In order to overcome the deficiency that the conventional buckling restrained braces(BRBs)were in elastic state under frequent earthquakes,and cannot dissipate energy,a novel two-level-yielding buckling restrained brace composed of conventional BRB and metal tube damper was developed,and its reliably and stable hysteretic characteristics under both frequent and large earthquakes were verified by experiments.Under frequent earthquakes,the metal tube damper yields to dissipate energy and the buckling restrained core plate keeps elastic.A series of braced frame models with the novel braces were established by means of the finite element software ETABS.By changing the stiffness ratios of braces and frames,the axial stiffness relationship of tube dampers and core plates,and the yield ratios of tube dampers,the dynamic elastoplastic analysis under frequent earthquakes of each model was carried out,while the base shear forces and the maximum inter-story drift angles were compared with the analysis results of corresponding BRB frames.The results show that when the axial elastic stiffness ratio of the novel two-level-yielding buckling restrained brace and core plate is about 2,and the yield ratio of tube damper is about 0.3,the structure can achieve better seismic reduction effect.The parameter change of the two-level-yielding buckling restrained brace for the influence tendency of reducing structural seismic response does not vary with the different stiffness ratios of braces and frames.For braced frames with large brace stiffness,compared with the conventional BRB,the inter-story drift angles of the structure can be reduced by setting the two-level-yielding buckling restrained brace.If the base shear force is to be reduced at the same time,the yield ratio of damper should not be higher than 0.3.
Journal of Architecture and Civil Engineering
disaster prevention and mitigation
metal tube damper
buckling restrained brace