In Seismic Provision mode the structure is checked in accordance with the detailing and design requirements of a selected seismic code. The checks performed in this mode rely heavily on the load combinations and design criteria established in the Standard Provision Mode. Note that only the AISC 05 - LRFD post processor will be used in this tutorial although the AISC-02, AISC - 97 and UBC - 97 codes work in a similar manner.
The Seismic Provision Mode is only accessible if one of the AISC Steel Design codes (ASD or LRFD) is used in Standard Provision Mode. There must also be at least one seismic load case defined. If your model is based on the British code or if you do not have a license of the Special Seismic provisions module, skip this entire section.
To switch to the Steel – Seismic Provision mode:
- Select Mode – Steel – Seismic Provisions.
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- In the Special Seismic Provision Codes dialog box that opens, select the button for AISC 05 - LRFD.
- Under Options, Check all checkboxes.
- Type 1.1 for the Cpr Factor and 4 for the EBF Cd Factor.
Note that you are not able to change to the AISC-05 ASD or the UBC 97 – ASD code because this requires that an AISC - ASD Steel Design Code be selected in Standard Provision mode prior to entering the seismic mode.
This dialog can be displayed any time while in Seismic Provision mode by selecting the Criteria - Codes menu item.
- Click [OK].
In the Seismic Provisions Load Combinations dialog box that opens
- Set the Live Load factor to 0.5
- Set the Sds value to 1.113
- Set Omega to 3.
- Click [Generate].
- Click [OK].
Additional Customized Load Combinations can be defined and selected in the same way that they are in Standard Provision mode.
Assign Frame Type
In order to check the members and joints for these provisions you must first define what type of lateral frames exist in the model:
- Select View – Elevation and pick the Moment frame on Grid 4, if not already selected.
- Select Assign – Frame Type.
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- In the Assign Frame Type dialog box select Special Moment Resisting Frame as the Frame Type.
- Click [Fence].
- Fence the entire moment frame.
- Click the 3D View icon in the toolbar to return to the 3D View.
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- Select View – Elevation and pick the braced frame on Grid A, if not already selected.
- Select Assign – Frame Type again.
- Change the Frame Type to Eccentrically Brace Frame.
- Click Fence and fence all of the steel members in the braced frame on Grid A.
- Repeat for the braced frames on grid F except change the frame type to Special Concentric Braced Frame for the upper 2 bays, and SCBF –Chevron for the lower bay.
- Return to 3D View.
Member Code Check – Seismic Provisions
To check the member design against the special seismic provisions, you will follow the same steps as for standard provisions: To start the code check:
- Select Process – Member Code Check.
A progress bar will keep you informed of the progress of the code check. When the code check is complete, the lateral system of the model will appear color coded to indicate the design status of the members.
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 lowest steel columns in the moment frame.
The Column View/Update dialog box should appear. In the lower box is a list of the various design provisions and an indication of which checks the member has passed, or failed. The signal light in the box will be lit red to indicate the member has failed one of these provisions.
NOTE: Double click on any icon in the results list box to view a short explanation of that icon. Refer to the technical manual for a description of all the View/Update icons.
- To see the details of the design Click [View Results].
The Seismic Provisions Member Code Check Report should come up. Review the report. For more information on the designs performed in this check refer to the technical portion of the RAM Frame – Special Seismic Provisions documentation.
- Click
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to exit the report. - Select the W14x43 section from the Column Size list box.
- Click [Analyze]. The design checks and signal light will be updated to reflect the results of the analysis.
- Click [Cancel] to revert to the original size.
to exit the report.NOTE: Some of the beams and braces in the chevron braced frames will fail the special seismic provisions code check. Feel free to increase the size of those members now. An HSS6x6x3/8 should work for the braces and a W12x30 should work for the beams. Besides using the View/Update command, member sizes can also be assigned directly using the assign menu options.
Joint Code Check – Seismic Provisions
You will now perform a code check on of the rigid beam to column connections according to the Special Seismic Provisions of the selected code. To perform a joint code check:
- Select Process – Joint Code Check.
When the code check is complete, the steel beam - column joints of the lateral system will appear as colorful dots indicating the status 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 top floor (blue) nodes in the moment frame (Frame on Grid F).
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- To see the details of the design Click [View Results].
- Feel free to investigate other sizes and click [Cancel] when finished. If you make the column slightly larger you can possibly avoid the need for stiffener plates.
Reports – Seismic Provisions
Many different reports can be generated from the seismic code check of the structure. The printed output is mostly generated using the Reports menu. The print options available in Seismic Provisions Mode are different than those available in Analysis Mode. To print the detailed seismic code check results for one or more member:
- Select Reports – Member Code Check – Single.
- Pick any lateral member.
- Close the report.
To print a summary of the results for all the member code checks:
- Select Reports – Member Check Summary.
A similar output is available for the joint code checks.
- Select Reports – Joint Check Summary.
Take time now to review the various reports available in the Reports menu.
- Continue to RAM Frame - Drift Control Tutorial
- Go back to RAM Frame Steel - Standard Provisions Tutorial
- Up to the RAM Structural System Tutorial