Mesh Input layer

Why is it necessary to have priorities?

Without the priority system the modeling of floors would require one of two methods:

•  Objects for slabs of different thicknesses, beams, openings etc. could not overlap - this would be very tiresome for all but very simple floors, or
•  Depths would have to additive. For example, you would have to deduct slab depth from beam depth. If you had to change the slab depth then a change would be required for the beam, unless its depth changed by the same amount.

Can I copy columns or walls below to the same above?

Yes.

1. Select all of the columns or walls you wish to copy.
2. Choose Edit > Copy (or right-click and choose Copy from the popup menu that appears). Then double click off the edge to select nothing.
3. Choose Edit > Paste (or right-click and choose Paste from the popup menu that appears). The pasted objects are the current selection.
4. Choose Edit > Selection Properties, or right-click and choose Selection Properties.
5. Change Support Set from Below to Above, and click OK.

Note: It is important that you do not abandon the process after pasting. Otherwise, you will have two supports below at various locations, which causes calculation errors.

Element layer

How can I view the slab without the mesh?

Choose Layers > Element > Slab Summary Plan or go to the visible objects dialog box and check the "Outline only" option under slab elements.

What is the difference between beam and slab elements?

There is no difference unless you modify their behavior. See discussion of behavior in “Slab area properties” on page 56 and “Beam properties” on page 57. The difference in only in the modeling, a beam always has two parallel edges offset from the two end points, while a slab area polygon can be any shape in plan.

How many nodes or elements are allowed?

There is no limit, other than the limitations of your computer. If you find the program performance too slow, consider any of the following to help:

1. increase the mesh size to reduce the number of elements 
2. delete an imported drawing file that is no longer needed 
3. reduce the number of load cases and/or load combinations
4. reduce the number of design strips or increase the spacing of the design strip cross sections.

How many elements should I use per span or panel?

This cannot be answered directly as it depends upon the structure and loads. The maximum is 32.8 feet (10 meters). To speed the analysis, it is useful to choose a coarse mesh for preliminary design and a fine mesh for final design.

• A coarse mesh might have an element size of span length /6.
• A fine mesh might have an element size of span length /12.

If in doubt, you should investigate the effects of different mesh element sizes.

Columns

Do columns restrain the slab?

Depending upon the defined fixity, columns can provide rotational and lateral restraint. If the far end of a column is defined as a “roller” support (or both ends of the column are pinned) then the column does not provide any lateral restraint to the slab. Columns above the slab do not support the slab vertically, they can only restrain the slab rotationally and laterally.

Why is there deflection at the face of a supporting column or wall?

Columns in Ram Concept connect to the slab finite element mesh at a single node located at the column centroid. They are not solid objects nor do they provide vertical support to multiple nodes. This is apparent viewing the Elements - Standard Plan.

As such, deflections in the slab start from that node and increase towards the face of the column. For small columns this may not matter much, but for large area columns this is significant. 

To mimic the behavior of a stiff column support, we suggest modeling a thick and stiff slab object that overlays the column volume like a mini-drop cap. Be sure to assign a higher priority to this patch of concrete. It is recommended to model this patch with an elevated top of concrete elevation such that the slab centroid aligns with the mid-depth of the patch in order to avoid eccentricity at this joint.

The same approach could be taken for thick walls supporting the slab as well. A beam or slab object can be used there.

Beams

Where should you define the end points of a beam, at the face of the column, passing the column or at the center line? 

The general preference is to model the beams through the column, extended to the slab edge since it best matches the built condition and how things are formed. Stopping the beam at the column centerline results in a slightly more flexible system.

Walls

Do walls restrain the slab laterally?

Yes, if you select Shear Wall as a property. If the Shear Wall is unchecked then the slab is allowed to slip freely over the top of the wall. The walls rotational stiffness is independent of the Shear Wall setting; use the fixity settings to control the walls rotational stiffness about its longitudinal axis.

What is the effect of specifying walls above?

Wall elements can be used to model the stiffness and spanning ability of walls connected to the slab. Walls above behave similarly to beams in that they stiffen the floor. One could actually model the walls above the slab as beams instead, but it is not generally recommended.

Using beam or slab elements does have some advantages over using wall elements (“wall-beams”):

• Concept design strip cross sections automatically integrate the forces across slab-beam elements; wall-beam elements are ignored in these integrations, however.
• Also, Concept provides you many controls over how slab element results can be displayed; wall-beam elements (like wall elements) can only plot their reactions to the slab.
• However, Concept’s standard slab elements have a torsional stiffness that is proportional to their depth cubed. This can cause a large over-estimation of the torsional stiffness for a very thick slab element if it is adjacent to relatively thin elements. “Wall-beam” elements do not have this problem. As such, walls above that are modeled as upturned beams should use the “No-torsion” beam property.

When modeling wall-beams above the slab, Concept interprets some of the wall element parameters differently than for walls below.

• If the wall-beam is not rotationally fixed to the slab then the wall-beam will have zero torsional stiffness.
• If the wall-beam is not a shear wall then it will have zero axial stiffness. The vertically compressible and rotationally fixed at far end parameters are ignored.

Wall-beam elements have one advantage over slab elements.

• Slab elements of drastically differing thicknesses in the same structure can cause the automatic plotting controls to show (correctly) huge force variations in and adjacent to thick slab elements and almost no variation within the thin slab element areas. This does not generally happen if walls above are modeled as wall-beams.

Do walls above the slab provide rotational restraint?

There is no restraint at the far end of a wall above. (Even if “Rotationally Fixed at Far End” is checked, it is ignored).

Mats (rafts)

Does Concept ignore soil tension?

You can reduce the tension by iteration. The tension gets closer to zero with an increase in the number of iterations. See “Zero tension iteration options” on page 126 for more information.

What value should I use for the area springs Z force constant?

The geotechnical engineer commonly provides a value called the “subgrade modulus” or “modulus of subgrade reaction”. As a guide only: realistic values vary from 100 pci (approx. 25 MN/m3) for soft clay to 750 pci (approx. 200 MN/m3) for very dense gravel.

Note: Area springs are always assumed to be compression only springs in the Z direction, but they behave elastically in the R and S axes. Line and point springs are also linear elastic supports resisting tension or compression.

If 2 or more area springs overlap, is the spring stiffness cumulative?

Yes, soil area spring stiffness values are cumulative. If you model two area springs with 100 pci stiffness you will get 200 pci stiffness in the intersection.

Does Concept design for soil heave?

Not directly. You could draw spring supports that approximate varying soil support.

Do I need to draw the columns above in a mat foundation model?

No, but it is a good idea. It ensures a node is placed at that location where there is likely to be a heavy point load. The columns also provide convenient snap points for tendons or design strips.

Can Concept design for pile supports?

Yes. Use either (flexible) columns under, or point springs. Skin friction is not considered.

Can Concept design for pile and mat (raft) action together?

Yes, but the results could be very susceptible to variations in geotechnical parameters. For example, if the soil’s stiffness is overestimated, the actual pile reactions could be significantly underestimated. Use caution.

Does the area spring support have to match the mesh?

No. An oversized area spring is fine. The program applies the individual nodal springs based on the mesh tributary area.

Can the soil stiffness vary?

Yes. You can vary the stiffness in two directions. See “Area spring properties” on page 55.

Where do I select the allowable soil bearing pressure?

This is not an input parameter. You need to look at soil bearing pressure plans (which have a maxima / minima legend) to assess the maximum pressures. 

Can I change the support conditions in my model and analyze different loads with different support conditions within a single model ?

Yes. One can have different support conditions specified within the same model, each with its own set of load cases followed by PERFORM ANALYSIS and CHANGE commands

Here are a few simple rules that one should follow for such definitions

1. Each set of support condition should be followed by corresponding load cases and PERFORM ANALYSIS and CHANGE commands.
2. Supports should be specified in the same order before and after the CHANGE.
3. The number of supports in subsequent specifications should not increase. If the later cases have more supports, it is required to specify dummy supports at such nodes for prior scenarios using FIXED BUT FX FY FZ MX MY MZ ( which means unrestrained ).

Here is an example file with multiple support specifications

STAAD PLANE EXAMPLE FOR MULTIPLE SUPPORTS
START JOB INFORMATION
ENGINEER DATE 28-Oct-14
END JOB INFORMATION
SET NL 2
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 0 10 0; 3 0 20 0; 4 15 20 0; 5 15 10 0; 6 15 0 0;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 3 4; 4 4 5; 5 5 6; 6 1 5; 7 2 6; 8 2 4; 9 3 5; 10 2 5;
MEMBER PROPERTY AMERICAN
1 TO 10 TABLE ST W12X26
UNIT INCHES KIP
DEFINE MATERIAL START
ISOTROPIC MATERIAL1
E 29000
POISSON 0.3
END DEFINE MATERIAL
CONSTANTS
MATERIAL MATERIAL1 ALL
SUPPORTS
1 PINNED
6 PINNED
2 TO 5 FIXED BUT FX FY FZ MX MY MZ
LOAD 1
JOINT LOAD
2 FX 15
3 FX 10
PERFORM ANALYSIS
PRINT SUPPORT REACTIONS
CHANGE
*
SUPPORTS
1 PINNED
6 PINNED
2 TO 5 FIXED BUT FY KFX 10000
LOAD 2
JOINT LOAD
4 FX -10
5 FX -15
PERFORM ANALYSIS
CHANGE
PRINT SUPPORT REACTIONS
*
FINISH

. 

What is the difference between Plate element , Shell element and Surface?

 Plate element and shell element

Both terms represent the same thing in the STAAD context, which is, a 3-noded (triangular) or a 4-noded (quadrilateral) element to which a thickness has to be assigned as a property.

In STAAD, this element has both attributes - membrane (in-plane effect) and bending (out-of-plane effect). The bending effect can be shut off by declaring it as ELEMENT PLANE STRESS. The in-plane effect can't be shut off.

Plate Element and Surface

If you want to model a structure which contains a wall, slab or panel type component, you have two choices in STAAD :

a) Model that panel using a collection of individual elements. This is called a finite element mesh. This is an assembly of the 2d triangular and/or quadrilateral elements described above.

b) Model that as a single physical object called a Surface.

Option (a) is achieved using the mesh generation facilities in STAAD.

In option (b), (surface object), what happens under the hood is that, during the analysis, STAAD transforms the surface into a finite element mesh. The type of mesh (number of elements, type of elements, size of elements, etc.) that is generated from the surface is based on the parameters that you provide at the time of defining the surface.The details of the mesh thus generated are to a large extent, masked from the user. Results are presented for that surface, not for the individual elements that it is made up of.

In other words, a surface is merely an object that represents a collection of elements. When the program goes through the analysis phase, it subdivides the surface into a plate elements . From analysis point of view, both plate and surface are the same thing . The difference is in the interpretation of results . For plates , the stresses are reported while for Surface the force is reported. Another significant difference is that STAAD.Pro reports the in-plane moment MZ for surfaces but the same is not reported for plates. 

In general it is recommended to use plates for modeling foundation slabs, elevated slabs, diaphragms and walls. Surface elements should only be used for modeling shear walls. 

Overview

This page is the landing page for user help for modeling design strips in RAM Concept. The page is divided into two main sections: Tech Notes and Frequently Asked Questions. The Tech Notes section includes links to web pages with in-depth discussion of other issues relating to design strips. The Frequently Asked Question section includes common questions relating to design strip modeling and properties.

It is recommended that users become familiar with the “Defining Design Strips” chapter in the RAM Concept Manual, which contains additional guidelines on design strips that are not included here.

Tech Notes

Generating Span Segments

Defining Manual Design Strip Boundaries

Cross Section Trimming including tips for Drop Caps and Drop Panels

Design Strips and Slab Openings

Frequently Asked Questions

When should design strips be modeled with column and ½-middle strips and when should they be modeled as full-width column strips?

RAM Concept uses a finite element analysis to determine design forces. These forces are determined by integrating (or averaging) the finite element forces across the width of the column or ½ middle strips. The wider the strip, the more the design force is averaged and the greater the difference to the peak design force in the strip.

Figure 1 shows a typical moment distribution. Note that the moments are highest near the column and decrease toward the middle of the span. Using the column/middle strip approach forces the program to integrate moments with similar magnitudes across the width of the strip. The design moment for the column strip will be closer to the peak moment than if a full-width design strip was used. It is important to remember that the use of column and middle strips only affects the integration of forces, but does not affect load distribution in the finite element analysis.

 Figure 1. Typical Moment Distribution Across Column and Middle Strips

In some cases, it may be desirable to use design strips modeled as full-width column strips instead of column and two half middle strips. If two columns are close together, for example, the moment distribution may not vary significantly over the width of the strip (see Figure 2). Averaging moments over the full tributary width may be justified.

 Figure 2. Typical Moment Distribution for Closely Spaced Columns

It is also acceptable to define full-width strips for the column strips and full middle strips manually in lieu of using column strips and ½ middle strips (see Figure 3). This allows for the middle strip to be designed as one strip instead of two separate strips. This approach may be the best option when the ½ middle strips are narrow. To model full-width middle strips, the span segments must be modeled independently using the span segment tool. RAM Concept will not generate the span segments for these strips automatically. Where the column support is large, you may want to may want to set the support width to the column dimension for the full-width column strip and 0 for the full-width middle strip. Assuming that the span segments are extended to the centerline of the support, this will force the program to locate the first cross-section at the support centerline as opposed to the centerline of the column (see Figure 3).

 Figure 3. Full-Width Column and Middle Strips

Full-width column strips are typically used for post-tensioned slabs for the following reasons:

• Capacity calculations of post-tensioned slab have generally assumed that the precompression in the slab is distributed over the full tribuary width.
• Tendons are often banded along column grid lines.
• The column/middle strip approach was developed for use for the approximate two-way slab method discussed in Chapter 13 of ACI 318-05. These do not apply to prestressed slabs per ACI 318-05 18.2.1.

Some design codes require column and middle strips for PT design and require some distribution of tendons in both the column and middle strips. Problems can occur in PT slabs with banded tendons if a column/middle strip layout is used and a tendon does not intersect the middle strip. See the following web page for more information:

Balance and Hyperstatic Loading

Are there any recommendations for modeling design strips for beams?

For design strips parallel to the beam, it is best to align the design strip with the axis of the beam. If the strip is skewed slightly, then the Orient Span Cross-Section tool should be used to keep the cross-sections normal to the beam.

Engineering judgment should be used to model the design strips perpendicular to the beam. Beams can be supported by columns or other beams. The end points of the span segment should be defined at the centerline of each support. When beams are supported by other beams, it will be necessary to uncheck the box for “Detect Supports and Edges Automatically” in the Strip Generation tab of the Design Strip properties dialog and manually enter support widths (See Box 1 in Figure 4). The Support Width defines where the first (and last) cross-section is located, i.e. the critical section for moment design. Typically, the critical section is taken at the face of the supporting column or beam, although some engineers take the critical section at the centerline of the support. When the critical section is taken at the face of the support, it is best to model the support width 2” larger than wider than the actual width to avoid any rounding or snapping errors. Note that when design strips extend past an intersecting beam, a portion of the cross-section may be trimmed by the inter cross-section slope limit. See the RAM Concept manual for more on this type of cross-section trimming.

Typically, design strips for beams have the Column Strip Width Calc set to “Code T-Beam” (See Box 2 in Figure 4) and the CS Design System set to “Beam” in the Strip Generation tab (see Figure 5). This ensures that the column strip includes the beam and its effective flange width and that the cross-sections are designed using the ACI provisions for beams as opposed to slabs. The Middle Strips tab will typically have the box for “Middle Strip uses Column Strip Properties” unchecked (see Box 4 in Figure 6). This allows for the beam and slab to be designed with different bar sizes. The MS Design System should be set to “Two-way slab” so that the code provisions for slab design are used for design (see Box 5 in Figure 6).

When modeling one-way slabs, it is convenient to use the “Design Column Strip for Column + Middle Strip Resultants (See Box 3 in Figure 4). When selected, forces are integrated separately over the column strip and each half middle strip, then added together, and used to design the column strip. This allows for the beam and its effective flange to be designed for the full design strip forces.

Figure 4. Typical Strip Generation Settings for Beam Design Strips

     Box 1. Option for manually defining support widths

     Box 2. Option for setting column strip width calc to "Code T-beam"

     Box 3. Option for designing column strip for column + middle strip resultants

Figure 5. Typical Column Strip Settings for Beam Design Strips

Figure 6. Typical Middle Strip Settings for Beam Design Strips

     Box 4. Option for choosing different properties for middle stips

     Box 5. Option for selecting design system for middle strips

Why does the Status Plan on the Design Status Layer show failures for ACI 318 18.3.3 (or other post-tension concrete code provision when the slab is a mild reinforced concrete slab and not a post-tensioned slab?

There is an option in the Default Span Properties dialog that controls whether the design strip is designed as a post-tensioned slab or a mild reinforced slab (see Figure 7 below). To change the setting for span segments that have been modeled previously, do the following:

1. Open the Latitude Design Spans Plan on the Design Strip layer.
2. Use the Selection Tool to select all span segments on the plan.
3. Right click in the plan window and choose "Selection Properties" from the menu to open the Default Span Properties dialog.
4. Click on the General tab.
5. Uncheck the box for "Consider as Post-Tensioned" (see Figure 7).
6. Repeat steps for the Longitude Design Spans Plan on the Design Strip layer.
7. Reanalyze model.

Figure 7. Consider as Post-Tensioned Option

See Also

Generating Span Segments

Structural Product TechNotes And FAQs

Description

When I try to create and ISM in STAAD, I get the following errors. Unable to cast 'STAAD.Pro' COM object to 'OpenSTAAD' object. Check if 'OpenSTAADUI.tb' type library file is properly registered. Also no STAAD filename is provided. Unable to connect to 'STAAD.pro' instance. Check if STAAD.Pro application is running.

Solution A

To solve the issue, manually register the OpenSTAADUI.tlb file.  You can do this by following these steps:

1. Go to the Windows Start menu and select Run.

   2.  Type “cmd” in the Run dialog box then click OK.

 3.   You will see the command prompt dialog box appear.

 4.  Type the folder directory “CD C:\SProV8i SS5\STAAD”, click on “Enter”

 5.  Type “regsvr32 OpenSTAADUI.tlb”, click “Enter”.  You should see a dialog box appear indicating the file has been registered.

 6.  Launch STAAD.pro and you should not receive the message anymore.

Solution B

Uninstall STAAD.Pro, OPENSTAAD and other STAAD Components (Pipelink, StrucLink) and reinstall them with full administrative privilege.

How can I Modify a Meshing Region in STAAD Foundation Advanced ? 

If you have defined a meshing region and have identified it as a boundary from within Meshing Setup, you can select the boundary name from within the Data Input Pane on the right hand side and then press Delete Selected Region button, available at the bottom of that window, to delete it. Alternately after you select the boundary name, you can also press the DEL key on the keyboard to delete it. To edit the boundary, simply select the boundary name from within the Data Input Pane and press the Edit Selected Region button and you will be presented with a table in which you can edit the coordinates of the corners.

If you have defined a meshing region but NOT identified it as a boundary, you may select it graphically. Once it is highlighted ( will turn red from cyan ) press the DEL key on the keyboard to delete it. There are no options to edit it as such. You may delete the current one and recreate a new one.

After I analyze a file and get out of STAAD.Pro, the analysis results are deleted. How can I retain the analysis results ?

You are most likely trying to Save the file before closing out of the software. STAAD.Pro automatically saves all analysis data and you do not need to do a Save on top of that. In fact if you do then your input file ( .std ) becomes more recent than the files in which the analysis output is saved which makes the software think that the analysis results are out of sync or outdated compared to the input. Consequently it goes ahead and deletes the results. It would show a warning message though saying that the post processing data would be deleted and once the user confirms the operation, it will go ahead and delete the results.

So once the analysis is done, you can simply go to the post-processing mode or the analysis output file to review the results and once you are done, you can simply close the software. You do not need to worry about Saving the file. In fact if any changes has been made to the file since the analysis, the software would automatically prompt you to save the data before you exit.

The desired company name to be reflected in reports and
printouts of STAAD.Pro results to be entered while asked for during installation
of STAAD.Pro. However, if the required entry was skipped by the user, he / she
may enter the company name by modifying one registry sub-key as described
below:



a) Go to command prompt

b) Type Regedit and hit enter

c) expand HKEY_CLASSES_ROOT

d) Scroll down through the displayed lists and expand STAADPro

e) Select 2007 (20.07.10 for STAAD.Pro SS5 or 20.07.11 for STAAD.Pro SS6)

f) Double Click on Username

g) Enter your desired Company name as shown in attached screen capture.

What Ram Concept features trigger usage of the Ram Concept Post Tension Module license?

In RAM Concept release 5.0.2 and earlier, both a "RAM Concept" (product #1477) usage and a "RAM Concept Post Tension Module" (product #1479)usage are incurred each time the program is opened. The RAM Concept Post Tension Module (1479) license is tracked even if the model does not contain tendons and no tendon tools were used while the program was open.

Starting with Ram Concept release 5.1 and later, opening the program, opening a file, and performing the calculation in Ram Concept only ever requires a license for "Ram Concept" (1477). In those versions, a "RAM Concept Post Tension Module" (1479) usage is only incurred when specific tools for tendon modeling are used. 

To avoid unwanted "RAM Concept Post Tension Module" (1479) usage, it is important to update to a recent release of the program.

The tools and features that require a "RAM Concept Post Tension Module" (1479) and incur usage in the current version of the program are listed in the table below:

Layer or menu	Tools
Tendon Parameters (layer)
Manual Tendons (layer)
Process (menu)

Once usage of the PT features is initiated, that usage will continue in parallel with the Ram Concept (1477) usage until the end of that session. 

Starting with the CONNECT edition of Ram Concept (version 6.0), an option under Help - Manage License Restrictions was added so that users can opt out of all PT features in advance, like a safety.

If this option is unchecked, then whenever the post-tensioning features mentioned above are selected, the user will have to acknowledge and accept that usage or cancel.

See Also

Structural Products Licensing [FAQ]

How products that use the Bentley IEG License Service are licensed

Structural Product TechNotes And FAQs

The P-Delta effect is one of the primary parameter that every structural designer would not want to ignore accounting for while performing the stability analysis and design of slender member, tall structure or any structure that experiences significant gravity loads in addition to the lateral force.

This is a second order analysis induced by the geometric non linearity which accounts for both the P-Large delta ( P-Δ) and P-small delta (P-δ) effect. No practical column is ideally straight and vertical and hence the effect of the initial imperfections, out of plumbness must be accounted for in the stability analysis. So it is suggested to take the P-Δ and P-δ effect while performing the analysis.

In the conventional first order structural analysis, the equilibrium is expressed in terms of the geometry of the un-deformed structure. In case of the linearly elastic structure, relation between displacement and external force is proportional and hence the unknown deformations can be obtained in a simple and direct manner, whereas second-order analysis requires an iterative procedure to obtain the solutions. This is because the deformed geometry of the structure is not known during the formation of the equilibrium and kinematic relationship.

Thus, the analysis proceeds in a step-by-step incremental manner, using the deformed geometry of the structure obtained from an iterative cycles of the calculation.

The structure that are more sensitive to 2^nd order effects are the structures with low flexural stiffness and under high compressive force. If the axial force “P” acting vertically on the element is compressive in nature and that is closer to the elastic buckling load “Pcr”, the P-delta effect becomes more significant and prominent.

Fig-1

However, depending on the load “P” acting axially on the member, the lateral stiffness of the members starts decreasing. So more the compressive force experienced by the member, lesser will be its lateral load carrying capacity. This phenomena is known as Stress Softening effect which is the result of the change in GEOMETRIC STIFFNESS of that member. In Staad, the change in the GEOMETRIC STIFFNESS can be captured by invoking the K_G option intended to modify the Stiffness Matrix [K] to [K + K_G].

A simple and approximate way to determine the result of second order effect is to simply magnify the result reported from the first order analysis by the amplification factor 1/(1-P/Pcr), where Pcr is the elastic buckling load of the concerned member. This approach is also known as Amplification Method.

In case of the heavy gravity loading or the flexible structure, the accuracy of capturing the actual P-Delta effect falls and result thus obtained from the Amplification method becomes unreliable. In such situation, performing the iterative P-delta analysis is must to predict the actual effect on the structure.

Staad has the facility to perform the iterative P-Delta analysis to capture the actual second order effect induced on the structure.

Unlike AISC 2005 code, the AISC 2010 implicitly exempts considering the P-small delta, so the use of “large delta” (Δ) is sufficient for analysis of most buildings. Following is a simple example of a cantilever column analyzed in Staad, where the “Small delta” (δ) is ignored and is verified and compared with that of the Hand- Calculation upto 4 iteration cycles.

Hand-calculation and Verification of Large P-delta effect in a Cantilever column with that of Staad result upto 4 iteration cycles.

Height, L = 10000 mm

E = 205000 N/mm²

I = 8.33 x10⁶ mm⁴

Vertical Load, P =50000 N

Horizontal Load, H = 2000N

First Iteration

Now, M= HxL = 20 kNm

So, the lateral displacement (Δ₁) at the column tip 

Δ₁ = (ML²)/(3EI)     = 0.3902 m

Also, the vertical load P acting on displaced Δ₁ column tip resulting in generation of the additional moment M₁ at the base.  

M₁ = P x Δ₁ = 19.51 KNm

Now, the total moment “M_t1” at the base = (M+M₁)   = 39.51 KNm

The modified horizontal displacement “Δ₂” undergone for the first modified moment M_t1

Δ₂ = (M_t1L²)/ (3EI) = 0.770 m

Second Iteration

Also, the vertical load “P” acting on the newly displaced column tip (Δ₂ - Δ₁) resulting in the additional moment M₂ at the base

M₂ = P x (Δ₂ - Δ₁) = 19.035 KNm

Now, the total moment at the base, M_t2 = (M+M₁+M₂) = (M_t1+M₂) = 58.54 KNm

The second modified horizontal displacement Δ₃ against the second modified Moment M_t2

Δ₃ = (M_t2L²)/3EI = 1.14 m

Third Iteration

Similarly, following the iteration steps of 1 and 2

M₃ = P x (Δ₃ – Δ₂) = 18.555 KNm

The total moment at the base, M_t3= M+M₁+M₂+M₃=  77.1 KNm

Δ₄ = (M_t3L²)/3EI = 1.50 m

Fourth Iteration

M₄ = P x (Δ₄ – Δ₃) = 18.15 KNm

The total moment at the base, M_t4 = M+M₁+M₂+M₃= M_t3 + M₄ =

                                                        M_t4 = 95.25

Δ₅ = (M_t4L²)/3EI = 1.85 m

Fig-2

 (Please visit the site to view this file)

Problem Description

On some machines, the error message below is produced followed by a program crash during the design process.

Solution

Disabling the Welcome Screen will prevent the crash from occurring.

The Welcome Screen identified below appears when the program is launched. After launching the program, the Welcome Screen can be opened by clicking on the Help button in the upper right corner of program window (see screen captures below):

In the Welcome Screen, uncheck the box to the left of Welcome Screen in the lower left corner to disable it.

After disabling the Welcome Screen, you will no longer see news information on program updates and other important items when opening the program. The Welcome Screen can be opened anytime by clicking on the link in the Help menu. The news information can also be found on the following web page:

http://feeds.rapidfeeds.com/8826/

Note, this setting is saved in a Config.ini file located in the user profile area at %UserProfile%\AppData\Roaming\Bentley\Engineering\RAM Elements. Look for a [DlgRssFeed] section, and set the ShowWelcome value to false to disable the Welcome Screen without opening the program.

[DlgRSSFeed]
ShowWelcome=False

Other Notes

A similar crash occurred in versions of RAM Elements prior to v13.03.00.117. In earlier versions, the crash also occurred when a model was opened by one of the following methods:

1. Double-clicking on the file in Windows Explorer.
2. Clicking on a recent model button on the Welcome Screen.

In earlier versions, the crash was avoided by opening the program within the program as noted below:

1. Launch the program from a desktop shortcut or a link in the Windows Start Button.
2. After the program opens, click on the RAM Elements button in the upper right corner of the program window and then click on "Open a Model" or simply click on the "Open a Model" button at the top of the screen. See screen capture below:

See Also

Structural Product TechNotes And FAQs

RAM Connection Crash

The Technical Support Group periodically receives requests for recommended computer specifications for our structural products. As a general rule, we rank the importance of computer specifications in the following order: memory, processor, and graphics card. The following paragraphs provide more details.

Memory – As a general rule, more memory is better since it serves as a temporary work area when viewing and editing models. Our products are offered in 32-bit and 64-bit releases to support a variety of Windows operating systems. The 32-bit releases, which can run on older operating systems, can use a theoretical maximum of 4 GB of memory, but 64-bit releases can use more, making them suitable for larger models. As such, Bentley encourages the use of 64-bit releases whenever possible. The RAM Structural System development team recommends 12-16 GB of memory as of September 2015.

Processor – While some of the solvers in our structural products can utilize multiple processors, the products as a general rule utilize one processor at a time. Consequently, processor clock speeds are more important than the number of processors. Also, please note that some of our solvers in RAM products use Intel-provided technology which run best on Intel brand processors.

Graphics card – A graphics card with dedicated memory will display 3D models most efficiently. This will help engineers examine and manipulate models faster in the graphical interface, but it will not affect analysis times. Memory and processor speed are the biggest factors for that.

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

Release Date: December 18, 2015

Full Version Number: 06.00.01.02

Download Instructions:

Current and past RAM Concept releases can be downloaded from Bentley Cloud Services at http://connect.bentley.com.

After signing in to the personal portal, select Software Downloads under My Support. Once on the Software Fulfillment page, RAM Concept installers can be located by performing a search on "RAM Concept", or by selecting Brand -> RAM. Note that although there are multiple listings for RAM Concept (RAM Concept, RAM Concept Post Tension Module, etc.), each of these takes the user to the same list of installers as all features of RAM Concept require only one installation.

Installation Instructions:

RAM Concept CONNECT Edition 06.00.01 can be installed side-by-side with V8i versions of RAM Concept (release 05.02.01 and earlier). However, installing release 06.00.01 will automatically uninstall release 06.00.00.

If using the RAM Concept integration with RAM Structural System, both products must be either the x86 or x64 version. For example, the use of RAM Concept x86 within RAM Structural System x64 is not supported.

Recommendations:

RAM Concept CONNECT Edition is recommended for all projects, except those that are nearing final design.

New Features in RAM Concept CONNECT Edition (6.0.1)

In addition to minor error corrections and enhancements, RAM Concept CONNECT Edition has the new features discussed below.

Punching Shear – Enhancement to “Auto Calc” of Column Condition

The algorithms for automatically determining the column connection type (interior, edge, or corner) for punching shear checks have been greatly improved. Detailed information is available in Section 68.4.1, “About Connection Type”, in the RAM Concept user manual.

Profile Polyline Split Command

Profile Polylines drawn on the Tendon Parameters plans may now be split at a point by drawing an intersecting segment. This command is available under Tools -> Split Polyline.

Error Corrections in RAM Concept CONNECT Edition (6.0.1)

This release of RAM Concept contains minor error corrections discussed below.

Colors not printed when printing color contour plots

Colors did not print (only contour lines) when printing color contour slab plots using the Window Preview, Print Window, or Export Window to pdf commands under the Reports menu.

Area spring reactions for overlapping area springs not correct

Where overlapping area springs were drawn at a particular node, the plotted area spring reactions would only include the stiffness from one of the springs. This has been corrected to include the cumulative reaction for multiple overlapping springs.

Unnecessary tendon mesh warning

In some situations an unnecessary warning would be issued that the current mesh was out of date with respect to tendon changes. The detection of the conditions that require a re-mesh due to tendon changes has been greatly improved. This tendon mesh warning should be experienced less frequently and generally only in circumstances where a re-mesh is desired.

RAM Structural System Integration – No Project Assigned

When running RAM Concept embedded within RAM Structural System, if the RAM Structural System (*.rss) file was not associated with a CONNECT Project, an error occurred when attempting to open a floor in RAM Concept from the integration dialog.

RAM Concept

Latest Major Version

• • RAM Concept CONNECT Edition Release Notes (06.00.01.02)
  • RAM Concept CONNECT Edition Release Notes (06.00.00.30)

Previous versions

• RAM Concept 3.1 Release Notes
• RAM Concept 3.1.1 Release Notes
• RAM Concept 3.2 Release Notes
• RAM Concept 3.3 Release Notes
• RAM Concept 3.4 Release Notes
• RAM Concept 4.0.1 Release Notes
• RAM Concept 4.1 Release Notes
• RAM Concept 4.1.1 Release Notes
• RAM Concept 4.1.2 Release Notes
• RAM Concept 4.1.3 Release Notes
• [[RAM Concept 5.0.1 Release Notes]]
• [[RAM Concept 5.0.2 Release Notes]]
• [[RAM Concept 5.1.0 Release Notes]]
• [[RAM Concept 5.1.1 Release Notes]]
• RAM Concept 5.2 Release Notes

External Links

Structural Analysis and Design Products

How to apply horizontal moving loads

As of now the Moving Load generator in STAAD.Pro can generate loads in vertical direction only. There is no automated facility to add horizontal loads to these generations. This feature would be implemented in a future STAAD.Pro version. For now as a temporary workaround, one can make use of notional loads to have these horizontal loads generated for each position of the moving load.

Here is an example of how this can be done. Let’s say there is a load case 100 which includes structure selfweight. It is followed by a moving load generation case which would generate 11 load combinations from 101 to 111

LOAD 100 LOADTYPE None TITLE SELFWEIGHT

SELFWEIGHT Y -1

LOAD GENERATION 11

TYPE 1 0 0 0 ZINC 1

…

Subsequently one can manually create additional cases ( using command editor ) where any of these generated load combinations can be combined with the horizontal load as shown below

…

LOAD 1001 LOADTYPE None TITLE LOAD CASE 1001

REPEAT LOAD

100 1.0 101 1.0

NOTIONAL LOAD

101 X 0.1

NOTIONAL LOAD

101 Z 0.1

The above load case 1001 is created by first combining the first of the generated combinations 101 with the selfweight load case 100. Horizontal loads ( Notional loads ) are then added by multiplying the load combination 101 by a factor of 0.1 and these are applied in X and Z directions simulating a longitudinal thrust and lateral thrust at the moving load location.

An example is attached uploaded below

(Please visit the site to view this file)

There are a few factors that one needs to keep in mind though

1. The notional loads can only be generated at nodes. So if the generated moving load is not on a node but is on a beam, STAAD.Pro would calculate the notional load and apply it at the nearest node.
2. One can split the beams into segments to match with the increment in which the moving load is generated if one needs to generate these horizontal loads at exactly the vehicle locations.
3. One needs to use the editor to create these load cases combining the generated combinations with notional loads and there is no option in the GUI to do that. 

Release Date: October 1, 2015

Full Version Number: 06.00.00.30

Download Instructions:

Current and past RAM Concept releases can be downloaded from Bentley Cloud Services at http://connect.bentley.com.

After signing in to the personal portal, select Software Downloads under My Support. Once on the Software Fulfillment page, RAM Concept installers can be located by performing a search on "RAM Concept", or by selecting Brand -> RAM. Note that although there are multiple listings for RAM Concept (RAM Concept, RAM Concept Post Tension Module, etc.), each of these takes the user to the same list of installers as all features of RAM Concept require only one installation.

Installation Instructions:

RAM Concept CONNECT Edition can be installed side-by-side with previous release versions of Concept. There is no need to uninstall previous versions. If using the RAM Concept integration with RAM Structural System, both products must be either the x86 or x64 version. For example, the use of RAM Concept x86 within RAM Structural System x64 is not supported.

Recommendations:

RAM Concept CONNECT Edition is recommended for all projects, except those that are nearing final design.

New Features in RAM Concept CONNECT Edition

In addition to minor error corrections and enhancements, RAM Concept CONNECT Edition introduces the new features discussed below.

Warnings and Errors Management Tool

This release features a new set of graphical tools dedicated to identifying, locating, and resolving errors and warnings produced during the meshing, analysis, and design process. In previous versions of RAM Concept, errors and warnings were stored in the calculation log, which was simply a text file. Querying details on a specific error or warning could only be done by word searches within the calculation log.

The new graphical features could potentially save hours of design time per project locating and resolving warnings and errors.

The feature offers several key capabilities:

• All warnings and errors are displayed on screen in a sortable list immediately after the calculation process has completed.
• The plan on which the warning or error can be corrected is opened simply by double clicking on the warning item.
• Where applicable, the object requiring modification is selected automatically.
• The user can zoom to the specific location on plan where the warning occurs.

A wiki introducing this feature in detail is available at the following link:

http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/24127.warnings-and-errors-management-tool

Bentley CONNECT Integration

The CONNECT Edition is a new Bentley software generation offering a set of features and services that will better connect project team members within and across organizations and enable easier access to resources such as learning materials. This collective set of services is called Bentley Cloud Services. The portal to this can be accessed from the Bentley Cloud Services menu in the RAM Concept CONNECT Edition interface. The set of cloud-based services available in the first CONNECT Edition releases will represent just a fraction of what will become available over the coming months and years.

An introduction to your personal portal on Bentley Cloud Services is available at the following link:

http://communities.bentley.com/communities/other_communities/sign-in_assistance_and_web_services/w/wiki/23738.personal-portal

A comprehensive introduction to Bentley CONNECT is available at the following link:

http://bit.ly/CONNECT-Overview

Effective Depth Calculation Enhancement

There are situations in both post-tensioned and reinforced concrete slabs and beams where the traditional method of determining the effective depth of reinforcement results in an overly conservative shear strength and shear reinforcement spacing. Specifically, this can happen when calculating the effective depth using all tension reinforcement and where reinforcement in the compression half of the member goes into tension. One common example of this is near the ends of post-tensioned members where the CGS of strands is placed at the centroid of the concrete section. To overcome this limitation, RAM Concept now permits the user to choose between two methods of calculating the effective depth: the method just described, and a new method which maximizes the effective depth using a set of logical assumptions.

Post-Tension Licensing Restrictions

RAM Concept now has a means of disabling all post-tensioning features within the program. This ensures that use of only a RAM Concept license, and not use of a RAM Concept Post Tension Module license, is logged.

Error Corrections in RAM Concept CONNECT Edition

This release of RAM Concept contains minor error corrections discussed below.

AS 3600-2009 ductility design

In the ductility design according to the AS 3600-2009 standard, clause 8.1.5, it was determined that ku was incorrectly being used in lieu of kuo. The correction was made to use kuo for the limitation of neutral axis depth ratio in accordance with clause 8.1.5. kuo is limited to 0.36.

Selection of open shear reinforcement where closed shear reinforcement is required

In certain instances where the shear reinforcement density requirement was greatest within a region of "open" shear reinforcement, the detailing of this "open" reinforcement could have extended into regions of lower shear reinforcement density requirements without consideration of possible "closed" requirements within these regions. This has been corrected so that "closed" shear reinforcement is detailed in regions that require it.

Depth of pan joists imported from RAM Structural System

Pan joists defined in RAM Structural System were being imported into RAM Concept with the pan joist depth as the total beam depth. In RAM Structural System the pan joist depth represents the depth of the pan/web, excluding the slab thickness. This has been corrected such that the total beam depth imported into RAM Concept is the pan joist depth plus the flange thickness.

Incorrect SSR system reported on Reinforcement Layer when Ancon systems used

When Ancon systems were specified and designed, the correct SSR system would be displayed on the "Design Summary" layer. However, when the SSR objects were created on the "Reinforcement" layer, the default SSR system would be shown, as opposed to the Ancon system. This has been corrected so that the correct SSR system is also be shown on the "Reinforcement" layer.

CAD import

Several rare defects related to the import of dwg/dxf files were corrected.

1. Since the STAAD Offshore loads already include a static component should the static (gravity) loads in the STAAD Pro load combinations be excluded when analysing for  transportation cases?
2. Can we specify Marine Growth above the Still Water Level in STAAD.Offshore?
3. When I generate the STAAD file with wave loads using the STAAD.Offshore module, the file throws up errors while opening in STAAD.Pro and the Wave Load Cases are messed up.
4. I have specified the added mass coefficient and the drag coefficient as zero. However, STAAD is still generating Wave Loads in the Vertical direction.
5. When I try to open my staad.pro model in offshore, I receive the error: “Structure file has syntax errors. check the <filename>.err file for reasons”. What is the cause of this error ?
6.  I added a section to the STAAD.Pro section database and used it in my model. Now I am trying to open the STAAD.Pro model in STAAD.Offshore and I am getting error messages saying “structure file has syntax errors”. How do I get Offshore to recognize my defined sections ?
7. Is it possible to specify the heave + roll and heave –roll in the same load case?

1.Regarding the Transportation module in STAAD Offshore, there is a Gravity/Tilt option on the Transport Definition/General page. When this is turned on it appears that STAAD Offshore generates static load components in the vertical and horizontal directions based on the tilted position of the structure on the ship. These static components are included in the overall inertia loads and transferred into STAAD Pro. Our question is: since the STAAD Offshore loads already include a static component should the static (gravity) loads in the STAAD Pro load combinations be excluded when analysing for  transportation cases? If they are included it appears that we are "double-dipping" on the static loads and resultant vertical loads are too high.

When you are analyzing with the transport loads in STAAD.Pro, you need not consider the self-weight loads separately in the load combinations because you have already considered the inertia force due to acceleration due to gravity in the STAAD.Offshore Module, which is the selfweight of the structure. This is in addition to the inertia force generated due to acceleration of the barge on which the structure is being transported.

2. Can we specify Marine Growth above the Still Water Level in STAAD.Offshore?

No, we cannot. As per the API code clause 1.3.8, the Marine Growth is the most near the Mean Water Level but can be significant 200 feet or below the Mean Sea Level. The STAAD.Offshore is designed to take the marine growth data at and below the Still Water Level.

3. When I generate the STAAD file with wave loads using the STAAD.Offshore module, the file throws up errors while opening in STAAD.Pro and the Wave Load Cases are messed up.

This is most likely due to the fact that you have specified the first wave load case number such that either that case number or the subsequent wave load case numbers match with primary or combination load case numbers in the original file. If this is the reason then you need to specify the wave load case number in such a way that there is no duplication.

4. I have specified the added mass coefficient and the drag coefficient as zero. However, STAAD is still generating Wave Loads in the Vertical direction.

The answer to your question as to why the wave loads are generated inspite of the drag and the added mass coefficients defined as zero is inherent in the Morison’s equation. If you look into the Morison’s equation, you will see the following:

Here,  C_m= Inertia coefficient = 1 + C_a

               C_a =Added Mass Coefficient

          C_d = Drag Coefficient

The first term on the right side of the equation is the inertial force and the second term is the drag force.

The inertia force is again the sum of Froude-Krylov Force and Hydrodynamic Mass Force. Expressing the Morison’s equation in these terms, we have the following:

The first term on the right hand side of the equation above is the Froude-Krylov Force and is not dependent on the added mass coefficient and the drag coefficient. So, even if you specify the added mass coefficient and the drag coefficient as zero, it is not necessary that the Force will be zero.

Also you have specified a 0 degree wave, the fluid particle acceleration is only in the vertical direction. Hence, we will have the force in the vertical direction of the structure.

5. When I try to open my staad.pro model in offshore, I receive the error: “Structure file has syntax errors. check the <filename>.err file for reasons”. What is the cause of this error ?

The error indicates that there is some problem in the command input in the .std that you are trying to open. A (filename).err file is created inside the same folder from where you are trying to open the .std file. This file can be opened using Wordpad or notepad and should indicate specifically where the software is failing to read the input.

6. I added a section to the STAAD.Pro section database and used it in my model. Now I am trying to open the STAAD.Pro model in STAAD.Offshore and I am getting error messages saying “structure file has syntax errors”. How do I get Offshore to recognize my defined sections ?

When you add a section to the STAAD.pro section database, it gets added to the mdb file corresponding to that country database. For example if you added a section to the American Section database, this data would be added to the AISCSections.mdb file. These mdb files can be found within the X:\SProV8i\STAAD\Sections folder where X represents the local drive in which STAAD.Pro is installed. You need select the appropriate mdb and copy it to the folder C:\Users\(user name)\AppData\Roaming\Bentley\OpenSTAADOEM\Sections from where Offshore reads the sections. There would be an existing file by the same name and that file needs to be replaced by the file you are trying to copy. You would then be able to open the file in STAAD.Offshore.

It is better to have STAAD.Pro and STAAD.Offshore closed when you do these external file transfers. Moreover it is always a good idea to keep a backup whenever you are trying to replace or modify any standard mdbs.

7. Is it possible to specify the heave + roll and heave –
roll in the same load case?

You cannot create heave + roll and heave – roll in the same load group. You need to create two different groups with the directional factor as + 1 for heave + roll case and -1 for heave – roll case.

In the STAAD file however, you can manually edit the load cases two specify all the load items in the same load case – however, doing that you run the risk of under estimating the inertial forces.

 8. What does the message “The section Type PIPE/TUBE/OPEN/PRISMATIC cannot be established for some members. These members have been shown in red. The property table contents of these members will also be shown in red.” means while opening the STAAD.Pro model in STAAD.Offshore and how does this affect?

If you are using a transportation module, the aforementioned message does not make a difference as only the lumped masses are used for calculation of inertial forces. But it does affect in case the Wave Loading module is used. The Wave loading is calculated using the shapes of the members. Currently the STAAD.Offshore program is able to account for the following sections only:

1- Pipe, 2- Rectangle hollow (including square hollow), 3- Wide flange or Channel, 4- Rectangular Solid and 5- Circular solid

If the STAAD.Pro model has sections other than the aforementioned ones, their shapes wil not be accounted for leading to an erroneous calculation of wave loads.

9. I notice that your verification is done using “joint lumped inertia force system”. What is the difference of running the load generation in “member distributed inertia force system”?

It influences the transportation load type created in STAAD.Pro file. If the “Member Distributed Inertia Force System” is selected, the transport loads are created as member loads in the _TRAN.std file. If the “Joint Lumped Inertia Force System” is selected, the transport loads created are nodal loads.

10. When I generate the _Wave.std File using STAAD.Offshore, I encounter a lot of messages like the following. What did I do worng?

  **WARNING** TRAP LOAD BEYOND ITS LENGTH. FULL LENGTH ASSUMED. MEMB    aaa CASE    bb

What you encounter is most probably due to an erroneous version of OpenSTAAD OEM packaged with your STAAD.Pro installer. This is most likely to happen if you have installed STAAD.Pro SS5 in your system. Please install the SS6 version of STAAD - which has the fixed version of OpenSTAAD OEM.

What is the maximum model size that STAAD.Pro can handle ?

The limits are as described below. The details are provided in technical reference manual section 5.2 titled Problem Initiation and Model Title

1.Joint number 1 to 999999
2.Number of joints: 200000
3.Member/Element numbers: 1 to 999999
4.Number of Members, Plates, and Solids: 225000
5.Load Case numbers: 1 to 99999
6.Number of primary and combination cases: 10101
7.Number of modes and frequencies: 2700
8.Number of load cases that may be combined by a Repeat Load or Load Combination command: 550

The above numbers should be considered as upper limits built into the software for those quantities on an individual basis. In practice, the actual maximums the program can handle are determined by the hardware resources as well as the limits imposed by the operating system. For example, it is highly improbable that a single model with 999,999 members and 99,999 load cases can be solved.

The memory demand of the program is determined by the combined effect of two or more of these terms. For example, when a steel design is performed, the memory required depends on the product of the members being designed (NMD) as well as the number of load cases being designed for (NL). That is, NMD ×NL. So the smaller the NMD, the larger the NL capacity and vice versa.

Also, operating systems impose limits on file and memory usage by applications and such limits can be reached with smaller models specially those with large number of load cases.

So for all practical purposes,  one should try to keep models within 20,000 members/plates. Bigger models with large number of load cases not only take large time to analyze but working with such models can be inconvenient too as simple operations like navigating between the pages, that require refreshing the model view, can be slow.

STAAD Advanced Analysis is a module of STAAD.Pro that provides enhanced performance during analysis and a number of additional analysis features.

The Advanced Analysis Module provides STAAD.Pro with the following additional major features:

1. Faster solver for matrix inversion (reduced analysis time in large models and for those models requiring iterative solution)
2. Memory efficient eigensolution method like Arnoldi/Lanczos for solving large scale eigen problems
3. Load dependent Ritz Vector for efficiently extracting relevant modes for fast and accurate calculation of structural responses. This is particularly useful for large models where huge number of modes has to be extracted to get adequate mass participation.
4. Geometric Non-linear Analysis

1. Pushover Analysis
2. Steady State Analysis
3. Buckling Analysis by eignesolution with ability to plot the buckling mode shapes 
4. Advanced Non Linear Cable Analysis

Within STAAD.pro SELECT series 6, the user must specifically request the use of the Advanced Analysis Plus Engine option on the start screen:

Otherwise, when attempting to run one of the Advanced Analysis options the following type of warning will appear:

See Also

[[SELECTsupport TechNotes and FAQs]]