Analysis of nonlinear dynamic second-order effect of a large-scale container crane under seismic excitations

Under seismic excitations, the second-order effect (P-Delta effect) exists in deformed structure under vertical loading even in linear-elastic system. For the vulnerability of the large-scale container crane, the effect is particularly remarkable in the slender structure, especially under large deformations. The current research on the rule of the static P-Delta effect has gained tremendous achievements, through systematic, reliable and simplified calculation methods. This paper however proposes the nonlinear dynamic second-order effect of the large-scale container crane. The aim of this paper is to analyze the influence of P-Delta effect on nonlinear dynamic seismic responses owing to different seismic conditions and seismic excitations. Meanwhile, by comparing with the methods of numerical FEM simulations, the simplified theoretical calculation conclusions of the dynamic second-order effect for the bending-type structure on portal frame can be verified. This research reveals clearly the regular pattern of P-Delta effect and influencing factors. The results have great significance on the seismic design of large-scale container crane. The main findings are presented in the paper