RAM Frame Steel - Standard Provisions Tutorial

Within RAM Frame there are two steel post-processing modes: the Standard Provisions mode and the Seismic Provisions mode. In Standard Provisions mode the ability of the structural members to carry the applied gravity and lateral loads (including seismic) is checked according to the primary design code. In Seismic Provisions mode the structure is checked for the seismic detailing and design requirements of the selected seismic code (US codes only).

These are optional modules and are not always included with the RAM Frame basic module. In order to perform this section of the tutorial you must have the RAM Frame – Standard Provision Module installed and licensed.

To switch to the Steel – Standard Provision mode:

• Select Mode – Steel – Standard Provisions .

• In the Steel Design Code dialog box that opens, check the button for AISC 360-05 LRFD . If your model was built using SI and British code selections, feel free to select the BS 5950:2000 code.
• Click [OK] .
• This dialog can be displayed any time while in Standard Provision mode by selecting the Criteria – Codes menu item.
• The AISC 360-05 LRFD Load Combination Generation dialog box should appear:

• Select IBC06/ASCE7-05LRFD (BS 5950) from the Code Combo drop-down list.
• Type 0.5 for LL Factor f1
• For Sds type 1.113 (this was taken from the loads and Applied Force report in Analysis Mode – Load Cases).
• Select Use Calculated for Rho .
• For Snow Factor, select Use Reduced Factors on Snow in Combinations with Seismic (for British code models Generate the combinations using the default criteria).
• For the Notional Loads select , Consider with Combinations containing only gravity loads .
• Click [Generate] .
• Click [OK] .

NOTE: Load combinations will only be generated using the load cases checked in the Analyzed Load Cases to include section. If the program generates any load combinations that you do not wish to be considered, uncheck the Use box for that combo.

Additional Customized Load Combinations can be defined and selected in the same way that they are in Analysis – Load Combinations Mode. The load combinations created within each mode are unique to that mode. Load combinations can be copied from one custom combination dialog to another using the cut and paste tool buttons in the dialog box.

Design Criteria

As in the analysis mode, the Steel Mode has a set of criteria that govern effect the design results of the structure. A complete discussion of these criteria appears in the RAM Frame documentation. It is recommended that you review and understand each of these criteria before accepting RAM Frame design results.

• To assign the  characteristic of the building:
• Select Criteria – B1 and B2 Factors (Moment amplification factors) .

• In the dialog box that opens , select Both Apply B1Factors and Apply B2Factors .
• Leave the Rmx and Rmy at 1.00 .

NOTE: S ince P-delta was selected in the original analysis, these factors are not necessary to complete the Direct Analysis Method set forth by the AISC 360-05 design spec. If P-delta was not selected this step would be required to complete the selected analysis.

• Click [OK] .

To assign Global Effective Length or K factors,

• Select Criteria – K Factors ( Effective Length).
• In the K Factor dialog box that opens , notice the only values that can be modified are the braces. Again this is due to the analysis code chosen at the beginning. Different codes give different levels of control (for British code models use the defaults).

• Click [OK] .

To set the flange bracing criteria for beams and columns:

• Select Criteria – Flange Bracing .

• Check Top Flange Continually Braced for Beams.
• Check Deck Braces Column for Columns.
• Uncheck the other options.
• Type 60 for Maximum angle from column axis for which beam or brace braces column.
• Click [OK] .

The Column Moments criteria can be used if you wish for the moment connections in the building to transfer only a portion of the end moment to the supporting column. This can be helpful in designing partially restrained, Type 2 connections (Refer to AISC Steel Specifications for more information), but will not be covered in this Tutorial.

To turn off the Axial Slenderness limits prescribed by the code:

• Select Criteria – Axial Slenderness Limits .
  

• Check both options.
• Click [OK] .

Besides member design criteria, RAM Frame also checks moment connections for stiffener and web plate (doubler) requirements.

To assign the criteria to be used in the Joint Design:

• Select Criteria – Joints .
• Click [OK] to accept all the defaults.

For the Special Moment Frames in this model, we can also assign Reduced Beam Section Criteria (US models only).

• Select Criteria – Reduced Beam Sections .

• For the W16X40 , type 8,10 and 1.75 (200,, 250, 44) for a, b and c respectively.
• Click [OK] .
• In order to have the reduced beam sections considered an assignment must be made to the Beams in the Special Moment Frames.
• Select View – Elevation and pick one of the moment frames.
• Select Assign – Beams – Reduced Beam Sections .

• Set the Action to Use Reduced Beam Section and select the beams with a single or fence option.
• Repeat for all other Moment Frame beams.

Member Code Check – Standard Provisions

You will now perform a code check on all lateral members using the load combinations you selected previously. To perform a code check:

• Select Process – Member Code Check .

A progress bar will keep you informed of the progress of the code check. Because the program needs to check each unbraced segment of each member for each load combination, the process can take several minutes.

When the code check is complete, the lateral system of the model will appear color coded to indicate to what degree the members are stressed. A color scale correlates the colors to the interaction values of the members. The display of each member is based on the controlling Interaction Equation from all the selected load combinations.

• Click [Show Values] to display the interaction equation values on screen.

NOTE: An interaction value of “–1” indicates that the member fails some prescriptive limitation (e.g. KL/r > 200).

The View/Update command can be used to interactively modify individual member sizes to improve the design.

• Select Process – Member View/Update .
• With the cursor, select one of the red beams in the braced frames at the roof level.

The Beam View/Update dialog box should appear. In the lower left hand corner is an indication of the maximum interaction equation or design warning. In this case, the bottom flange of the beam is completely unbraced. When there is compression in the member it will thus fail the KL/r limit of 200 (US codes) or it will fail the L/r limit of 300 when the member is in tension. The stoplight in the box will be red to indicate when the member has a design warning.

• Click [Close] .
• Select one of the Moment Frame beams.
• This beam should pass and the interaction value will be listed at the bottom.
• To see the details of the design Click [View Results] .

The Member Code Check Report should come up. Review the report. In particular, take note of the unbraced length for bending – Y-axis value.. A beam is typically broken into several unbraced segments, each with a different unbraced length. The single segment that yields the highest interaction ratio is the one segment that gets reported on the design report.

NOTE: When a member fails a prescriptive limit, the reports results are for the first combo that causes the problem. The reported forces are not necessarily the critical forces. 

For more information on the design performed in this check, refer to the technical portion of the RAM Frame Manual.

• Click  to exit the report. Select a different section from the Beam Size list box. Click [Analyze] . The interaction equation and signal light will be updated to reflect the results of the analysis. Click [Close] to exit without saving the modified design. (Click [Update Database] if you want to make the change permanent.)

If you modify any member size using the view/update command, the color of the member will change to indicate the new level of stress. As with View/Update in Analysis Mode, a second member can be selected without closing the View/Update dialog box.

NOTE: The program uses the member forces from the original analysis, but uses the section properties of the currently selected size when a redesign is performed. Once sizes have been changed the analysis of the model is no longer technically valid. Notice that the status indicator light on the status bar in the lower right corner has turned yellow to indicate that you should view all results with caution as they no longer represent the analysis of the current member sizes in the database. Whenever member sizes are changed, the analysis should be re-run to insure accuracy. This applies to all of the View/Update commands in RAM Frame.

To rerun the analysis and verify the new sizes:

• Select Mode – Analysis – Load Cases .
• Select Process – Analyze .
• When the Analyze dialog box opens , make sure that all of load cases are selected and Click [OK] .
• Select Mode – Steel – Standard Provisions .
• If you want to skip the slenderness limit checks this time, select Criteria – Axial Slenderness Limits and turn off both parameters.
• Select Process – Member Code Check .

The new code check results should be indicated on screen. By working through a few cycles of this process, you can quickly converge on an efficient working design.

Joint Code Check – Standard Provisions

You will now perform a code check on the rigid beam to column connections. To perform a joint code check:

• Select Process – Joint Code Check .

A progress bar will keep you informed of the progress of the code check. When the code check is complete, the nodes of the lateral system will appear as colorful dots indicating the status of the joint. The status represents if the joint is valid (refer to Technical Section in the RAM Frame manual), and what strengthening is required of the joint.

The View/Update command can be used to interactively modify individual column sizes to improve the connection design.

• Select Process – Joint View/Update .
• With the cursor, select one of the green colored nodes.

The Joint Web Plates and Stiffeners dialog box should appear. A graphic shows the various member sizes that meet at the selected joint and the signal light indicates the status of the column. The size of stiffeners and web plate are listed when necessary.

NOTE: The graphic displayed in the View/Update dialog represents a view from the minor axis direction of the column. The graphic shows the steel beams that frame into the flanges of the steel column. No members supported on the web of the column are shown.

As with Member – View/Update , this dialog box allows you to select other column sizes and investigate the stiffener plate requirements by clicking [Analyze] . You can view the Joint Code Check Report by selecting [View Results] and you can update the column size if desired by Clicking [Update Database] .

Moment frame joint code check

Reports – Standard Provisions

Many different reports can be generated from the design results of the structure subject to the various load combinations. The printed output is generated using the Reports menu. The print options available in Steel Mode are different than those available in Analysis Mode. The forces and reactions printed while in Steel Mode are based on load combinations in that mode. To print the minimum and maximum reactions for any load combination:

• Select Reports – Screen .
• Select Reports – Reaction Envelope .

• In the Select Frame Numbers dialog box that opens , choose which frames you would like to review and click [OK] .

The Reactions Envelope report should come up. Hit the Page Down Key to see the rest of the report. Notice that the reaction values are given for the worst case among all load combinations in that mode.

• Click  to exit the report.

To print a summary of the results for all the member code checks:

• Select Reports – Member Check Summary .
• Select a frame or frames and click [OK] .
• The Member Check Summary report should come up.
• Click  to exit the report.

Take time now to review the various reports available in the Reports menu . See the Direct Analysis Validation report in particular for the AISC 360-05 design code.

• Continue to RAM Frame Steel - Seismic Provisions Tutorial
• Go back to RAM Frame - Shear Wall Analysis Module Tutorial
• Up to the RAM Structural System Tutorial