Study On Seismic Behavior Of High-Rise Frame Structure In Karst Area

The soluble rocks are widely distributed in our country, numerous types, tall buildings are built in complex karst foundation, give engineers put forward many new problems and challenges. At present our country in view of the karst area, the seismic research of structures are relatively few, this article USES the large general finite element software ANSYS, based on the soil-structure dynamic interaction analysis method, research on karst geological influence on the upper frame structure seismic performance, provide a reference for construction in karst area, main work includes:(1) This paper studied the geological features of the karst area, simulated the karst foundation using Drucker-Prager constitutive model, and deeply discussed the value of the parameters in this model. Carbonate is the most widely distributed one among all the soluble in karst area, while the red clay is most typical one. Carbonate has good mechanical properties, but its bearing capacity is often weakened by its own caves, grooves resulted from its solubility. The distribution of the red clay in karst area is hard on the top and soft in the below, and its moisture content is more than the general clay. However, the red clay has a high bearing capacity, and caves can often be found in it.(2) Seismic response analysis on common earthquake was conducted with the karstic site foundation model to study the propagating characteristics of seismic wave in karstic area; The soil of karstic area has " filtering action " on seismic wave.The component of seismic wave which is close to the site natural frequency is fully reserved. And the seismic wave with high frequency is reserved Because of the high stiffness of the karstic foundation; The soil of karstic area has "amplification effect" on seismic wave, and this effect may be reinforced when there are holes in the karstic foundation.(3) Seismic response analysis of the frame structures on karstic foundation was conducted using method of fixed base assumption and interaction respectively, and the two results were compared. Compared with fixed base assumption model, the displacement of upper structure of interaction model was bigger, and so as to the shear force of the middle and lower column. The shear force of the middle and upper column was smaller, and the maximum shear force occurs in the bottom of inner column.(4) Basing on the analysis of the finite-element seismic response of structure-foundation-soil interaction, it is studied that the soil caves have seismic influence on the upper frame structure in the karst foundation.The in fact is:the soil caves can enhance the upper structure seismic force and so that have bad influence on the antiseismic of the structure.(5) Basing on the analysis of the finite-element seismic response of structure-foundation-soil interaction, it is studied that the variation of the foundation stiffness has seismic influence on the upper frame structure in the karst foundation. The study shows that the seismic force of the seismic force of the upper structure increases with the stiffness of the foundation, hence, for the karst foundation which has larger stiffness, it is necessary to enhance the anti-seismic ability of the upper frame structure.