Research On Seismic Design Method Of Bottom Frame Masonry Structure Strengthened By Viscous Damper

The bottom frame masonry struct ure is a unique mixed structu re form in China,which has good function but poor seismic performance,so a large number of existing masonry structures with bottom frame need to be upgraded and reinforced.The damping technology relies on the dampers arranged in the structure to dissipate the seismic energy,so as to reduce the deformation and damage of the main structure.At present,viscous damper is lack of simple and effective design method in the reinforcement design of bottom frame masonry structure,but its a dvantages such as simple construction and cost saving will be widely used in the reinforcement of bottom frame masonry structure in the future.This research work is based on the social status,seismic performance and the theory of viscous damper strengthe ning technology of bottom frame masonry structure.through the finite element analysis of seismic performance and reinforcement design of bottom frame masonry structure,the mechanical performance tests of viscous dampers and the theoretical calculation of design method of viscous damper,the application of viscous damper in bottom frame masonry structure is deeply studied.The main research results are as follows:First of all,the seismic responses of the unreinforced bottom frame masonry structure model,bottom frame masonry structure model strengthened with seismic wall and bottom frame masonry structure model strengthened with viscous dampers are compared and analyzed by using ETABS,so as to further grasp the seismic performance of bottom frame masonry structure and study the feasibility of adding viscous dampers to strengthen bottom frame masonry structure and its advantages compared with traditional seismic wall strengthening methods.Secondly,taking three kinds of viscous dampers as examples,the mechanical performance tests are carried out,and the output of dampers under different working conditions is measured by two excitation loading modes of input sine wave and seismic wave.the energy dissipation law and energy dissipation characteristics of d ifferent specifications of dampers are studied,and the differences between the design and the actual mechanical properties of the dampers are quantitatively analyzed by comparing the factory test results of the dampers.In addition,a design method of vis cous damper applied to the reinforcement of bottom frame masonry structure is proposed,and the effectiveness of the design method is verified by an engineering application example,and there is a difference between the factory performance and the actual p erformance of the damper.The results show that the ground floor of the bottom frame masonry structure is weak,and the damage concentration phenomenon will occur under the earthquake,and the addition of seismic walls can effectively improve the seismic capacity of the ground floor and increase the stiffness of the ground floor,but it will increase the seismic response of the upper masonry structure,the additional viscous damper greatly improves the overall seismic performance of the structure while cont rolling the weak layer.On the basis of the traditional seismic strengthening method for the existing bottom frame masonry structure,this paper provides an idea and method of seismic reinforcement for the existing bottom frame masonry structure.The dampe r has good working performance and excellent energy dissipation capacity,but the output of the damper in different working environments is slightly less than the theoretical calculation value.Therefore,according to the actual energy dissipation capacity of the damper,a modified formula is proposed for its restoring force model.The proposed damping and strengthening design method is simple to calculate and can be effectively applied to the bottom frame masonry structure strengthening engineering.The fa ctory test overestimates the energy dissipation capacity of the damper,and the damper parameters should be properly reduced in the design.