Performance Index And Seismic Fragility Analysis Of Partially-restrained Steel Frame With RC Infill Wall Structural System

Partially-restrained Steel Frame with RC Infill Walls(PSRCW)is a new composite structural system.It combines the advantages of steel frame and RC shear wall structure,which has not only large lateral strength and stiffness but also good ductility and energy dissipation capacity.Currently,the related researches on PSRCW structure mainly focused on the hysteretic behavior,the lateral shear distribution and transferring mechanism,failure modes,and so on.However,the researches on the performance index and seismic fragility analysis of PSRCW have not been investigated.In order to propose the collapse criteria and performance index of PSRCW,a detailed statistical analysis based on the previous test results of PSRCW structures has been completed in this paper.Also,the nonlinear time history analysis method was adopted to develop the seismic fragility curves of PSRCW which was designed and built in high earthquake intensity region in China.The variabilities of materials,the thickness of RC infill walls,and the rotation stiffness of PR connection were also considered.The overstrength,ductility reduction factor,and strength reduction factor of PSRCW were evaluated using pushover analytical approach.Combined with the fragility curves at "collapse" state,the collapse margin ratio(CMR)of PSRCW structure was also quantified.The researches of this dissertation can provied some useful reference for the performance-based seismic design method of PSRCW.The primary content in this dissertation includes:(1)A detailed statistical analysis on 12 previous test results of PSRCW structures has been concluded in this paper.The inter-story drifts at the initial crack,significant yielding state,and peak point were analyzed based on the probability approach.The collapse performance point of PSRCW still was quantified using the ultimate inter-story drifts,cumulative inter-story drifts,cumulative ductility ratio,and cumulative inter-story hysteretic energy ratio.The ultimate inter-story drifts is chosen as the collapse criteria of PSRCW structure.(2)Combined with the earthquake levels provided by the Chinese Seismic code,five performance levels which are fully operational,operational,life safety,near collapse,and collapse,were established to describe the performance objectives of PSRCW.The performance indices of PSRCW were determined using the modified Park-Ang damage model and pre-assigned the ultimate inter-story drifts.(3)The OpenSees program was adopted to analyze the previous experiments,including of partially-restrained steel frame and PSRCW structure.A total of four basic PSRCW examples which considing the influences of the number of story were designed based on the capacity design method.In addition,the variability of material properties,the rotation stiffness of connection,and the thickness of RC infill wall were considered,and the Latin Hypercube Sampling method was used to expand examples to four groups totaling 160 examples.(4)Based on the nonlinear time history analysis method,the seismic fragility curves of four groups PSRCW,which using PGA and Sa as ground motion parameters and the inter-story drift as structural response,were established,and the exceeding probability of PSRCW under different earthquake levels were given.(5)The overstrength,ductility reduction factor and strength reduction factor of PSRCW structure considering the variability of materials,the rotation stiffness of connection,and the thickness of RC infill wall were quantified through the pushover analysis method.(6)Based on the seismic fragility curve at "Collapse" state,the CMR of PSRCW was also determined.