Seismic Behavior Of A Novel RC Frame Incorporating Beams With Kinked Rebar Configurations And Post-yielding Hardening Columns

As one of the most widely used structural systems,reinforced concrete(RC)frame faces the risks from multiple collapse mechanism.It draws wide attention of researchers that how to simutaneousluy increase the resistances of RC frame to global lateral collapse under strong earthquake and local vertical progressive collapse caused by explosion,earthquake,fire,etc.In view of this,this thesis proposed a novel RC frame structure incorporating beams with kinked rebar(KB)configurations and post-yielding hardening(PYH)columns.KB is a novel configuration which can improve the seismic performance and progressive collapse resistance of RC frame;the PYH columns can help control the residual deformation of RC frame under seismic loading.Therefore,this novel RC frame has large lateral deformation capacity,great collapse resistance,small residual deformation under seismic loading and great progressive collapse resistance.This thesis focused on the seismic performance of this novel RC frame.A series of studies were conducted as follows.(1)Study on the mechanical properties of the bare KB.Firstly,the uniaxial tensile/compressive behavior of KB were studied by experimental test and numerical simulation.It was found that the KB can be straightened followed by being broken under tensile force,showing a new “two-step” loading cruves.Based on this,a theoretical constitutive model was proposed.Secondly,the cylic loading behavior including hysteretic and low-cycle fatigue performance of KB was studied.(2)Study on the sesimic behavior of concrete beam with KB.Firstly,the cyclic loading test on 14 half-scaled concrete beams was conducted.The test results show that,the concrete beam with KB exhibited a new skeleton curve showing “two-step”behavior,and a new failure mode showing “two-hinge” behavior.In addition,the concrete beam with KB has better deformability than normal beam.Secondly,numerical simulation using fiber model was carried out.Finally,a theoretical hysteretic constitutive model for the beam plastic hinge with KB was proposed.(3)Study on the sesimic behavior of the novel RC frame structure.Firstly,the cyclic loading test on 3 half-scaled one-bay one story frame substructures was conducted.The test results show that,applying KB is effective to help the structure realize strong column-weak beam(SCWB)failure mechanism and increase the loading capacity again at large lateral drift.Based on this,the deformation mechanism of single-story and multi-story frame structures was analyzed,showing that the KB configuration is only suitable for frames with four or more stories.Based on this,it was also found that PYH column is benefit for the seismic performance of RC frame.Then,the lateral deformability of PYH column was also analyzed,clarifying the mechanism that high-strength materials with small deformability can fabricate RC columns with good deformability.(4)Study on the design theory and method for the novel RC frame structure.Firstly,the design response spectrum for this novel frame was established.In addition to initial stiffness,ductility and bearing capacity,the post-yield stiffness is taken as the fourth critical structural parameter.Secondly,the design method of this novel frame was proposed.A 6-storey RC frame was designed as a case.Based on the time history analysis and incremental dynamic analysis results,it was shown that this novel RC frame has better seismic performance than the normal one.This thesis provides a theoretical reference for engineering structural design of the novel RC frame,thus providing a technical way to enhance the comprehensive collapse resistances of RC frame.