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To assign Global Effective Length or K factors, • Select Criteria - K Factors (Effective Length). • In the K Factor dialog box that appears, set the Column Kx value to Use Nomograph and set all other values to 1. You will assign a K factor of 1 to the strong axis of the braced frames in the next section. (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 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 the other Moment Frame beams.
Since some of the lateral columns in this model are part of braced frames, it is necessary to override the global Nomograph selection of Kx. This global selection was made previously using the Criteria - K Factor menu item. To assign a K factor to an individual member: • Select View - Elevation and pick one of the braced frames. • Select Assign - Columns - K Factor (Effective Length). • In the Assign Column K Factor dialog box that appears, set Major Axis - Kx (Le / L) to Use and Type 1.0 for the value. • Click [Fence]. • With the cursor fence all of the steel columns in each of the braced frames. (Note; it is OK to also fence the concrete columns on those frames, as these commands will only be assigned to steel columns. Concrete column slenderness parameters are set within the Concrete Design Module). • Repeat for the other two frames. Note; the assignment can also be made in 3D view provided you can select the column of the braced frames without selecting the columns in the moment frames. The rotation angle of the 3D view can be altered using view - rotate. The screen should now display the K Factor setting that has been applied. To clear the screen, • Select View - Reset Model.
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 appears, 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.
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].
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 that 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 appears, 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 the circled X to close 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 the circled X to close the report. Take time now to review the various reports available in the Reports menu.