Seismic Behavior Analysis Of Typical Single-Layer Masonry Structure In Tibet

Tibet is the area with high incidence of earthquake in china.Limited by economic conditions,housing construction quality is poor in Tibet rural,thus the earthquake disaster tend to cause a lot of casualties and economic losses.It is important to study seismic behavior of folk houses in Tibet and improve their seismic capacity and anti-collapse properties in the limited economic conditions.This study has important implications for ensuring the safety of people's life and property,and has directive significance for ensuring the smooth implementation of rural earthquake safety project.By using the empirical theory method and the numerical simulation method,taking the shaking table test of Tibet single-layer masonry houses as the reference,the paper has analyzed Tibet single-layer masonry'seismic behavior,failure mechanism and collapse mode,and provided the suggestion for the seismic design and anti-collapse design of Tibet single-layer masonry houses.The main work and conclusions are as follows:Firstly,according to the transcendence strength rate calculation method of multi-layer masonry structure and related standards,the similar calculation method of Tibet single-layer masonry structure has been derived.Meanwhile,combined with the previous research results,it provides the rapid assessment method of Tibet single-layer masonry folk-houses seismic capacity.The examples show that calculation results without considering the correction factor agree well with the test results,but the determination of correction factors need further studies.Secondly,numerical simulation analyses of the shaking table test model of Tibet typical single-layer masonry have been carried out;and based on the existing research results on masonry mechanical properties,calculation methods of uniaxial tensile and compressive strength and elasticity modulus of concrete solid block and masonry have been derived.Through comparative analyses between calculation results and test results,it is verified that the simplify method of finite element and material parameter values are reasonable.Thirdly,a masonry crack propagation simulation method is proposed,which is on the basis of winfrith material model in LS-DYNA.Calculation results show that the crack propagation simulation results agree well with test results.Fouthly,using finite element analysis method,modal analyses and elastic-plastic seismic response analyses have been carried out for Tibet single layer folk-houses of different mortars and construction measures.Mmeanwhile the effects of different factors on the structural natural periods,displacement responses and strain responses have been analyzed.The relationship is derived between the displacement angle of concrete block masonry and damage state,thus the damage state of various models are provided under the action of different earthquake intensities.Calculation results show that:the structure with M1 masonry mortar does not meet the design demands of "mendable in moderate earthquakes ",and the structure with M4 masonry mortar meets the demand;the reinforcement measure of polypropylene band(PP-band)meshes does not have an obvious influence for the seismic bearing capacity of the structure;the construction measure of setting construction columns in corners and ring beams in the height of the house can not meet the demand of "no collapsing with strong earthquake ".Fifthly,through using the crack propagation simulation method on the basis of winfrith material model in LS-DYNA.,the paper analyzed the crack propagation process of different structures with different mortars or construction measures,and compared the crack propagation state of different structures under the action of different earthquake intensities.Through analyzing the results and combining the analysis results of elastoplastic seismic response,suggestions have been provided for the seismic design of Tibet single-layer houses.These suggestions include that Tibet single-layer house without any construction measures should not be built by using M1 masonry mortar,the connection between vertical and horizontal wall should be strengthened,etc.Sixly,collapse simulation analyses of Tibet single-layer houses have been carried out by using the "birth-death element" method.The failure strain value of the prototype structure has been given by the calculation method on the basis of crack propagation.Through comparing the results of the collapse analyses of the prototype structure with different failure strain values,it gives the suggested values of failure tension strain and failure crack width;For different models with different mortars or construction measures,the paper conducted a collapse simulation,and analyzed their acceleration and displacement reaction and collapse process.By comparing the collapse modes of different models,some suggestions have been provided for the seismic and anti-collapse design of Tibet single-layer masonry structure.