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Structural Analysis Modeling:
Model Haunches in the Slabs
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If this option is selected then the stiffness of the haunches (if any) are incorporated into the structural model at the top and bottom of the exterior walls. This will cause a redistribution of the wall moments mid-height to the top and bottom of the walls.
Critical Sections:
Consider Haunches
Select this option to have haunches considered in the selection of the location of the critical section. If haunches are specified and this is checked then the program will design the member using moment and shear values beyond the face of support in accordance with whether or not the user has selected to extend the critical section (see below). If this is not checked then the program will design the member using moment values at the face of the intersecting members and shear values at the dv (or d for STND) from the face of the intersecting members regardless of the specified haunch lengths. This will provide a more conservative design.
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By default the haunch is only used to position the critical section, although the haunch may also be used to stiffen the corners of the structural model. By selecting this option, the user may also direct the program to use the haunches in the calculation of the flexural and shear resistance.
Flexure:
Use Eq. 12.10.4.2.4a-1
If checked, the flexural moment capacity is calculated using LRFD Eq. 12.10.4.2.4a-1. The program applies a factor to the Nu term in the equation, thereby allowing the user to ignore the effects of axial thrust if desired. Note that this equation is modified in CHBDC. See the theory section for the revised equation.
Ignore Axial Thrust
If unchecked, the flexural moment capacity is taken from a location (based on the applied P) on a P-M diagram built internally by the analysis routine for AASHTO Codes. If checked, the flexural moment capacity is set to where the P-M diagram crosses the horizontal axis (P = 0), causing Ma (allowable) to be equal to Mu (pure flexure) in the printout. Also if checked, the variable phi will not be calculated under LRFD, and will be set to that which the user has input on the Load and Resistance Factors page.