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

How can I assign a member to be tension only?

Any vertical or horizontal brace member may be assigned to be tension-only. The assignment is made in RAM Frame using the Assign menu - Braces - Tension-Only command. Assigning a brace to be tension only does not automatically release the brace for moments or torsion, however. That is controlled through the Assign menu - Braces - Fixity command.

If no assignment is made, then the braces will resist tension and compression elastically. Beams, columns and walls are always capable of resisting compression.

How can I resolve an error, "tension-only member in compression"?

In the steel design mode, you might see the warning "T-O in comp" on the View/Update dialog box or "Member with Tension Only Shape is in Compression" on the design report. There are some cross sections that the RAM Frame Steel postprocessor can only check when they are in tension. If a single angle, rod or flat bar goes into compression, then the design will always give these warnings. You can manually check the design of such using the member force envelope results.

The same error message, "T-O in comp", can also occur for a member that is defined as a tension-only brace if there are custom load combinations utilizing negative terms on lateral load cases. It's important for models with any tension-only braces that the lateral loads be applied in all directions so that the load combos can use positive terms exclusively.

Why is my tension-only brace failing in compression?

If a brace that was specifically assigned to be tension only is going into compression, that usually indicates a problem with the load combinations. For models with tension only members, the load combinations should never include negative terms in any load combinations (generated or custom). If there is a combo with a negative term, the resulting brace force could be compression and the warnings above will occur.

Consequently, any model with tension only members requires one lateral load case in the positive direction and another load case in the opposite direction if all the braces are to be correctly evaluated. For program generated loads, there is a check box for "Generate Additional Load Cases for Analysis with Tension-Only Members" that can be selected to do this automatically, but for user defined story forces or nodal loads, an additional case for the reverse direction must be manually input.

How is a tension only brace considered during dynamic analysis?

For any dynamic, response spectrum load case, all braces are assumed to be 50% effective. This generally accounts for an appropriate amount of stiffness for a symmetrically braced frame, but does not prevent the braces from showing compression results. This approach is also used for the eigensolution.

Why am I getting large deflections under gravity loads?

In the RAM Frame analysis, braces that are designated to be tension-only are completely ignored during the analysis of the gravity load cases (dead, live, roof and snow). For the evaluation of lateral loads the program uses an iterative approach to determine which braces are in tension under each lateral load case. Then the program superimposes the results based on the defined combinations in order to code check the braces.

In structures where all the braces are tension-only, a global instability can often result for gravity loads. If you get an instability warning or if the deflections are significantly large under gravity load cases there are several things you can do.

1. Simply ignore the gravity load deflections. For the purpose of evaluating deflections, use the lateral load cases alone (uncombined). So long as there are no significant shears or moments developing in the other lateral members due to the drift, there is really no harm in this.
2. Provide a secondary system to give the structure some lateral stiffness even when the tension-only braces are ignored. Typically, this is a matter of fixing the columns all the way to the base. If a fixed base condition is too stiff, try adding a rotational foundation spring at the base of the columns to reduce the lateral stiffness.
3. Remove the tension-only assignment from the braces altogether. In this case, the braces can typically be hand-designed for tension equal to two times the maximum (or minimum) axial force from any combination (obtained from a member force envelope report). This approach can alter the load path affecting column and foundation design however.  

An enhancement was added in RAM Structural System v14.06, which should resolve the problem with large displacements and instability errors. Beginning with this version, P-Delta effects will not be included when analyzing gravity load cases with the special tension-only analysis. This is a reasonable implementation since in virtually all cases the P-delta moments due to lateral sway caused by gravity loads is extremely small. P-Delta effects will still be considered with the lateral load cases. More on this can be found in the v14.06 release notes, which are located here: V14.6 Release Notes.

See Also

RAM Instability In Finite Element Analysis

[[Ram Elements - Tension Only Members]]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

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

Installation and Licensing  

• [[HWLockDLL internal error]]
• [[Ram Elements - Configuration settings]]

Ram Elements User Interface 

• RAM Elements Importing from RAM SS FAQ
• RAM Elements - View Control FAQ
• Ram Elements - Modeling FAQ
• Creating custom Sections, Materials, etc. in RAM Elements
• RAM Elements Deck Areas
• Ram Elements Shells FAQ

Ram Elements Analysis Topics

• RAM Instability In Finite Element Analysis
• RAM Elements Load Combos FAQ
• Ram Elements - Distributed Load errors
• [[Ram Elements - Tension Only Members]]
• RAM Elements Dynamic Modal Analysis FAQ

Ram Elements Design Topics

• RAM Elements Unbraced Lengths
• RAM Elements Effective Length Factors
• RAM Elements AISC Stability

Ram Elements Modules

• RAM Elements Masonry Wall FAQ
• Ram Elements Can't Save Integrated Wall or Footing designs

How do I get RAM Elements to perform a Response Spectra Dynamic Analysis?

1. After the geometry of the model is defined, place nodal masses using the Nodes>Masses spreadsheet input,

2. Define a dynamic load case for each X and Z direction,

3. On the Gen>Earthquake acceleration spreadsheet input, enter a scale factor, direction and damping percentage,

4. On the Gen>Response spectrum spreadsheet, enter some response spectrum,

5. Run the analysis and choose the desired combination method (e.g. CQC),

6. Click the View menu>Finite elements toggle,

7. Use the View>Modal deflection results to see the mode shapes or Output>Analysis> Dynamic analysis to get periods and modes info.

For more details, refer to Help>RAM Elements Manual>Chapter 10: Dynamic Seismic Analysis. 

to see example files go to;

C:\ProgramData\Bentley\Engineering\RAM Elements\Data\Samples

and open Dynamic1.etz or Dynamic2.etz.

How can I change the number of modes used in the dynamic analysis?

Click the Process menu>Analyze model toggle, and under Dynamic and Response Spectra change the number of modal shapes to calculate.

What scale factor should I apply to the response spectrum?

See RAMSS Dynamic Modal Analysis FAQ

Can RAM Elements perform an Eigenvalue solution to determine mode shapes without the response spectrum data?

RAM Elements will perform an Eigen solution without the response spectrum curve data. The program only requires that the Mass is entered in the Node>Masses spread sheet. Once the mass is defined the program will perform the Eigen solution and the View>Model shapes options and the Output >Analysis >Dynamic Analysis results will be available for viewing.

How do I generate the data for the response spectrum curve?

The data can be generated using ASCE7-05/10 section 11.4.5.  Sample curve data can be loaded using the "Open response spectrum file" toggle.  The following spread sheet shows how to generate this data given a site specific S_DS and S_D1.

http://communities.bentley.com/products/structural/structural_analysis___design/m/structural_analysis_and_design_gallery/255161.aspx

What loads are included in the automatic mass generation and how does the program determine which members or shells to include per rigid floors?

Here’s what’s included in the automatic mass generation (from selected dead and live loads with their percentage):

•             Point loads in nodes

•             Members self-weight

•             Members distributed loads

•             Pressure in members

•             Shell self-weight

•             Shell pressures

The requirements to consider a member in a specific rigid floor are:

•             Both nodes have the same floor number

•             One node belongs to the floor and the other one is below it

The condition to consider a shell in a specific rigid floor is:

•             All its nodes have the same floor number

See Also

RAMSS Dynamic Modal Analysis FAQ

STAAD.Pro Response Spectrum FAQ

Steel Unbraced Lengths in RAM Elements

General

The format for steel unbraced lengths (Lb pos, Lb neg, L33, L22, and LTorsion) changed in V11. The help context in the member design parameters worksheet discusses the format. This can be accessed by clicking on a cell in the Members – Steel Design Parameters worksheet and hitting F1 on your keyboard.

Old Implementation

Prior to V11, unbraced lengths were entered as a single value in the steel design parameters. If no value was entered, the unbraced length was assumed to be equal to the physical length of the member (j node to k node). If a non-zero value was entered, that value was used as the unbraced length for every station considered during the design of the beam. However, parameters such as Cb were always calculated using the physical length of the member. This limitation could be unconservative.

V11 Implementation

In V11, unbraced lengths need to be entered such that the sum of the unbraced lengths is equal the physical length of the member. For example, if a beam is 20’ long and the unbraced length is 5’, the unbraced length should be entered as 5;5;5;5. This allows the program to calculate parameters such as Cb for the actual unbraced segment rather than the physical length of the member. A tool button was introduced to rapidly generate the unbraced lengths.

However, this new method introduced some limitations into the program. For example, it is not possible to enter an unbraced length that is longer than the physical length of the member. This might be a necessity if you are modeling a bent or simulating a curved member. In addition, it is not possible to assign multiple Cb values to correspond to the unbraced lengths that were assigned. In other words, only a single Cb value can be entered and it will be used for all segments. If Cb is left blank, it will be calculated for all segments.

V12 Implementation

The V12 implementation functions as described below.

i. The engineer doesn’t type anything in the spreadsheet cell (either directly or with the tool) and thus the value remains the default “0”:  RE uses the physical length of the member as Lb and Cb will be automatically calculated based on the physical length of the member.

ii. Just one value is entered in the cell

     a. If the value is less than the member’s physical length, RE uses that value for all pertinent code checks (just like before v11.0) and Cb = 1. Besides printing Cb (as 1) in the design report, RE adds a note at the bottom of the report saying “Cb not calculated for the Lb specified. It is conservatively prescribed as 1”. However if there’s a value in the Cb cell other than zero “0”, then that value is used in all segments and the note is not printed.

     b. If the value is equal to the physical length of the member, then it would be exactly the same as i.a above.

     c. If the value is larger than the member’s physical length, RE uses that value for all pertinent code checks and Cb = 1. Besides printing Cb (as 1) in the design report, RE adds a note at the bottom of the report saying “Cb not calculated for the Lb specified. It is conservatively prescribed as 1”. However if there’s a value in the Cb cell other than zero “0”, then that value is used in all segments and the note is not printed.

iii. Multiple values are entered in the cell (either directly and separated with semicolon or using the tool):

     a. If the sum of the values is less or equal to the physical length of the member, RE calculates the difference for the last segment and Cb is automatically calculated for each segment. The sum is validated for unintended, non-summing entries.
 
     b. If the sum of the values is larger than the physical length of the member, RE does NOT allow it. In other words, one single unbraced length for the member, could be larger or smaller than the distance from node to node, but multiple unbraced lengths, must match the member’s physical length.

Note: Old models (prior to v11.0) opened in v12.0 will retain the original unbraced length assignments. These will fall under option ii above. The engineer must keep in mind that the final results may still vary because before, Cb was calculated with the physical length (which now only applies to option i above) and now with Cb = 1.

Similar behavior is applicable to L33, L22 and Ltorsion.

Adjusting the unbraced length of Built-Up members (double angles) to accommodate Intermediate Connectors locations.

In the Steel design criteria for AISC 360 there are two user variables that control this:

1. Intermediate Connectors - This option is used to define the use of two equations in the design of built-up members subjected to compression. The available options are:
   1. Intermediate connectors that are snug-tight bolted, to use the equation E6-1.
   2. Intermediate connectors that are welded or pretensioned bolted, to use the equation E6-2.
   3. Intermediate connectors in shear and bolt values based on bearing values (but pretensioned), to use the equation E6-2..
2. a (Connectors) - The distance between connectors in built-up members. It is used to calculate the modified slenderness of the built-up member following Section E6 specially 2L sections.

See AISC 360 Section E6 for further details.

See Also

RAM Elements Effective Length Factors [TN]

Structural Product TechNotes And FAQs  

Effective Length Factors in RAM Elements

General

AISC effective length factors (K33 and K22 factors) can be automatically calculated in V12.  This document discusses the implementation prior to V12 and the changes made in V12.  The value of K Torsion did not change.  It defaults to K=1.0 unless another value is entered in the AISC steel design parameters.

Old Implementation

If the K22 or K33 field was left blank or set to zero in the AISC Steel Design Parameters, the program automatically assumed K = 1.0.  There was tool buttons to calculate K33 and K22. If this tool was selected, the program used the following equations to calculate K.

Members Assigned as Sway
K = SQRT((1.6*GB*GA+4*(GB+GA)+7.5)/(GB+GA+7.5))

Members Assigned as Non-Sway
K = min(min(0.7+0.05*(GB+GA),0.85+0.05*min(GB,GA)),1.0)

GA and GB values depend on member stiffness as described by specification commentary.  Values that were theoretically infinity (pinned) were assumed to be 10.  Values that were theoretically fixed were assumed to be 1.

V12 Implementation

V12 added new Value Type K33 and Value Type K22 parameters.  When the Value Type is set to ‘None’, the program functions as it did in previous versions and K will be assumed to equal 1.0 unless a value is entered for K.  If the Value Type is set to ‘Recommended’, the program will use the recommended approximate values in Table C-C2.2 in the 13th Ed AISC Manual.  If the Value Type is set to ‘Theoretical’, the program will use the theoretical approximate values in Table C-C2.2 in the 13th Ed AISC Manual.

When the tool button in the steel design parameters is used to calculate K, the alignment charts in Chapter C of the commentary in the 13th Ed AISC Manual are used.  This method considers the stiffness of rigidly connected members and uses the equations below.  The tool button cannot be used when the multiple unbraced lengths (L33 and L22) are entered for the member.

Members Assigned as Sway
(GA*GB*(Pi/K)^2-36)/(6*(GA+GB))-(Pi/K)/(tan(Pi/K)))=0

Members Assigned as Non-Sway
(GA*GB/4)*(Pi/K)^2+((GA+GB)/2)*(1-(Pi/K)/(tan(Pi/K)))+(2*tan(Pi/(2*K)))/(PI/K))=0

GA and GB values depend on member stiffness as described by specification commentary.  Values that were theoretically infinity (pinned) were assumed to be 10.  Values that were theoretically fixed were assumed to be 1.

Special Considerations

The automatic calculation of K is based on the physical length of the member.  Therefore, members framing into intermediate nodes along the member have no impact on the calculated effective length.  For this reason, it is best to segment the member so the physical length matches the unbraced length.

When 2D frames are designed, the out-of-plane effective length factor will be calculated for the columns unless a value is entered in the steel design parameters or the out-of-plane value type is set to ‘None’.  Typically, the calculated value would be incorrect and the effective length should be assumed to be 1 for the out-of-plane direction.

There are many instances where the effective length method should not be used and K should equal 1.0.  The program does not attempt to determine these conditions and will always calculate a value based on the parameters and the analytical model.  For example, members with theoretical pinned ends (GA = GB = 10) will always have a calculated effective length of 3.01 for sway frames and 0.96 for non-sway frames.


Practical Example

Consider a simple portal frame with 15’ long W12X96 columns and a 20’ long W21X83 beam.  Assume the bases of the columns are pinned and there are no releases at the top of the column or ends of the beam.  The column is oriented such that the beam frames into the column flange (strong axis bending).

The frame would be classified as sway in the plane of the frame (frame type 2).  In the out-of-plane direction, the K22 value should be assumed to be 1.0 since the frame will lean against the diaphragm or some other support for stability.  Do not simply set frame type 3 to non-sway.  The Value Type K22 should be set to ‘None’.  It is also appropriate to set K33 for the beam to 1.0 or assign Value Type K33 as ‘None’.

If the tool button is used to compute K33 for the columns, the equations below are used.  Looking at the figure C-C2.4 in the 13th Ed AISC manual, K should be around 1.8.  The equation below is nearly zero when K = 1.81.  That matches the value calculated by the program when the tool button is used in the steel design parameters worksheet.

GA = (EI/L column) / (EI/L beam)
GA =( 29000*833/15) / (29000*1830/20) = 0.607

GB = 10 Assumed at pinned end

(0.607*10*(Pi/1.81)^2-36)/(6*(0.607+10))-(Pi/1.81)/(tan(Pi/1.81)))=0.01

When Value Type K33 is set to ‘Recommended’ for the columns, K33 will be assumed to be 2.1 is indicated in Table C2-2.2(e).

When Value Type K33 is set to ‘Theoretical’ for the columns, K33 will be assumed to be 2.0 is indicated in Table C2-2.2(e).

Does the steel design impose a limit on the slenderness ratio, KL/r?

No, but if the KL/r ratio of a compression member exceeds 200, or if the L/r ratio of a tension member exceeds 300, you will get a warning in the steel design report (and a yellow status color on screen using View - Status). Here's an example from the concise steel report:

Design code: AISC 360-2005 ASD

Member : 3 (BC)
Design status : With warnings

DESIGN WARNINGS

- The slenderness ratio KL/r about major axis of the member in compression should not exceed 200
- The slenderness ratio KL/r about minor axis of the member in compression should not exceed 200
- The slenderness ratio L/r of the member in tension should not exceed 300

These warnings can be totally suppressed by not checking the option, "Include slenderness recommendations" in the Process - Design dialog.

See Also

Steel Unbraced Lengths in RAM Elements [TN]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs  

RAM Elements AISC 360 Stability Analysis and Design

General

Chapter C of the AISC specification (2005 and later) covers stability analysis and design. This document discusses how the requirements are met in RAM Elements.


Analysis and Design Using General Second-Order Elastic Analysis

RAM Elements has the ability to perform a general second-order elastic analysis per AISC 360 C2.1. It is an option in the Process tab – Analyze Model – Analysis tab. This method captures big P Delta effects but will not capture small P delta effects unless the individual members are segmented into smaller pieces in the finite element analysis. For example, imagine a column that is 15’ long. If it is modeled as a 15’ long member, small P delta effects are not captured. If it were modeled as five 3’ segments, small P delta effects are captured because there are additional nodes between the ends of the member. Currently, there is no option to automatically segment the members this way in the finite element model and it must be done manually. Please note, if you segment a member, be sure to specify the proper unbraced lengths in the steel design parameters. The unbraced lengths will always default to the physical length of the member.

AISC 360 C2.2a(2) requires an analysis for ASD design to be carried out under 1.6 times the ASD load combinations and the results divided by 1.6 to obtain the required strengths. It is currently not possible to divide the results by 1.6 in RAM Elements. Therefore, you must use LRFD.

AISC 360 C2.2a(3) requires notional loads to be considered in the gravity only combinations unless initial out-of-plumbness has been modeled. Currently, notional load cases do not exist in the program as a predefined load type. They need to be manually modeled as unique load cases and manually accounted for in the load combinations. For example, imagine you have a structure with dead load and live load. One would create a notional dead and live load cases in two independent directions. Let’s assume they were called NDX, NDZ, NLX and NLZ. For the typical gravity combinations 1.4 DL and 1.2 DL + 1.6 LL, you would need to create a total of four load combinations to account for the notional loads.

1.4 DL + 1.4 NDX
1.4 DL + 1.4 NDZ
1.2 DL + 1.2 NDX + 1.6 LL + 1.6 NLX
1.2 DL + 1.2 NDZ + 1.6 LL + 1.6 NLZ

AISC 360 C2.2a(4) discusses effective lengths. This Wiki page discusses how effective lengths are implemented in RAM Elements. Effective Lengths in RAM Elements

A practical example for the general second-order elastic analysis is discussed here.  RAM Elements AISC 360 Stability Example

Other Limitations

It is not possible to run P Delta with dynamic load cases. Second order effects must be accounted for by hand.

Currently, the Direct Analysis Method discussed in AISC 360 Appendix 7 is not implemented in RAM Elements V12. Therefore, structures with a second order drift to first order drift ratio exceeding 1.5 cannot be designed in RAM Elements per AISC 360 C2.2.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs  

Deck areas are a convenient tool for generating distributed loads associated with surface loads on members. For general information on modeling deck areas, please see Chapter 18 in the RAM Elements Manual. Additional modeling tips and common issues with deck areas are discussed below.

Deck area distribute load to members that border the deck area only. A load will not be distributed to any members that are inside but do not border the actual deck area.

Shells do not qualify as perimeter member. If a deck is bordered by a shell on one side as shown in the screen capture below, a error indicating that no member is connected between two nodes of the deck area will be displayed during the analysis (see error message below). To work around this problem, model a GEN section with very low stiffness between the nodes at the top of the shell.

Because loads are only distributed to members that border the deck area, a separate deck area needs to be modeled in each bay of framing. The fastest way to do this is to first select all members on a level and then click on one of the active spreadsheet tools shown below to generate the deck area:

This will generate a deck area in each bay as shown below:

In some cases, it may be convenient to use a deck area for both in-plane and out-of-plane pressures. One practical example is a perimeter wall that is subject to out-of-plane pressure due to wind load and in-plane pressure associated with the dead weight of the cladding. The current implementation of the deck area feature will not calculate distribute loads for some in-plane pressures. If the surface load vectors are defined so that they are parallel and in-plane of the deck area, then no distributed load will be calculated. However, if the surface load vectors are defined so that they are in-plane of the deck area but perpendicular to the deck span, then a distributed load will be calculated.

In the screen capture below, the deck area on the right is defined with Vector Y = 1 for the deck span and Y Dir = -1 for the surface load. Since the surface load is in-plane and in the same direction as the deck, no load is distributed to the members. The deck area on the left is defined with Vector X = 1 for the deck span and Y Dir. = -1 for the surface load. Since the surface load is in-plane but perpendicular to the deck, an in-plane distributed load is applied to the members.

There is also a bi-directional feature for deck areas that can be used to distribute loads in two directions. When using this feature to model two-way decks, it is important to note that the program calculates the tributary area of the member, determines the tributary load to the member, and applies a uniformly distributed load over the length of the member based on this load. The program will not distribute a triangular or trapezoidal load as may be expected.

For bi-directional deck areas, the resultant of the deck span vector (Vector X, Vector Y, and Vector Z) should always be a unit vector. The magnitude of the load that is applied is scaled by the resultant. In the screen capture below, a 1 ksf pressure is applied to a 20 ft x 20 ft deck area. The deck area on the left is defined with Vector X = 0.707 and Vector Z = 0.707. The resultant = [0.707^2 + 0.707^2]^0.5 = 1. The deck area on the right is defined with Vector X = 1 and Vector Z = 1. The resultant = [1^2 + 1^2]^0.5 = 1.414. Note that the total load for the deck area on the right is 1*(1 psf)*(20 ft)*(20 ft) = 400 k. However, the total load for the deck area on the left is 1.414*(1 psf)*(20 ft)*(20 ft) = 565.6 k.

Why are the yellow lines for members shortened at the nodes? 

The lines are drawn slightly short of the nodes so that the nodes are clearly visible in line mode.

In the fully rendered view you can see the members full length (or shrunken)

I have a small model and the support icons appear very large, how can I make them smaller?

The size of the nodal support, member hinge and other icons is typically adjusted based on the overall size of the model, but the user can force the icons to appear larger or smaller. 

To control the size of the icons go to the e menu (file menu) and pick General Configuration. On the Display tab, uncheck the box for  Data and Results - Automatic Scale and then enter a number >1 to make the icons larger, <1 to make them smaller.

How can I rotate the view?

In order to rotate the view, click and hold the right mouse button, then drag the mouse to dynamically rotate the view. Note, in RAM Elements, the Y axis typically points upward and this axis is always plumb on the screen.

If you find the rotation is too fast or too slow for your liking, go to the e menu - General Configuration and on the General tab, adjust the Mouse rotation sensitivity slider.

How can I Save a View?

In Ram Elements you can save a particular type of view including the angle of the view, the zoom, perspective settings and display options. To do so, first adjust the graphic as desired, then right click on the view and choose Customized Views - General - Create. Provide a name for the view, check the desired attributes to save and click Create.

These general views work across all files.

The program also allows you to save model-specific views. To do so, again adjust the view the way you like it. Then right click on the view and pick Customized Views - Current Model.

In addition to the attributes mentioned above, Current Model views also store the active selection set and any hidden members for instant recall.

To recall a saved view, simply right click on the graphic and pick the saved view by name from the Customized Views.

How can I make the on screen text easier to read?

At the bottom right corner of the Ram Elements window are the controls for increasing or reducing the text size on screen. Just to the left of that is the control for units.

By not Showing the units more significant digits are shown, filling roughly the same screen area.

Using Larger or Smaller units under Units Configuration can affect the displayed number of digits. For example. if the axial force in a column is -2471.45 pounds, switching to kips changes the display to -2.47 kips which is shorter.

Regretfully, there is no other user control over significant digits displayed.

How can I view the design properties, things like unbraced length?

From the View Ribbon menu, in the Design Toolbar, select Design Properties and one or more of the options:

• Effective length factors (i.e. K22 and K33)
• Axial and torsional unbraced lengths (i.e. L22 and L33)
• Flexural unbraced lengths (i.e. Lbpos and Lbneg)

Note, for unassigned default values (0) nothing will be shown on screen. Only user specified values are plotted.

How do I change the scale of the deflection multiplier?

Click on RAM Element button in the top left corner and click on the button 'General configuration'. Then select tab Display and change the deflection multiplier as shown in the screenshot:

How can I assign a member to be tension only?

Go to the Members tab of the spreadsheet input, and go to the hinges sheet. The first field is for "Axial rigidity". Set this to tension only by selecting that option from the drop down list, or use the Ribbon menu tool "Tension only" once you have only the desired members selected.

Why is my tension-only brace failing in bending?

There are three typical reasons why a tension-only member will induce bending.

1. If the member ends are fixed, a tension-only member can still develop and end moment. Tension-only members are typically hinged at both ends in both M3 and M2 axis, if not also torsion.
2. If self-weight loads are applied this will cause the member to bend or sag under its own self-weight. To alleviate this issue we suggest using a weightless, zero density material for tension only member. An "A36 weightless" material is provided out of the box for this purpose.
3. If the tension-only member intersects other members and the Finite Element analysis option to "Add intermediate nodes at member intersections" is checked, then there will be intermediate points of connection (without hinges) leading to force transfer and potentially bending. We suggest not using this option for models with tension-only braces. If there are other places where you really want joints at member intersections, manually segment those portions using Process - Segment selection.

See Also

RAM Instability In Finite Element Analysis

RAM Frame - Tension Only [FAQ]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

How can I change user permissions?

If you are the SELECT Administrator at your site, the User Permissions area lets you view or edit permission levels for all the users at your site. This includes the Software download role, Webshop user role (for creating service requests on line) and more. Site administrators can also add new contacts or assign additional site administrators. A list of the site administrators is also provided for general users, so you can view who you need to contact about your current permission levels.

Video:How do I review and edit User Permissions?

Video:How do I add a user to the SELECTservices site?

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

Currently, only I-shaped (wide flange) sections can be assigned to beams in RAM Connection. It is not possible to assign other section types, like HSS or channels, to beam members, though they can be used as columns or braces in many connection templates.

What is the difference between Basic Connections and Smart Connections?

The RAM Connection Manual defines these connections as follows:

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

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

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

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

Some complex connection templates like gusset pate or base plates only have a smart variety. 

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

The abbreviations are defined in the RAM Connection Manual (available from the help ? or as a pdf from the Windows Start menu). The naming conventions for both joints and connections are listed in Chapter 2, The Connection Database - Database organization. Here is a list of the joint types from that section:

1. Beam – Column Flange (BCF)
2. Beam – Column Web (BCW)
3. Beam – Girder (BG)
4. Beam Splice (BS)
5. Column Splice (CS)
6. Continuous beam over column (CC)
7. Column, beams and braces (CBB)
8. Chevron braces (CVR)
9. Vertical X braces (VXB)
10. Column – Base (CB)
11. Column – Base – Braces (CB)

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

RAM Connection Standalone:

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

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

RAM Connection for RAM Structural System:

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

RAM Connection for Elements:

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

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

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

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

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

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

 * In Ram Connection 9.0 this arrow is blue.

Can I design a Gusset Connection using a Pipe Column?

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

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

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

RAM Connection Standalone or Ram Connection for RAM Structural System :

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

RAM Connection for Elements:

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

 RAM Connection Standalone (Versions Prior to v9.0)

1. Enter the Connection Pad by either double-clicking the large 3D display of the connection or clicking on the Design menu tab – Connections toolbar – Edit.
2. In the Connection Pad, click on <Loads> to open the Loads worksheet.
3. Click on the Load # associated with the load case and then click on the Delete button on the keyboard to delete it from the worksheet.

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

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

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

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

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

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

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

See Also

Troubleshooting Errors when Assigning Connections

Product TechNotes and FAQs

Structural Product TechNotes And FAQs

External Links

Bentley Technical Support KnowledgeBase

Bentley LEARN Server

Comments or Corrections?

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

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

Installation and Licensing  

• [[HWLockDLL internal error]]
• [[Ram Elements - Configuration settings]]

Ram Elements User Interface 

• RAM Elements Importing from RAM SS FAQ
• RAM Elements - View Control FAQ
• Ram Elements - Modeling FAQ
• Creating custom Sections, Materials, etc. in RAM Elements
• RAM Elements Deck Areas
• Ram Elements Shells FAQ

Ram Elements Analysis Topics

• RAM Instability In Finite Element Analysis
• RAM Elements Load Combos FAQ
• Ram Elements - Distributed Load errors
• [[Ram Elements - Tension Only Members]]
• RAM Elements Dynamic Modal Analysis FAQ

Ram Elements Design Topics

• RAM Elements Unbraced Lengths
• RAM Elements Effective Length Factors
• RAM Elements AISC Stability

Ram Elements Modules

• RAM Elements Masonry Wall FAQ
• Ram Elements Can't Save Integrated Wall or Footing designs

How do I get RAM Elements to perform a Response Spectra Dynamic Analysis?

1. After the geometry of the model is defined, place nodal masses using the Nodes>Masses spreadsheet input,

2. Define a dynamic load case for each X and Z direction,

3. On the Gen>Earthquake acceleration spreadsheet input, enter a scale factor, direction and damping percentage,

4. On the Gen>Response spectrum spreadsheet, enter some response spectrum,

5. Run the analysis and choose the desired combination method (e.g. CQC),

6. Click the View menu>Finite elements toggle,

7. Use the View>Modal deflection results to see the mode shapes or Output>Analysis> Dynamic analysis to get periods and modes info.

For more details, refer to Help>RAM Elements Manual>Chapter 10: Dynamic Seismic Analysis. 

to see example files go to;

C:\ProgramData\Bentley\Engineering\RAM Elements\Data\Samples

and open Dynamic1.etz or Dynamic2.etz.

How can I change the number of modes used in the dynamic analysis?

Click the Process menu>Analyze model toggle, and under Dynamic and Response Spectra change the number of modal shapes to calculate.

What scale factor should I apply to the response spectrum?

See RAMSS Dynamic Modal Analysis FAQ

Can RAM Elements perform an Eigenvalue solution to determine mode shapes without the response spectrum data?

RAM Elements will perform an Eigen solution without the response spectrum curve data. The program only requires that the Mass is entered in the Node>Masses spread sheet. Once the mass is defined the program will perform the Eigen solution and the View>Model shapes options and the Output >Analysis >Dynamic Analysis results will be available for viewing.

How do I generate the data for the response spectrum curve?

The data can be generated using ASCE7-05/10 section 11.4.5.  Sample curve data can be loaded using the "Open response spectrum file" toggle.  The following spread sheet shows how to generate this data given a site specific S_DS and S_D1.

http://communities.bentley.com/products/structural/structural_analysis___design/m/structural_analysis_and_design_gallery/255161.aspx

What loads are included in the automatic mass generation and how does the program determine which members or shells to include per rigid floors?

Here’s what’s included in the automatic mass generation (from selected dead and live loads with their percentage):

•             Point loads in nodes

•             Members self-weight

•             Members distributed loads

•             Pressure in members

•             Shell self-weight

•             Shell pressures

The requirements to consider a member in a specific rigid floor are:

•             Both nodes have the same floor number

•             One node belongs to the floor and the other one is below it

The condition to consider a shell in a specific rigid floor is:

•             All its nodes have the same floor number

See Also

RAMSS Dynamic Modal Analysis FAQ

STAAD.Pro Response Spectrum FAQ

Steel Unbraced Lengths in RAM Elements

General

The format for steel unbraced lengths (Lb pos, Lb neg, L33, L22, and LTorsion) changed in V11. The help context in the member design parameters worksheet discusses the format. This can be accessed by clicking on a cell in the Members – Steel Design Parameters worksheet and hitting F1 on your keyboard.

Old Implementation

Prior to V11, unbraced lengths were entered as a single value in the steel design parameters. If no value was entered, the unbraced length was assumed to be equal to the physical length of the member (j node to k node). If a non-zero value was entered, that value was used as the unbraced length for every station considered during the design of the beam. However, parameters such as Cb were always calculated using the physical length of the member. This limitation could be unconservative.

V11 Implementation

In V11, unbraced lengths need to be entered such that the sum of the unbraced lengths is equal the physical length of the member. For example, if a beam is 20’ long and the unbraced length is 5’, the unbraced length should be entered as 5;5;5;5. This allows the program to calculate parameters such as Cb for the actual unbraced segment rather than the physical length of the member. A tool button was introduced to rapidly generate the unbraced lengths.

However, this new method introduced some limitations into the program. For example, it is not possible to enter an unbraced length that is longer than the physical length of the member. This might be a necessity if you are modeling a bent or simulating a curved member. In addition, it is not possible to assign multiple Cb values to correspond to the unbraced lengths that were assigned. In other words, only a single Cb value can be entered and it will be used for all segments. If Cb is left blank, it will be calculated for all segments.

V12 Implementation

The V12 implementation functions as described below.

i. The engineer doesn’t type anything in the spreadsheet cell (either directly or with the tool) and thus the value remains the default “0”:  RE uses the physical length of the member as Lb and Cb will be automatically calculated based on the physical length of the member.

ii. Just one value is entered in the cell

     a. If the value is less than the member’s physical length, RE uses that value for all pertinent code checks (just like before v11.0) and Cb = 1. Besides printing Cb (as 1) in the design report, RE adds a note at the bottom of the report saying “Cb not calculated for the Lb specified. It is conservatively prescribed as 1”. However if there’s a value in the Cb cell other than zero “0”, then that value is used in all segments and the note is not printed.

     b. If the value is equal to the physical length of the member, then it would be exactly the same as i.a above.

     c. If the value is larger than the member’s physical length, RE uses that value for all pertinent code checks and Cb = 1. Besides printing Cb (as 1) in the design report, RE adds a note at the bottom of the report saying “Cb not calculated for the Lb specified. It is conservatively prescribed as 1”. However if there’s a value in the Cb cell other than zero “0”, then that value is used in all segments and the note is not printed.

iii. Multiple values are entered in the cell (either directly and separated with semicolon or using the tool):

     a. If the sum of the values is less or equal to the physical length of the member, RE calculates the difference for the last segment and Cb is automatically calculated for each segment. The sum is validated for unintended, non-summing entries.
 
     b. If the sum of the values is larger than the physical length of the member, RE does NOT allow it. In other words, one single unbraced length for the member, could be larger or smaller than the distance from node to node, but multiple unbraced lengths, must match the member’s physical length.

Note: Old models (prior to v11.0) opened in v12.0 will retain the original unbraced length assignments. These will fall under option ii above. The engineer must keep in mind that the final results may still vary because before, Cb was calculated with the physical length (which now only applies to option i above) and now with Cb = 1.

Similar behavior is applicable to L33, L22 and Ltorsion.

Adjusting the unbraced length of Built-Up members (double angles) to accommodate Intermediate Connectors locations.

In the Steel design criteria for AISC 360 there are two user variables that control this:

1. Intermediate Connectors - This option is used to define the use of two equations in the design of built-up members subjected to compression. The available options are:
   1. Intermediate connectors that are snug-tight bolted, to use the equation E6-1.
   2. Intermediate connectors that are welded or pretensioned bolted, to use the equation E6-2.
   3. Intermediate connectors in shear and bolt values based on bearing values (but pretensioned), to use the equation E6-2..
2. a (Connectors) - The distance between connectors in built-up members. It is used to calculate the modified slenderness of the built-up member following Section E6 specially 2L sections.

See AISC 360 Section E6 for further details.

See Also

RAM Elements Effective Length Factors [TN]

Structural Product TechNotes And FAQs  

Effective Length Factors in RAM Elements

General

AISC effective length factors (K33 and K22 factors) can be automatically calculated in V12.  This document discusses the implementation prior to V12 and the changes made in V12.  The value of K Torsion did not change.  It defaults to K=1.0 unless another value is entered in the AISC steel design parameters.

Old Implementation

If the K22 or K33 field was left blank or set to zero in the AISC Steel Design Parameters, the program automatically assumed K = 1.0.  There was tool buttons to calculate K33 and K22. If this tool was selected, the program used the following equations to calculate K.

Members Assigned as Sway
K = SQRT((1.6*GB*GA+4*(GB+GA)+7.5)/(GB+GA+7.5))

Members Assigned as Non-Sway
K = min(min(0.7+0.05*(GB+GA),0.85+0.05*min(GB,GA)),1.0)

GA and GB values depend on member stiffness as described by specification commentary.  Values that were theoretically infinity (pinned) were assumed to be 10.  Values that were theoretically fixed were assumed to be 1.

V12 Implementation

V12 added new Value Type K33 and Value Type K22 parameters.  When the Value Type is set to ‘None’, the program functions as it did in previous versions and K will be assumed to equal 1.0 unless a value is entered for K.  If the Value Type is set to ‘Recommended’, the program will use the recommended approximate values in Table C-C2.2 in the 13th Ed AISC Manual.  If the Value Type is set to ‘Theoretical’, the program will use the theoretical approximate values in Table C-C2.2 in the 13th Ed AISC Manual.

When the tool button in the steel design parameters is used to calculate K, the alignment charts in Chapter C of the commentary in the 13th Ed AISC Manual are used.  This method considers the stiffness of rigidly connected members and uses the equations below.  The tool button cannot be used when the multiple unbraced lengths (L33 and L22) are entered for the member.

Members Assigned as Sway
(GA*GB*(Pi/K)^2-36)/(6*(GA+GB))-(Pi/K)/(tan(Pi/K)))=0

Members Assigned as Non-Sway
(GA*GB/4)*(Pi/K)^2+((GA+GB)/2)*(1-(Pi/K)/(tan(Pi/K)))+(2*tan(Pi/(2*K)))/(PI/K))=0

GA and GB values depend on member stiffness as described by specification commentary.  Values that were theoretically infinity (pinned) were assumed to be 10.  Values that were theoretically fixed were assumed to be 1.

Special Considerations

The automatic calculation of K is based on the physical length of the member.  Therefore, members framing into intermediate nodes along the member have no impact on the calculated effective length.  For this reason, it is best to segment the member so the physical length matches the unbraced length.

When 2D frames are designed, the out-of-plane effective length factor will be calculated for the columns unless a value is entered in the steel design parameters or the out-of-plane value type is set to ‘None’.  Typically, the calculated value would be incorrect and the effective length should be assumed to be 1 for the out-of-plane direction.

There are many instances where the effective length method should not be used and K should equal 1.0.  The program does not attempt to determine these conditions and will always calculate a value based on the parameters and the analytical model.  For example, members with theoretical pinned ends (GA = GB = 10) will always have a calculated effective length of 3.01 for sway frames and 0.96 for non-sway frames.


Practical Example

Consider a simple portal frame with 15’ long W12X96 columns and a 20’ long W21X83 beam.  Assume the bases of the columns are pinned and there are no releases at the top of the column or ends of the beam.  The column is oriented such that the beam frames into the column flange (strong axis bending).

The frame would be classified as sway in the plane of the frame (frame type 2).  In the out-of-plane direction, the K22 value should be assumed to be 1.0 since the frame will lean against the diaphragm or some other support for stability.  Do not simply set frame type 3 to non-sway.  The Value Type K22 should be set to ‘None’.  It is also appropriate to set K33 for the beam to 1.0 or assign Value Type K33 as ‘None’.

If the tool button is used to compute K33 for the columns, the equations below are used.  Looking at the figure C-C2.4 in the 13th Ed AISC manual, K should be around 1.8.  The equation below is nearly zero when K = 1.81.  That matches the value calculated by the program when the tool button is used in the steel design parameters worksheet.

GA = (EI/L column) / (EI/L beam)
GA =( 29000*833/15) / (29000*1830/20) = 0.607

GB = 10 Assumed at pinned end

(0.607*10*(Pi/1.81)^2-36)/(6*(0.607+10))-(Pi/1.81)/(tan(Pi/1.81)))=0.01

When Value Type K33 is set to ‘Recommended’ for the columns, K33 will be assumed to be 2.1 is indicated in Table C2-2.2(e).

When Value Type K33 is set to ‘Theoretical’ for the columns, K33 will be assumed to be 2.0 is indicated in Table C2-2.2(e).

Does the steel design impose a limit on the slenderness ratio, KL/r?

No, but if the KL/r ratio of a compression member exceeds 200, or if the L/r ratio of a tension member exceeds 300, you will get a warning in the steel design report (and a yellow status color on screen using View - Status). Here's an example from the concise steel report:

Design code: AISC 360-2005 ASD

Member : 3 (BC)
Design status : With warnings

DESIGN WARNINGS

- The slenderness ratio KL/r about major axis of the member in compression should not exceed 200
- The slenderness ratio KL/r about minor axis of the member in compression should not exceed 200
- The slenderness ratio L/r of the member in tension should not exceed 300

These warnings can be totally suppressed by not checking the option, "Include slenderness recommendations" in the Process - Design dialog.

See Also

Steel Unbraced Lengths in RAM Elements [TN]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs  

RAM Elements AISC 360 Stability Analysis and Design

General

Chapter C of the AISC specification (2005 and later) covers stability analysis and design. This document discusses how the requirements are met in RAM Elements.


Analysis and Design Using General Second-Order Elastic Analysis

RAM Elements has the ability to perform a general second-order elastic analysis per AISC 360 C2.1. It is an option in the Process tab – Analyze Model – Analysis tab. This method captures big P Delta effects but will not capture small P delta effects unless the individual members are segmented into smaller pieces in the finite element analysis. For example, imagine a column that is 15’ long. If it is modeled as a 15’ long member, small P delta effects are not captured. If it were modeled as five 3’ segments, small P delta effects are captured because there are additional nodes between the ends of the member. Currently, there is no option to automatically segment the members this way in the finite element model and it must be done manually. Please note, if you segment a member, be sure to specify the proper unbraced lengths in the steel design parameters. The unbraced lengths will always default to the physical length of the member.

AISC 360 C2.2a(2) requires an analysis for ASD design to be carried out under 1.6 times the ASD load combinations and the results divided by 1.6 to obtain the required strengths. It is currently not possible to divide the results by 1.6 in RAM Elements. Therefore, you must use LRFD.

AISC 360 C2.2a(3) requires notional loads to be considered in the gravity only combinations unless initial out-of-plumbness has been modeled. Currently, notional load cases do not exist in the program as a predefined load type. They need to be manually modeled as unique load cases and manually accounted for in the load combinations. For example, imagine you have a structure with dead load and live load. One would create a notional dead and live load cases in two independent directions. Let’s assume they were called NDX, NDZ, NLX and NLZ. For the typical gravity combinations 1.4 DL and 1.2 DL + 1.6 LL, you would need to create a total of four load combinations to account for the notional loads.

1.4 DL + 1.4 NDX
1.4 DL + 1.4 NDZ
1.2 DL + 1.2 NDX + 1.6 LL + 1.6 NLX
1.2 DL + 1.2 NDZ + 1.6 LL + 1.6 NLZ

AISC 360 C2.2a(4) discusses effective lengths. This Wiki page discusses how effective lengths are implemented in RAM Elements. Effective Lengths in RAM Elements

A practical example for the general second-order elastic analysis is discussed here.  RAM Elements AISC 360 Stability Example

Other Limitations

It is not possible to run P Delta with dynamic load cases. Second order effects must be accounted for by hand.

Currently, the Direct Analysis Method discussed in AISC 360 Appendix 7 is not implemented in RAM Elements V12. Therefore, structures with a second order drift to first order drift ratio exceeding 1.5 cannot be designed in RAM Elements per AISC 360 C2.2.

See Also

Product TechNotes and FAQs

Structural Product TechNotes And FAQs  

Deck areas are a convenient tool for generating distributed loads associated with surface loads on members. For general information on modeling deck areas, please see Chapter 18 in the RAM Elements Manual. Additional modeling tips and common issues with deck areas are discussed below.

Deck area distribute load to members that border the deck area only. A load will not be distributed to any members that are inside but do not border the actual deck area.

Shells do not qualify as perimeter member. If a deck is bordered by a shell on one side as shown in the screen capture below, a error indicating that no member is connected between two nodes of the deck area will be displayed during the analysis (see error message below). To work around this problem, model a GEN section with very low stiffness between the nodes at the top of the shell.

Because loads are only distributed to members that border the deck area, a separate deck area needs to be modeled in each bay of framing. The fastest way to do this is to first select all members on a level and then click on one of the active spreadsheet tools shown below to generate the deck area:

This will generate a deck area in each bay as shown below:

In some cases, it may be convenient to use a deck area for both in-plane and out-of-plane pressures. One practical example is a perimeter wall that is subject to out-of-plane pressure due to wind load and in-plane pressure associated with the dead weight of the cladding. The current implementation of the deck area feature will not calculate distribute loads for some in-plane pressures. If the surface load vectors are defined so that they are parallel and in-plane of the deck area, then no distributed load will be calculated. However, if the surface load vectors are defined so that they are in-plane of the deck area but perpendicular to the deck span, then a distributed load will be calculated.

In the screen capture below, the deck area on the right is defined with Vector Y = 1 for the deck span and Y Dir = -1 for the surface load. Since the surface load is in-plane and in the same direction as the deck, no load is distributed to the members. The deck area on the left is defined with Vector X = 1 for the deck span and Y Dir. = -1 for the surface load. Since the surface load is in-plane but perpendicular to the deck, an in-plane distributed load is applied to the members.

There is also a bi-directional feature for deck areas that can be used to distribute loads in two directions. When using this feature to model two-way decks, it is important to note that the program calculates the tributary area of the member, determines the tributary load to the member, and applies a uniformly distributed load over the length of the member based on this load. The program will not distribute a triangular or trapezoidal load as may be expected.

For bi-directional deck areas, the resultant of the deck span vector (Vector X, Vector Y, and Vector Z) should always be a unit vector. The magnitude of the load that is applied is scaled by the resultant. In the screen capture below, a 1 ksf pressure is applied to a 20 ft x 20 ft deck area. The deck area on the left is defined with Vector X = 0.707 and Vector Z = 0.707. The resultant = [0.707^2 + 0.707^2]^0.5 = 1. The deck area on the right is defined with Vector X = 1 and Vector Z = 1. The resultant = [1^2 + 1^2]^0.5 = 1.414. Note that the total load for the deck area on the right is 1*(1 psf)*(20 ft)*(20 ft) = 400 k. However, the total load for the deck area on the left is 1.414*(1 psf)*(20 ft)*(20 ft) = 565.6 k.

Why are the yellow lines for members shortened at the nodes? 

The lines are drawn slightly short of the nodes so that the nodes are clearly visible in line mode.

In the fully rendered view you can see the members full length (or shrunken)

I have a small model and the support icons appear very large, how can I make them smaller?

The size of the nodal support, member hinge and other icons is typically adjusted based on the overall size of the model, but the user can force the icons to appear larger or smaller. 

To control the size of the icons go to the e menu (file menu) and pick General Configuration. On the Display tab, uncheck the box for  Data and Results - Automatic Scale and then enter a number >1 to make the icons larger, <1 to make them smaller.

How can I rotate the view?

In order to rotate the view, click and hold the right mouse button, then drag the mouse to dynamically rotate the view. Note, in RAM Elements, the Y axis typically points upward and this axis is always plumb on the screen.

If you find the rotation is too fast or too slow for your liking, go to the e menu - General Configuration and on the General tab, adjust the Mouse rotation sensitivity slider.

How can I Save a View?

In Ram Elements you can save a particular type of view including the angle of the view, the zoom, perspective settings and display options. To do so, first adjust the graphic as desired, then right click on the view and choose Customized Views - General - Create. Provide a name for the view, check the desired attributes to save and click Create.

These general views work across all files.

The program also allows you to save model-specific views. To do so, again adjust the view the way you like it. Then right click on the view and pick Customized Views - Current Model.

In addition to the attributes mentioned above, Current Model views also store the active selection set and any hidden members for instant recall.

To recall a saved view, simply right click on the graphic and pick the saved view by name from the Customized Views.

How can I make the on screen text easier to read?

At the bottom right corner of the Ram Elements window are the controls for increasing or reducing the text size on screen. Just to the left of that is the control for units.

By not Showing the units more significant digits are shown, filling roughly the same screen area.

Using Larger or Smaller units under Units Configuration can affect the displayed number of digits. For example. if the axial force in a column is -2471.45 pounds, switching to kips changes the display to -2.47 kips which is shorter.

Regretfully, there is no other user control over significant digits displayed.

How can I view the design properties, things like unbraced length?

From the View Ribbon menu, in the Design Toolbar, select Design Properties and one or more of the options:

• Effective length factors (i.e. K22 and K33)
• Axial and torsional unbraced lengths (i.e. L22 and L33)
• Flexural unbraced lengths (i.e. Lbpos and Lbneg)

Note, for unassigned default values (0) nothing will be shown on screen. Only user specified values are plotted.

How do I change the scale of the deflection multiplier?

Click on RAM Element button in the top left corner and click on the button 'General configuration'. Then select tab Display and change the deflection multiplier as shown in the screenshot:

How can I assign a member to be tension only?

Go to the Members tab of the spreadsheet input, and go to the hinges sheet. The first field is for "Axial rigidity". Set this to tension only by selecting that option from the drop down list, or use the Ribbon menu tool "Tension only" once you have only the desired members selected.

Why is my tension-only brace failing in bending?

There are three typical reasons why a tension-only member will induce bending.

1. If the member ends are fixed, a tension-only member can still develop and end moment. Tension-only members are typically hinged at both ends in both M3 and M2 axis, if not also torsion.
2. If self-weight loads are applied this will cause the member to bend or sag under its own self-weight. To alleviate this issue we suggest using a weightless, zero density material for tension only member. An "A36 weightless" material is provided out of the box for this purpose.
3. If the tension-only member intersects other members and the Finite Element analysis option to "Add intermediate nodes at member intersections" is checked, then there will be intermediate points of connection (without hinges) leading to force transfer and potentially bending. We suggest not using this option for models with tension-only braces. If there are other places where you really want joints at member intersections, manually segment those portions using Process - Segment selection.

See Also

RAM Instability In Finite Element Analysis

RAM Frame - Tension Only [FAQ]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs