Seismic Fragility Analysis Of Unreinforced Masonry Structures With Consideration Of Uncertainty

Unreinforced masonry structures are one of the extensive forms of structure in China and it is of great engineering practical significance to study its seismic performance.Seismic fragility analysis is a powerful method to evaluate the seismic performance of structures.With the development of fully probabilistic theory,considering the uncertainty of earthquakes and structural parameters in seismic fragility analysis has become a research hotspot in the field of earthquake engineering.However,there are still few studies on the uncertainty analysis of seismic fragility of masonry structures.The high dispersion of structural parameters and high nonlinearity of seismic response of unreinforced masonry structures make it necessary to consider the uncertainty of earthquakes and structural parameters in its seismic fragility analysis.Based on the above reasons,this paper takes four unreinforced masonry structures with different stories as the research object,and conducts an in-depth study on the influence of uncertainty on the analysis of seismic fragility analysis of unreinforced masonry structures.In order to analyze the seismic fragility of unreinforced masonry structures effectively,it is necessary to select a suitable numerical analysis finite element model.The realization method of the equivalent frame model of the unreinforced masonry structure in OpenSees is introduced.The results of pushover calculation are compared with the experimental data to verify the validity of the model,which provides a reliable finite element model for the seismic analysis of the paper.The First-Order Second-Moment method(FOSM)is combined with the seismic fragility analysis method based on Incremental Dynamic Analysis(IDA)and get the results considering the uncertainty of earthquakes and structural parameters.Taking the mean value and logarithmic standard deviation of the seismic fragility curve as indicators,combined with the fragility curves,quantitatively evaluate the impact of uncertainty of earthquakes and structural parameters on the seismic fragility analysis of unreinforced masonry structures.The results show that the influence of uncertainty on the results of fragility analysis cannot be ignored,and the impact between the uncertainty of structural parameters and earthquakes is almost the same.At the same time,the damping ratio is the most sensitive parameter among the nine structural parameters considered in this paper,and the seismic response of the unreinforced masonry structure exhibits obvious nonlinear characteristics.Furthermore,the Latin Hypercube Sampling(LHS)method is used to consider the uncertainty of structural parameters and combined with the IDA method to obtain seismic fragility analysis results,which are compared with the results of method based on FOSM-IDA.The results show that the change of parameters calculated by the two methods is similar,and the results of the LHS-IDA method are more regular.Compared with the FOSM-IDA method,the LHS-IDA method can consider the nonlinearity of the seismic response of the unreinforced masonry structures,and the calculated average value of the seismic intensity of the fragility curve is smaller,which means the results calculated by LHS-IDA method are more conservative.The results of Monte Carlo verification analysis show that LHS method has the advantage of high computational efficiency and high computational accuracy in considering the uncertainty of structural parameters.And scientific researchers should give priority in the selection of uncertainty transmission methods.