Seismic Fragility Analysis Of Masonry Building

Since the 1990 s,performance-based seismic engineering has developed rapidly.The US Pacific Earthquake Research Center has established a full-probability seismic performance assessment framework.In this framework,seismic fragility analysis of building structures is one of the important components of seismic loss prediction,which describes the engineering structure's seismic performance from the view of probability.It is mean that the structure beyond the probability of different damage states at a given ground motion intensity level.Therefore,the study of seismic fragility analysis has a great significant on Earthquake Loss Prediction.The uncertainty of ground motion has influence on dispersion of structural seismic response.But it can reduce the discreteness by chosing the reliable intensity measure.Then,as the study shown,the uncertainty of structure has a higher influence than ground motion when structure is nearly come to collapse state.In the last,the vertical stiffness irregular masonry structures are widely existing in our city.In response to these problems,this paper takes a typical three-story and six-story masonry structure as examples to study the influence factors of seismic fragility of masonry structures by using nonlinear time-history analysis methods.First,adequacy and effectivene of intensity measure parameters in the fragility analysis was studied,and a reasonable intensity measure parameter was selected for seismic fragility analysis of masonry structures.Second,quantitative analysis the impact of various uncertainties on the fragility of masonry structures.Finally,the influence of vertical stiffness change on the fragility of masonry structures is analyzed.The main research content is as follows:1)In this chapter,we select 90 actual seismic records as input to evaluate the“adequacy”and“validity”of the 30 ground motion intensity parameters and the seismic response parameters of the masonry structure?this paper selects the maximum interlayer displacement angle?.The study found that when PGA,Sa?T₁,5%?and EPA were input as ground motion parameters,the damage of ground motion to masonry structure could be more reasonably revealed.2)In this chapter,PGA is used as the ground motion input parameter,and 21 seismic records are selected.Using the method of combining first-order second-moment and IDA,the typical three-and six-story masonry structures are established to collapse seismic fragility analysis.The effects of dynamic input and structural parameter uncertainty were taken into consideration.Sensitivity analysis method was used to analyze the influence of various uncertain parameters on the collapsed seismic fragility of masonry structures.3)In this chapter,based on multi-degree-of-freedom shear type models,we take the vertical stiffness irregular masonry structure of three-story and six-story as example.Through change the position of stiffness irregular,structural behavior is evaluated from story drift ratios obtained through nonlinear time history analysis.Then,the structural response was obtained through incremental dynamic analysis,and the fragility curve of masonry structure based on the peak ground acceleration was established.At last,the influence of the stiffness change on the probability of the structure beyond the different damage states is analyzed.Meanwhile,the different lateral stiffness ratio of two adjacent structures is analyzed.4)In this chapter,we set up 90 structural numerical analysis models via Latin hypercube sampling technique,then they were randomly combined with 90 seismic records to form a seismic-structural model system,and a series of nonlinear time-history analysis was performed to record the ground motion intensity index?PGA in this chapter?and the structure seismic response(?_maxselected in this chapter).Through Cloud analysis we calculate the damage probability of a given ground motion intensity and form a seismic fragility curve.