Error or Warning Message

When opening STAAD.Pro, the following message can occur:

Unable to activate RSS Feed connection

Explanation

This message indicates that STAAD News Feed cannot be activated successfully. In such situation, STAAD News are not shown in the start-up window of STAAD.Pro.

How to Avoid

1. In most cases, it should be enough to install BentleyRSS.msi file, which can be downloaded from here.

2. If installation of BentleyRSS.msi file does not help, check if you are able to go to the page http://feeds.rapidfeeds.com/8131/ or not. If not, then there is potentially some firewall/security in your network that is blocking the communication when STAAD.Pro is trying to communicate with the RSS feed page.
   
   If you are able to connect to the webpage through Internet Explorer, it means that specifically when STAAD.Pro tries to access information over the internet, that particular communication is being blocked. You may check your firewall settings in your network and add STAAD.Pro (C:\SProV8i\STAAD\Staadpro.exe) to the list of Exceptions. If you have a proxy server in your network then check if that is blocking the communication or not.

The same solution can also be used to correct a problem with the RSS Feed in Ram Manager 14.06 or later.

Instability in Finite Element Analysis

A typical 3-dimensional Finite Element analysis of a structure requires that every node must be stable in all 6 degrees of freedom (TX, TY, TX, RX, RY,RZ). This is achieved by specifying fixity conditions for the columns, beams and braces spanning to a given node or through nodal restraint. While many programs can analyze a structure using fewer degrees of freedom, for this discussion all 6 are assumed to be active.

There are many discussions related to FEA online and whole courses devoted to the topic, but the purpose of this article is merely to show by example a few of the most common causes of instabilities in structural models. The rules apply to RAM Elements (aka RAM Advanse), RAM Frame, RAM Concrete or STAAD.pro as well as other FEA applications. The images and examples below are taken from RAM Elements where a light blue circle indicates a hinge, or member release, at the end of a member. A translational restraint is depicted as a triangle on rollers and a rotational restraint is a "T".

Pinning the free end of a cantilever.

Take the case of a single member fixed at the base for all 6 DOF similar to a flagpole. This structure is stable, except that the free end of member away from the support is hinged or released for major axis bending. As a result, node 2 can spin about the global z axis.

For some applications, this type of "nodal instability" will terminate the analysis. For other applications, a small stiffness may be automatically assigned to the z axis rotational stiffness of the node and you may only get a warning, so long as a moment about the z axis is not applied directly to node 2. This would cause infinite rotation of the node and should terminate any analysis.

The same situation often occurs for a beam with a cantilever, where the cantilever beam is the only member connected to the node at the tip. In short, the free end of any member, where that member is the only member in the model connected to a particular node should never be released. 
 

Beam, column and brace intersections.

When multiple members frame to a single node, it is acceptable to release some, but not all of those members. If the beam, column and brace are all released at the same node, then the problem is the same as case 1 above. At least one of those members should be fixed ended. In most situations, it is the column top that should remain fixed to the node.

Releasing the tops of columns.

In this case we have a fixed ended beam setting on two columns, both of which are released at the top node. This case differs slightly from Case 2 because the nodes are fixed to the beam and not themselves instable. The problem is that the beam along with both top nodes can spin as a group on top of the columns similar to a log on water. This is an example of why it is usually better to keep the tops of the columns fixed and release the beams.

Torsional releases

It's hard to envision a realistic connection that allows a member to spin or swivel, but most FEA application do allow member torsional releases. A general rule is to leave the member torsion fixed except in a situation where member rotation really is free. The most common problem occurs in a chevron brace configuration where the beam is two finite elements. If each beam half is released in torsion, then the node at the top of the braces is instable.

2-dimensional frame in a 3-dimensional analysis

Often it is desirable to analyze a 2-dimensional frame using a 3-dimensional analysis. In some applications there is plane frame option that can be used to ignore the deflection out of plane (e.g. z axis) or rotation about the other axes, but if not, the frame can generally be stabilized one of two ways.

• An out of plane, z axis restraint can be applied to some or all of the nodes to effectively keep the frame from falling over, or
• Rotation about the in-plane axes can be restrained at the base nodes (e.g. rotation about the X axis).

The same situation often occurs in RAM frame when no rigid diaphragm is used. This can leave the model with several, isolated, 2D frames in space with no connection between them. If the frames are pinned at the base then they can fall over and an instability results. Fixing the base of the frames against out-of-plane rotation is generally the solution to this problem, though connecting the frames together with lateral members or some other simulation of a diaphragm is also possible.

Other Global stability issues

A certain number of nodal restraints are always required to keep the structure as a whole from moving. Another common case is one where a shell or mat foundation is supported by a series of vertical springs. While that is stable in relation to vertical loads, some mechanism must be provided to keep the mat as a whole from sliding around like a skateboard. This is generally achieved through the use of horizontal springs in addition to the vertical springs, or by restraining the translation of a node (or line of nodes) along the edge of the structure.

This is a common problem in Ram Concept if a vertical resistance area spring is the only support for the structure. When there are no lateral loads, you might get away with providing an area spring with only vertical stiffness, but when there is any external load applied in the plan directions, some resistance to sliding must be incorporated into the model.

Diaphragm stability

In most building type structures there is a horizontal diaphragm that ties the frames together and prevents in-plane deformation of the plan. This is typically modeled using a rigid floor diaphragm. The diaphragm constraint forces the nodes of the floor to move together preventing the plan from racking for example.
In space frame models where no rigid diaphragm is modeled (perhaps because the roof is sloped), there must be some other mechanism to keep the plan from racking. This is generally achieved by providing diagonal members in that plane. Fixing the minor axis of the beams in the plan is another approach. Think of this like creating a Vierendeel truss in plan. Using shell elements is another option, though the interaction between the shells and the members is not always desirable.

Using tension-only members or compression-only springs

When a model utilizes non-linear members or springs most FEA applications iteratively solve for each load case and load combination. On each iteration, if a tension-only member is found to go into compression, that member is thrown out of the analysis and a new iteration is started. If too many of the members go into compression, the frame or structure as a whole can become instable.

There are a couple of ways to effectively deal with such a situation

• Apply a pre-tensioning force to the braces. By putting the member into an initial tension state it is less likely to go into compression and fall out of the analysis.
• Assign some of the members to be tension and compression members. For X braced frames or other symmetric structures it is typically acceptable to analyze the structure with a single tension + compression brace rather than a pair of tension-only braces. This does affect the load path through the columns somewhat, however, and may require two versions of the model to capture the worst condition. A similar option is to leave both braces in the model, but then check the braces or twice the determined force.
• Applying self weight to tension only braces will cause bending moments in the members which usually is not the intent for tension-only braces. in those cases, a zero density material is suggested.
• Additionally, for X braced frames in Ram Elements, the program may be introducing a node at the intersection of the braces. This can be prevented using Process - analyze - FE Model tab - by turning off the option to "Add intermediate nodes at member intersections".

P-Delta effects and model instabilities

There are cases where a structure might be perfectly stable under a first-order analysis, but as the analysis incorporates P-Delta effects the deflection is amplified and instability can result. Different applications handle P-Delta analysis in different ways, but there are usually controls for the tolerance required for P-Delta convergence. Increasing the tolerance often leads to a solution, but some structures may have to be stiffened in order to complete a P-Delta analysis on all load cases.

See Also

RAMSS Eigenvalue Error

RAM Frame P-Delta [TN]

Structural Product TechNotes And FAQs

STAAD.Pro Instability And Zero Stiffness

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!   

In the License Management Tool, if you see the RAM Modeler license is 'Disabled", it is possible that your license has a restriction set up and all the licenses you are entitled to are in use. If you know who might be using the license, you can ask him to let you know when he is done and ask him to exit from RAM Manager. Now, wait for a little while and go back to your License Management Tool -> Activation Status; select RAM Modeler and click on 'Activate'. It should change from 'Disabled' to 'Activated'.

Hi,

I'm getting shear reinforcement in the slab where there shouldn't be any shear reo. According to AS3600 there shouldn't be any shear reo if V*<phiVuc 8.2.5).

Why RAM Concept constantly provides shear reo? In the report it specifies: transverse bar found, but there's no mentioning where it's coming from (see part of report below, where V*=64<phiVuc=272)

Starting 8.2 Shear Check
Considering Effect of Torsion on Shear:
No torsion to consider
No torsion reinforcement required
General Shear Design Parameters
bv = 1828 mm
do = 219.1 mm
bvd = 400500 mm²
Ac = 457100 mm²
Ast = 2632 mm²
Apt = 0 mm²
Ac = 457100 mm²
fc = 40 N/mm²
fsyf = 500 N/mm²
V* = 64.12 kN (absolute value)
M* = 20.26 kN-m
Setting Vo to zero for RC cross section
Setting Pv and Apt to zero for RC cross section
Calculating Web-Shear Cracking Vuc (8.2.7.2(b))
Precompression Stress = -0.0002275 N/mm² (at centroid)
Failure Tensile Stress = 2.277 N/mm²
Shear Stress Limit = 2.277 N/mm² (at centroid)
I = 2380000000 mm⁴
Q = 14280000 mm³
Vt = 693.7 kN [(limit stress) * bv * (I/Q)]
Vuc (web cracking) = 693.7 kN (Vt + Pv)
Calculating Flexure-Shear Cracking Vuc (8.2.7.2(a))
Beta1 = 1.519
Beta2 = 1
Beta3 = 1
Shear Stress Term = 0.6406 N/mm² ([..]¹´³)
Vuc (flexure-shear) = 389.7 kN
Vuc = 389.7 kN
Vu,max = 3204 kN
Less than minimum ligatures required, using large shear lig spacing (0.75D or 500 mm)
Maximum lig spacing = 187.5 mm (considers torsion lig spacing also)
Calculating Compression Strut Angle
Using 0.6062 instead of 0.6 for compatibility of 8.2.8, 8.2.9 and 8.2.10
Asv,min = 260.2 mm² (at max spacing)
Vu,min = 653 kN
Vu,max = 3204 kN
V*/phi = 91.6 kN
Theta-v = 30 degrees
Adjusted Vu,max = 3204 kN (after considering 8.3.3)
Transverse Bar Found:
As = 260.2 mm²
Fy = 500 N/mm²
Spacing = 187.5 mm
Vus = 263.3 kN
Total Vus = 263.3 kN
Vu = 653 kN
phi Vu = 457.1 kN

The most recent version of FloorVibe I have on my machine is 1.3 - is it possible to get an update posted here?  This wiki article seems to indicate a more current version is available: http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8142

Thanks

Error or Warning Message

When attempting to perform floor vibration analysis from the Steel Beam module, the following error appears:

Please specify the location of the FloorVibe.exe program using the following dialog.","FloorVibe location?

If canceled, the following error occurs:

FloorVibe program not found. Please verify that it is properly installed.

Explanation

FloorVibe is a third-party product developed by Dr. Murray of Structural Engineers, Inc. A link has been developed between the Steel Beam module in RAM Structural System and FloorVibe. Although FloorVibe integrates with RAM Structural System, it is installed separately. The two error messages occur when FloorVibe is not installed on a workstation.

Starting with RAM Structural System v14.07.00.00 the FloorVibe v2.02 installation will be embedded into the RAM SS installer and deployed on each workstation. 

How to Avoid

Install FloorVibe on the workstation. Based on a third-party agreement, users in the United States and the United Kingdom are provided with a copy of the FloorVibe installer through Bentley when a perpetual license for RAM Steel is originally purchased. Users in other countries can purchase FloorVibe directly from Dr. Murray by visiting http://www.floorvibe.com/.

Users who cannot locate a FloorVibe installer should contact technical support via the forums or SELECTsupport to obtain another copy of the installer. FloorVibe is distributed as a zip archive. To install the product, please expand the zip archive, and run Setup.exe. To avoid installation issues, do not run FloorVibe.msi or FloorVibeUK.msi directly. Regretfully we can no longer send the very latest version of FloorVibe. If you need to user version 2.10 or later, visit http://www.floorvibe.com/.

See Also

[[RAMSS FloorVibe FAQ]]

[[SELECTsupport TechNotes and FAQs]]

How can I display the code provision that governs the design of program reinforcement?

The code controlling provision can be displayed on screen for all cross sections on any reinforcement plan on the Design Status or Rule Set Design Layer. To view the controlling criteria:

1. Open a reinforcement plan on Layers - Design Status or Layers - Rule Set Designs.
2. Open the Visible Objects dialog. This can be done by clicking on the visible objects dialog or clicking on
   View - Visible Objects or right clicking within the active plan window and choosing
   Visible Objects.
3. In the Visible Objects dialog, check the box for Controlling Criteria.
4. Click OK to close the dialog. The governing code provision will display on screen.

In some cases, "Det" will display before the code provision. This means that the reinforcement is not explicitly required at that cross section but is extended into the section to satisfy another code rule. Typically, this is associated with span detailing requirements.

How do I model user reinforcement?

See Chapter 25 “Drawing Reinforcement Bars” in the RAM Concept Manual for more information. There are two main types of user reinforcement: concentrated reinforcement and distributed reinforcement. Concentrated reinforcement is a fixed number of bars over a parallelogram area. This type of reinforcement is convenient for modeling beam reinforcement. Distributed reinforcement is a bar spacing applied over a polygon area. This type of reinforcement is convenient for modeling layers of reinforcement over a portion or the entire slab area.

There are six tool buttons that can be used to model the reinforcement:

• Concentrated Reinf. (Click at Bar End Points)

• Concentrated Reinf. (Click at Center Point and an End Point)

• Concentrated Reinf.  Cross (Click at Cross Point and an End Point)

• Distributed Reinf. (Click along Region Boundary)

• Distributed Reinf. in Perimeter (Click at Bar End Points)

• Distributed Reinf. Cross in Perimeter (Click at Cross Point and an End Point)

The “Cross” tools are convenient for defining the reinforcement in both directions. The “Distributed Reinf. in Perimeter” tools are convenient for modeling reinforcement over the entire slab area.

The bar elevation is referenced from the center of the reinforcement segment. When defining reinforcement over an area with slab and beams or slabs with drop panels, make sure that this point is in the correct area. For example, if the reinforcement shown in the screenshot below is referenced to the drop panel and not the typical slab as was intended.

I am modeling an existing slab. Can I prevent the program from adding program reinforcement?

Go to Criteria – Calc Options and check the box for “Check capacity of user reinforcement without designing additional program reinforcement.”

When this is done, program reinforcement will not be added, and cross sections that do not satisfy the code requirements are shown as failing. Some users like to plot the bending moment demand and capacity diagrams at this point to see how badly the failure it, though of course there are other possible failures besides bending.

If user reinforcement has been provided and you are confident that it satisfies the code minimum requirements, you can also turn off the Code Minimum design rule completely under Criteria - Design Rules, though we do not generally recommend this practice.

What is the significance of defining the reinforcement “Slab Face”: Top, Bottom, or Both?

Slab face controls on what plan the reinforcement is displayed. By default, reinforcement defined as “Top” and “Both” are displayed on the top reinforcement plans; reinforcement defined as “Bottom” and “Both” are displayed on the bottom reinforcement plans.

The Slab Face also affects the way the reinforcement is used in the Code Minimum Check and Span Detailing. Options for the “Code Minimum Reinforcement Location” include Elevated Slab, Mat Foundation, Top, and Bottom. Each of these options is based on where the reinforcement is placed (top of slab versus bottom of slab). Span detailing extends top and bottom reinforcement to a certain percentage of the span length (see ACI 318-08 Fig 13.3.8 for an example of a span detailing rule). If "Both" is selected for the Slab Face, then the reinforcement will be extended to meet both top and bottom reinforcing requirements.

For mat foundations, the ACI code (R15.10.4) permits the minimum reinforcing steel to be split between the top and bottom faces. If "Both" is selected for the Slab Face, then the program will use both layers in the minimum reinforcement check.

Can I design a slab with one layer of reinforcement?

Program reinforcement is always detailed in two layers: top and bottom. Slabs with one layer of reinforcement can be modeled and designed using user reinforcement as follows:

1. Model user reinforcement in the slab. Set the Elevation Reference and the Elevation so that the reinforcement is in the correct location. Set the Slab Face to “Both.” This will force the program to use the reinforcement in the code minimum check at each cross section.
2. In Criteria – Calc Options, check the box for “Check capacity of user reinforcement without designing additional program reinforcement.” This will prevent the program from adding program reinforcement at the top and bottom face.
3. Run the analysis.
4. Check the Design Status for failures.
5. If needed, make changes to reinforcement size and spacing.
6. Re-run the analysis.
7. Repeat Steps 4 through 7 as needed.

How can I change the format of reinforcement on the Reinforcement Layer?

By default, program reinforcement is displayed showing bar quantity, bar size, length, and bar face. The format can be modified to include other information, like bar spacing, by doing the following:

1. Select the reinforcement on a plan on Layers – Reinforcement.
2. Click on Edit – Selection Properties. A dialog showing the bar information will display.
3. In the dialog, click on the Presentation tab.
4. Change the key value in the “Callout By Quantity Format.” See key and screenshot below:

$Q - Bar quantity       

$F - Bar face

$B - Bar name

$L - Bar length

$U - Bar length units

$u - Bar spacing units

$S - Bar spacing

\n - Start new line

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!

Can mat foundations be designed in RAM Foundation?

Mat foundations cannot be designed in RAM Foundation. Mat foundations modeled in RAM Structural System can be exported into RAM Concept for analysis and design using the Ram Manager - Design - Ram Concept option or from within Ram Concept using File - Sync Ram Structural System - New from RAM SS.

The estimated perimeter of the mat must be modeled to encompass all of the supported columns and walls, and some concrete deck also needs to be assigned to the mat in Ram Modeler.

See the following web page for more on importing RAM Structural System models into RAM Concept:

RAM Concept-RAM Structural System Integration

I can't assign base plates or anything else in the Foundation module, what's wrong?

Though foundations are designed in the Foundation module, they must be initially modeled like everything else in the Modeler. Rather than having a whole extra level type for foundations, we expect users to model foundations (using Layout - Foundations...) on the lowest framed level (e.g the second floor framing plan).

How is 1/3 overstress accounted for?

The allowable soil stress assigned to the footing is constant for all combinations. So, there is no good way to accommodate 1/3 allowable overstress in the design if it pertains to some, but not all of the load combinations. 

We suggest incorporating the equivalent allowable overstress into the soil combos, by using reduced load factors on the combos with short duration loads.

Alternatively, the model could be designed twice; once with only gravity combos and a lowered allowable soil stress, once using gravity and lateral combos with the higher allowable.

How is uplift and overturning design done for spread footings?

See this blog post for details: Spread Footing Overturning and Uplift Checks in RAM Foundation

Why does the required area of steel increase when I use larger diameter bars?

In small foundations, the longitudinal bars are only partially developed at the critical moment location. When the program reports the area of steel required it is increasing the value reported by dividing by the percentage of full development. With smaller bars the development length is shorter so less net area of steel is commonly required.

This check can be circumvented by assigning the bars to be hooked (Assign - Geometry command)

The same rule also affects continuous footings in the transverse direction.

Are foundation design live loads reduced?

Yes, the Foundation module uses the same live load reduction values for columns.

For lateral columns, the foundation loads should match Ram Frame analysis results.

For gravity columns, the loads can be taken from either the Ram Steel analysis results or the Ram Concrete analysis results, both of which are subject to Live Load reduction. See RAM SS Analysis Types for reasons why those two results can differ. See RAMSS Two Way Decks for limits on LL reduction for two-way decks.

See Also

RAM SS Analysis Types

RAMSS Two Way Decks

Structural Product TechNotes And FAQs

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!

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), 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 when the deck is two way. 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.

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

RAMSS Common Framing Table Errors

RAM SS Semirigid Diaphragms

Transfer Slabs

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 Structural Analysis and Design TechNotes and FAQs are now organized by Application in the navigation tree at the left. The links on this page are maintained for popular content. 

General (Licensing and Installation)

STAAD.pro  

STAAD Foundation Advanced

Ram Structural System  

Ram Elements  

Ram Connection  

Ram Concept

Microstran, Limcon and MStower 

What floor-to-floor height should I enter in the story data?

Whatever story height you enter into RAM Modeler, that is where the centerline of the frame beams will fall in the finite element model and vertical braces always connect to a work point at the beam and column centerlines. This is done for simplicity in the finite element analysis.

For drift sensitive structures, using a first story height that is equal to the distance from the ground level (or foundation level) up to the top of steel - average frame beam depth / 2 is probably the most accurate modeling (see "Alternate Story El." below). But using a distance from ground level to beam top of steel (a.k.a. deck bearing) is more common practice and is conservative in most aspects (see "Common Story El." below).

The common story approach is also used when the RAM SS 3D model is exported to ISM. In the ISM model the beam locations are established relative to the story datum based on the following rules:

• Non composite deck – top of beam, deck bearing at story datum
• Composite deck – top of beam, deck bearing at story datum
• Concrete slab – top of slab at story datum

Keep in mind, story height can also affect the following calculations:

• Calculated wind exposure (and Kz factors)
• "h" in the vertical distribution of seismic loads calculation (wi*hi/Sum (wi*hi))
• Overturning moment (related to lateral force times story height)
• Unbraced length for columns
• Slope angle and length of braces
• Material takeoff quantities
• And the elevation of the beams shown in the 3D view, or exported out to Revit, ISM, or dxf, which are all artificially adjusted to show all beams with top of steel at the story height.

How can I model a continuous beam?

In Ram Structural System, the framing must all be determinate, so multi-span indeterminate framing is not directly possible. There are two approaches to modeling and designing continuous beams. 

The first is to model each span as a lateral beam. use the same size for each span and be sure to assign the ends to be fixed. The supporting columns also need to be lateral, but they may be pinned (in the plane of the framing). To see the accurate member forces or steel design of the beams, use Ram Frame analysis and the Steel Standard Provisions respectively.

Alternatively, for those that do not have Ram Frame, the system can be approximated using a cantilever and suspended span approach. In other words, model one span normally and add a cantilever extension into the second bay. Then add a suspended span from the end of the cantilever to the third support (or add a cantilever beam in every other bay for continuous beams more then 2 spans long). The length of the cantilever is important here since it dictates the inflection point or point of zero moment.

When using the cantilever approach one side effect is that the supporting columns will assume zero eccentricity in the design.

Can a beam cantilever directly from a support with no back-span?

Yes, the option to create a stub cantilever or beam with a single support was added in version 14.02.  Prior to that version a dummy column of near zero stiffness and a lateral beam with one end fixed was required.

How can I create a sloping floor or roof?

There are some basic limitations to what you can model with RAM Structural System, so it may not be possible to model some structures perfectly, but you can usually get close. The following guidelines should help

• Every beam must have exactly two supports, never 1 or 3, and those supports must be on the same level type. So you can't directly model a bent beam forming a gable unless there is a support at the peak.
• You must be able to model the structure as a flat (wedding cake) type structure first, then create the slopes by changing column (and wall) elevations.
• Any time you have a step (two beams framing into the same support at different elevations), two levels types and two stories are required and the higher beam must be on the higher story.
• You can raise or lower a column (or wall) using the Layout - Column - Modify elevation command and thus slope beams that connect to it. If you want to lower the column more than the story height, then you must also lower the same column on the next lower story. If you want to raise the column more than the story height of the level above, then you must also raise the same column on the level above. Think of the column like a string with beads on it at each story. As you modify the elevation you are lowering the bead, but you cannot cross another bead. In the end, the beads must be at least 0.1’ apart (more separation is preferred).

Other things to note:

• You can have a rigid diaphragm that is sloped, but in RAM Frame this is treated as a horizontal diaphragm. We don't analyze sloped rigid diaphragms. Furthermore, if your structure is subject to trust, diaphragms should be turned off at least while investigating gravity loads. Using a sloped semi-rigid diaphragm is an alternative.
• The gravity steel and concrete beam design will not include any effects of axial forces.

How can I model a 2 story brace, or one that skips a level?

When a brace needs to skip a level use Layout - brace - Add Special and follow the prompts at the bottom left.

For details on how these braces effect frame story shear reporting, please reference [[RAM Frame - Building and Frame Story Shear]].

I have a brace in 3D that does not appear in any elevation view. How can I delete it?

There are two ways to remove rogue braces that are no longer in an elevation view that can be selected.

1. If the braces do not connect to any frame members at either end, then an integrated data check can be performed and the following message will appear: "Some Braces do not attach to Nodes. Do you want them deleted?". Click "Yes" to have them removed. Note – if the brace is connected to a lateral member at one end, but not the other, this message will not appear, so you may need to make some supporting beams or column gravity temporarily.
2. Delete and re-enter the story data for this particular level. This will remove all braces at that level.
    

How do I model a transfer girder, or a column setting on a beam?

On the upper story level model the column as a standard column (not a hanger).

On the lower level model the beam passing through the location of the column above. This could also be a beam cantilever.

Use Reference layout types (under the options menu) or construction grids to aid in the alignment of the column and beam below.

I have a column that supports the roof, but does not support anything at the lower level. Do I have to model the column on both layouts in RAM Modeler?

Think of the RAM SS Layout type like a section through the whole structure. Any columns that are cut by the section should be modeled on that layout typically. Don't worry, the program will design the column for the correct, longer unbraced length so long as there are no beams (or optionally decks) at the intermediate story to brace the column.

There is one alternative, however. If the column is only modeled on the Roof, and not modeled on the lower level at all, then you can add a foundation under that column and lower the foundation to stretch the column to the full height. This approach can be helpful in cases where the column is sloped and the story heights are not constant making it hard to determine the exact bottom offset to keep the two-story column in one straight line.

Why am I unable to copy information or import a DXF into a layout?

The Copy and Import from DXF features (RAM Modeler - Layout - Type menu) are only active for layout types that contain no information. These commands are deactivated in RAM Modeler even if the layout contains only grids and no other objects. To use either command, create a new layout and then use the copy or import features before any other information is defined on the layout.

How Do I Model Grade Beams?

Although there is currently no direct way to model grade beams in RAM Structural System, they can be simulated by modeling concrete beams and designed in RAM Concrete. These basic steps produce satisfactory results for most configurations.

1. Model a grade level that contains the concrete grade beams supported by columns. The top of the columns should be pinned and the bottom fixed.
2. Model a slab edge on the grade beam level and assign a noncomposite deck with no self-weight. This is necessary so that there is a diaphragm present on the level in RAM Frame.
3. Add the grade level to your story data.
4. In RAM Frame, set the ground level to the grade level.
5. Run the RAM Frame analysis and RAM Concrete Beam design.

By creating a rigid diaphragm at the grade level with the nodes at the grade beam - column intersections to it, translation is restrained when the ground level is set to the grade level. Therefore, no shear will exist in the column stubs. Since the top of the column stubs are pinned, no moment will be developed in the column stub below the grade beams. Spread footings or pile caps can be modeled at the column stub locations. The foundation loads will only be vertical forces.

There are a couple of important things to note. First, automatic calculation of effective length factors may be inaccurate for this procedure. No boundary condition is assumed at the lower node of the column above the grade beam level. Therefore, the G value for the lower node is a function of the column and grade beam stiffness in the direction being considered. If this is not an accurate assumption, the effective length factor should be explicitly defined. Second, don't specify a story height on the grade beam level that is too small. Using an extremely small story height is not necessary because there will be no translation of the grade beam level and only vertical forces in the stub columns. The only ramification of using a larger story height is an increased self-weight for the stub columns. If you use too small of a story height you might produce a poor mesh if lateral walls are modeled on the grade beam level.

How can I change a Beam’s material property from Steel to Concrete?

In the RAM Modeler first change the material to “Concrete”. Then go to Layout>Beam>Change Material. This process also applies to columns and braces.

See Also

RAM SS - Using DXF as a Reference Layout

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

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!

Problem Description

1. After installing RAM Connection v9.0, converted v8 stand-alone .cnx files originally designed using the AISC-05 ASD code are switched to AISC-05 LRFD without notice.

2. Changes to the design code in Ram Connection Stand-Alone do not affect existing joints in the file.

3. Changing the design code in one file affects the design code for future connections in existing files. In other words, the design code setting is per user, not per file.

4. Changes to the either the main Hot-rolled Steel design code or the Connection design code in Ram Elements do not affect the design code used for existing connections in the model.

Explanation

The connection templates associated with different codes are not interchangeable, so switching the design code could invalidate existing connections. Rather than break the existing connections in that way, it was decided to keep the original assigned code for each connection even when the assigned code is changed.

A change request has been logged to allow changes in the design code for the 4 US codes to retroactively alter existing connections, however. 

Steps to Resolve

In all three cases, the design code must be set to the desired code and then new connections assign to the joints. The following article shows where to set the codes: Ram Connection Codes

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

>

Note:  Version 14.06.01 is now available for download. Instructions for downloading installation files can be found here:

Accessing SELECT Services Online

RAM Frame In-Core Direct Solver

Problem:  Analysis time with the In-Core Direct Solver (selected in RAM Frame - Criteria - General, see figure below) is significantly slower in v14.06 than in earlier versions.

Work Around:  Analyze using the In-Core Direct Sparse Solver.

Resolution:  This issue was resolved in v14.06.01.

RAM Concrete Shear Wall Performance

Problem:  In the 64-bit version, models take a significant amount of time to load into the module. Other operations, like assigning wall groups and running the designs, are significantly slower.

Work Around:  Install the 32-bit version. Note that this can affect integration with RAM Concept. See following web page:

RAM Concept-RAM SS Integration

Resolution:  This issue was resolved in v14.06.01.

Fixed Braces and Calculated Reactions and Story Shears

Problem:  If braces are not pinned, the moment and shears in the brace member is not accounted for in the calculated reactions, frame story shears, and building story shears.

Work Around: None.

Resolution:  This issue was resolved in v14.06.01.

Column and Footing DXF

Problems:  When changing the Color/Layer options in the Footing Schedule tab, a crash occurs. When attempting to create the dxf, an “Error Opening Master Table” error appears:

After clicking Ok and trying to generate the DXF again, a series of “Key Already Present…” errors similar to the one below appears:

After clicking OK to bypass these errors and generate the DXF again, no file is created.

Work Around:  None

Resolution:  This issue was resolved in v14.06.01.

CAN/CSA S16-09 Minimum Composite

Problem:  The S16-09 Specification permits a percent composite as low as 40% when using composite action for the strength requirements, but the program was using a minimum of 50%.

Work Around:  None.

Resolution:  This issue was resolved in v14.06.01.

CAN/CSA S16-09 Modular Ratio, n_s

Problem:  In the calculation of shrinkage deflection the modular ratio n_t is used in S16-01 but the modular ratio n_s is used in S16-09. These values are quite different. The program allows for the user to specify n_t in Criteria – Canada Parameters in the RAM Manager but there is nowhere to specify n_s. The program, without indicating so in the user interface, is using the value specified for n_t for n_s when designing per S16-09.

Work Around:  When designing per S16-09, input the correct value of n_s where n_t is input. Note that S16-09 doesn’t use n_t, so there is no conflict with inputting the one value for the other.

Resolution:  This issue has been resolved in v14.06.01. The program will internally calculate n_s, it will not need to be specified by the user.

Defaults Utility setting for Snow vs. Roof Live load reversed

Problem:  If the option "Consider Snow Loads, Ignore Roof Live Loads" is selected in the default utility, then roof live loads are incorrectly considered and snow loads are ignored in new models. If the option "Consider Roof Live Loads, Ignore Snow Loads" is selected in the default utility, then snow are considered and roof live loads are ignored in new models. In other words, the setting works in reverse.

The selected setting for each model under Criteria - Member Loads works correctly, it is only the default setting for new models that is reversed. 

Resolution:  This issue was resolved in v14.06.01.

ISM - Update Repository Does Not Add New Items

Problem:  When updating an ISM repository from RAM SS, members or properties that were added to the RAM SS file are not added to the repository. This includes new beams, braces or composite beam stud zones to name a few.

Work Around:  This issue was resolved in v14.06.01.

When I try to create a new file, I get an error regarding tables.

Problem: When I try to create a new file, I get the following error:

"The specified Default Castellated Smartbeam Table (ramuk) could not be found, and neither was the table corresponding to the current setting from RAM Defaults (ramuk)."

Solution:

• Go to tools - Ram Defaults Utility (click OK if you get a message)
• Scroll down to Steel Beam defaults
• Double Click Steel Beam Tables options
• Make sure you have a valid selection, then click next and next until done with the tables part.

Note, with version 14.06.00.00 tables now get saved with the file which is a new thing. If you try to convert a model from an older version and the custom tables used with the original file are not present on the PC converting the file you can get similar error.

When I convert a v14.05 file with embedded Concept files, all design strips are missing.

Problem:  Embedded RAM Concept files are deleted during file conversion when v14.05 are opened in RAM Concept for both 32-bit and 64-bit versions. This removes all design strips and any other modified data, like changes made to slab areas or beams, that were saved with the file.

Work Around:   

1. Open the file in v14.06 and convert the file to the new version format.

2. Open Windows Explorer and find the .zip file with "Orig v14.5" at the end of the file name that is automatically created during the conversion process. Double click on the file. Find the embedded .cpt files. The file name will be same as ram model with .cpt###E at the end. Copy the files to the clipboard.

3. In Windows Explorer, navigate to the working directory (C:\Program Data\Bentley\Engineering\RAM Structural
System\Data\Working). Paste the embedded .cpt files from the v14.5 backup into this folder.

4. Launch RAM Concept from RAM Manager.

Resolution:  This issue was resolved in v14.06.01.

See Also

RAM SS V14.06.01 Release Notes

[[SELECTsupport TechNotes and FAQs]]

As Windows 8 becomes more prevalent, compatibility of structural products with the new operating system becomes a concern. This article lists what products are officially compatible.

How to determine compatibility

The search results on Bentley's Software Downloads page display the supported operating systems for each program. Programs that support Windows 8 will display "Windows 8" and/or "Windows 8 x64" in the Certified On column. Programs that do not list Windows 8 may still run, but they have not been adequately tested yet under the new operating system. Consequently, use of the programs on an unsupported operating system is at your own risk.

Products that support Windows 8

As of September 23, 2013, the following products officially support Windows 8:

• RAM Elements V8i 13.00.03.45
• RAM Connection V8i 08.00.01.34
• STAAD.Pro V8i 20.07.09.21 and later

See Also

[[SELECTsupport TechNotes and FAQs]]

I have a valid license for Multiframe Advanced module; when I generate a report, I see watermark in it saying "not for commercial use".

There was probably a “text” added in the “Printing Title” heading for printing reports of your model. In this case, you can do the following;

1.             Go to “File” menu

2.             Select “Print Window…”

3.             Click on “Titles” button

4.             Untick “Title” selection box or delete the “text” in the fill in box

Activation - Licensing - Multiframe

Semirigid Diaphragms in RAM Frame

General

Semirigid diaphragms are discussed in section 6.12.3 of the Ram Frame Analysis documentation.

Diaphragm Flexibility

ASCE 7-05 Section 12.3 (note IBC 2006 Section 1613.6.1 modifies this slightly) discusses diaphragm flexibility. Diaphragms should be analyzed as semirigid unless they can be idealized as flexible or rigid. A diaphragm idealized as rigid is assumed translate and rotate as a rigid membrane. That is, there are no relative horizontal displacements between nodes attached to a rigid diaphragm and the nodal rotations about the vertical axis are always the same. In RAM Frame, even if the diaphragm is sloped the rigid diaphragm constraint is applied to a horizontal plane. The distribution of story shears to the individual frames/walls is a result of the analytical behavior which depends on the relative rigidities of the individual frames/walls. If the load is not applied through the center of rigidity then there will be a torsional moment on the diaphragm. A diaphragm idealized as flexible has no stiffness and there is no torsional moment. Shears should be distributed to the individual frames/walls based on tributary area. A semirigid diaphragm is somewhere between these idealized cases. An infinitely stiff semirigid diaphragm will behave like a rigid diaphragm and a complete lack of stiffness in the diaphragm will result in behavior similar to a flexible diaphragm. The figure below was taken from http://www.gostructural.com/article.asp?id=1131and is a nice flowchart for determining if your diaphragm can be idealized as flexible or rigid.

You can understand what the code is trying to do by thinking about a continuous beam with spring supports. With pinned supports, the reactions under any loading will be pretty much the same regardless of the beam stiffness. However, if the support deformation is not negligible (springs), then the reactions will be highly dependent on the beam stiffness unless the beam is extremely flexible or rigid relative to the spring stiffness.

The criteria for determining if a diaphragm can be idealized as flexible are pretty clear in ASCE 7-05. Section 12.3.1.1 basically says that untopped metal decks and wood diaphragms should be considered flexible unless you have moment frames. If you do have moment frames, Section 12.3.1.3 can be used to determine if the diaphragm can be considered flexible. The requirements for idealizing a diaphragm as rigid are not as straight forward because concrete slabs and concrete topped decks must have a span to depth ratio less than 3 and not have any horizontal irregularities that are defined in ASCE 7-05 Table12.3-1. RAM Frame does not determine if you have a horizontal irregularity. However, the output can be used to help determine if you have an irregularity. For example, RAM Frame Analysis > Process > Results > Drift at a Point or Drift at Control Points can be used to look at rigid diaphragm displacements at locations other than the center of mass. The displacements at the center of mass are shown in the RAM Frame Analysis > Reports > Story Displacements.

Semirigid Diaphragm Stiffness

The deck property tables in RAM Modeler require that you enter an Effective Thickness, Poisson's Ratio, and Modulus of Elasticity for non-composite and composite decks. For concrete slabs, the Modulus of Elasticity is calculated from the concrete properties. You still specify Poisson's Ratio and the Slab Thickness. There is an additional parameter that allows you to apply a diaphragm cracked section factor for concrete slabs.

ASCE 7-05 does not provide guidance as to what the stiffness of semirigid diaphragms should be. The stiffness of untopped steel roof decks is a function of many parameters including warping and fastener patterns. The Steel Deck Institute has published a method for determining a shear stiffness parameter (G`) in their diaphragm design manual. This method is typically presented in the deck manufacturer's catalogs. RAM Frame requires a modulus of elasticity be defined and the shear modulus is calculated based on Poisson's Ratio. Appendix A shows a method to approximate the effective modulus of elasticity for untopped steel decks and provides an example for a Vulcraft deck.  This effective modulus should be used in conjunction with a deck thickness equal to the gage of the sheet metal. 

Concrete slab and composite deck stiffness require engineering judgment. ACI 318-02 Section 10.11.1 provides effective moment of inertias for various structural members. There isn't a factor for diaphragms but the wall factors are probably the most appropriate. ACI states that 0.7Ig should be used for uncracked walls and 0.35Ig should be used for cracked walls. You could run a hand calculation on your diaphragm to get an idea of what the stresses might be and compare those stresses to the modulus of rupture. Alternatively, you could envelope the stiffness and run the model twice: once with 0.35Ig and once with 0.7Ig. For a concrete slab you just need to enter the factor for the diaphragm cracked section factor. For a composite deck you would incorporate the cracked factor into the assumed effective thickness. For example, if you have 4 inches of concrete above the flutes and want to use 0.35Ig the effective thickness is 0.35 * 4 = 1.4 inches. It is probably appropriate to enter the Modulus of Elasticity and Poisson's Ratio for concrete and ignore the stiffness of the steel deck. If you want to consider a portion of the concrete within the flutes you should modify the effective thickness accordingly.

The maximum distance between nodes in the mesh specified in RAM Frame > Criteria > General will impact the behavior in the model. If you are not sure what mesh size to use, run a few iterations with smaller and smaller maximum distances. The displacements should converge. Once the change in the displacements is negligible you know your mesh size is adequate. The program also has the ability to use the slab edge or the perimeter beams/walls as the diaphragm boundary. If you have small slab edge offsets the elements within the edge will be poorly meshed. In these situations use the perimeter beams/walls as the diaphragm boundary.

Effect of beams connected to the diaphragm

In Ram Frame, only the lateral members are considered in the finite element model (see RAM SS Analysis Types for details). Consequently, any beam that needs to stiffen the diaphragm through its axial rigidity needs to be defined as a lateral member.

Dynamic Analysis with Semirigid Diaphragm

RAM Frame ignores the stiffness of gravity members in the finite element analysis. When a semirigid diaphragm has little out of plane stiffness you may see mode shapes associated with the vertical vibration of the deck. There are options in RAM Frame > Criteria > Diaphragm to include out-of-plane stiffness and/or include gravity columns and walls as springs to help prevent these mode shapes from occurring. In some scenarios, primarily with sloping diaphragms, this might not completely alleviate the issue. In these situations you may have to model all of the framing as lateral members so that their stiffness is considered in RAM Frame. Please note, static wind and seismic cases default to using calculated frequencies and periods. These calculated values require an Eigen solution (dynamic analysis). A simple work around would be to explicitly define the frequencies and periods rather than use the calculated value. That way the Eigen solution is not required unless you have created a dynamic load case. If you are unsure of what frequencies or periods to enter you could run the model with rigid diaphragms using the calculated values. The loads and applied force report shows the frequencies and periods used in the wind and seismic cases.

Mass is distributed spatially when semirigid diaphragms are used.  It is not lumped at the center of mass (or eccentric location) like a rigid diaphragm.  Therefore, there are many more mass degrees of freedom in the model.  Also, since the mass distributed spatially, there are no rotational mass degrees of freedom.  If you have semirigid diaphragms, create an dynamic - Eigen solution load case and reduce the number of periods the program attempts to find.  In general three times the number of diaphragms is a reasonable number of modes to start with.  Then, review the periods and modes report and ensure that you have at least 90% mass participations (minimum per ASCE 7) in the X and Y directions.

In version 14.06 an option to use Ritz vectors to solve the eigensolution was added (see Criteria - General). Using the Ritz vector approach has helped to eliminate the presense of these diaphragm flapping mode shapes in some cases.

Analytical Behavior of Semirigid Diaphragms Under Gravity Loads

RAM Gravity calculates the gravity load tributary to the lateral members and applies them as point loads or line loads in the finite element analysis in RAM Frame. A semirigid diaphragm has stiffness and will impact the forces in your lateral members. For a flat diaphragm with no out-of-plane stiffness these effects will be minimal. Including out-of-plane stiffness in the diaphragm will have a significant impact on the member forces. Essentially, the diaphragm will behave as a flange at the beam centerline. However, the forces in the diaphragm are not included in the beam results. You get into a scenario where the diaphragm is now acting like a slab and is spanning from column to column and is sharing the beam load. This is probably not the behavior that you are looking for and the results will not be correct.

When the diaphragm is sloped the impact on the member forces is even more significant. Consider gabled roof framing modeled as lateral members. The ridge beam will see very little bending because it is being propped up by the diaphragm which has a large stiffness component in the vertical plane of the ridge beam. The diaphragm acts like a deep beam and ends up taking the majority of the load and spans from column to column. Similarly, the gable frame which normally would resist the horizontal trust under gravity loads will see little load. There really is no way to get accurate gravity forces for this configuration in RAM Frame while using a semirigid diaphragm. It is best to size the beam for gravity loads in RAM Frame with the diaphragm assigned as flexible. If the member is part of the lateral force resisting system you would then take these gravity forces and combine them manually with the semirigid analysis lateral forces and design the beam by hand.

Analytical Behavior of Sloped Semirigid Diaphragms Under Lateral Loads

Lateral loading applied to sloped semirigid diaphragms is applied in the XY plane, not in the plane of the diaphragm. Therefore, a component of the applied load acts out of the plane of the diaphragm. The stiffness of gravity members is ignored and significant out-of-plane deformations might be observed depending on the diaphragm stiffness. In particular, this is a problem when trying to simulate metal deck stiffness as described in Appendix A. Appendix A is a method to approximate the in-plane stiffness of metal decks and the resulting diaphragm properties will yield very little out-of-plane stiffness. Currently, it is not possible to model an orthotropic material or specify different stiffness factors in-plane and out-of-plane. The only way to control the diaphragm displacements is to model the gravity members as lateral so their stiffness is not ignored. However, this will impact the forces in the actual lateral force resisting system.

Semirigid Diaphragms for Two Way Slabs

Out-of-plane stiffness is assumed when the deck is two way. 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 but the shears stay the same. The rotation of the building is being resisted by the gravity column springs and out-of-plane diaphragm stiffness. 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 would decrease. Conversely, if there was negligible diaphragm stiffness the moments would not change. In the RAM Concrete Shear Wall Module all of the forces, including gravity forces, come from RAM Frame. If you intend to design the shear walls in RAM Concrete it is important to recognize how the Frame results will be impacted when the diaphragm is semirigid and out-of-plane stiffness is being considered.

Appendix A

See Also

[[RAM SS Walls FAQ]]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

RAMSS Two Way Decks

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 TechNotes and FAQs in this section cover various topics that pertain to RAM Connection. Use the navigation tree on the left to browse or the popular links below.

• RAM Connection is installed, but the Connection button fails to appear in RAM Elements
• RAM Connection Capabilities and Modeling FAQ
• Troubleshooting Errors when Assigning Connections
• RAM Connection Stalls When Assigning Base Plate Connection
• Catastrophic Failure Error when Using Customized Anchor Position
• RAM Connection Extended End-Plate Moment Connections (MEP)
• RAM Connection Base Plate FAQ
• Tips for Using RAM Connection within STAAD.Pro [TN].
• How to Customize a RAM Connection Template in STAAD.Pro
• What Connection Types are available in RAM Connection to the design code BS 5950?

Problem Description

After installing RAM Structural System x64, the program fails to open. Attempting to open either the desktop or Start menu shortcut for RAM Structural System does nothing.

Steps to Resolve

This is a known issue (TR 4020) that affects only some workstations running a 64-bit operating system. Until the issue is resolved, install the 32-bit release as a workaround.

The following steps should be followed to apply the workaround:

1. Uninstall RAM Structural System x64 from either the Add or Remove Programs (Windows XP) or Programs and Features (Windows Vista/7/8) control panel.
2. Install RAM Structural System. The installer starts with ramm instead of ram (e.g. ramm14060100en.exe) and does not include 64 in the name (e.g. ram6414060100en.exe).

The issue also occurs when the Ram Modeler license is disabled.

Problem Description

If the Ram Modeler license is disabled you will not be able to open Ram Structural System (Ram Manager) at all. 

Steps to Resolve

Open the License Management Tool. This is ordinarily done from Ram Manager - Tools - Manage Licenses..., but if the Ram Manager won't start it can also be done by starting the License Management Tool from another application, or by double clicking the LicenseTool.exe from the folder where it is installed. A Windows Search for "LicenseTool.exe" usually finds it quickly.

In the License Management Tool, on the Activation Status screen, if you see the RAM Modeler license is 'Disabled", it is possible that your license has a check-out only restriction set up and all the licenses you are entitled to are currently in use. Check on the License Checkout tab in this case. If a License for Ram Modeler is available, check it out using the current version information. If no license is available, then one must be checked back in before using RAM Modeler on this machine. 

After the license is checked back in, return to the License Management Tool -> Activation Status screen, select RAM Modeler, and click on 'Activate'. It should change from 'Disabled' to 'Activated'.

See Also

[[RAM Manager fails to open on 64-bit OS]]