Use of Two way decks in RAM Structural System

The table below clarifies how One way and Two way decks can be used in RAM SS v14.00 or later:

1. One way deck always requires a complete nodal network, a network of supported beams or walls such that a tributary for every member is defined and encompasses the entire one way deck area.
2. If you have a semi-rigid diaphragm with a one way deck that is not properly supported by a network of beams, RAM Frame or RAM Concrete may run without warning, but loads will be zero.
3. When Two way deck is used, only two modules can give results. RAM Frame with a semi rigid diaphragm option (2-way rigid diaphragms are also allowed starting in v14.03 and were altered in 14.07 see Criteria - Diaphragms for details), or RAM Concrete. Furthermore, the user must specify the deck effective E value, thickness and Poisson's ratio for those modules to work. The diaphragm will always be meshed, and out-of-plane stiffness will always be assumed. Hence the beams (if there are any) will resist less force compared to a one way system. Any such beams have a centroid alignment to the center of the slab.
4. No automatic Live Load reduction calculation is performed for members carrying loads from two-way slabs. The reduction to be applied to the Live Load on such members must be assigned to the member in the Modeler (e.g. Layout - Columns - LL Reduction). 
5. RAM Concrete typically considers skip loading for live loads on the beam lines lying under one way decking, if desired. A beam line lying under a two way deck can have skip loading cases only if line and point live loads are applied directly on it. Currently, the surface loading applied to two way decks does not generate any skip loading cases.

Other notable warnings:
RAM Frame, using a Two way deck without using a semi-rigid diaphragm (only applies to versions 14.00 to 14.02):

RAM Frame: Two-way Deck Found Inside Diaphragm 1 of Story 2.  The Diaphragm Type is not Semirigid.  Gravity Loads on the Diaphragm Disregarded for the Analysis.  Do you want to continue?

RAM Steel - using Two way decks always gives an error of some sort, example:

Warning: Failed to Create Slab Edge Load Polygons for diaphragm 1 on Layout Type Roof. Slab edge loads will not be applied to any beams around the perimeter of that diaphragm. Disregard this warning if the slab edge is Two-way deck.

Hybrid Decks

For Hybrid Deck levels, those that include areas of both one way deck and two way deck, the rules for nodal networks still apply to the one-way decked area. If the network is not complete various framing tables errors can occur.

Furthermore, when the level is meshed in Ram Frame or Ram Concrete you will see that the mesh covers the entire floor so that the diaphragm is continuous. This can cause some unexpected behavior in the one-way regions. Specifically the meshed slab can help in resisting some of the applied loads, effectively holding up the beams.

There is an option in the Concrete Analysis mode, under Criteria - Analysis to alleviate this effect. 

By not checking the option to "Include Out-of-Plane Stiffness for One-Way Decks in Hybrid Slabs" you are telling the program to use a near zero stiffness element in the one-way deck areas so that the beams have to do the work.

For these reasons, mixing one and two way decks in the same diaphragm is not generally recommended.

Concrete Column design with Two-Way Slabs

In Ram Concrete, the column K factor is determined based on the relative stiffness of the beams to the columns. The stiffness of 2-way slabs is not considered in this calculation, so the user should manually assign the proper K factor for columns supporting 2-way slabs.

As noted above, Live Load reduction percentages also need to be manually assigned.

Semi-rigid Diaphragms for Two-Way Slabs

Out-of-plane stiffness is assumed not only for gravity loads, but also for lateral loads when the deck is two-way and semi-rigid only. When the diaphragm is set to rigid, out of plane stiffness is ignored in the lateral load cases. Prior to version 14.07, rigid diaphragm two-way decks considered the out-of-plane stiffness for all loads. This was a major change in version 14.07. Consequently if you have a 14.06 or earlier model where your are relying on slab out of plane stiffness to tie your columns together and provide frame action, you will now must change the diaphragm setting from rigid to semi-rigid to get similar behavior out of the new version. The effect of this is most notable when transferring lateral Self Equilibrium result to Ram Concept.

There are some general concerns in RAM Frame for these diaphragms. The distribution of gravity loads is determined by meshing the diaphragm and then the program calculates the gravity load that is tributary to each node.  Gravity columns/walls are ignored in the Frame finite element analysis. If you have gravity columns and/or walls, the gravity forces on the lateral members will be inaccurate unless you utilize the consider gravity columns/walls as springs options. However, utilizing this option will have an impact on the lateral analysis as well. The following concepts apply to one way decks with out-of-plane stiffness considered, too.

Consider a five story shear wall building with two way 8 inch concrete slabs. Here is the typical plan.

The moments at the base of the walls for a lateral load case in the X direction are 13555 k-ft and the shears are 242 kips.

If you run the same load case and include the gravity columns as springs the moments drop to 11163 k-ft as the gravity column spring form couples that resist much of the overturning moment. The wall major axis shear forces stay the same. You would get similar results if you modeled all of the columns as pinned lateral columns.

As the out-of-plane stiffness of the diaphragm and axial stiffness of the columns increase the moments in the walls decrease. Conversely, when there is negligible out of plane stiffness to the diaphragm, the moments in the walls would not be affected. (Using version 14.07 or later with rigid two-way decks transforms this behavior so that the slab out-of-plane stiffness is only considered for gravity load cases. See Criteria - Diaphragms for details.)

In the RAM Concrete Shear Wall Module all of the design forces, including gravity load results, come from the RAM Frame analysis. For the design of shear walls it is important to understand the impact gravity columns have on the forces in the walls.

Transfer Forces

A column or wall may set directly upon a 2-way deck without the need for a beam on the story below (using version 14 or later). The force from the vertical member will transfer through the meshed slab to the supports below. Since this requires a finite element analysis of a meshed two way slab, it has the same limitations in the table above, i.e. it only works using Ram Frame or Ram Concrete analysis.

Generally we recommend that the columns or walls that offset should be modeled as lateral members so that the analysis in RAM Frame will consider those members in the analysis.  That way the program can display or report important information like axial member forces and nodal displacements.

We also recommend modeling a transfer beam in addition to the slab when reasonable to do so.

There are some special considerations when using RAM Structural System in conjunction with Ram Concept for transfer slabs. See these topics for further details:

• RAM Concept-RAM Structural System Integration TN
• Modeling Podium Slabs TN

See Also

RAM SS Analysis Types

RAM Frame - Criteria - Diaphragms

RAMSS Common Framing Table Errors

RAM SS Semirigid Diaphragms

Transfer Slabs

Structural Product TechNotes And FAQs

What is the relationship of initial deflection and camber?

The Criteria - Camber and Criteria - Deflection criteria together determine if beams will get cambered in the program design. Refer to the Ram Steel Beam manual, section 10.13 for details on exactly how this is done, below is an example for the most common case, Unshored, Composite Construction.

This example uses default camber and deflection criteria:

Which means that beams will be cambered if and only if, the deflection caused from 80% of the applied Construction Dead load is greater than 0.25".

The beam in question is a 20' long girder and the CDL stems from the beam and deck self weight. With 100% of that load considered acting on the pre-composite unshored beam, the deflection is 1.061" downward at mid-span. The deflection due to 80% of the CDL is therefore 0.8 * 1.061 = 0.85". Thus the program cambers 0.75" which is 3 times the 0.25" camber increment.

The Live load deflection is calculated using the composite properties (Ieff) and is therefore a smaller total deflection even though the applied loads may be more than the CDL. This Live load may already be reduced if the beam tributary area is large enough. Construction live loads are used in the Pre-composite strength check of the beam only, not in the initial deflection check.

The Post Composite value is also based on the composite beam effective inertia. The Post Composite load considered is any dead load above and beyond the CDL plus the Live Load. This is often referred to as the superimposed load. 

Thus the Net Total load can be calculated using the formula:

Net Total deflection = Initial defl + Post Composite delf - Camber

In the case above that is 

0.759 = 1.061 + 0.448 - 0.75

It's also worth noting that the initial deflection in this case is large enough to surpass the common L/240 deflection limits for dead loads, but that's OK because there is no limit on initial deflections (using our default deflection criteria). So long as the Live load deflection and Net Total deflection limits are OK, no warning will be given.

It is also worth noting that even with camber, this beam theoretically deflects 1.061 " - 075" = 0.311 inches during construction. The program does not increase the construction dead load to account for the additional topping concrete that might occur from such ponding. The applied loads should manually be increased where this is a concern.

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: 

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.

I have input a composite beam but it is designed with 0 studs, which deflection criteria are used?

In the case where a composite beam is designed non-compositely (i.e. with 0 studs), the deflection checks are performed using the non-composite deflection criteria. For more on reasons why composite beam are design without any studs, refer to Ram Steel Beams FAQ.

See Also

RAMSS Beams [FAQ]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

Problem Description

Since I have upgraded SACS version from 5.3 to 5.6 , I am not able to activate my license. License Management Tool shows it checked out , but it is not visible in sacs executive.

Reason

Your license setup requires a checkout license and version 5.6 fails to run with checked out licenses.

Steps to Resolve

Since your license setup requires you to check out a license, please install SACS version 05.07.

If you do not wish to check out the licenses physically, move to version 5.5. This version uses the Bentley IEG License Service and it automatically checks out the licenses once you start the program and checks in the licenses once you exit from SACS.

Can I use a response spectrum load case in a DIRECT ANALYSIS ?

In a response spectrum analysis, you are essentially finding out the maximum responses at various nodes/members. So the various responses are not at the same time instant. Also due to the modal combination, the results lose their signs which makes it impossible to find the true nature of the force or the direction of displacement. One cannot carry out a second order analysis without knowing the actual real time values for the displacements at all nodes. Moreover in direct analysis the structural stiffness changes between iterations depending on the forces in the members which makes the analysis type nonlinear in nature. As of now there is no way to handle nonlinear dynamic analysis in STAAD.Pro. The closest you can get, would be to carry out a PERFORM ANALYSIS for the response spectrum load case and do a Direct Analysis for all other cases. The response spectrum cases would then have to be combined with the solved Direct analysis cases using LOAD COMBINATION.

Alternately one may use an equivalent static approach for generating the seismic load instead of using a response spectrum. The DIRECT ANALYSIS would then be able to account for the Pdelta effects due to seismic plus gravity loads.

Can you please explain with an example as to how one should define the unsupported lengths of members ( Ly and Lz)

For demonstration purposes a truss model is attached. The bottom chord of the truss is broken into segments by the in-plane ties/struts. So there is no need to define the unsupported lengths for the in-plane bending (Lz) as the segment lengths correctly represent the unsupported lengths. If defined, the LZ should be set to the segment length which is 7.5 ft.

As far as out of plane bending of the bottom chord is concerned, let us assume that there are restraints at the end and at the midpoint of the bottom chord. However since the restraint normal to the plane of the truss is NOT modeled, this information needs to be communicated to the software through the design parameter Ly so that design correctly accounts for that. The entire length of the bottom chord ( consisting of members 20 to 23 ) is 30 ft. So all the bottom chord members need to be assigned a LY of 15 ft as shown next.

…

PERFORM ANALYSIS

LOAD LIST 3

PARAMETER 1

CODE AISC

LY 15 MEMB 20 TO 23

TRACK 2 ALL

CHECK CODE MEMB 20 TO 23

FINISH   

(Please visit the site to view this file)

I have a mat which has different thickness at different locations. How can I model that ?

You can define as many control regions within your mat boundary as you wish. Boundary represents your entire mat and it can have holes or control regions within it. Control region is a region within the mat ( or boundary ) that may have different properties than the rest of the mat. For example a control region can have a different thickness or a different soil property associated with it. Holes are used for defining openings within the mat ( or boundary ).

One you define a boundary for your mat, please follow the steps listed next to define the control region

1. Add a meshing region from within Mat foundation Job > Mesh Generation > Add Meshing Regions to define the region of different thickness.
2. Go to the Meshing Setup.
3. Click on the boundary name within the tree structure ( mesh1 in the figure below )
4. Now within the graphics screen, select the meshing region defined in step 1. It will turn red when selected.
5. Add selected region as Control Region by choosing the appropriate radio button, putting a name for the region identifier and clicking on Add ( see figure below )
6. The name of the control region would now show up under the boundary name in the tree as shown.
7. Add as many control regions as needed following steps 1 to 6.
8. Once the control regions are generated, you would need to regenerate the mesh.

Once the control regions are defined, go to Analysis Properties > Slab thickness and assign the required thickness to the boundary or the control regions.  

Is pattern loading possible?

Yes, but the user must graphically define the load patterns. Refer to the program manual for further details:

• Section 10.9 - About load patterns
• Chapter 20 - Creating Pattern Loading

Are area loads additive?

Yes, the program considers the cumulative total of overlapping surface loads.

Note, it is possible to assign loads with negative magnitude which sometimes makes surface load modeling simpler.

Also note, this is opposite to the behavior of surface loads in RAM Structural System where only the top load counts. When you import surface loads from RAM SS into Concept, they are automatically adjusted to be equivalent.

Is self-weight considered?

In Ram Concept Self-weight of the slab mesh is always considered. The weight of the columns and walls above the slab may optionally be considered using the Criteria - Calc options command and checking the General option to "Include supports above slab in self-dead loading"

Just above this is an option to "Create viewable self-dead loading". When this option is on, the Layer - Loading - Self-Dead Loading will include graphics and text for the applied self dead loading once the Calc All process is complete. This can be very slow and somewhat difficult to read due to the amount of data however, so this option is off by default. 

The Calc Log reports the total self-weight as does the Estimate.

How are lateral loads with elevation treated?

Every point, line and surface load in Concept has a property for "Elevation above slab surface" that can place the load above (positive elevation) or below (negative elevation) the slab surface. 

These elevated loads are connected to the slab centroid with vertical rigid links analogous to a stiff flagpole. For an elevated line load it's a series of such links connecting the load to the slab.

Can I make a line load that's triangular or non-uniform?

Yes, when entering the magnitude of the line load, enter two values separated by a comma. For example, if you enter the following properties:

The load you create will linearly vary from 2 k/ft at the first point to 1 k/ft at the end.

You can similarly enter surface loads that slope using three magnitude values separated by commas.

Why do I get a Analysis Error that says, "Rule Set "Service Design" is being used by load combinations that appear to have load factors set for different purposes.  This is likely an error."

Ram Concept has a hard coded set of load factors for each design code and for each rule set. You can find more about the default load factors in the manual in chapters 54-64 in the second sub-sections for "default load combinations."

When the load combinations are manually altered by the user and the load factors are changed, or when new combinations are added that do not use the expected load factors, then such an error will occur.

If the changes are intentional then the warning can be ignored.

To reset the load combinations to program presets use the Criteria menu option - Rebuild Load Combos...

We recommend saving the file, printing out the current load combinations, then using the Rebuild Load Combinations tool to reset values and finally compare the values when deciding what is best.

Why don't I see any Live Load Reduction?

Refer to the program manual, Chapter 27 "Using Live Load Reduction" and Chapter 52, “Live Load Reduction Notes” for further details.

There are 3 main requirements for Live Load reduction to occur in Ram Concept.

1. A code for LL Reduction must be selected under Criteria - Calc options. There is not a one-to-one association of the design codes and the codes for Live Load reduction, so the program defaults this to "None".

2. The loading type where the loads are modeled must be of a "Reducible" type (including some storage and parking types):

3. The Design Strips, Design Sections, Columns, Walls, and/or Punching Checks which are to have reductions applied must have the Max Live Load Reduction % set to a value greater than 0. When using Specified LLR Parameters, they must also have non zero values for LLR Levels, Trib. Area and Influence area.

As noted in Chapter 52, “Live Load Reduction Notes”, the program only applies live load reduction when combinations of loads are at work. The results for individual load cases are given before any reduction has taken place.

In concrete structures, the determination of tributary area and influence area can be rather complicated. Refer to section 52.2 and 52.3 for details on how Ram Concept performs these calculations for Columns, Walls, Punching Checks, Design Strips and individual Design Sections.

See Also

RAM Concept Lateral Self Equilibrium Analysis

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

If a “SPRING TENSION” command is specified and the spring is stretched along the positive global direction (due to a positive global deflection of the node to which the spring is attached), then the spring is identified to be in tension and you will have the spring support reaction as negative by the virtue of it being opposite to the displacement. If however, the displacement is negative, the spring is identified to be in compression and the spring will be switched off from the model.

If a “SPRING COMPRESSION” is specified and the spring is compressed along the negative direction of the global axis (due to negative global deflection of the node to which the spring is attached), the spring is identified to be in compression and you will have the spring support reaction as positive by the virtue of it being opposite to the nodal displacement in the negative direction. If the displacement is positive, the spring will be identified to be in tension and will be switched off.

In the following figure, consider a compression only spring support is specified in Global X direction. Due to the applied load in negative X direction, the support node (node 9) will displace in the negative global X direction. So the spring support will be under compression and the support reaction in Global X direction is positive. The support will therefore be active in this case. Had it been a SPRING TENSION type support, it would have got deactivated.

How to open License Configuration and License tool within MicroStran.

Background

It is important that to know how to check the settings of the current license configuration that you have set within MicroStran.

There are different ways on how you can open the MicroStran License Configuration and the License Management tool.

Steps to Accomplish

Option 1 - By Default

1. By default when you open MicroStran you should see this Dialog Box.

   This should show up automatically if you have set the option “Shown on startup”

    

2. From the Same Dialog Box you can also see the “License Management Tool” tab.

What is the License Management Tool?

Just below the Product Activation Wizard button in the Microstran Licensing Configuration dialog is a button called License Management Tool. This tool allows users to revise and manage licensing settings for all Bentley products. This includes the checking out of a license. Information on this feature is available in the following article:

http://communities.bentley.com/products/licensing/w/licensing__wiki/license-management-tool.aspx

Option 2 – When “Shown on Startup” option is disabled

1. Open MicroStran

2. Go to “File” menu

3. MicroStran License Configuration

    

Option 3 – When “Shown on Startup” option is disabled

1. Open MicroStran

2. Go to “Help” menu

3. About MicroStran

4. MicroStran License Configuration

Option 4 – – MicroStran no longer opens because the 30 Trial has expired.

1. Go to C:\Program Files (x86)\Bentley\Engineering\Microstran\Program

2. Look for MsLicensingUtility.exe double click on the exe file

3. It will open the MicroStran License Configuration tool

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!

Error or Warning Message

When trying to use RAM Concept through RAM Structural System, I get the following error.

I can open RAM Concept on it's own just not through my model in RAM Structural Systems. I am running RAM Structural System V14.07.01.01 and RAM Concept V5.2.1 .

Explanation

This error message pops up if you have 32 bit version of RAM Structural System and 64 bit version of RAM Concept or vice-versa.

Solution

RAM Structural System and RAM Concept have to match 32 or 64 bit operating system. So, you need to install either the 32 bit version of RAM Structural System and 32 bit version of RAM Concept or 64 bit version of both the software.

1.      When will STAAD(X) be released?

A:         The intended release date is Q4 2015

2.      What will it cost?

A:         STAAD(X) will be one product with three different “flavors” depending on the user’s needs. These tiers will be controlled by licensing. We will have:

• STAAD(X): The entry level that will eventually replace RAM Elements, QSE and MultiFrame.
• STAAD(X) Professional: That will in time replace STAAD.Pro and Microstran.
• STAAD(X) Advanced: The option that will one day replace STAAD.Pro + Advanced Analysis option.

The official cost of these programs will be determined later, but it will likely be $ 3K, $ 5K and $ 7K USD respectively.

3.      Can I continue to use older products?

A:         Yes of course. During the transition phase (likely to be one year), you’ll be able to use your existing product or the equivalent SX tier interchangeably with the same license.

4.      Will older products still be supported?

A:         When we launch STAAD(X) in August, we will not develop RAM Elements, QSE and MultiFrame any further. However we will continue to provide tech support for them. Only minor updates with bug fixes (if any are found) will be released.
On the other hand STAAD.Pro will continue to coexist with STAAD(X) for 3 to 4 years and will continue to be developed, enhanced and supported.

1-Introduction:

Torsion in induced in a floor when there is eccentricity between center of mass through which the resultant of seismic loading at a floor level acts and center of rigidity through which the resultant of the restoring force of the system acts. This is known as natural or inherent torsion of the system and the eccentricity is called the static eccentricity.

In addition to the natural torsion, there is also something called accidental torsion which is considered to account for rotational component of ground motion etc.

The design eccentricity is taken as a combination of static and accidental eccentricities and is given by the following equations.

e_di = αe_si + βb_i ---------   (1)

e_di = δe_si - βb_i ---------- (2)

e_di = Design Eccentricity at the ith floor

e_si = Static Eccentricity at the ith floor or the projected distance between the centre of mass and centre of rigidity at the ith floor.

b_i =plan dimension of the ith floor normal to the direction of ground motion.

α, β, δ = specified constants in the codes

IS: 1893-2002, as in clause 7.9.2 has specified the following values of contants.

α = 1.5

= 1.0, if 3D dynamic analysis is carried out

β = 0.05

δ = 1

2- Static Seismic Analysis:

The easiest and the effective way to do the static seismic analysis as per IS 1893-2002 with the effect of torsion is to define the Rigid Diaphragms. Once can also manually specify the Master Slave in ZX direction and do a seismic analysis. In both the aforementioned cases, one does not actually need to model the slabs. Thus the last method of doing seismic analysis with torsion is to actually model the slabs.

2.1- Model with Rigid Diaphragms:

When the Rigid Diaphragm is modelled at a specified height, the program identifies the center of mass of the floor at that level based on the mass definition in the Mass Reference Load Case. By default, the Data of the Mass in the Y direction is used to determine the center of mass. In absence of mass data in the Y direction, the masses in the other directions are used.

Once the center of mass is identified the calculated seismic force at that level is applied at the center of mass. The center of rigidity is based on the distribution of the elements that provide lateral stiffness and thus does not need an exclusive determination. Thus the inherent torsion is automatically determined.

However, if the design static eccentricity component of the design eccentricity is greater than the natural static eccentricity (α > 1), then an additional torsional moment of the value of (α-1) e_si *Fi is introduced at the center of mass to achieve the full torsion condition. Please refer to the figure below. The value of β*bi*Fi is added or substracted to the additional natural torsion to incorporate the effect of accidental torsion.

2.2- Specifying the values of α, β and δ:

The general format of specifying the seismic loading in STAAD with Rigid Diaphragm is as follows:

LOAD n

1893 LOAD { X | Z } (f₁) (DECCENTRICITY f2 ) (ACCIDENTAL f₃)

The DEC parameter should be used to specify the value of α and δ, represented by the value of f2 in the above command line. The ACC parameter should be used to specify the value of β, represented by the value of f3 in the command line above.

Thus, the equivalent specification for static seismic analysis with design eccentricity represented by equation (1) in section 1 as follows:

LOAD 1

1893 LOAD X 1 DEC 1.5 ACC 0.05

PERFORM ANALYSIS

CHANGE

Similarly, the equivalent specification for static seismic analysis with design eccentricity represented by equation (2) in section 1 as follows:

LOAD 2

1893 LOAD X 1 DEC 1 ACC -0.05

PERFORM ANALYSIS

CHANGE

FAQa and Validations on various Seismic Code Implementations.

FAQs and Validations on IS:1893-2002

FAQ1:

I have specified Rigid Diaphragms in my model. But when I run the STAAD file, it stops with the following warning.

   ** ERROR: NO REFERENCE LOAD CASE OF TYPE MASS/GRIVITY/DEAD/LIVE IS DEFINED FOR MASS MODELING.

     CENTRE OF MASS CALCULATION IS NOT POSSIBLE.

Answer:

If you are specifying Rigid Diaphragms, it is a must that you specify the Mass reference Load Case. One of the important functions of specifying the Rigid Diaphragms is to calculate the torsion on the floor due to seismic loads and the program needs to identify the center of mass for the same. This is done with the help of the mass data defined in the mass reference load case.

FAQ2:

Which masses in the Mass reference Load Case is used to calculate the centre of mass of the diaphragm?

Answer:

By default, the masses specified in the Global Y directions are considered for the mass calculations. In absence of global masses in the Y directions, the masses along the Global X directions are considered for the same. In absence of the masses specified along the Global X and Global Y directions, the masses along Global Z directions are considered.

Description

I have installed Structural Synchronizer successfully in my machine; when I try to access it from RAM Structural System, it says it is not installed.

Explanation:

There could be two reasons behind it,

• 64 bit of Structural Synchronizer and 32 bit of RAM Structural System is installed in the machine
• Structural Synchronizer has been installed, but there is a version mismatch with the one that is supported by the specific version of RAM Structural System

Solution

Please note that Structural Synchronizer is the engine that makes ISM work. 

1) In case there is a mismatch in Structural Synchronizer (64bit) and RAM Structural System (32 bit), download the 64 bit version of RAM Structural System by following the steps stated in the link below.

Software Download Instructions

2) If you have installed Structural Synchronizer (64 bit) and RAM Structural System (64 bit) and the ISM says nit installed, then there is a version mismatch between RAM Structural System and Structural Synchronizer.

Uninstall Structural Synchronizer from the machine. Download and install the latest version od RAM Structural System and Structural Synchronizer.

They can be downloaded from the Fulfillment Center .

I have a pier foundation that I would like to analyze against axial plus lateral load. I see two options in STAAD Foundation for drilled piers, one in toolkit mode and the other within Plant Mode. Which one should I use ?

The one within the Toolkit mode is only for axial loads. The Drilled/Driven pier option within the Plant mode is equipped to carry out analysis of piers with axial and lateral loads and should be the one you would use for your case.

How do I merge Two STAAD.Pro models ?

There are a couple of ways to do this

Method 1 : Although it is a quick tool, it is only applicable if you need to merge the wireframe geometry. If you need to merge all other attributes of the models, you should use the Method 2.

Here are the list of steps :

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

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

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

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

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

Method 2 : More generic method. Applicable for all scenarios.

A problem with simply copying and pasting the members from one STAAD file to another as outlined in method 1 is that the properties and other attributes can get messed up.

For example STAAD uses reference numbers to identify the properties. You see those in the Properties dialog box as R1, R2, R3, etc.

Suppose you have two models you want to merge. Model 1 has members designated R1 and so does Model 2, but in Model 1, R1 is a wide flange whereas in Model 2, R1 is a single angle. If you paste members with properties designated R1 from Model 2 to Model 1, the program will assign the R1 members from Model 2 with the R1 properties the way they are defined in Model 1. Under this scenario, members you had intended to be single angles will thus end up as wide flange sections.

One approach you can use that may help resolve this problem involves the use of your input files (i.e. *.STD files). You can copy and paste your member incidences and properties from your STAAD input file. If you have two STAAD models, you can open both of them and use the copy and paste commands in the editor to copy the joint coordinates, member incidences, member properties, constants, etc. to merge the two smaller files into a single input file. You will need to exercise a certain amount of care in doing this. In particular, there are two items of concern you should be careful to consider.

1. The copy/paste will not work correctly if you have duplicate entity members, plates, solids and/or nodes) numbers. To prevent conflicts from duplicate numbers in the input file, you should check that each STAAD model you intend to merge has completely unique entity numbers. If there are duplicate numbers in the models you wish to merge, you can use STAAD's RENUMBER command from the Geometry menu to renumber the entities in your model before you begin editing the input files.

2. Be careful to copy and paste the various items from you models in the correct order. For example, the member incidences and joint coordinates must precede the properties, constants, etc. for the members and joints. You cannot tell the program that Member 35 is a W18x35 without first specifying the member incidences and joint coordinates for member 35.

Can I combine two models in STAAD Foundation Advanced ?

Here are a couple of scenarios you may encounter

Scenario 1

If you have created these foundation models in STAAD Foundation Advanced ( SFA ) itself, then you can export these models individually to excel spreadsheets using the option “Export to Spreadsheet”. One you have the two excel files, you can copy the data from one excel to the other using copy and paste. Before you do that you must ensure that there is no overlap between the items like Nodes, Load Cases, Load Combinations etc. If there is, please renumber these items carefully before copying. For example if you are trying to combine two models with isolated footings, you would have a spreadsheet as shown next for each model after the export. You would need to carefully check the data on each of the sheets as marked below and copy the data to the appropriate locations to create one single excel file containing data for both models.

Once the data is copied, you can create a new STAAD Foundation Advanced model by importing the data from the combined excel file using the option Import Spreadsheet.

Scenario 2

Alternately if you have the superstructure for both models analyzed in STAAD.Pro and you would like to create a single SFA model containing foundations for both, it is much easier to merge the STAAD.Pro models into one single file first. Instructions for combining two STAAD.Pro models can be found here

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

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

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

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

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

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

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

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

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

 

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

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

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

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

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

LOAD 1

or

LOAD 2

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

UNIT POUND FEET

For example

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

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

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

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

Example :

plate-list PLATE MAT DIR Y SUBGRADE 0.4

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

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

Example :

plate-list PLATE MAT DIR YONLY SUBGRADE 0.4

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

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

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

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

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

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

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

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

Method 1 :

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

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

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

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

Method 2 :

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

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

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

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

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

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

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

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

 Start STAAD.Pro. Select File - Configure.

Click on the tab called Input File Format

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

Click on Accept.

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

12. How do I merge 2 staad models?

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

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

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

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

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

A more comprehensive answer to this question is available here

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

There are a couple of things you can do.

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

OR

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

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

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

Click on the Create button and this window will appear:

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

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

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

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

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

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

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

For example, let us consider the following example load cases

LOAD 1
SELFWEIGHT Y -1
…

LOAD 6
SELFWEIGHT Z -2.015
…

LOAD 10
SELFWEIGHT Z -1
…

LOAD 113
REPEAT LOAD
1 1.603 6 1.5 10 0.003
…

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

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

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

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

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

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

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

18. How to assign offsets to the plate elements?

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

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

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

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

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

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

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

2 things should be checked:

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

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

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

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

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

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

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

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

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

23. In the past when I hovered over the beams or nodes, I was able to see lot of information like node numbers, displacements, coordinates for nodes and beam numbers, properties, end forces, ratio for beams. Now I only see the node and beam numbers. How can I get back the old setting ?

You need to go to the top menu and choose View > Structural Tool Tip options and you will find a number of check boxes using which you can turn on the items that you want to be displayed.

24. In my structure the load transfer does not appear to be as per expectation. What could be wrong ?

Generally these can happen due to modeling issues. Some of the common modeling problems arise from improper connectivity between members/elements or from application of releases/truss specifications which in turn leads to zero stiffness/instabilities.

To view documents related to connectivity issues between elements and how to fix these, please click here. To find out more on Zero stiffness and Instabilities in the model please clickhere.

25. I accidentally modeled using incorrect units. Can I scale my STAAD.Pro model in any way ?

Here are the steps to scale the model

Close the STAAD model and create a new model.

Go to Geometry > Run Structure Wizard  to bring up the Structure Wizard program. Change the model type to Import CAD Models.

Double click on the STAAD.Pro logo and browse to the original STAAD file that you want to scale.

Click on Open.

Once the model comes in, go to the top menu inside StWizard and choose Edit > Scale.

In the box provide appropriate factors for XScale, YScale and ZScale and click on Ok.

Go to File menu inside StWizard and choose Merge Model With STAAD.Pro model.

Choose the appropriate X, Y and Z location where to place the model inside the new STAAD.Pro file

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Link

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

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

Couple of comments:

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

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

Q. How do I merge 2 staad models?

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