Dynamic stability analysis of beam string structures under earthquake loads

Beam String Structure (BSS) is composed of an upper structural member, lower strings and struts, which is a new type of long-span hybrid structure. The study on the static behavior is extensive. However, there is still a certain extent of blank in the field of dynamics, especially the dynamic stability. Owing to the limitation of the existing dynamic stability judgment criterion, most of which are based on Lyapunov dynamic stability theory and the highly nonlinear earthquake response of BSS, the nonlinear finite element analysis and time history method (THD) are adopted. THD is effective to the highly nonlinear structures. Based on the displacement time history curves and structural deformation, the critical load of dynamic stability was obtained. The dynamic stability of the plane BSS is analyzed under earthquake loads in respect of the number of struts, height-span ratio, sag-span ratio, moment of inertia, prestressing force of string and restraint type of supports. The results are compared with those of static stability. Some suggestions are put forward to selecting a proper structural model and analysis in project design.