Study On The Seismic Performance Of Multi-story Masonry Structures With Bottom Strengthening

The damage caused by previous major earthquakes indicates that the seismic performance of masonry structures is poor.The seismic damage of multi-story masonry structures is mainly manifested in the bottom stories,and scholars and engineering communities in China and abroad are very concerned about the issue of multi-story masonry structures with bottom strengthening.In this study,the weak stories of multistory masonry structures and the weak parts within the stories were summarized,and a more in-depth study on the seismic performance of multi-story masonry structures with bottom strengthening was studied.The seismic performance test of the masonry wall with small opening and the seismic performance analysis of the masonry structure with small openings were also conducted.The seismic performance of multi-story masonry structures can be further improved through the study conclusions,and the study has some theoretical significance and engineering application value.The main work and contribution are as follows:(1)The seismic concept of the multi-story masonry structures with bottom strengthening based on the improvement of bearing capacity and ductility was proposed.The earthquake damage characteristics of multi-story masonry structures were summarized in terms of both structural weak stories and weak parts in the stories,and the current status of research on the multi-story masonry structures with bottom strengthening and the seismic performance of open-cell masonry structures in China and abroad was sorted out.The range of bottom strengthening was clarified,and the theoretical analysis on bearing capacity strengthening and ductility strengthening was conducted by combining the characteristics of multi-story masonry structures.Also,lateral stiffness ratio control was introduced.(2)The nonlinear analysis and the vulnerability analysis of multi-story masonry structures with bottom strengthening were conducted,and the influence law of bottom strengthening on each story’s deformation and the seismic vulnerability of multi-story masonry structures were obtained.The study shows that the maximum inter-story displacement angle of the bottom stories of the multi-story masonry structure is significantly greater than that of the upper floors,and the deformation is concentrated at the bottom stories of the structure.Strengthening the bottom helps to improve the seismic capacity of the bottom stories,reduce the deformation concentration,and make the damage of each story tend to be uniform.The risk of collapse damage of the structure under a rare earthquake is high when the bearing capacity reserve of the multistory masonry structure is small.Strengthening the bottom helps to reduce the seismic vulnerability of the structures and meet the requirements of performance-based seismic design.(3)The low cyclic reversed load test and the finite element simulation of the masonry wall with small opening were conducted,as well as the nonlinear analysis and the vulnerability analysis of multi-story masonry with small openings.The damage characteristics of the masonry wall with small opening and the influence law of small openings on the seismic performance of multi-story masonry structures were clarified.The study shows that the phenomenon of prominent brittle failure of the masonry wall with small opening was existed.Small openings will increase the seismic vulnerability of the multi-story masonry structure,increase the maximum inter-story displacement angle of the structure under the seismic action,and make the concentration of deformation at the bottom of the structure more prominent.Bottom strengthening will help to reduce the seismic vulnerability of the multi-story masonry structure with small openings and improve the deformation concentration of the structure.