1. How does Staad "direct" a spring to determine if it is in compression or tension?
2. What is the difference between a LOAD COMBINATION and a REPEAT LOAD?
3. In a structure which has wall panels in addition to other things, is it possible to temporarily disable some of the outer panels and analyse just the rest of the structure consisting of interior beams, columns, and slabs?
4. What's the difference between ELASTIC MAT and PLATE MAT for spring support generation?
5. The output from my STAAD run contains the warning message :THIS STRUCTURE IS DISJOINTED
6. Warning message in output file: This structure is disjointed, accompanied by several instability warnings
7. I am using STAAD.Pro 2002. When the STAAD Analysis and Design engine is running, you can't minimize the box that shows the activities in progress - it is always on top. I like to start the "run analysis" then go on to work on something else while it is running. It is not very convenient having the box on top of everything. How can i fix that?
8. I need to specify a cable member. Can I give it the proper properties using user define tables?
9. My STAAD outout file contains the warning message : **WARNING** THE POISSON'S RATIO HAS NOT BEEN SPECIFIED FOR ONE OR MORE MEMBERS
10. Read/write Error in Unit No. 17
11. I need to analyze a frame whose members have been rotated about the local z axis. Is there anyway to model this situation using STAAD? Can you input a point and define the orientation of the local axis of that point? Or is there some other way to model this situation?
12. Is IX the St. Venant's Torsional Constant or is it the Polar Moment of Inertia?
13. How does one get a report indicating whether the applied loads are in equilibrium with the support reactions?
14. How can I check whether the story drift of the floors are within allowable limits?
15. I have a structure with supports marked as elastic foundation. I am getting an error message "Error 0550" when I run the analysis. What could be the cause of this?
16. I want to use the Master/slave command to model a rigid diaphragm in STAAD.Pro 2001. The problem is two columns separated by 40 ft. One column goes from joints 1 to 2 and the second column goes from joints 3 to 4. I wish to have a rigid link between joint 2 and joint 4. The program gives an error of multiple structures. What additional connections do I have to do to tie these joints together?
17. I am going to incorporate into my model, rock anchors which will be installed down the center of the pipe piles. In case you are not familiar with these, they are a thread rod attached to the top of the pile, go down the center and are anchored into the rock and are used to take the uplift forces in the pier. I was planning on using the post tensioning command. Is this correct?
18. When I try to analyse a model which contains the ELASTIC MAT command for generation of soil spring supports, I encounter an error message : Error 0550* support joints are collinear
19. Do you have any thumb rule/ formula for estimating the time required for solving a structure involving plates elements?
20. I have to analyse a structure for temperature load. The temperature difference is 600 deg C. (from 0 deg C to 600 deg C). Which value of alpha I shall use, (i.e. alpha for 0 deg or alpha for 600 deg) for the analysis? Can I use an alpha value for the mean temperature?
21. Can I carryout a machine foundation analysis using STAAD PRO (Embedded Block foundation and Pile foundation)?
22. UNEXPECTED COMMAND IN LOAD DATA CHECK SPELLING AND ORDER OF DATA IN CASE NO. 1
23. What is the procedure used by STAAD.Pro in computing the stiffness matrix of a tapered beam?
24. While using the "Master Slave" command to define a rigid diaphragm in a framed multi-storeyed structure, what criteria should one adopt to determine the "Master node"?
25. I am analyzing a simply supported beam, which is 20 feet long. There is a concentrated force acting at the mid-span point of the beam. In one case, I model it as a single member and apply the load at midspan using the member load option. In another case, I model it as 2 separate members, each 10 ft long, and apply the load at the central node using the JOINT LOAD option. The member cross section is a W12X26 from the American steel table. When I look at the deflection at the 10 ft point, using the PRINT SECTION DISPLACEMENT command for case (a) and the PRINT JOINT DISPLACEMENT command for case (b), the values do not match. Why?
26. Can I design a stringer using STAAD.Pro?
27. In the member end forces output, why are two values being reported for axial forces? Also, why is it that sometimes the numerical values of these two are the same and sometimes they are not?
28. When I try running the analysis on STAAD.pro 2001, I get the error message error message as "Fatal Error: Cannot start analysis Engine". However, when tried with another machine with Win 95/98. The same software is working fine without giving any error.
29. I have a continuous beam, and all members have the same E and same properties. I run it once with one set of member properties. I double the depth of the members and run it a second time. The results of the second run (midspan moment, reactions, etc.) do not match those from the first run. Shouldn't the results stay the same as the EI remains constant for both the beams?
30. During the analysis of a large model, the analysis engine stops with the error message Read/write ERROR in Unit No. 17
31. I want to ignore the stiffness of certain members during analysis but want the loads applied on them to be transferred to the structure. Can I use the INACTIVE MEMBER command for this ?
32. How to add/change/modify sections to the Section Database?
33. ERROR-STAAD BUILT IN MEMORY BLOCK HAS OVERFLOWED
34. When I save my file in STAAD.Pro, all REPEAT commands are changed by STAAD to the expanded format. The same thing happens when I do a File > Save As. I would like to retain my input using the REPEAT commands. Is there any way to do that ?
35. What is a Reference Load Case?
36. Can we specify time-history loads in a Reference Load Case?
37. Some of the STAAD.Pro icons are missing from the toolbar region. How can I get those back ?

1. How does Staad "direct" a spring to determine if it is in compression or tension?

For the purpose of defining the sense of the force in the SPRING TENSION/SPRING COMPRESSION facility, the following rules are adopted in STAAD :

A support reaction force is considered TENSILE if it is opposite to the positive direction of the axis under consideration. Another way of putting it is that, for this condition, the displacement along that axis of the support node is in the same direction as the positive direction of that axis.

A support reaction force is considered COMPRESSIVE if it is along the positive direction of the axis under consideration. Another way of putting it is that, for this condition, the displacement along that axis of the support node is in the direction opposite to the positive direction of that axis.

These rules are applicable for global axis supports, as well as inclined axis supports.

Hence, use the center of the circular pipe as the REFERENCE POINT for the INCLINED supports. The local X axis for the inclined supports will then point from the perimeter towards the center of the circle. The supports around the circumference can then be assigned COMPRESSION only springs. .

2. What is the difference between a LOAD COMBINATION and a REPEAT LOAD?

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 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.

3. In a structure which has wall panels in addition to other things, is it possible to temporarily disable some of the outer panels and analyse just the rest of the structure consisting of interior beams, columns, and slabs?

STAAD has an INACTIVE MEMBER command. This command can be used with beam/columns as well as plate elements. The members and elements subjected to this condition will have their stiffness, as well as any applied loading on them, ignored. This means, only the remainder of the structure will be treated as being active. So, what you can do is use the INACTIVE MEMBER command in conjunction with CHANGE to create a multiple analysis model.

In this manner, a single STAAD input file can represent various stages of construction of the structure. Take a look at example 4 in the Examples manual. Although that example illustrates the procedure using just beams, the same can be used with plates included in the structure.

4. What's the difference between ELASTIC MAT and PLATE MAT for spring support generation?

With the ELASTIC MAT you enter a list of joints from which STAAD will attempt to form a perimeter which encloses an overall area. This is done with a convex hull algorithm. Lastly, areas are assigned to each joint. If the convex hull rules are met, the algorithm works well. However for mats with irregular edges or holes, the algorithm may not do what the user expects and one may end up with springs with unreasonable spring constant values.

Since many mat foundation problems have plates defining the entire mat, we have added the PLATE MAT option where you enter a list of plates that entirely define the mat. Roughly 1/4th of the area of each plate is assigned to each joint in the plate in the same manner as uniform pressure or self weight is distributed.

So if you have the foundation support entirely defined by plates, then use the PLATE MAT option. Otherwise use the ELASTIC MAT option. With this option please observe the rules listed in the Tech Ref Manual. Avoid convex angles. You may have to subdivide the region into several sub-regions with several ELASTIC MAT commands. Add "PRINT" to the end of the command to see the areas assigned to each joint where a support is generated.

5. The output from my STAAD run contains the warning message :

THIS STRUCTURE IS DISJOINTED. IGNORE IF

MASTER/SLAVE OR IF UNCONNECTED JOINTS.

Is STAAD telling me that my structure is in several pieces?

This is referred to in STAAD as Multiple structures. The outline below explains the process for identifying the disparate components and merging them so they form a single structure. One of the consequences of having multiple structures, namely, structural instabilities, is also discussed. 

6. Warning message in output file: This structure is disjointed, accompanied by several instability warnings.

The error message, "this structure is disjointed..." is caused by multiple structures in the model. Multiple structures exist when one portion of the model does not have any way of transferring forces to another portion. It is possible to create a model that visually appears to be a single structure, but upon closer inspection it is revealed that the model contains two or more unconnected structures. Instability warnings may also appear in the output file, due to the fact that the structure appears to be properly supported when, in fact, it is not.

What do we mean by member connectivity? What determines whether two members are connected so that one can transfer loading to another? Consider two lines that intersect in 3D space, with the starting point of one line lying on the longitudinal axis of the other line. The fact that the end of one member lies on the axis of another is not sufficient to ensure connectivity. Connectivity is insured only when intersecting members are divided into segments that meet at a single, common node. ("Common node" means a single node number. Two separate node numbers, both having the same X,Y,Z coordinates is called a duplicate node situation. You can test for duplicate nodes in the model by pulling down the Tools menu and selecting the Check Duplicate command, then select the Nodes command from the Check Duplicate sub-menu).

7. I am using STAAD.Pro 2002. When the STAAD Analysis and Design engine is running, you can't minimize the box that shows the activities in progress - it is always on top. I like to start the "run analysis" then go on to work on something else while it is running. It is not very convenient having the box on top of everything. How can i fix that?

If you click on the top left corner of that box, you will find an option called "Do not Stay on Top". Switch that on. You can then make that window recede behind other windows.

8. I need to specify a cable member. Can I give it the proper properties using user define tables?

The only property that a cable requires is the cross section area. So any property type which can enable the program to obtain the area would be acceptable. A few examples are :

As a PRISmatic section with the diameter specified using the term YD :

MEMBER PROPERTY
1 PRIS YD 1.0

or

As a PRISmatic section with the Area specified using the term AX

MEMBER PROPERTY
1 PRIS AX 0.35

or

As a PIPE section with the outer and inner diameters specified using the terms OD & ID

MEMBER PROPERTY
1 TA ST PIPE OD 1.1 ID 0.0

If you wish to specify it as a user defined section using a user table, that would be acceptable too.

9. My STAAD outout file contains the warning message :

**WARNING** THE POISSON'S RATIO HAS NOT BEEN SPECIFIED FOR ONE OR MORE
MEMBERS/ELEMENTS/SOLIDS. THE DEFAULT VALUE HAS BEEN SET FOR THE SAME.

What does this message mean?

The Poisson's ratio is one of the fundamental material properties required to perform the analysis of a structure. It is generally used to obtain the value of G (Modulus of Rigidity) using the relationship

E=2G(1+Poisson)

where E is the Young's modulus

If you have failed to specify the Poisson's ratio, STAAD attempts to "guess" the value of that term based on the value defined for E. For example, if E is in the neighbourhood of 29000 ksi (steel), Poisson's will be chosen to be about 0.30. If E is in the neighbourhood of 3150 ksi (concrete), Poisson's will be chosen to be about 0.17.

If you would like to see what value has been chosen by the program, you may specify the command

PRINT MATERIAL PROPERTIES

after all the CONSTANTs have been provided. The Poisson's ratio will be reported in the output file along with some of the other CONSTANTs.

It is best to specify a value explicitly instead of having the program estimate a value on its own.

10. After I launch the analysis, the program completes some of the processes, and then comes up with the message :

*** STAADPro ERROR MESSAGE ***
** Read/write Error in Unit No. 17
++ Calculating Joint Displacements. 16:24:21

What does this error mean, and what can I do to avoid it?

This is very likely due to the fact that you have run out of disk space, particularly on the drive which is being used for the SET TEMP environment variable in NT and 2000 operating systems. Since this is usually the C: drive, you need to increase the free space available on the C drive, or whichever is being used for SET TEMP.

 11. I need to analyze a frame whose members have been rotated about the local z axis. Is there anyway to model this situation using STAAD? Can you input a point and define the orientation of the local axis of that point? Or is there some other way to model this situation?

We presume you mean that the member is rotated about the local "X" axis and not the local "Z" axis. When you use STAAD's default coordinate system, the local "X" is the longitudinal axis of the member, and local Z is generally the major axis of the member. So, changing the orientation of a member involves rotation about the local "X" axis, and not the local "Y" or local "Z" axes.

There are a couple of ways to change the orientation.

a) By specifying an angle using the BETA command. This is explained in Sections 1.5.2, 1.5.3 and 5.26.2 of the Technical Reference Manual. You may also refer to example 1 of the Examples manual for a sample problem which shows the usage of the command.

b) Using the REFERENCE POINT method. This too is explained in Sections 1.5.2, 1.5.3 and 5.26.2 of the Technical Reference Manual.

In the STAAD.Pro GUI, you may click the right mouse button, select Labels, and switch on Beam Orientation to get a visual representation of the directions the local X and Y axes point to.

Graphically, you can specify the BETA angle from 2 places :

If you go to the General - Property page on the left side of the screen, you will find the Properties dialog box on the right side and it contains a tab called Beta Angle through which the value can be specified.

If you go to the Commands menu on top of the screen, choose Geometric Constants - Beta Angle.

Graphically, you can specify the REFERENCE POINT by going to the Commands menu on top of the screen, and choosing Geometric Constants - Member Reference Point.

12. Is IX the St. Venant's Torsional Constant or is it the Polar Moment of Inertia?

IX is generally known just as the Torsion Constant. For a circular cross section, the torsion constant equals the Polar moment of inertia. For non-circular cross sections, it usually is less than the polar moment of inertia. If you have the AISC publication T114, you will see it referred to in that document using the expression J. If you have the textbook "Roark's Formulas for Stress & Strain, 6th edition, Warren C.Young, McGraw-Hill", you will find it being referred to using the expression K in section 9.2 of the book.

13. How does one get a report indicating whether the applied loads are in equilibrium with the support reactions?

There is an option which can be provided along with the PERFORM ANALYSIS command for getting this information. It is called PRINT STATICS CHECK. It is explained in Section 5.37 of the STAAD.Pro Technical Reference Manual. The sample below shows how this is done.

LOAD 3 LATERAL FORCES
JOINT LOAD
4 6 8 10 FX 12.5
LOAD COMBINATION 10
1 1.2 2 1.4 3 0.9
PERFORM ANALYSIS PRINT STATICS CHECK
PRINT ANALYSIS RESULTS
UNIT NEWTON MMS
START CONCRETE DESIGN
CODE BRITISH
FYLD 425 ALL
FC 35 ALL
DESIGN COLUMN 45 57
END CONCRETE DESIGN
FINISH

If you prefer to use the graphical method for specifying this option, this is how it can be done.

In the Modelling mode, click on the Commands menu from the top of the screen. Select Analysis | Perform Analysis. A Perform Analysis dialog box will be displayed. Set the radio button on Print Statics Check. Click on OK.

Save the file and run the analysis. Then view the output file. (This can be done from File | View | Output file | STAAD Output). If you scroll down to the region where the PERFORM ANALYSIS command is specified, the equilibroum report will be available after that command.

14. How can I check whether the story drift of the floors are within allowable limits?

If you have STAAD.Pro 2001 Build 1005 or Build 1006, you can specify a command called

PRINT STORY DRIFT

in your input file. Run the analysis. Then check your output file, The drift for each story will be reported. You will have to manually verify that this is within your allowable limits.

15. I have a structure with supports marked as elastic foundation. I am getting an error message "Error 0550" when I run the analysis. What could be the cause of this?

There are a few reasons why you will run into this error :

1) The ELASTIC MAT command is meant for generating support spring constants for the support nodes of plate elements. The feature does not work in the case where the support spring generation is requested at nodes which aren't connected to any plate.

STAAD attempts to find the tributary area of each node for which the elastic mat command is specified. It determines this area on the basis of the "influence area" of the nodes. If those nodes are attached to a non-plate entity such as a beam, the corresponding nodes do not have an "influence area".

2) The plates might be inclined to the global horizontal plane (XZ). Presently, the feature works satisfactorily only if the plate is truly horizontal. An inclined plate or a vertical plate cannot presently be handled by this feature.

16. I want to use the Master/slave command to model a rigid diaphragm in STAAD.Pro 2001. The problem is two columns separated by 40 ft. One column goes from joints 1 to 2 and the second column goes from joints 3 to 4. I wish to have a rigid link between joint 2 and joint 4. The program gives an error of multiple structures. What additional connections do I have to do to tie these joints together?

You would need to split the columns into 2 members each.

There is a limitation that a master joint cannot have supported directions or be connected to a member or element that is connected to a support; similarly, the slave joints may not have supported directions or be connected to a member or element that connects to a support.

17. I am going to incorporate into my model, rock anchors which will be installed down the center of the pipe piles. In case you are not familiar with these, they are a thread rod attached to the top of the pile, go down the center and are anchored into the rock and are used to take the uplift forces in the pier. I was planning on using the post tensioning command. Is this correct?

If the prestressing force is applied after the piles are driven into the soil and the pile cap is cast, the load type you may want to apply in analysing the model is the one involving the MEMBER PRESTRESS command. That is because, there is a small anomaly in STAAD in the definition of the terms PRESTRESS and POSTSTRESS. The way STAAD defines these terms and the way they are conventionally defined are opposite to each other. You will find an explanation of this anomaly in Section 1.16.5 of the STAAD.Pro Technical reference manual under items 4 and 5.

If you want an example which demonstrates the usage of these commands, please refer to example problem 6 in the STAAD.Pro Examples manual.

18. When I try to analyse a model which contains the ELASTIC MAT command for generation of soil spring supports, I encounter an error message :

Error 0550* support joints are collinear.

If you look under the "Notes" item of Section 5.27.3 of the STAAD.Pro
Technical Reference Manual, you will find that the program attempts to put
together a closed surface from the joint-list that accompanies each ELASTIC
MAT command. When you specify the commands in the following manner :

SUPPORTS
1 ELASTIC MAT DIRECT Y SUBGRADE 259
2 ELASTIC MAT DIRECT Y SUBGRADE 259
3 ELASTIC MAT DIRECT Y SUBGRADE 259
4 ELASTIC MAT DIRECT Y SUBGRADE 259
5 ELASTIC MAT DIRECT Y SUBGRADE 259
6 ELASTIC MAT DIRECT Y SUBGRADE 259
7 ELASTIC MAT DIRECT Y SUBGRADE 259
8 ELASTIC MAT DIRECT Y SUBGRADE 259
9 ELASTIC MAT DIRECT Y SUBGRADE 259

it fails to find a closed surface, because a single joint does not form a
closed surface.

Based on the type of model you have, you can replace those multiple ELASTIC
MAT commands with a single command as follows :

SUPPORTS
1 TO 625 ELASTIC MAT DIRECT Y SUBGRADE 259

19. Do you have any thumb rule/ formula for estimating the time required for solving a structure involving plates elements?

Run times depend on many factors. For static analysis without master/slave, the run time for large problems is dominated by the triangular factorization time.

Triangular Factor. Time = '[ (Fac) * (6 * no. of joints / 1000) * (bandwidth /100)**2 ] / 3600 in hours.

The bandwidth is printed with problem statistics.
Fac is a computer dependent factor.
Use Fac = 0.20 if you have 1.5GHz with 1 GB memory and 9600 SCSI drives.
Use Fac = 0.70 if you have 1.0GHz with 256 MB memory and 7200 drives.
Use Fac = 1.50 if you have 0.5GHz with 128 MB memory and 5400 drives.

As an example:

500Mhz, high bandwidth
Triangular Factor. Time = '[ (1.50) * (6 * 23000 / 1000) * (9000 /100)**2 ] / 3600 = 466 hours = 19.4 days

1000MHz Faster computer, more supports, lower bandwidth:
Triangular Factor. Time = '[ (0.70) * (6 * 22000 / 1000) * (5000 /100)**2 ] / 3600 = 64.1 hours = 2.67 days

20. I have to analyse a structure for temperature load. The temperature difference is 600 deg C. (from 0 deg C to 600 deg C). Which value of alpha I shall use, (i.e. alpha for 0 deg or alpha for 600 deg) for the analysis? Can I use an alpha value for the mean temperature?

The following answer was supplied by Ray:

Since STAAD is linear for material behavior, an alpha that results in the desired strain and displacement would be best. You can enter any positive value for alpha. The units of the alpha value must be the same as the temperature change units since STAAD does not explicitly enter temperature units.

21. Can I carryout a machine foundation analysis using STAAD PRO (Embedded Block foundation and Pile foundation)?

The answer is Yes. The piles have to be modelled as columns. If the machinery sits on a slab, that will be modelled using plate elements. The supports for the model are going to be the resistance (based on subgrade modulus) offered by the soil, which may be modelled as springs. The dynamic loads due to the machinery will be modelled as forcing function loading, either as discrete time-force pairs as shown in example 16, or as a sinusoidal loading as shown in example 22.

22. Attached is a portion of my STAAD output file which contains an error messsage as shown :

30. LOAD 1 (1.4DL + 1.7LL)
31. SELF Y -1.4
32. MEMB LOAD
33. 11 TO 16 UNI Y -2.8
34. 11 TO 16 UNI Y -5.1
35. START CONCRETE DESIGN

**WARNING - UNEXPECTED COMMAND IN LOAD DATA
CHECK SPELLING AND ORDER OF DATA IN CASE NO. 1
COMMAND= START CONCRETE DESIGN
CHECK RESULTS CAREFULLY, LOADS MAY HAVE BEEN LOST
***STAAD.Pro WARNING***
ANALYSIS NOT PERFORMED - SO ABOVE COMMAND CAN NOT BE PROCESSED.
*********** END OF THE STAAD.Pro RUN ***********

Can you explain what it means?

You are following up your load instructions with a concrete design statement. (Notice that after 11 TO 16 UNI Y -5.1, you are specifying START CONCRETE DESIGN). There is no instruction for performing the analysis. A concrete design cannot be done until after the analysis has been performed. So, you need to specify the command PERFORM ANALYSIS in between those 2 lines, as in,

11 TO 16 UNI Y -5.1

PERFORM ANALYSIS PRINT STATICS CHECK

START CONCRETE DESIGN

23. What is the procedure used by STAAD.Pro in computing the stiffness matrix of a tapered beam?

1. Define the static deflection curves of a beam due to unit displacement at each of its 12 degrees of freedom while maintaining the displacements at the remaining 11 degrees of freedom as 0. These curves are usually referred to as shape functions.

2. Using the principle of virtual work, calculate each term of the stiffness matrix. This is an integral involving E (modulus of elasticity), I (moment of inertia for the applicable axis), and the product of the second derivative of the two shape functions which are relevant to the specific stiffness matrix term being generated. The integration is performed over the full length of the member.

Simpson's method is used in performing the integration. STAAD uses 100 integration points over the member length. The moment of inertia is calculated at the start and end of each integration point.

24. While using the "Master Slave" command to define a rigid diaphragm in a framed multi-storeyed structure, what criteria should one adopt to determine the "Master node"?

For an ordinary static analysis, any of the joints in a master/slave system can be the master joint.

A second point to understand about the Staad.Pro 2001 input is that the command

SLAVE ZX MASTER j JOINT joint-spec

should be used for ordinary floor rigid diaphragms (assuming they are parallel to the ZX axes). This command sets the ZX plane to behave rigidly for inplane actions; while out-of-plane shear and bending will behave flexibly.

The command

SLAVE RIGID MASTER j JOINT joint-spec

should be used if the master/slave connections behave rigidly in all directions and rotations.

For a natural frequency calculation and dynamic analysis, the master joint should be the joint nearest to the c.g. of the masses associated with the master/slave joints.

If the c.g. is well off the structure as in an L shaped structure with narrow wings, you may want to add a joint at the c.g. just for the purpose of being the master; [remember to connect that joint to another joint with a dummy (low E value) member if it is not already connected].

25. I am analyzing a simply supported beam, which is 20 feet long. There is a concentrated force acting at the mid-span point of the beam. In one case, I model it as a single member and apply the load at midspan using the member load option. In another case, I model it as 2 separate members, each 10 ft long, and apply the load at the central node using the JOINT LOAD option. The member cross section is a W12X26 from the American steel table. When I look at the deflection at the 10 ft point, using the PRINT SECTION DISPLACEMENT command for case (a) and the PRINT JOINT DISPLACEMENT command for case (b), the values do not match. Why?

The difference is due to shear deformation.

When STAAD computes the displacement at a node using the stiffness method, the bending stiffness coefficients in the stiffness matrix include the contribution from

1. flexural deformation

2. shear distortion if the shear areas are part of the user specified member property input.

As a result, the joint displacements consist of the pure bending component plus the shear deformation component.

When you ask for intermediate section displacements along a member span, STAAD calculates these using the moment area method from

* the joint translation and rotation (which includes the shear deformation component as explained above)

* flexural deformation of the member (the shear deformation component is not considered here)

In other words, in the implementation of the moment area method, only the term (a) contains shear deformation where as term (b) does not. This is an error in the program, albeit a small one.

If shear deformation is eliminated from all of the above calculations, this discrepancy will be removed. Shear deformation is part of the above calculations only when the shear areas AY and AZ are non-zero values. When member properties are specified using methods such as defining sections from the built-in steel tables, or by specifying them as PRISMATIC sections with a DEPTH and WIDTH value, STAAD internally calculates the shear area before proceeding with the stiffness matrix assembly.

The user may nullify the effect of shear deformation by doing one of the following :

* Provide the properties using the PRISMATIC attribute, and specify just AX, IX, IY and IZ, as in,

1 PRI AX 21 IX 35.4 IY 45.3 IZ 85.75

In this case, since AY and AZ are not specified, shear deformation will not be calculated.

* Provide a very large value for the shear areas AY and AZ, thereby minimizing the shear deformation, as in

1 PRI AX 21 IX 35.4 IY 45.3 IZ 85.75 AY 1E10 AZ 1E10

In this case, the large shear area will result in negligible shear deformation.

26. Can I design a stringer using STAAD.Pro?

To answer your question, we would like to offer some insight into how the capabilities of a structural engineering software are related to the type of sections you wish to analyze and design.

Typically, almost all structural engineering programs have 2 parts to them :

* Analysis - Computing forces and moments in beams, columns, plates, etc., nodal displacements, support reactions.

* Design - Checking the adequacy of a section for a beam or column to carry the forces induced into that member from the applied loads on the structure.

For analysis, these programs do not care about the shape of the cross section. Regardless of what the shape is, the programs simply look for 4 pieces of information : Area, Moments of Inertia about the 2 principal axes, Torsional Constant. If shear deformation calculation is desired, the shear areas should be provided too. However, to help you avoid the chore of specifying these 4-6 values, these programs also allow you to specify the section as one of the standard shapes built into the program, and then internally calculate these 4 quantities using the property calculation rules for that shape. So, if the shape you wish to have analyzed is one such standard shape, you can simply define it in that way, as for example, the flange width, flange thickness, web depth and web thickness for an I shape.

However, if the shape of your section does not conform to one of the built-in shapes that the program supports, you will have to type in these 4-6 property values using a property type usually called PRISMATIC.

For design however, shape does matter. That is because, all design codes are written to allow design of only certain specific shapes, due to the fact that buckling of elements of the cross section plays a major role in determining the capacity of the section. Usually, these shapes are limited to I shapes, T shapes, Channels, Angles, Double angles, Z shapes, Rectangular tube shapes, Circular pipe shapes, etc.

So, the answer to your question is :

Analysis - Yes.

Design - Depends on the shape of the section, and the code according to which it should be designed.

27. In the member end forces output, why are two values being reported for axial forces? Also, why is it that sometimes the numerical values of these two are the same and sometimes they are not?

There are two values because member end force output consists of the forces and moments at the start node as well as at the end node of the member.

At the start node, a positive value of the axial force indicates axial compression, and a negative value indicates axial tension. At the end node, a positive value indicates axial tension, and a negative value indicates axial compression.

Generally, if the values at the start and at the end are not the same in magnitude, it is due to a load acting along the local X axis of the member. A typical example of this is a column (vertical member) subjected to selfweight loading. The difference in magnitude of the axial forces at start and end should be equal to the load acting along the local X axis of the member.

28. When I try running an analysis in STAAD.Pro, I get an error message "Fatal Error: Cannot start analysis Engine" .

The error may be caused by the fact that the paging file size which has been set in Windows in your machine is not large enough to run the program.

1. You can determine whether this is true by doing the following. Make sure you are logged in with Administrative privileges before you attempt any of the following steps.

Using Windows Explorer, locate the file "SProStaad.exe" which should be present in the folder "\Sprov8i\staad\sprostaad".

Run that file by double clicking on it. If it comes up with a message that the paging file size is not large enough, that is an indication of the problem mentioned in step 1 above.

2. If the above is true, you can remedy the error by doing the following:

In Windows, go to Control Panel - System - Advanced Settings

Select performance options. The total paging file size for all drives will be listed in a window. You may want to increase it.

Exit those settings dialog boxes, and try running the program again. Chances are it should work this time.

If that does not resolve the issue, please uninstall STAAD.Pro and reinstall the software.

29. I have a continuous beam, and all members have the same E and same properties. I run it once with one set of member properties. I double the depth of the members and run it a second time. The results of the second run (midspan moment, reactions, etc.) do not match those from the first run. Shouldn't the results stay the same as the EI remains constant for both the beams?

The difference is due to shear deformation. Instead of specifying properties as YD and ZD (which would trigger a shear deformation calculation), provide the values as

AX, IX, IY and IZ

and check the results. They should stay the same.

Or, if you are running STAAD.pro 2004 or later, specify the command

SET SHEAR

on the second line of your input file. This will forcibly switch off shear deformations from the calculations.

Now, changing just YD or ZD should have no effect on the results.

30. During the analysis of a large model, the analysis engine stops with the error message

*** STAAD.Pro ERROR MESSAGE ***
** Read/write ERROR in Unit No. 17

*** ERRORS IN SOLVER ***

Even though the hard disk may have plenty of free space, the problem might be caused by the fact that the disk is formatted with the FAT32 format. This format has a file size limit of 4.2GB. So although there is enough disk space, the single file size limit is exceeded for the STAAD solved matrix file (.L17).

You can determine the type of formatting in effect for your drive by going through the following simple steps.

• On your Windows Desktop, go to My Computer.
• Select the drive which serves as the repository for your SET TEMP settings on your machine. If there is only one hard drive on the machine, it will be that drive. 
• Right click on the drive and select  Properties
• Make sure the file system is NTFS
• Make sure there is enough Free space

If the above also indicates FAT32, you need to find a computer that has its disk formatted with the NTFS format (which does not have a file size limit). Most new Windows XP based computers have the NTFS format.

31. I want to ignore the stiffness of certain members during analysis but want the loads applied on them to be transferred to the structure. Can I use the INACTIVE MEMBER command for this ?

Loads defined on inactive members are not considered in analysis. If you are trying to ignore the stiffness of the members, you may consider defining a dummy material for these members with low E value so that the stiffness contribution from these members become negligible. That way loads applied on these members are still going to get transferred to the rest of the structure.

32. How to change /modify the Section Database?

Or

How to add new sections to the Section Database?

 Please download the  video file from the following link  which demonstrates this feature :

 http://communities.bentley.com/products/structural/structural_analysis___design/m/structural_analysis_and_design_gallery/258994.aspx

 An arbitrary section ISMB 200 has been added to the Indian Section Data Base.

33. When users run the analysis, it gives an error message... "ERROR-STAAD BUILT IN MEMORY BLOCK HAS OVERFLOWED".

If you are trying to analyse a large model, you may need to increase the memory alloted to STAAD.

From the Edit menu, choose Edit Input Command File and go to the STAAD.Pro input editor. Please add
the following statement as the first line in your model, on the line before the command STAAD SPACE—

MEMORY 85

STAAD SPACE

Run the analysis. This input will allow up to 85,000,000 4-byte words for STAAD's internal memory
block (default is 80 million).

If you still get the error message, increase the memory block till the error message is eliminated.

34. When I save my file in STAAD.Pro, all REPEAT commands are changed by STAAD to the expanded format. The same thing happens when I do a File > Save As. I would like to retain my input using the REPEAT commands. Is there any way to do that ?

The REPEAT and REPEAT ALL commands were used at times when the graphic user interface was not
so advanced and the primary mode of data input used to be by typing commands in the input file. But these days, the graphic user interface in Staadpro is so developed that there is no need for the users to go to input file and type in information. Consequently the commands like REPEAT and REPEAT ALL lost importance and have now been replaced by GUI features like Translational Repeat , Circular Repeat etc.

However they are still recognized as valid commands by the engine so that if your file contains those commands, Staad would be able to read the geometry information. When the file is saved using the GUI, the REPEAT commands get replaced. This improves the performance of the software because it no longer has to remember blocks of information that used to appear within the REPEAT commands.

However if you want to retain the REPEAT commands in the input file, keep a copy of the full set of commands like
JOINT COORDINATES, MEMBER INCIDENCES and  ELEMENT INCIDENCES which predominantly use the REPEAT options,  and place them after the FINISH command at the end of the input file. When you are done with
the full job and would not be saving the model using the GUI any more, you can finally replace the JOINT COORDINATES, MEMBER INCIDENCES, ELEMENT INCIDENCES sections with the copied blocks containing the REPEAT commands placed at the end of the file . Then run the analysis again and you will have your analysis results and at the same time your input file will contain the REPEAT commands. 

When you do a File > Save As, the file is saved by the GUI and hence the REPEAT commands are again replaced. If
you would like to save the file by a different name and retain the REPEAT commands, the best thing to do is to do the Save from outside the STAAD environment. You may use Windows Explorer. You can simply copy the original .std file and then rename it using Explorer to get your second file.

35. What is a Reference Load Case?

Reference Load is an array of load data. It is not a primary load case and STAAD will not analyse the Reference Load Case. The Reference Load Case forms an input in the primary load case.

The advantage of using the reference load case in models having non-linear analysis like a P-Delta or Member Tension/Compression is that it can be used to specify load combinations in a primary load case and thereby make the program analyse the combinations directly without analysing the individual component cases specified as Reference Load Cases. This can result in saving of time and computer resources significantly.

36.Can we specify time-history loads in a  Reference Load Case?

No, we cannot. We can only specify static load items like nodal loads, member loads, floor loads, surface loads, temperature loads etc directly in a reference load case. Loads like Wind Load, Seismic Load, Time History Load, Moving Load etc., which needs the program to generate the load items, cannot be specified within a Reference Load Case.

37. Some of the STAAD.Pro icons are missing from the toolbar region. How can I get those back ?

These icons can be turned on/off from the top menu by going to View > Toolbars and checking the appropriate check box. This should fix the problem. In case it does not, you may reset the toolbar settings back to the default by carrying out the following steps

Close STAAD.Pro
Go to Start menu -> Click Run-> Type REGEDIT , Click Ok.
The Registry Editor window will appear
Please click HKEY_CURRENT_USER ->Software->Research Engineers-> STAADPro-> select 2007 ( or the version number that you may have ) and delete it.
Close the registry editor window and re-open STAAD.Pro.

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!

What Rigid End Zone setting should I use in RAM Frame

In Ram Frame within Criteria General, the user can choose to consider a rigid end zone or ignore it.

The program help defines this attribute as follows:

 Rigid end zones in Ram Concrete analysis can also be considered but with solid concrete sections the assumption are usually different.

See Also

[[RAM SS Analysis Types]]

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!

How are torsional irregularities considered?

In general, the program automatically accounts for any eccentricity in the stiffness of the structure during the finite element analysis. For each structure, there is a center of rigidity (which you can report if you create a special center of rigidity load case). If the load is applied to the diaphragm eccentric to this center of rigidity location, then torsion in the structure develops.

Accidental torsion is also considered based on the percentage set under loads - masses (default is 5% of the diaphragm dimension). Currently, the application of accidental torsion is limited to rigid diaphragm analysis. A method for incorporating accidental torsion in semi-rigid diaphragm analysis is in development now.

What the program does NOT do, is amplify these torsion effects according to any specific code provisions (e.g. "A_x" from ASCE 7-02 12.8-14) . It is up to the user to account for additional torsion resulting from plan or vertical irregularities. Most people increase the mass eccentricity under loads - masses from 5% to some larger value to account for the extra torsion required by code, though user defined story forces with a modified location also work well.

Are the seismic results ultimate?

For program generated seismic load cases from any modern code (e.g. ASCE 7-05), the force magnitudes are at an ultimate level.

It's important to note, however, that the drift associated with any static seismic load is the elastic deformation (δ_xe from ASCE 7-02 Eq 12.8-15). The user should amplify the program drift results to determine design deflection for comparison against the allowable drift (δ_x  from ASCE 7-05 Eq. 12.8-15)

Also note, the vertical component of the earthquake (Ev) is handled though the generation of load combinations by increasing or decreasing the Dead load factor, it is not part of the individual seismic load cases themselves. Furthermore, increases in the seismic force required by a lack of redundancy (Rho) are only accounted for in the load factors applied to the seismic loads in generated combinations.

What is the difference between seismic loads that use provisons for member forces and provisions for drift?

When creating a seismic load case suing the IBC/ASCE7 equivalent lateral force procedure, there is an option to use provision for member forces or provision for drift (see screenshot below).

The difference between these options is the upper limit of the calculated period used to calculate the seismic loads.  When provisions for member forces are used, an upper limit of T = CuTa is used for the calculated period per ASCE 7-05 12.8.2. When provisions for drift are used, the upper limit on the period is not used per ASCE 7-05 12.8.6.2

Why do I get a warning about mass that's not associated with any diaphragm?

When you have line loads or any members with self weight masses considered (Under Ram Manager Criteria - Self-Weight) that occur outside of the boundary of the diaphragm slab edge you will get the following type of warning:

Some mass has been detected on one or more stories that is not associated with any diaphragms.
It will be ignored in Analysis unless it is combined with one or more diaphragms.
See the Loads - Masses command.

Under Loads - Masses you can evaluate the total diaphragm masses and you can combine these values with some diaphragm, override with User Specified Values or choose to ignore them by doing nothing.

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!

Why do I get a warning about gravity loads not associated with any diaphragm?

When you have line loads or any members with gravity loads applied (or self-weight) that fall outside of the boundary of the diaphragm slab edge you will get the following type of warning:

"Some Gravity Load has been detected on one or more stories that is not associated with any diaphragms.
It will be ignored in Notional Loads unless it is combined with one or more diaphragms.
See the Loads - Gravity for Notional command."

Under Loads - Gravity Loads you can evaluate the total diaphragm dead and live loads for each level, each diaphragm. For levels a "None" entry, you can combine these values with some near by diaphragm, override with "User Specified Values" or choose to ignore them by doing nothing and leaving the "Combine To" field set to None.

A similar error message also occurs when the masses for things outside of the slab edge are uncombined. See [[RAMSS Seismic [FAQ]]] for details.

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!

The features within Microstran available to a given user depend on which tier of Microstran is activated on the respective user’s computer, as well as which design code options are activated (for information on activating products, see [structural_analysis_and_design__wiki:SELECT Licensing of Microstran]. There are three different tiers of Microstran, each containing more features than the last. These tiers are:

• Microstran
• Microstran.Pro
• Microstran.Advanced

In addition to the basic modeling, analysis, design, and interoperability options available in all tiers of the product, Microstran.Pro and Microstran.Advanced contain advanced analysis and element options.

Microstran.Pro contains the following features that are not available in Microstran:

• Dynamic analysis (calculation of periods and modes)
• Cable element
• Export to Steel Detailing Neutral Format
• Reinforced concrete design to AS3600-94

Microstran.Advanced contains the following features that are not available in Microstran:

• Dynamic analysis (calculation of periods and modes)
• Cable element
• Export to Steel Detailing Neutral Format
• Reinforced concrete design to AS3600-94
• Application of moving loads
• Nonlinear gap and fuse elements
• Response spectrum analysis

There are a number of design code standards that can be activated on any of the three Microstran tiers. They allow beam, column, and brace design to specific code standards. They are:

• AS4100
• NZS 3404
• AS/ANZ 4600:05
• AISC ASD 9^th
• AS 1250/AS3990
• SSCJ/AIJ
• BS 5950:2000
• BS8110:85

Steel member design includes requirements for beams, columns, and braces. Concrete member design to AS3600-94 and BS8110:85 includes requirements for beams and columns.

In addition to member design, an add-on for steel connection design within Microstran is available and can be activated on any of the three tiers. This feature is referred to as Integrated Connection Design.

While hardware locks were previously the means of licensing Microstran, this is no longer the case. Microstran is now licensed through Bentley CONNECT SELECTservices (BCSS). The fundamental concept in gaining access to software licensed through BCSS is product activation. Activation of a product is required regardless of the type of agreement a customer has with Bentley, the products owned, and the permissions set by a systems administrator. This article describes how to activate the desired tier of the Microstran product on a computer, as well as any design codes or features.

Activating Microstran and Associated Features

To configure and activate a Microstran license, go to Manage Licensing under the File menu within Microstran. Note that this dialog will appear automatically after the first launch of Microstran following installation.

Select the tier of Microstran to be activated on the computer: Microstran, Microstran.Pro, or Microstran.Advanced. For a list of features associated with each tier, see Section XX.XX of this manual. The design codes and integrated steel connection design feature can then additionally be selected as desired. Selecting Apply at the bottom of the dialog will enable only the features that have been selected. Note that at this point the product is not activated, but the desired tier and additional features chosen will be communicated to SELECT server once activation takes place.

To activate the product, select Product Activation Wizard at the bottom of the dialog. The ensuing screen will list four activation options. To determine which option is appropriate, consult the systems administrator at your organization or contact Bentley technical support. Generally speaking, users new to Bentley will, in most cases, be activating against a hosted SELECTserver.

Detailed instructions for completing the product activation, dependent on which activation method is utilized, are available at the following links:

Activating against a hosted (Bentley) SELECTserver:

https://communities.bentley.com/products/licensing/w/licensing__wiki/4987.aspx

Activating against a deployed (local) SELECTserver:

https://communities.bentley.com/products/licensing/w/licensing__wiki/5277.aspx

Activating as a NON-SELECT or Node Locked User:

https://communities.bentley.com/products/licensing/w/licensing__wiki/5278.aspx

Although a given organization may own a set number of licenses of a specific Bentley product, authorized users may activate and use as many licenses as needed, with no cap enforced on usage. For detailed information on Bentley’s licensing policies and benefits, see the following link:

https://communities.bentley.com/products/licensing/w/licensing__wiki/12388.bentley-connect-selectservices-formerly-selectserver-quick-start-guide.aspx

The technotes and FAQs in this section cover topics that pertain to MStower. See the subtopics listed under this page for information on specific topics.

***THIS PAGE IS CURRENTLY UNDER CONSTRUCTION***

***THIS PAGE IS CURRENTLY UNDER CONSTRUCTION***

Error Messages

Angle Between AB and AC Too Small

Windows Topics

Where Are My Toolbars?

Toolbars and Extra Buttons

How To Initialize Microstran Configuration Settings

Dual Monitor Operation

Windows Terminology

Exchanging Data Between Microstran and a Spreadsheet

Hardlock and Windows XP

Graphical Input

Extrusion

What's the Use of the Grid When Most Nodes Are Not on a Grid Point?

How Can I Input Nodes that Are Not on a Grid Point?

Load Sub-division

Restraints and Releases

What's the Difference Between Restraints and Releases?

Why Are There Different Conventions for Restraints and Releases?

Why Are "1" and "0" Used Instead of "F" and "R" for Restraints and Releases?

Modelling

What's the Difference Between a Constraint and a Restraint?

Master-Slave Constraints

Instability and Ill-Conditioning

Common Modelling Problems

Plastic Analysis of Frames

Analysis of Tilt-Up Panels

Design of Fall Arrest Systems

Non-Linear Analysis

Why Do I Have to Select Which Load Cases Are Analysed?

Saving Time with Non-Linear Analysis

Steel Design

Adding a Section to the Steel Library

Restraints for Steel Design

How Can Normal Grade Be Stronger Than High Grade

Angles

Dynamic Analysis

What Does Microstran Dynamic Analysis Do?

What's the Difference Between Lumped  and Consistent Mass?

What is Response Spectrum Analysis?

Earthquake Analysis to AS 1170.4

Earthquake Analysis to NZS 4203

Elastic Critical Load Analysis

Why Does ECL Analysis Give Such High k Factors?

What Effective Length Factor Should I Use for Design?

This is a recording of a webinar that was presented earlier this year for our new Microstran user base interested in learning how Bentley's acquisition of Engineering Systems will affect their products and services. A number of topics are covered including:

• Simplified packaging of Microstran and MStower
• s SELECT maintenance program
• Plans for interoperability between Microstran and Bentley’s larger structural portfolio
• Exciting new products and technology coming later this year and in 2015
• Upcoming road shows in Australia which will showcase product development advancements

(Please visit the site to view this video)

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 ?
28. I am trying to analyze a staad.pro model with IBC loading and getting an error message  “*** STAAD.Pro ERROR MESSAGE *** NO LOADING DEFINED FOR UBC LOAD. RUN TERMINATED.”

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.

28. I am trying to analyze a staad.pro model with IBC loading and getting an error message  “*** STAAD.Pro ERROR MESSAGE *** NO LOADING DEFINED FOR UBC LOAD. RUN TERMINATED.”

Although the error message says UBC but it is a generic message that is applicable to seismic load generations as per all other codes as well, including IBC.

The reason for getting the error is that, no seismic weight has been specified as part of the seismic definition and hence Staad is unable to calculate the Base Shear ( V = Cs x W ). As part of the seismic definition you need to specify various seismic parameters like Ss, S1, TL, I , SITE CLASS etc which are used to compute the coefficient Cs. In addition you need to define the seismic weights which will be used by the software to calculate the W term in the base shear equation. One can specify seismic weights in the form of selfweight , member weight , joint weight , element weight etc for. A sample input is provided below

DEFINE IBC 2006
SS 2.16 S1 0.80585 I 1 RX 3 RZ 4 SCLASS 4 TL 12
SELFWEIGHT 1
JOINT WEIGHT
50 51 54 55 WEIGHT 2
MEMBER WEIGHT
125 TO 127 UNI 1

An example problem EXAMP14.std is included with the software to explain the seismic load generation.

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!

How can I evaluate an existing composite beam?

Using the Process - View/Update command, select the beam in the model. Change the selected member size, set the stud number to the desired value and click Analyze. Then click Update Database when finished.

If the existing stud count is insufficient to achieve 25% composite action (or the code minimum), go to Criteria - Stud Criteria and for the last option, select to "Use Composite section properties".

Note: the program will never optimize a member with less than 25% composite action (US codes), but you can reduce the number of studs and evaluate this way.

Can I lock or freeze all the beam designs?

Yes, once the designs are correct, use the Process - Freeze Design command to freeze the designs for some or all of the beams. This is often a good idea once construction documents for the project have been released.

The same command can be found in other modules, too.

Why are my composite beams being designed as non-composite members?

Beams that have been defined as composite, may be designed as non-composite for the following reasons:

• Non-composite deck
• Opening or exposed beam 
• Cantilever 
• No load

Non-composite deck: Composite beams will be designed as non-composite if the deck on both sides of the beam is non-composite for any portion of the beam span.

Opening or exposed beam: A beam that spans through an opening or penetration or for which there is a portion supporting no deck, such as an inset beam, will be designed as non-composite. Some times it is desired to design inset beams as composite. In order to do this, you can add a short beam from the column to the perimeter beams at an angle (say 45 degrees). Then define the slab edge so that it follows along these short beams, going out and around the perimeter column. That way, the entire beam is covered by the deck and it can be designed as composite (see below).

Cantilever: If the negative bending moment at the support of a cantilever beam is greater than twice the positive moment of the back span, the beam will be designed as non-composite. When a cantilever beam is designed compositely, the program determined number of studs should all be placed in the back-span. Note, for some codes no negative moment is allowed for composite beam design and in those cases a cantilever will always result in non-composite design.

No Load: If there is no load on the beam it will be designed as non-composite. This is sometimes a result of accidentally orienting the deck in the wrong direction such that the infill beams are not loaded.

Note: once a beam has been designed as a non-composite member, the composite flag for the beam will be set to non-composite. You have to go back to the Modeler and use the layout - beams - change properties command to turn it back into a composite member.

Why is the unbraced length reported less than the maximum unbraced length?

The program evaluates bending for each of the various unbraced segments of a beam along with the maximum moments in that segment. The design might be controlled by a shorter unbraced segment with larger moments, or it might be controlled by a longer unbraced segment with smaller moments.

The design report shows the critical condition and indicates where from the left end the critical case occurs.

Can I turn off the pattern loading on beam cantilevers?

Regretfully, not at this time. Live loads are always consider to act on the cantilever, on the back-span or on the entire beam, whichever condition provides the most conservative design for shear, bending and deflection. This is true even for snow loads which can be overly conservative. Only dead loads are not subject to patterning.

Can I turn off Camber on specific beams?

The Criteria - Camber controls whether to camber or not camber composite beams or non-composite beams for the whole model. In cases where you want no camber on specific beams consider adding a special deflection criteria with an initial deflection limit equal or less than the minimum camber and assign that deflection criteria to the beam in question: 

Can I customize the load combinations used in RAM Steel Beam?

Regretfully, not at this time. The load combinations used in RAM Steel are internal to the program and cannot be modified.

See Section 10.3.11 in the RAM Steel Beam Manual for a list of combinations used for each design code.

Note that floor live load and snow or roof live loads are combined and applied as a single live load. Some building codes, such as IBC, permit a reduction (0.75 factor) for combinations including two or more transient loads. RAM Steel uses the combination 1.0 DL + 1.0 LL (effectively, 1.0 DL + 1.0 LL + 1.0 SL). Using the reduction noted above, a load combination of 1.0 DL + 0.75 LL + 0.75 SL is permitted. If the IBC is selected for the code for load combination generation in RAM Frame, 1.0 DL + 0.75 LL + 0.75 SL and not 1.0 DL + 1.0 LL + 1.0 SL. This can cause some design differences for beams designed in RAM Steel Beam versus RAM Frame.

Are transfer loads from columns or hangers affecting composite beams considered pre-composite or post-composite?

All transfer dead and live loads affecting composite beams are part of the post-composite design. For transfer columns, that typically makes sense since the lower level composite beam should be hardened by the time the upper level is loaded. For hanging columns it's not so clear cut, but the transfer load is still only considered in the post-composite design in Ram Steel.

Transfer loads do not include the column self-weight since column design typically takes place after beam design. A point load for the estimated column self-weight is advised.

Can I override the unbraced length of a steel gravity beam?

In cases where you want the unbraced length to be reduced you can add brace points in the Modeler using Layout - Beams - Brace points. Alternatively adding additional short beams framing into the beam in question will brace the top and bottom flange at those locations. Use joists where you want only the top flange braced.

In cases where you want the program to use a longer unbraced length, for example where a beam is set higher than the deck in reality, set the Criteria - Design Criteria - Unbraced length so that neither deck perpendicular nor parallel to the beam braces the top flange. Since it's a global criteria it will affect all beams, however, so you might have to set the criteria this way and check the one beam, freeze the design, and then check the rest using the preferred criteria.

Alternatively, you could add a long penetration (Modeler - Layout - Slab - Slab Penetrations) along the beam covering most of the span.

Why are my beams being designed per the Canadian (or British) code with a Design Fy (or py) less than the Nominal yield stress assigned in the Modeler?

Please review the Ram Manager manual, section 2.4.7 Canada Parameters, 2.4.8 BS 5950 Parameters and the Ram Steel Beam manual section 10.4 Design Yield Strength.

To summarize, When using either of these codes for design, the steel material type for each type of structural member must be determined from a table. This steel type is combined with the nominal yield strength assigned to each individual member in the model to determine the steel grade and the design yield strength of the section.

For example, a section of type W with a nominal Fy of 350N/mm2 is assigned a steel grade of 350W. But, a nominal Fy of slightly less than 350 will result in a steel grade of 300W. Consequently, assigning a yield stress of exactly 50 ksi while using English / Imperial units, will result in a steel grade of only 300W being used, since 50ksi = 344.7 N/mm^2 which is less than 350.

Specifying a nominal Fy or material type that has no matching steel grade will result in a design yield strength of 0.0 and no grade assignment.

In the Ram Manager under Criteria - Canada Parameters (or BS 5950 Parameters) where the specific grade for various section types can also be specified.

For the example above, if the Material type A572/A992 is selected, then the beam will be designed with a Design Fy=50ksi

 The same is also true when using Ram SBeam as explained in the manual for that program. 

For more on treatment of Class 4 sections in RAM Frame, see this article.

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Product TechNotes and FAQs

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British Sections designed, in RAM Frame, in accordance with BS EN 1993-1-1:2005, can, depending on the initial section size assigned, be classified as Class 4 in accordance with section 5.5 of this standard. As a reminder, the role of cross section classification is to identify the extent to which the resistance and rotation capacity of cross-sections is limited by its local buckling resistance.  

Four classes of cross section are defined in BS EN 1993-1-1:2005 as follows:

Class 1 -  cross-sections are those which can form a plastic hinge with the rotational capacity required from plastic analysis without reduction of the resistance.

Class 2 - cross-sections are those which can develop their plastic moment resistance, but have limited rotational capacity because of local buckling.

Class 3 - cross-sections are those in which the stress in the extreme compression fiber of the steel member assuming an elastic distribution of stresses can reach the yield strength, but local buckling is liable to prevent development of the plastic moment resistance.

Class 4 - cross-sections are those in which local buckling will occur before the attainment of yield stress in one or more parts of the cross-section.

For a member subject to both bending and axial compression as shown below, the critical section checks may occur at the beam ends or at the point of contra flexure where the beam is subject to compression only:

The above continuous beam comprises two spans, one 6.0m and one 4.0m. The 6.0m span will be considered for this example.

It should be noted that all UB sections which are classified as Class 4 when subject to a compressive force only, that the section classification is controlled by the web dimensions. This is confirmed in pages B – 62 and B – 63 of SCI Publication P 363.

RAM Frame does not check the design capacity of Class 4 sections in accordance with the requirements of BS EN 1993-1-1:2005 and this article outlines how users can perform a hand calculation to verify the adequacy of a Class 4 section.

Assume the section being designed is a 457x191x67 UB, its properties for section classification are:

See Also

RAMSS Beams [FAQ]

Structural Product TechNotes And FAQs

Is there a way to add a node or connect two members that are crossing each other?

Select the two crossing or nearly crossing members. Then use Process - Segment selection to introduce a node at the intersection point.  Be sure to check the box that indicates, "Add intermediate nodes at memebr intersections"

There is a tolerance for this that you can control.

There is a similar option in the automatic meshing under Process - Analysis - Finite Element Model tab.

In cases where you have crossing members that should slip past each other, this option should be turned off.

How can I move all or part of my model?

In Ram Elements the position of all members and shells are derived from the node coordinates. To move a structure, you simply need to move the nodes. Tools are provided to make it easy to add, subtract or even multiply the nodal coordinates by a constant as shown in the video below:

(Please visit the site to view this video)

See Also

RAM Elements - View Control FAQ

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

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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

Can I assign a section such as a HSS or channel to a beam?

Currently, only I-shaped sections can be assigned to beams in RAM Connection. It is not possible to assign other section types, like HSS or channels, to beam members.

What is the difference between Basic Connections and Smart Connections?

The RAM Connection Manual defines these connections as follows:

Basic Connection:  A connection template that can automatically adjust the geometry (position or dimensions) of the connection pieces to fit the connection members. It does not calculate the quantity or dimensions of the connecting pieces (bolts, plates, etc) to resist the applied forces.

Smart Connection: A connection template that can automatically calculate the quantity and dimensions of the connecting pieces (bolts, welds, plate sizes etc) to resist the applied forces.

When basic connections are designed, the program searches through a list of predefined connection templates and selects the first connection in the list that satisfies the design requirements.

When smart connections are designed, the program optimizes the connection parameters. See the RAM Connection Manual for a list of parameters that are optimized for each connection type. If a parameter is not optimized, the program uses a default value that be modified in the Connection Pad as needed.

Where are the abbreviations used for joint types and connections defined?

The abbreviations are defined in the RAM Connection Manual. In the v8.0 Manual, the naming conventions for both joints and connections are listed on page 42 and 43.

How can I change the design code (AISC 360 or BS 5950) or the design method (ASD or LRFD)?

RAM Connection Standalone:

1. Click on the Design menu tab at the top of the program window.
2. Find the Assignment toolbar.
3. Double click on the small square box with arrow pointing to the lower right corner to open the Customize Connection Design dialog.
4. Edit the design code (or design method in version 8).

Note, in Ram Connection Stand-alone version 9.0, changing the design code does NOT retroactively alter the assigned code for the existing joints in the file. This was done intentionally so that the user can have some joints designed to one code and other joints designed to another code within a single file. Consequently, if the design code for existing joints needs to be changed, the code should first be changed, then reassign connections tot he joints.

RAM Connection for RAM Structural System:

1. Click on the Design menu tab at the top of the program window.
2. Find the Assignment toolbar.
3. Double click on the small square box with arrow pointing to the lower right corner to open the Customize Connection Design dialog.
4. Edit the design code (or design method).

RAM Connection for Elements:

The design code and design method is controlled by the code selected for design when performing a design in the RAM Elements model. To change the design code or design method, redesign the model and choose the desired design code.

Changing the design code will not automatically update generated load combinations. After changing the design method, delete and regenerate the load combinations.

When designing a base plate connection, the ACI 318 Appendix D checks are not completed.

Since the ACI Appendix D checks are based on ultimate limit state design, RAM Connection will only complete the ACI Appendix D checks if LRFD is selected for the design method. See frequently asked question above for information on changing the design method.

Information that is modified in the Connection Pad is not saved after clicking the Save button and exiting the dialog.

Any item that has an icon with a red arrow to the left of it (see figure below) is defined in a dialog outside the Connection Pad. These parameters can be edited in the Connection Pad, but the information will be lost after closing the dialog. To change the parameters permanently, modify the values in the dialog where the information is initially defined. Edit the Joint to modify loads, section, materials, etc. Edit the seismic provision options in the Customize Connection design dialog.

Can I design a Gusset Connection using a Pipe Column?

No, currently in Column-Beam-Brace joints (CBB) only Wide flange (W) and Square or Rectangular Tube (HSS-rect) shaped sections can be used for columns. Circular shapes can be used as columns in some joints but not the gusset type. A change request for pipe columns in these joints has been logged.

Why is the controlling load condition as a single load case?

RAM Connection completes a design check for all load conditions, including individual load cases and load combinations. For some connection types, such as a base plate connection with wind uplift, the design for an individual load case may control the design. The single load cases can be removed from consideration as follows:

RAM Connection Standalone or Ram Connection for RAM Structural System :

1. Click on the Design menu tab at the top of the program window.
2. Find the Assignment toolbar.
3. Double click on the small square box with arrow pointing to the lower right corner to open the Customize Connection Design dialog.
4. To have only the load combinations considered click the button, "Select all load combinations", or manually check the desired conditions.

Please note that this will not permanently delete the load case results from the worksheet. See frequently asked question above for details.

RAM Connection for Elements:

1. Click on the Modules ribbon menu.
2. Double click on the small square box with arrow pointing to the lower right corner to open the Customize Connection Design dialog.
3. To have only the load combinations considered click the button, "Select all load combinations", or manually check the desired conditions.

I'm designing a connection with seismic provisions, but the Ry and Rt values don't look right, what's wrong?

Ry (Yield strength ratio) and Rt (Tensile strength ratio) are properties of the material in Ram Connection. The can be reviewed using Home - Databases - Materials - Edit.

To add your own materials with different values, refer to the wiki Creating custom elements in RAM Elements which also applies to Ram Connection.

Note, imported materials from RAM Structural System or STAAD.pro may not have the expected values for Ry and Rt since those are not directly supplied by either of those applications. For Ram Elements users with imported RAM SS files, edit the imported RAM SS materials as shown below (or reassign different steel material to the members):

For STAAD users, be careful to define the proper values when using the RAM Materials dialog box within the connection mode.

For further details refer to Tips for Using RAM Connection within STAAD.Pro [TN]. and How to Customize a RAM Connection Template in STAAD.Pro 

See Also

Troubleshooting Errors when Assigning Connections

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!