Investigation Of Basic Mechanical Properties And Damage Of Ancient Brick Masonry

As the carrier of history and culture,ancient architecture reflects the glory of national history and human civilization,and shows the great achievements of cultural art and scientific and technological development in China.Among them,brick and stone materials are one of the important materials in the existing ancient buildings in China.They occupy an extremely important position in the history of Chinese ancient buildings.They are witnesses and bearers of Chinese national historical development and architectural technology and culture.They are also important resources and ways of modern scientific research.Due to the long history,material deterioration and natural environment changes of traditional ancient buildings,the material properties and mechanical properties of existing masonry ancient buildings are affected and damaged to varying degrees.These ancient buildings,such as city walls,bell towers and drum towers,belong to national key protected cultural relics and have great historical,cultural and scientific research value.Once damaged,the historical and cultural information carried will disappear.Based on the axial compression test and fatigue test of ancient brick masonry,this paper studies the basic mechanical properties,constitutive relationship,crack development and fatigue performance under cyclic compression-compression load of ancient brick masonry structure.The main work and conclusions are as follows:(1)Study on the performance of ancient brick masonry materials.The chemical composition,micro-analysis and compressive strength test of solid brick for a demolition ancient residential in Shanxi were carried out.XRD,SEM analysis and compressive strength test were carried out on the glutinous rice ash mortar samples,and the consolidation mechanism of glutinous rice mortar was explained from the micro perspective.(2)Axial compression test of ancient brick masonry.two groups of 16 ancient brick masonry specimens were tested under axial compression.combined with experimental data and proposes aunified constitutive model of masonry under compression.and gives the elastic modulus and Poisson’ s ratio of this kind of ancient brick masonry.(3)The development law of ancient brick masonry cracks.Based on the cracking and failure mode of ancient brick masonry under axial compression,combined with the stress process of masonry,the load-displacement curve mutation point,single brick stress-strain curve mutation point,single crack length and crack development are proposed to comprehensively evaluate the cracking load.A trilinear model is established to simulate the crack development of ancient brick masonry,which can accurately reflect the relationship between crack length and load.(4)Study on axial compression fatigue of ancient brick masonry.The axial compression fatigue tests of 74 ancient brick masonry specimens under different fatigue loading frequencies and maximum stress levels were carried out.At the same time,with the help of VIC-3D system,the surface displacement,strain characteristics and crack development of masonry were observed.The ε-N curve presents a typical ’S’ structure with three different stages of development.Combined with VIC technology ’ virtual extensometer ’ statistical crack width corresponding to the number of cycles and specimen failure maximum crack width,drawing ω-N curve and analysis of the relationship between the number of cycles and crack width.Based on the axial compression test and fatigue test of ancient brick masonry,this paper focuses on the material changes and macroscopic mechanical properties degradation of ancient brick masonry structure from two aspects of masonry materials and components,and gives thought and suggestions for the future investigation of ancient brick masonry,the damage mechanism of ancient masonry materials and structures,so as to provide reference for the repair and protection of ancient brick buildings.