Evaluation of ACI 318 and AISC (LRFD) strength provisions for composite beam-columns

Abstract

The development of an interactive computer program for modeling biaxial bending of encased composite steel-concrete columns and its application to design are presented. Included is a description of an analytical procedure for modeling inelastic behavior based on the fiber element method. Results of fiber element analyses are used to evaluate nominal uni- and biaxial bending strengths of composite columns calculated according to the ACI-318 and AISC-LRFD specifications. Slender column behavior and the effect of residual stresses and built-in forces (resulting from the construction sequence) in the steel sections are included. In addition to providing insight into behavior and assessing current design provisions for composite columns, the implementation of the fiber element method demonstrates the feasibility of using inelastic simulation programs in design.