currently considers Snow OR Roof LL, but not both at the same time. In RAM Manager under Criteria - Members loads there is a toggle to select which the program should consider. Set the toggle to “Consider snow loads, Ignore roof live loads” when snow loads are modeled.

Note: Live Reducible, Unreducible and Storage type loads are always considered, it is only the Live - Roof type loads that are excluded when the option to consider snow loads is turned on.

Are my snow loads automatically added to the building weight for seismic load determination?

No, the program only uses the assigned Mass Dead Loads plus whatever self-mass options are turned on under RAM Manager - criteria - self weight when determining the total building mass or weight used in Seismic load determination (and in P-Delta calculations). The user should increase the Mass DL of applied surface loads to account for the weight of the snow load (or a percentage of the weight as required.

Note, the provided templates for load combinations do correctly consider snow load acting simultaneously with Dead, Live and Seismic loads, however.

This also applied to Storage Live Loads, even if the magnitude entered for the Storage Live load is large (e.g. > 125 psf) no portion of the storage live load is automatically considered in the seismic mass. The user must increase the Mass DL (or manually alter the masses in Ram Frame) when part of a storage live load needs to be added to the seimsic mass.

How can I apply a drift snow load?

Within the snow loads, only the top load counts. Since only the top snow load counts, the drift snow load should typically taper down from the max value to the flat-roof snow load as a minimum. The program gives a warning when any portion of the sloping plane of snow load is 0 or less magnitude.

In general, it’s best to define snow drift loads with M1 and M2 set to the highest value, and M3 set to the flat roof level. Then the loads can be applied in rectangular or trapezoidal areas as required. In the image below, the total snow load on the left is 50 psf tapering down to 30 psf on the right. This would be used in conjunction with a flat roof snow load of 30 psf applied first to the whole roof.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

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Can the edges of shells be pinned or hinged?

Regretfully no, the shell edges are always continuous or fixed to all the object that connect to them. In cases where you do not want the shells to transfer out-of-plane bending moments to the supports, like an edge beam or wall, there are only a few options.

1. Make the shells thinner. Since the out-of-plane inertia relates to the thickness cubed, reducing the thickness quickly reduces the out-of-plane stiffness. An increase in the shell material E value can counteract this reduction for in plane shear and axial stiffness.
2. Release the supporting member. Sometimes you can release the supporting beam, in torsion for example, to prevent the development of out-of-plane moments at the edge of the supported shells.
3. Separate the edge of the shell from the support, then connect the two together periodically with short members. These connector members can then be released in any of the 6 degrees of freedom to achieve the desired connectivity.

    

How can I report the flexural area of steel required for shells in Ram Elements?

For shell elements that are primarily subject to out of plane bending, Ram Elements can provide output for the area of steel required in the two principal directions per ACI 318-05.

The shells must be concrete and the model must include design combos to take advantage of this feature fully. Mechanical cover for the shells should also be assigned in the Shells - Materials spreadsheet.

To see the output on screen first select the desired combo at the bottom and then use View - Stresses to see stress contours. In the list of stress options, pick As 1 or As 3 top or bottom.

To get a report of the same information use Output - Analysis - Analysis Results - and select the last option "Flexural reinforcement in shells", Be sure to select the desired combo or combos on the right and then OK. 

Obviously having shells with local axes aligned to the direction of the reinforcement is critical for making this output useful.

Also note, this does not take into acount shear design nor the effects of axial tension or compression acting on the shells.

Can Ram Elements be used to design a mat foundation on soil?

Yes, one of the keys to modeling the mat foundation is to define a regular mesh. Since the nodes of the mesh need to be supported by vertical compression-only springs, we need the mat to be manually meshed. Using a regular size mesh will help so that the tributary area of each node is fairly constant allowing you to use the same spring stiffness.

The assigned spring stiffness should be derived from the soil subgrade modulus and the average shell area. Note, the spring units are in force/length, e.g. kip/in, meaning how many kips of compression at this point does it take to yield 1 inch of deflection. To make the springs compression-only, just check the Compression only - TY box (assuming Y is vertical).

In order to insure stability some soil friction resistance or edge restraint should also be modeled. Modeling the self-weight of the foundation may also be required for stability (this can be modeled using the Gen - Self weight option). If self weight is included as part of the dead load, also make sure that the dead load is used in all of the combos. Because the model includes compression-only springs, iterative analysis is required. It may be that the model is stable for combinations, but not for the lateral load cases alone, but that's OK so long as the combos all produce valid results.

A sample file can be found here.

The method above outlines how to get steel requirements for the shells. Bearing stress results can be derived from the spring reactions.

For something a little more automated, consider Ram Concept. 

How can I apply a point load somewhere on a shell?

You can apply a nodal load anywhere on the surface of the shell and that load will be resisted by the meshed elements of the shell. All that is required is to add a node at the location of the load.

If the load is close to the edge, put the node right at the edge to avoid a tiny mesh between the node and the edge. Ram Elements - Meshing Errors [TN]

Make sure you have the option to segment shells turned on under Process - Analyze - Finite element model tab:

Also make sure you are running version 13.00.03.45, this is a fairly recent enhancement to Ram Elements.

Why are the corner node reactions less than the applied load?

When shells are meshed automatically by the program, a determination about the support for the edge nodes must be made. On the Shells tab of the spreadsheet, the fifth sheet is for "Intermediate Supports", and the first control is a check box labeled "Only at Ends"

If this box is unchecked (which is the default setting) then the program will extrapolate similar supports along the meshed edges of the shell. You can verify the support conditions for the meshed nodes using View - Finite Elements. In the example below, since all 4 corners has some restraint, all four edges are also restrained in 1 or more degrees of freedom.

If you plot or report the nodal reactions for such a wall, you need to report all of the nodes, not just the corner nodes to see the total reaction on the system.

If the option is checked, then only the original corner nodes are restrained, and only those points will have reactions.

 Press F1 on the "Intermediate Supports" spreadsheet to get more Help on the "Extent" option. 

See Also

RAM Elements Masonry Wall FAQ

Ram Elements - Meshing Errors [TN]

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

Why do I get an error about "Too many slab shapes intersecting the column shape"?

The location in the error message is the location of a column and punching shear check in the model. The error usually occurs where multiple beams of varying thickness intersect the column creating an overly complex punching shear failure plane.

Often in those cases no punching shear check is even required (provided the beams have sufficient one way shear capacity in both directions). If that's the case simply delete the offending punching shear check to proceed. In cases where a punching shear check really is required, try simplifying the geometry to limit the number of changes in thickness at the column. For edge columns, the concrete beams or slabs should typically cover the full column area.

Modifying the punching check by reducing the Search Radius or changing the Edge Treatment could potentially help as well.

The warning message "No column critical sections were found at a punch check" can also occur under the same conditions.

This warning is more likely when the search radius is so small that the critical section a distance "d" from the face of the support is bound to be beyond the search radius.

Can Ram Concept check punching shear for a pair or group of columns?

No, in Ram Concept each column reaction is used in an independent punching check, No group punching for close columns is considered.

Punching around walls is also not considered. For this reason we do not recommend checking punching for column pilasters at wall locations.

How does Ram Concept calculate the demand for punching shear calculations?

Refer to the program manual, section 66.2 "How does RAM Concept handle punching shear?" and 66.2.1"Step 1: Determine the force envelopes to be checked" for details. In brief, the program uses the column reactions, less any point loads or column above reactions inside the column shape. Surface loads around the column within the punching failure plane are not discounted from the demand.

Can Ram Concept design a standard reinforcement cage to prevent a punching failure?

No, Ram Concept designs stud rails (including the Ancon Shear fix) but not a traditions shear cage.

Is the beam shear reinforcement considered in the punching check design?

No, the punching check, and potential stud rail design, is performed independently from the one way shear reinforcement in the design strip design.

See Also

RAM Concept Design Strips [TN]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

The following TechNotes and FAQs are provided as a reference by Bentley's Technical Support Group.

Licensing & Installation

• Configuring Structural Products For SELECT Server
• Accessing SELECTservices Online And Downloading Files
• Manually Removing Bentley IEG Licensing Software
• Viewing And Checking In Licenses Using The Site Administration Page
• [[Using Bentley Structural Products Offline]]
• [[Structural Products Compatibility With 64 Bit Operating Systems]]
• [[Non-Interactive Installation Of Structural Products]]
• [[Performing A Clean Installation]]
• [[Structural Products Licensing FAQ]]
• [[Recommended Computer Specifications For Structural Products]]
• [["Another installation is already in progress, you must complete the installation first"]]
• Why do RAM Structural System modules open in trial mode?

 

STAAD.Pro

• STAAD.Pro TechNotes and FAQs 

 

STAAD.Offshore

• STAAD.Offshore Technotes And FAQs

STAAD(X)

• STAAD(X) TechNotes and FAQs

 

STAAD(X) Tower

• STAAD(X) Tower TechNotes and FAQs

 

STAAD Foundation Advanced

• STAAD.Foundation Technotes and FAQs

 

RAM Structural System

Release Notes and New Issues

• RAM Structural System Release Notes
• Known Issues in RAM SS v14.06.00

TechNotes and FAQs

General

• [[RAM SS - Modules Overview]]
• RAMSS Installation FAQ
• RAM Defaults Guide
• RAMSS Files FAQ
• RAM SS File-Open Troubleshooting [TN]
• RAM Table Editing
• RAM SS 3D Viewer FAQ
• RAMSS Polygon Intersection Error
• RAM SS Analysis Types
• RAMSS Two Way Decks
• RAMSS Common Framing Table Errors
• New Workflow for tables in RAM Structural System Version 14.06

RAM Modeler

• RAMSS Modeling FAQ
• RAM SS Walls FAQ
• Importing DXF Files into RAM SS

RAM Steel

• RAMSS Gravity Loads FAQ
• RAMSS Beams FAQ
• RAMSS Joists FAQ
• RAMSS Columns FAQ

RAM Frame

• RAM Frame Troubleshooting
• RAMSS Eigenvalue Error
• RAM Frame Meshing and Segmentation
• RAM Instability In Finite Element Analysis
• RAM Frame P-Delta
• RAM SS Semirigid Diaphragms
• RAMSS Pseudo Flexible Diaphragms FAQ
• [[RAM Frame - Building and Frame Story Shear]]
• RAMSS Truss Modeling And Design
• RAMSS Wind Loads FAQ
• RAMSS Seismic Loads FAQ
• RAMSS Dynamic Modal Analysis FAQ
• RAMSS Tension Only FAQ
• Star Seismic Buckling Restrained Braces
• CoreBrace™ Buckling Restrained Braces
• RAM Frame AISC 360 Stability Analysis and Design

RAM Concrete

• RAM Concrete Beam [FAQ]

RAM Foundation

• RAM SS - Foundation [FAQ]

Revit Link

• RAM Structural System Revit Link

RAM DataAccess

• What is RAM DataAccess?

RAM Elements

NOTE: RAM Advanse is now RAM Elements

Release Notes

• RAM Elements Release Notes

TechNotes and FAQs

• RAM Elements Importing from RAM SS FAQ
• RAM Elements - View Control FAQ
• RAM Instability In Finite Element Analysis
• Creating custom elements in RAM Elements
• RAM Elements Load Combos FAQ
• Ram Elements Shells FAQ
• RAM Elements Masonry Wall FAQ
• RAM Elements Unbraced Lengths
• RAM Elements Effective Length Factors
• RAM Elements AISC Stability
• RAM Elements Dynamic Modal Analysis FAQ

RAM Connection

Release Notes

• RAM Connection Release Notes

TechNotes and FAQs

• [[RAM Connection is installed, but the Connection button fails to appear in RAM Elements]]
• RAM Connection Capabilities and Modeling FAQ
• Troubleshooting Errors when Assigning Connections
• RAM Connection Stalls When Assigning Base Plate Connection
• Catastrophic Failure Error when Using Customized Anchor Position
• RAM Connection Extended End-Plate Moment Connections (MEP)
• Tips for Using RAM Connection within STAAD.Pro [TN].
• How to Customize a RAM Connection Template in STAAD.Pro

RAM Concept

Release Notes

• RAM Concept Release Notes

TechNotes and FAQs

• RAM Concept-RAM Structural System Integration TN
• Modeling Podium Slabs TN
• RAM Concept T-Beams and Axial Force TN
• RAM Concept Lateral Self Equilibrium Analysis TN
• RAM Concept Design Strips TN
• RAM Concept Punching Shear Checks [FAQ]
• RAM Concept Load History Calc Options TN
• [[RAM ConceptCapabilities and ModelingFAQ|RAM Concept Capabilities and Modeling FAQ]]
• RAM Concept Files FAQ
• RAM Concept Plans And Perspectives FAQ
• RAM Concept Structure FAQ
• RAM Concept Tendons FAQ
• RAM Concept Reinforcement [FAQ]
• RAM Concept Loading FAQ
• RAM Concept Shear Reinforcement FAQ

Multiframe

• General FAQS

Maxsurf

Structural Modeler
PowerStructural Modeler
Structural DocumentationCenter

• Technotes have been moved to Structural Drafting and Detailing

See Also

Product TechNotes and FAQs

External Links

STAAD.Pro from Bentley

Structural Analysis and Design Products 

Comments or Corrections?

Bentley's Technical Support Group requests that you please confine any comments you have on this Wiki entry to this "Comments or Corrections?" section. THANK YOU!

What can Concept design?

Elevated (suspended) concrete floors and mat foundations (rafts). They can be reinforced concrete, post-tensioned concrete or hybrid.

Is there a limit on the size of structure modeled?

The only limit is the performance of the computer hardware. The analysis run time is approximately proportional to the square of the number of nodes in the model, so large structures may take a significant amount of time to analyze. Design time is approximately proportional to the number of span segment strip cross sections. See “Decreasing calculation time” on page 128 for more information.

Is there any restriction to the maximum thickness of slab that can be modeled?

Concept's analysis of slab elements considers shear deformation as well as bending deformation. This ensures that Concept gives reasonable results for both thin slabs and thick slabs. In general, Concept's design provisions apply the code requirements that are appropriate for slabs with typical span-to-depth ratios. If the geometry of your slab is outside the usual ranges, you may need to consider if any special design considerations are necessary.

Can Ram Concept model a sloped slab or one that tapers in thickness?

No, You can model steps in Ram Concept, but each slab and beam is a level member of a single thickness.

Can Concept design more than one story at a time?

Not by itself. You can use the RAM Structural System to integrate numerous floors into one large model.

Can I use Concept to design slab-on-ground?

The expression “slab-on-ground” is often used to described residential house slabs. The designer has to use engineering judgment to determine if mat analysis and design techniques are suitable for such structures.

Is Concept capable of running a single design strip for quick preliminary runs without modeling the whole building?

Yes. See Chapter 35, “Using Strip Wizard” and Chapter 45, “Strip Wizard Tutorial”.

Can I model a pour strip?

Yes, although there are limitations.

1. Use the orthotropic properties for the pour strip area such that the axial stiffness perpendicular to the strip is signifi¬cantly reduced. See the discussion below Figure 16-6 on page 57
2. Terminate tendons either side of the pour strip.

Note: Modeling a pour strip in this manner does not consider the temporary situation before the strip is poured back. This could affect deflections and resultants.

How can I model curved edges or walls?

Use a series of straight lines. The approximation should have negligible effect.

Can Concept be used to design retaining walls by drawing the wall as a slab?

While Concept is not optimized for this use, it can perform most of the analysis and design tasks if you are very careful. Care must be used as Concept assumes that gravity loads are in the downward Z direction. You need to set all of the self-dead loading load factors to zero and create your own self-weight loadings. You probably want to apply these loads at the mid-slab depth; otherwise the eccentricity will add a self-weight moment to the slab. While Concept's design cross sections reports all of the moments and forces on the design cross section, Concept does not perform design considering all of the forces and moments. Specifically, Concept does not consider the Mz value in design, because Concept does not specify the positioning of reinforcement that is important for Mz design. Concept does not consider “P-delta” effects.

What does “hybrid” mean?

A hybrid floor is one that contains both PT and RC areas. Most post-tensioned floors have some RC elements such as pour strips and elevator core slabs. By selecting the appropriate design rules these regions can be designed at the same time as the PT elements.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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