Seismic Fragility Analysis Of Confined Masonry Structures With Consideration Of Uncertainty

Previous earthquake damage surveys show that the seismic capacity of rural buildings is relatively weak.As the main structure of rural buildings,the masonry structure faces serious risk of earthquake damage.Scholars have proposed a form of confined masonry structure that can improve seismic performance based on experience and experimental results,but research on the seismic fragility analysis of confined masonry structure is still very lacking.The limitations of human knowledge level and the randomness of things themselves will produce uncertainty and affect the seismic fragility analysis result.How to quantify the impact of these uncertainties is the current research focus.Therefore,this article takes the confined masonry structure as the research object,analyzes its seismic fragility,quantifies the influence of uncertainty on the fragility analysis result,and compares it with the analysis result of the unreinforced masonry structure.The main research contents are as follows:(1)Based on the OpenSEES analysis platform,an equivalent frame model of confined masonry structure is established,and the rationality and effectiveness of the model are checked.Aiming at confined masonry structure and unreinforced masonry structure,three to six layers of example structures are designed and their corresponding numerical models are established.20 seismic records are selected,and the incremental dynamic analysis method(IDA)is used to analyze the seismic fragility of the 8 structural examples considering the uncertainty of seismic action,and the seismic fragility curves corresponding to the three limit states are obtained.Finally,the difference between the calculation results of confined masonry structure and unreinforced masonry structure is compared.(2)In order to simplify the analysis and reduce the amount of calculation,this paper uses sensitivity analysis to screen important uncertain parameters.Firstly,introduce the classification and modeling of modeling-related uncertainties in detail,summarize the probability distribution information of 20 uncertain parameters,and analyze the sensitivity of confined masonry structure and unreinforced masonry structure by tornado graph analysis method.After sorting all the parameters in order of importance,nine important uncertain parameters are selected for the study of uncertainty propagation.(3)Based on the important uncertainty parameters obtained by sensitivity analysis,FOSM,LHS and MCS methods are used to study the propagation effect of uncertainty in the seismic fragility analysis of masonry structures,and the advantages,disadvantages and applicability of the three methods are evaluated.The influence of modeling-related uncertainties on the median value and logarithmic standard deviation of the masonry structure seismic fragility function are quantitatively studied.The difference of uncertainty propagation effect between confined masonry structure and unreinforced masonry structure is compared and studied.