| The unbonded steel plate brace encased in panel(panel BRB)is a typical type of buckling restrained brace in which the panel,working as partition wall,provides lateral restraint to the encased brace also.The panel BRBs can be used to improve the seismic behavior of concentrically braced steel frames.At present,the tests show that steel frames with the panel BRBs(PBRBFs)exhibit good seismic behavior when they have reasonable constructional details.However,as the data acquired by the tests are very limited,it can not deeply investigate the effects of the main construction details on the working mechanism,hysteretic behavior and yielding development of the PBRBFs under the cyclic load.In particular,there is a lack of research on reasonable construction details,as well as corresponding design methods,for the PBRBFs.Therefore,the numerical simulations based on the test results were done to examine the constructional details,seismic behavior,design methods,etc.for the PBRBFs.The main contents of this research are as follows.(1)The program ABAQUS was employed to simulate some tests of unbonded steel plate braces encased in panel,and the mixed isotropic-kinematic hardening behavior of the encased steel plate brace under axial cyclic load is reflected.Thus,the key parameters used to reflect the mixed behavior were determined based on the fact that results got from the simulations agree well with those from the tests,and the parameters were applied to the subsequent simulations of PBRBFs.(2)The finite element analysis models of the three tested PBRBFs were established by using the shell element in the ABAQUS program.The feasibility of the analysis models was ensured by full comparison between the results of the tests and those of the simulations.Further analysis was hence done to investigate the effects of the shape of braces,beam-to-column connections,reinforced ways of connections,etc.on the hysteretic behavior of PBRBFs.Besides,simplified methods by employing beam and truss elements to simulate hysteretic behavior of PBRBFs were explored.(3)Together with the tested PBRBFs,other PBRBFs,in which the steel frames have moment(or non-moment)-resisting beam-to-column connections,with chevron panel BRBs were designed.The difference between the actual member forces in PBRBFs by considering the influence of lateral drift and the member forces used in the design was investigated within the lateral drift of 1/50,and therefore the practical design suggestions and analysis figures considering actual forces were given.According to the fact that one brace in a chevron panel BRB failed locally in the tested PBRBFs,the parameters analysis was done to examine the effects of the cross section of the braces and frames,the story and span of the structures,the configuration of braces,etc.on the seismic behavior of PBRBFs considering the condition that local failure of one brace occurs in one story,and therefore the relevant design suggestions were proposed.(4)The effects of the reinforced measures,the eccentric distance of brace,the force transmission mechanism,along with the shear deformation of panel zone,in the moment-resisting beam-to-column connections,etc.on the working behavior of PBRBFs were further examined.The emphasis of analysis is focus on the force transmission mechanism on the moment-resisting beam-to-column connection locations,as well as the connections between brace and beam(or column),in the PBRBFs with chevron(or diagonal)panel BRBs.Based on the reinforced configuration in the commonly used moment-resisting beam-to-column connection locations of the steel frame,both reinforced measures and design methods for connection locations in the PBRBFs were proposed. |
PDF Full Text Request