Moment amplification factor for P-delta effect of steel beam-column

The American Institute of Steel Construction load and resistance factor des ign (AISC-LRFD) Specification states that second-order effects should be co nsidered in the design of frames; however, most designers are experienced o nly in first-order analysis. To accomplish the second-order design requirem ent, the AISC-LRFD Specification provides an approximate method to account for the second-order effect bases on first-order analysis, where moment amp lification factors B-1 and B-2 are introduced to account for the P-delta ef fect (member instability) and P Delta effect (frame instability), respectiv ely. However, the B-1 factor of the AISC-LRFD Specification may vary greatl y from the exact solution, especially when the member is under a high axial load. In this paper, a new moment amplification factor B-1* is proposed fo r calculating the P-delta effect in the design of steel beam-columns. Param etric studies were performed to examine the accuracy of the proposed moment amplification factor and to compare it with that from theoretical analysis and from current design specification. It was found that the proposed meth od is simpler and more accurate than that given in the current design speci fication.