The purpose of DIRECT ANALYSIS is to compute the member forces for strength design. For computing drifts, deflections you should use a PDELTA 15 ANALYSIS with the un-reduced stiffness and not a DIRECT ANALYSIS. Both analysis commands could be part of the same model. Start with the un-factored service cases followed by PDELTA 15 ANALYSIS and CHANGE. Subsequently specify the strength cases followed by DIRECT ANALYSIS.
↧