Direct design of three-dimensional frames using practical advanced analysis

A new design method of three-dimensional frames using practical advanced analysis is presented. In this method separate member capacity checks encompassed by the code specifications are not required, because the stability of separate members and the structure as a whole can be rigorously treated in determining the maximum strength of the structures. To capture second-order effects associated with P-δ and P-Δ effects, stability functions are used to minimize modeling and solution time. Generally, only one or two elements are needed per member. The Column Research Council (CRC) tangent modulus concept is used to account for gradual yielding due to residual stresses. A softening plastic hinge model is used to represent the transition from elastic to zero stiffness associated with a developing hinge. The load-displacements predicted by the proposed analysis compare well with those given by other approaches. A design example has been presented for a 22-story frame. The analysis results show that the proposed method is suitable for adoption in practice.