“…where e p 0 is the normal strain threshold beyond which damage occurs in the material, e p u is the ultimate normal strain of the material, e p m is the highest normal strain sustained by the member during the analysis, e p i is the peak normal strain sustained by the member during the ith half loading cycle, N is the total number of half loading cycles, b D is the weight coefficient of cumulative damage during the analysis and taken as 0.0268 based on past cyclic tests on steel tubes (Zhi et al, 2012), E is the initial elastic modulus without damage, E D is the damaged elastic modulus of material, s y is the initial yield stress without damage, s D y is the damaged yield stress of material, j 1 is the reduction factor of elastic modulus of material and taken as 0.404 based on past cyclic tests on steel tubes (Zhi et al, 2012), and j 2 is the reduction factor of yield stress of material and taken as 0.063 based on past cyclic tests on steel tubes (Zhi et al, 2012).…”