Moment Amplification Factor for P-δ Effect of Steel Beam-Column

Abstract

The American Institute of Steel Construction load and resistance factor design (AISC-LRFD) Specification states that second-order effects should be considered in the design of frames; however, most designers are experienced only in first-order analysis. To accomplish the second-order design requirement, the AISC-LRFD Specification provides an approximate method to account for the second-order effect bases on first-order analysis, where moment amplification factors B1 and B2 are introduced to account for the P-δ effect (member instability) and PΔ effect (frame instability), respectively. However, the B1 factor of the AISC-LRFD Specification may vary greatly from the exact solution, especially when the member is under a high axial load. In this paper, a new moment amplification factor B1* is proposed for calculating the P-δ effect in the design of steel beam-columns. Parametric studies were performed to examine the accuracy of the proposed moment amplification factor and to compare it with that from theoret...