Study On The Structural System Composed Of High Strength Steel Columns,Ordinary Strength Steel Beams,and Low Yield Point Steel Buckling-Restrained Braces

In view of the wide application prospect of high-performance steels and highperformance steel structural systems,this dissertation innovatively proposes a highperformance structural system composed of high strength steel columns,ordinary strength steel beams,and low yield point(LYP)steel buckling-restrained braces(BRBs),and focuses on its seismic performance and design method.The main work of this dissertation is as follows:(1)Cyclic tests of BRBs with the core plates machined from LYP steel plates of LY100,LY160,and LY225 were conducted.The failure mode and hysteretic behavior were analysed,which provided the basic test data for the mechanical properties of BRBs using domestic low yield point steel as core material,and also provided a basis for the subsequent research work as well as the development of numerical models.(2)A total of eight full-scale single-bay two-story buckling-restrained braced frame(BRBF)specimens including one specimen composed of ordinary strength steel columns and beams,and low yield point steel BRBs for comparison,and another seven specimens using this new structural system,were designed,constructed,and tested pseudo-statically.Beams were all fabricated with Q345 ordinary strength steel and three grades of low yield point steel(i.e.,LY100,LY160,and LY225)were considered for BRBs while Q345 ordinary strength steel and three grades of high strength steel(i.e.,Q460,Q690,and Q890)were used in columns.The global responses of the specimens and the mechanical behaviors of their members and joints were analyzed.Based on the test results,the seismic performance of this system was comprehensively evaluated,and the influence of relevant design parameters was discussed.(3)From the component to the structure,the finite element analysis model for this system was gradually established.For the BRBs,a simplified model represented by a uniform cross-section truss element was used.For the frames,after demonstrating the reliability of the modeling method through refined models,a multi-scale model of shell element-beam element-truss element was developed on the basis of comprehensive consideration of calculation cost and calculation accuracy.Compared with the experimental results,the accuracy and reliability of the model were fully demonstrated,which provided an effective means for the numerical analysis of the system.(4)On the basis of extensive investigation of existing codes and literatures,considering the characteristics of this system,a performance-based seismic design method was developed in this dissertation.The recommended values for key parameters in this design method and some recommended seismic structural measures were also given.Example frames with different patameters were designed using the propsed method,which further clarified the design process and provided examples for subsequent numerical analysis.(5)Static pushover analysis and time history analysis were used to comprehensively evaluate the seismic performance of this structural system.The results verified the rationality of the design method and the excellent seismic performance of this structural system.In addition,based on the analysis results,some design suggestions are supplemented.