Study On Seismic Performance Of New Assembled Masonry Structure For Low-rise Buildings In Villages And Towns

The implementation of the strategy of Rural Revitalization is a major decision made in the report of the 19 th National Congress of the CPC Central Committee.As the existing mainstream structural form in villages and towns,masonry structure is affected by many factors such as history,technology,social management,and economy.Generally,it belongs to the low-rise structural system without professional design and professional construction,and it is built by the residents according to the customer experience.On the other hand,the performance of the masonry structure can still be guaranteed during normal use.Once encountering earthquake s,the phenomenon of cracking wall and collapsing house is easily observed which causes casualties and property losses.In addition,after several years of theoretical analyses,experimental researches and engineering applications,reinforced block masonry shear wall structure based on the concrete hollow block becomes a new development direction of the modern masonry structure.With the development of construction industrialization and combined with assembly technology,the reinforced block masonry shear wall structure has been successfully transformed and applied,which reflects the theoretical significance and engineering value of reinforced block masonry shear wall structure.At present,the phenomenon of the damage and collapse of the low-rise masonry structure after the earthquake still exists in the villages and towns.The research on structural performance and damage mechanism is still insufficient from the perspective of damage,and few new structural systems are more suitable for the construction and characteristics of villages and towns,which can help to realize rural revitalization.Based on the needs of village construction and the realization of the goal of disaster prevention and mitigation,this thesis uses the method of damage data statistics,experimental research,and numerical analysis to analyze the earthquake damage mechanism of the vertical load-bearing wall of low-rise buildings in villages and towns and carry out systematic research on the new structural system which is suitable for the low-rise masonry structure in villages and towns.The main research work includes:(1)The typic seismic damage data of vertical load-bearing wall of the low-rise masonry structure in several earthquakes were summarized,and vulnerable parts and failure modes of those components were classified.Based on the common understanding that the lack of structural integrity leads to earthquake damage of structure,further analyzes of this topic was carried out.Considering the factors of structural quality,seismic shear force,component capacity,and stability,etc,the earthquake damage mechanism of the low-rise masonry structure in villages and towns was obtained and verified by the finite element model of the single-story masonry structure.The in-plane damage of the unreinforced masonry vertical wall was due to the lack of normal stress and the out-of-plane collapse of it was due to failure of connection and poor self-stability,which established the technical and theoretical foundation for proposing a new type of assembled structural system.(2)Considering the characteristics of earthquake damage mechanism,development needs and target requirement of the vertical load-bearing wall of low-rise masonry structures in villages and towns,an assembled prestressing reinforced block masonry shear wall structural system was proposed,which can increase the vertical compressive stress of load-bearing wall and improve the seismic performance of load-bearing wall by applying axial prestressing force to the wall;through a combination of rigid and flexible connection of integration design of the vertical load-bearing structure and infill wall,the failure zone under the earthquake force is set under the premise of ensuring the performance of the structure,and the cooperative working performance of the load-bearing structure and infill wall in the process of earthquake stress was improved.(3)To study the seismic performance of the vertical load-bearing structural system,8 specimen tests were completed,including 4 quasi-static tests of assembled reinforced block masonry shear walls and 4 quasi-static tests of reinforced block masonry shear wall and infill integrated structures.The influence of prestressing,the section type of load-bearing structure and infill wall on seismic performance of the vertical load-bearing structural system was analyzed.The results showed that prestressing technology improved the initial stiffness and max lateral resistance of the specimen on the premise that the failure mode remains unchanged;flange improved the initial stiffness and max lateral resistance of the specimens,however it changed the failure mode of the specimens;infill wall participated in the early loading process of the specimens,improved the initial stiffness and lateral capacity of the specimens,and realized itself due to the failure of the preset area after the specimens exceeded the max lateral resistance.The separation of the infill wall and the load-bearing component can protect the infill wall and reduce the impact of the infill wall on the load-bearing structure at the same time,and the expected failure state is obtained.(4)Based on the experimental study,the mechanical model analyses and finite element simulation analyses were carried out,and the seismic performance of the new assembled load-bearing wall and infill integrated structure was studied.The results showed that the softened strut-and-tie model considering the compression softening of the grouted concrete block masonry material can effectively predict the shear capacity of the reinforced block masonry shear wall with the shear span ratio less than 2.0.Considering the interface model,a new assembled structure was established with a refined finite element model.The rationality and applicability of the model were verified by the experiments in this paper.The increase of vertical compressive stress improved the max lateral resistance and initial stiffness of the new assembled masonry wall,while the compressive strength of the aac block has little effect on its max lateral resistance.Combined with the experimental and numerical model research work,the preliminary suggestions for the design,construction,and constructional measures of the new assembled masonry structure were proposed.