Analysis/Design Parameters (LRFD) Screen
For LRFD design code, the Analysis/Design Parameters screen will appear. You can modify or review the resistance factor, Eta factor, multiple presence factor, dynamic load allowance, shear and torsion calculations, and clear concrete cover and ff for fatigue limits. User's have the option of changing the modulus of rupture to be used in the flexural calculations. You can choose to perform flexure design either as per LRFD 3rd Edition with interims of 2006 or using the older approach named, classic approach on this dialog. You can choose to perform crack control check either as per AASHTO LRFD 2004 or as per Interims of 2005. You can also switch between the simplified and general method for shear and torsion design.
When Phi as per classic approach is chosen, program asks and uses the φ values for flexure and axial force. For cap beam and footing only the values for flexure are used. For columns φ is computed based on the axial force in the column. When the Phi as per 2006 classification is chosen, user will need to specify φ value for tension controlled sections and compression controlled sections. Additionally you will need to specify c/dt ratios where the φ changes (i) from tension controlled sections to in-transition sections and (ii) from in-transition sections to compression controlled section. Please see Resistance Factors/ Strength Reduction Factors φ for details on how the Phi factor is computed.
The 2006 interims for AASHTO LRFD 3rd Edition allow computation of column effective length factor k which can be less than 9.0. If you would like to calculate k using the formula of 2006 interims, check the compute k for braced columns as per LRFD 2006 box in the column slenderness area of this screen.
If inverted Tee cap is selected in pier configuration, shear and torsion tab shows cohesion and friction parameters.
Clicking on the Seismic Design Parameters button opens another dialog on which parameters related to seismic design may be specified.
- Option of Use concurrent shear and torsion, and the default is unchecked. However, when this option is checked, two typical scenarios (i.e., the max shear force together with the concurrent torsion load; the max torsion load together with the concurrent shear force) at each point of interest (POI) will be used and reported at in the shear/torsion design.
- Option of Shear force is equally distributed among stirrups, and the default is unchecked. However, when this option is checked, it assumes the equal distribution of shear force among all legs at failure, where the demand of transverse reinforcement is based on the controlling case of exterior legs.
