The TechNotes and FAQs in this section cover various topics that pertain to SACS. Additional content resides in the Offshore Product Community

Hi,

In the below picture I'm happy with the shape of the BMD (plot on tension face), however I would like it to report the midspan moment as positive and the support moment as negative. Is this easy enough to change? 

Hello again.

I was adding some user shear reinforcement to a model recently (hurray for this being a feature now), and had some things happened that piqued my interest.  I started digging around in the audit report to better understand how Concept is calculating the required shear reinforcement.  So far, I have everything worked out except for the 'Available Vn'.  I cannot seem to resolve how this value is being calculated. I have a feeling it still has to do with Eqn 11-18, but have not been able to quite work out what is being used for that value.

Also, in the attached model and auditor screen shot, you can see that the calculated value for 'Minimum additional design Av/s' (0.03765 per ACI eqn 11-23) is greater than the Av/s calculated for torsion (0.03337).  However, the final design Av/s used is the (shear Av/s) + (the torsion Av/s), which is less than the (shear Av/s) + (minimum torsion Av/s).  Is this done for a certain reason?

Finally, on a totally unrelated note, I was hoping that I could get some assistance in the forum with this post:

http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/16105.ram-concept-tabular-input-etabs-link.aspx

Is there a working version of the spreadsheet mentioned in this post that could be shared before the examples in that post are finalized?  Having the ability to use tabular input in Concept will be extremely helpful for a project that I have coming up in the near future.  If the VBA spreadsheet isn't near completion yet, would it be possible for one of you to send me a GCFF example file that I could use to begin making my own version of this spreadsheet (not really interested in converting STAAD to Concept...more in creating input files from scratch and importing to concept).  If you could send me a GCFF file that represents the attached Concept model...I feel like that would be more than enough for me to get moving with this tool on my own.

Thanks for the help

Phil

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

Available MEP Connections

RAM Connection can design extended end-plate connections using the design guidelines in AISC Design Guide 4 (DG4) or AISC Design Guide 16 (DG 16).

Older versions of RAM Connection only support extended MEP connections designed per DG4. The DG16 MEP connections were added in v8.0.0. In the same release, the ability to specify flush end plates and multiple rows of bolts was also added in the same release. Release notes for RAM Connection v8.0 can be found here: RAM Connection v8.0 Release Notes

Differences between DG4 and DG16 Connection Templates

The design philosophy in DG4 is discussed in detail in Section 2.2.3 of the Design Guide. Briefly, the design method in DG4 assumes a strong column, strong connection, and a weak beam. The end plate and column flange are assumed to remain elastic, and no prying forces are assumed in the bolts. The design guide refers to this behavior as "thick plate behavior." Thick plate behavior is ensured when the no prying bolt strength is less than or equal to 90% of the end plate and column flange strength. See equations below:

Where, Mnp =  No Prying Moment and M = Flexural Strength of Plate or Column Flange

The design philosophy in DG16 allows for prying action in the bolts. Connections designed per DG16 are designed for either "thick plate behavior" (no prying action) or "thin plate behavior" (prying).

Comments on RAM Connection Design

RAM Connection checks both the end plate and column flange for thick plate behavior using the equations from the applicable Design Guide. A summary of the plate/column flange behavior is summarized in the Section "Plate/Column Behavior" in the Results Report:

If either the end plate or the column flange exhibits thin plate behavior, a warning message will be identified in the Results Report:

When using a DG4 Connection, this warning should not be ignored. It means that one of the assumptions of the design method has been violated. Changes will need to be made to either the end plate or column size for a valid design.

See Also

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!

I am about to design the frame connection and I choose to use RAM Connection in staad.. but I find it difficult to use... my connection is a Shear and Moment resisting connection but the choices in Basic, and Smart are separate design for Moment and Shear, is their any hint on how to design that connection in one assignment. Please help me enlighten with this issue. Thank you

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!   

RAM Structural System

Latest Major Version

• [[RAM SS V14.06.00 Release Notes]]
• [[RAM SS V14.06.01 Release Notes]]
• [[RAM SS V14.06.02 Release Notes]]

Previous Versions

• RAM SS V12.1.X Release Notes
• RAM SS V13.0 Release Notes
• RAM SS V13.0.2 Release Notes
• RAM SS V13.0.3 Release Notes
• RAM SS V13.0.4 Release Notes
• RAM SS V14.00 Release Notes
• RAM SS V14.00.01 Release Notes
• RAM SS V14.00.02 Release Notes
• RAM SS V14.00.03 Release Notes
• RAM SS V14.00.04 Release Notes
• RAM SS V14.02 Release Notes
• RAM SS V14.02.01 Release Notes
• RAM SS V14.02.02 Release Notes
• RAM SS V14.03 Release Notes
• RAM SS V14.03.01 Release Notes
• RAM SS V14.03.02 Release Notes
• RAM SS V14.03.03 Release Notes
• RAM SS V14.04 Release Notes
• RAM SS V14.04.01 Release Notes
• RAM SS V14.04.02 Release Notes
• RAM SS V14.04.03 Release Notes
• RAM SS V14.04.05 Release Notes
• RAM SS V14.04.06 Release Notes
• RAM SS V14.04.07 Release Notes
• RAM SS V14.05.00 Release Notes
• RAM SS V14.05.01 Release Notes
• RAM SS V14.05.02 Release Notes
• RAM SS V14.05.03 Release Notes
• RAM SS V14.06.00 Release Notes
• RAM SS V14.06.01 Release Notes
• RAM SS V14.06.02 Release Notes

Hi, 

In regards to the following:

"The reactions are shown per straight section of wall. Can I see the reaction per element?

No. This is not available because there would be too much information shown. "

Obviously in most cases we design walls per metre length (1m wide vertical strips). In the past I have resorted to modelling walls below as a line supports and then trying to average/rationalise the Fz loads to get an idea of the compression loads. 

Surely this could be a future area where RAM Concept could be improved. The amount of information reported would be similar (if not less!) than modelling walls as line supports. 

If this isn't possible, then what advice would you be able to give in regards to accurately determining wall reaction per metre? Get the total Fz reaction and divide by the length of the wall? I know that is very very lower bound....

Thanks for the help

Problem Description

After installing RAM Connection v9.0, the Connection toolbar and Conn tab in RAM Elements no longer appear.

Explanation

RAM Elements 13.00.03.47 and earlier does not support RAM Connection v9.0. RAM Connection for RAM Elements v8.0 must remain installed in order to use the connection module in those versions of RAM Elements. If RAM Elements for RAM Connection was uninstalled before installing RAM Connection v9.0, then the Connections toolbar and Conn tab will be removed.

Steps to Resolve

Option 1

1. Install Ram Elements 13.02.00.99 or later.

2. Make sure the License configuration within Ram Elements is set to "use a Ram Connection License in each session". See this article for details. 

Option 2

The following steps can be used to restore Ram Connection 8 functionality with Ram Elements 13.00.03.47 or earlier.

If RAM Connection v9.0 has not been installed, make sure that RAM Connection for RAM Elements is not uninstalled prior to running the installation setup.

If RAM Connection v9.0 has been installed and RAM Connection for RAM Elements was uninstalled, open the Setup.exe file in C:\Bentley Downloads\rc08000023en. If this file is not found, download the installation for RAM Connection v08.00.00.23 from the SELECT download page. Click here for instructions on accessing the download page.

In the setup dialog, click the link labeled "Install RAM Connection for RAM Elements" as shown in the screen capture below to reinstall the component.

See Also

[[RAM Connection is installed, but the Connection button fails to appear in RAM Elements]]

Why does RAM Elements also retrieve a RAM Connection license?

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

Error or Warning Message

When opening RAM Elements, the following error occurs:
HWLockDLL internal error. Unable to get license.

Explanation

HWLockDLL is a licensing library used by some RAM programs to communicate with the Bentley IEG License Service. The error will occur if the 32-bit release of the Bentley IEG License Service is not installed. This can occur if the 64-bit release, known as Bentley IEG License Service x64 is installed instead. Programs that are 32-bit will only communicate with the 32-bit release of the Bentley IEG License Service.

How to Avoid

Please open the Add or Remove Programs (Windows XP) or Programs and Features (Windows Vista/7/8) control panel, and ensure that the Bentley IEG License Service is installed.

To locate the IEG License Service using the new Fulfillment Center, just start typing IEG in the search box.

Important: RAM Elements and other 32-bit programs cannot communicate with Bentley IEG License Service x64.

If the above does not resolve the problem, remove the HWLockDLL.dll file from the following location:

C:\Program Files (x86)\Common Files\Bentley\Engineering\RAMHWLock

Then, perform a repair of the RAM Elements installation to restore the file.

Server Based Installations

Typically we recommend that the software be installed on each PC that needs to use it. In at least one case on a Windows 2012 terminal server, a user was able to get Ram Elements to function, but only after manually registering the HWLockDLL. To do that go to Start - and type "Run" + enter to get the command prompt. On the command prompt execute:

regsvr32  "C:\Program Files (x86)\Common Files\Bentley\Engineering\RAMHWLock\HWLockDLL.dll"

If it succeeds, a message should appear like this:

See Also

[[SELECTsupport TechNotes and FAQs]]

Problem Description

After installing RAM Connection v9.0, there is no longer a desktop shortcut for RAM Connection for RAM Structural System like there was in previous versions.

Reason

Beginning with RAM Connection v9.0, RAM Connection is directly launched from RAM Manager using the either the RAM Connection tool button or Design - RAM Connection. See below. There is no longer a separate desktop shortcut for RAM Connection for RAM Structural System.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

This article pertains to Ram Connection 8. For details on why the Connection toolbar is not visible using Ram Connection 9, see this article.

Problem Description

After installing RAM Connection 8.0, the Connection button still fails to appear in the Database ribbon within RAM Elements. 

Reason

With the RAM Connection 8.0 installer, RAM Connection for RAM Elements is no longer installed automatically with RAM Connection Standalone. It must be installed separately.

Steps to Resolve

1. Open the RAM Connection 8 installer by running Setup.exe in the following directory:
   C:\BentleyDownloads\rc08000023en
2. Click the link labeled "Install RAM Connection for RAM Elements" as shown in the screenshot below.

A valid license for Ram Connection (or Structural Enterprise) must be available when launching Ram Elements, otherwise the connection toolbars are still hidden.

Finally, go into Ram Elements - e menu - General Configuration - Licenses tab and make sure the box to "Check RAM Connection license” is checked. If it is not, check it and restart. This wiki explains why some users turn that option off intentionally.

See Also

[[Why does RAM Elements also retrieve a RAM Connection license?]]

[[RAM Connection v9.0 and Ram Elements]]

Unable to Satisfy All Prerequisites for RAM Connection Release 9.0

Structural Product TechNotes And FAQs

This TechNote pertains to the direct one-way link from Ram Structural System into Ram Elements. For information about using ISM to synchronize products, see Integrated Structural Modeling.

Importing a RAM Structural System database file into RAM Elements

Importing

1. Open RAM Elements Go to File > Import > RAM SS (full model)… -or- File > Import > RAM SS (lateral model)…
2. 1. “Full model” is referring to all the members in the RAM Structural System that are flagged as “gravity” and “lateral”,
   2. “Lateral model” is referring to only the “lateral” members being imported. When the lateral only model is imported, the members that were defined as lateral are loaded based on the RAM Gravity analysis (see What’s Imported > gravity loads below), and in addition to the directly applied loads, the gravity member end reactions will be applied to the lateral members as point loads.
3. Browse to Find the RSS model, select it, and click [OK].
   1. The RAM SS file must not already be open.
   2. The version of the model must match the currently installed version of RAM SS.
   3. It may take a minute or a few minutes to import the model.

General Notes on Importing

Foremost, RAM Structural System divides the model in gravity members and lateral load resisting members. In RAM Frame, gravity members transmit only vertical reactions to the supporting lateral members and provide brace points). They do not get considered further in the RAM Frame analysis. In Ram Elements (Advanse) there is no separation of gravity and lateral members and the behavior of the structure is analyzed all together (when the full model is imported).

What’s Imported?

Nodes, Members and Shells 

•  All member geometry, beams columns and walls. Note, the Axes in RAM Elements (Advanse) place the Y direction up, so the node Y and Z coordinates between the files will not match.
• Member sizes when section labels exist in RAM Elements (Advanse) Section tables. For steel members there will typically be a match. Be careful with double angles as the separation between the angles is not imported. 
• Member materials when materials exist in RAM Elements (Advanse) Material tables. This typically works for Steel and Concrete but not for Joists, Smartbeams or "Other" materials in RAM SS.
• Member fixity for members defined in RAM Structural System as Lateral. All imported gravity members will be pinned in the major and minor axis at both ends. In some situations this can result in a nodal instability in RAM Elements (Advanse).
• Horizontal rigid diaphragms. In RAM Frame horizontal diaphragm constraints can be assigned to sloping levels. This is not allowed in RAM Elements (Advanse). If the nodes assigned to a rigid diaphragm are not at the same elevation in RA you will get an error.
• Walls are imported as shells and openings in walls are also imported.

Loads

• Point loads on members.
• Line loads on members.
• Surface loads are not directly imported, rather they are distributed to members based on RAM Gravity, which calculates the tributary areas and attributes gravity loads to each member based on the deck orientation, and surface load applied to the deck area. This also applies to point and line loads applied directly to the deck in RAM SS.
• Vertical loads on walls from the deck, beams or line load are imported, but RAM Elements (Advanse) cannot apply a load to the edge of a shell, so these loads are translated to the corners of the walls. This can be unconservative in the analysis and design of the wall, especially if the wall is subject to beam bending, like a lintel.
• If the self-weight is indicated to be included with the gravity dead loads in RAM Structural System, then the self-weight gets applied in RAM Elements (Advanse) within the Dead Load case as follows:
  • Uniform load on beams
  • point loads on ends of walls
  • point loads at the top of columns
• All live loads (reducible, un-reducible, storage, roof) or snow loads get imported to RA as a single load case defined as Live Load.  See more about live load reduction below.
• Wind and Seismic Load story forces are imported as node loads. Special nodes are created for this purpose and assigned to the appropriate diaphragm in RAM Elements (Advanse).

What’s Not Imported?

Nodes, Members and Shells

• Member sizes or materials when no such section or material exists in the RAM Elements (Advanse) databases.
  • Joists size labels and material labels will be indicated, but these are not available in RAM Elements (Advanse). Some other prismatic section and material will have to be assigned to every steel joist in RAM Elements (Advanse). 
  • Concrete members sections are not based on the dimensions entered in RAM SS. They are based on the “labels”. The section size is only imported when the Section Label (from Concrete Beam/Column Section Properties in RAM Modeler) perfectly matches the section names in RAM Elements (Advanse) (i.e. "RcCol 18x18in"). 
  • "Other" material sections are the same as concrete members.
• Composite beams. The section size is imported to RAM Elements (Advanse), but the composite properties and studs are not, so the bare beam in RAM Elements (Advanse) will likely fail any code checks. 
• Member fixity for gravity concrete or other members are assumed to be pinned at each end regardless whether they are fixed or pinned in RAM SS.

Loads 

• Lateral story forces for rigid diaphragms (User Defined Story Forces) other than Wind and Seismic loads.
• Nodal loads applied in RAM Modeler.
• Dynamic Load Cases are not imported. You can perform a dynamic analysis in RAM Elements (Advanse), but the nodal masses and response spectrum data must be entered again.
• Notional Load Cases are not imported. 
• Center of Rigidity Load Case is not imported.
• Virtual Work Load Cases are not imported. 
• Lateral nodal forces from a Pseudo Flexible or Semi-rigid Diaphragm analysis in RAM Frame are not imported. Instead of the distributed loads based on percentages identified in RAM Frame Pseudo Flexible Diaphragm Properties, the original lateral story force is imported along with a rigid diaphragm assignment. 

Other limitations and differences 

These differences can significantly affect the results, even for a model that is imported into RAM Elements (Advanse) from RAM Structural System

• Physical members: When partial floors modeled in RAM Structural System are imported to RAM Elements (Advanse), gravity columns that are continuous outside the partial floor (two story columns) will be segmented and a node created at the floor level. These members need to be unsegmented in RA, or at a minimum the end releases fixed at that node to prevent a local instability. Furthermore, the unbraced length of the column should be adjusted. Girders that form physical members are imported correctly, but it's critical that the option to Automatically segment members in RAM Elements (Advanse) is turned on or the secondary beams will not be supported.
• Live load reduction: In RAM Structural System all of the live loads are analyzed. Then, when performing a code check on a member the live load results (axial, bending, shear) are reduced based on the LL reduction % for that specific member. In RAM Elements (Advanse) this cannot be done so the external Live Load that is applied is all there is. If the live load is reducible, and if the tributary area of the directly loaded member is large enough (i.e. the beam trib area) then a reduction will be made prior to loading this member, but no additional reduction can be made to the columns supporting these beams.
• Cracked section factors: In RAM Structural System, you can assign cracked section factors to columns, beams and walls. This property isn’t available in RAM Elements (Advanse) for walls. You should reduce the thickness or E value of the walls in RAM Elements (Advanse) if you want to be consistent. For beams and columns, an Ig effective stiffness factor can be defined, but this is not imported from RAM SS.
• Rigid end zones can be assigned in RAM Elements (Advanse), but this is not automated as it is in RAM Frame.
• Meshing: each program does it's own wall meshing and while they use the same meshing engine, you may not get the same results even when using the same desired mesh size.
• P-Delta, the programs have completely different methods of performing P-Delta analysis (RAM Frame - Global Stiffness method, RAM Elements (Advanse) - iterative method), and while RAM Frame includes AISC 360 options for direct analysis (Stiffness reduction, B1 and B2 factors, etc), none of these are in RAM Elements (Advanse).
• Multiple rigid diaphragms on a single floor in the RAM Structural System will be imported to RAM Elements (Advanse) with the same Rigid Floor #.
• Member Design parameters: none of the member design parameters like unbraced length or K factors are imported from RAM SS to RAM Elements (Advanse).  They need to be redefined in RAM Elements (Advanse) whenever the default value is not correct.
• Member self-weight: wall openings are accounted for in the self-weight calculation in RAM Structural System, but shell openings are not included in the self-weight calculation in RAM Elements (Advanse).

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

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

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

There is a tolerance for this that you can control.

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

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

How can I move all or part of my model?

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

(Please visit the site to view this video)

See Also

RAM Elements - View Control FAQ

Structural Product TechNotes And FAQs

What Rigid End Zone setting should I use in RAM Frame?

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

The program help defines this attribute as follows:

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

See Also

[[RAM SS Analysis Types]]

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!

Lateral Self-Equilibrium Analysis

Any static loading on a structure, when combined with the structure support reactions (considered as additional loads), is a self-equilibrium loading. In such a loading the total loads upon the structure are in force and moment equilibrium. However, the equilibrium loads still produce moments and forces in the structure.

In certain cases, it is desirable to analyze a self-equilibrium loading upon a floor system while ignoring the effects of the floor system supports. We call this type of analysis a self-equilibrium analysis.

Uses of Self-Equilibrium Analyses

The most common use of self-equilibrium analyses is to ensure that a load path in Concept is consistent with a load path in a lateral analysis performed by a separate program.

If a lateral analysis of a building (perhaps using RAM Frame) is performed, and that analysis considers the slab to be part of the lateral load path, the slab (including the slab-column connections) needs to be designed to resist the forces and moments determined in the lateral analysis. This design can be performed using a self-equilibrium analysis. The forces/reactions from all of the supports (above and below the slab) onto the slab are considered as loads to the slab.

The result of this self-equilibrium analysis is a slab load path that is fully consistent with the lateral analysis of the entire building. The distribution of forces (and the displacements) within the slab may not match those in the building lateral analysis, but the distribution of slab forces in Concept is almost always more accurate than those predicted in the full building analysis.

There is no limit to the type or quantity of loads that can be applied in a self-equilibrium loading. However, the loads applied must be nearly in self-equilibrium. If the loads are out of equilibrium Concept will apply restraints to the slab to ensure that equilibrium can be maintained. The restraint reactions can be viewed in the Calc Log.

Note: See Chapter 14, “Importing a Database from the RAM Structural System” for information on how to automatically import self-equilibrium lateral loads.

Note: Mat/Raft foundations are typically not well suited for self-equilibrium analyses as the soil reactions are not known before the analysis.

Self-Equilibrium Analyses Details

“Floating” Stiffness Matrix

If you use self-equilibrium loadings, Concept creates an internal floating stiffness matrix in addition to the regular stiffness matrix. The floating stiffness matrix considers the slab, but not the supports above or below the slab. Concept also adds some minimal supports to the matrix to make it stable.

Minimal Supports

The minimal supports that Concept adds to the floating stiffness matrix are located at real support locations, but not at every real support location. Typically, Concept adds three supports to provide full stability, but not to provide any restraint.

Note: Concept gives a warning if there are not at least two support locations where minimal supports can be added. The motivation for adding the minimal supports at the same location as real supports is that these locations are likely to be locations where self-equilibrium loads are applied, so any reactions at these locations can typically be considered as “corrections” to the self-equilibrium loads.

Punching Check Reactions

Punching checks consider the loads applied at the punching check location in their reaction calculations. Punching checks are the only “support” that have reactions from self-equilibrium analyses.

Displacements

Concept reports all displacements for self-equilibrium loadings as zero. Self-equilibrium loadings have no effect on the displacements calculated for load combinations or rule sets.

Pattern Loading

Pattern loading can be used in a self-equilibrium analysis, but it should almost never be used. When used, all patterns should contain a self-equilibrium set of loads.

Example 

Perhaps the best way to understand Lateral SE could be this simple example:

Consider the structure with two elevated floors shown in the Figure below. Each level is 3m high and the structure is 10m wide.

Assume the following:

• a frame analysis has been performed on the building for this 100kN loading and the column forces are known
• a very simple distribution of forces (reasonable for beams much stiffer than columns)

The forces on the top level slab (including column reactions) are:

Fx0 = 100kN
Fx1 = -50kN      Fx2 = -50kN
Fz1 = -15kN      Fz2 = 15kN
My1 = 75kN-m     My2 = 75kN-m

These forces are in equilibrium and are applied directly to the slab in a lateral SE loading. Concept then calculates the correct forces in the slab, design strips and punching checks.

For the intermediate level there are more forces to consider (all of these are from the frame analysis). The forces that the columns apply to the slab are:

Fx3 = 50kN       Fx4 = -50kN
Fx5 = 50kN       Fx6 = -50kN
Fz3 = 15kN       Fz4 = -45kN
Fz5 = -15kN      Fz6 = 45kN
My3 = 75kN-m     My4 = 75kN-m
My5 = 75kN-m     My6 = 75kN-m         

These forces are in equilibrium and are applied directly to the slab in a lateral SE loading. Since the “3” and “4” forces occur at the same location, they can be added together and applied as a single load (same for “5” and “6”).

Concept then calculates the correct forces in the slab, design strips and punching checks.

Note: There is one simplification - if you do not care about diaphragm forces, then you can ignore all the Fx and Fy forces. This assumes that the Fx and Fy forces act at the center of your slab and that the centroid elevation of your slab is constant. When these two assumptions are not true, the effects of these forces are typically still not large, but you may need to use some judgment before you ignore them.

Overview

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

Primary Load Cases

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

LOAD n

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

LOAD 3

MEMBER LOAD

2 UNI GY -3.4

JOINT LOAD

10 FX 12.5



LOAD 4

ELEMENT LOAD

23 PR GY -1.2



LOAD 5

TEMPERATURE LOAD

15 17 TEMP 40.0 -25.0

Combination Load Case

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

LOAD COMBINATION n

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

LOAD COMBINATION 40

3 1.2 4 1.6 5 1.3

REPEAT LOAD Type

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

LOAD 10

REPEAT LOAD

4 1.4 5 1.7

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

LOAD 10

ELEMENT LOAD

23 PR GY -1.68

TEMPERATURE LOAD

15 17 TEMP 68.0 -42.5

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

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

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

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

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

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

[Kinv] {P}

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

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

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

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

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

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

In July this year we released a new version of STAAD.Pro V8i SELECTseries 5 (20.07.10.64), which included a number of enhancements principally with the addition of Russian and Canadian design codes and also designed for use on Russian projects.  However despite extensive testing, after the release we were notified that some of these enhancements unfortunately included a number of errors.  We posted notification of the issues on the RSS feed and Bentley Communities site as soon as the nature of the issues were clear and have been working to get the issues addressed as quickly as possible.

We are pleased to announce that we have been able to address the issues and posted a new build on the Bentley SELECT server and recommend that this be downloaded and the earlier versions of STAAD.Pro be updated with this version.  The Revision History document included in the ReadMe outlines all the issues that have been addressed which can be summarized as:-

• Russian Steel Design
  • Correct variable initialisation to support multiple member design
  • Improved pagination
  • Design results available in the GUI
• Russian Wind Design
  • Correction for use with the Basic solver
• Canadian Steel Design S-16-01
  • Class 4, slender section effective areas for angle profiles
• AISC 360-10/05
  • Compression capacity and torsion capacity for circular hollow sections
  • Double angle section design
  • Designs governed by slenderness
• IS 1893
  • Command processing updates
• Advanced Cable Analysis
  • Vertical cable analysis
• Concrete Mode
  • Support for changing member dimensions after an initial design
• Connection Mode
  • Support of double angle sections for bracing

For full details please refer to the Revision History document.

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

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