| The blind bolted assembly composite frames consist of concrete-filled steel tubular(CFST)columns and steel-concrete composite beams with steel-bars truss deck(SBTD).The steel beams were assembled to the CFST columns by the blind bolts and the end plates.The assembly frames have good application prospects in multiple and high-rise buildings and industrial plants due to obvious advantages,such as high bearing capacity,excellent seismic performance,and fast construction speed and so on.In addition,the bucking restrained braces(BRBs)could effectively improve lateral stiffness and energy dissipation of the assembly CFST composite frames.At present,there are many researches on the CFST frames with rigid joints.However,few studies on the assembly CFST composite frames with blind bolted joints were reported.Especially,little study has been conducted on this novel typed composite frames with BRBs in terms of the seismic test,design method and failure mechanism.In order to promote the use of this structure,an extensive research needs to be presented in this paper.(1)Two one-span two-story assembly CFST composite frames with BRBs were conducted under lateral cyclic loading.The specimen was connected by high strength blind botls and end plates,and the BRBs were set in the specimen.The effects of column cross-section type and the endplate type on the seismic behavior of the structure were inspected.In addition,failure modes and hysteretic curves of the structures were investigated in detail.Meanwhile,skeleton curves,strength and stiffness degradation,ductility and energy dissipation were also analyzed.The experimental results provide a verification basis for the theoretical analysis of the blind bolted assembly CFST composite frame with BRBs.(2)The key parameters,such as composite column,composite beam,composite joints and BRB,were determined.The nonlinear analysis method of whole structure was proposed by the macrosfcopic model and corresponding simplified calculation methods of three levels for this novel structure was respectively developed,including calculation method based on fiber model theory,multi-scale model theory and beam model theory.These models were verified by the experimental data and showed that the simplified calculation methods provided a convenient way in routine and performance analysis for this typed structure.(3)The elastic-plastic analysis models of the blind bolted assembly CFST composite frame with BRBs were established by the software SAP2000.The stiffness of joints and the BRB arrangement were used as the analysis parameters.The nonlinear static analysis of this composite frame was carried out by displacement-based capability spectrum method.The results showed that the stiffness of joints and the BRB arrangement had obvious influence on the seismic performance of the typed structure.(4)Through the finite element software Perform 3D,the elastic-plastic time history of the assembly CFST composite frames with BRBs were respectively analyzed based on the energy method.The analysis parameters included the stiffness of joints and the BRB arrangement.The results demonstrated that the ground motion spectrum had an influence on the total input energy,damping energy,hysteretic energy.Besides,the damping ratio of the structure had a significant effect on the ratio of hysteretic energy consumption to total energy consumption of this structure.The joints stiffness has a great influence on the energy dissipation of the frame.The transverse and vertical distribution of the energy dissipation was also greatly affected by BRB arrangement.(5)The critical design steps of the blind bolted assembly CFST composite frames with BRBs were proposed based above-mentioned experiment and theory analysis,including ordinary and performance analysis.The design checking formulas of CFST columns,composite beams,composite joints and BRB were also given.Furthermore,the seismic design method of this novel structure was established and the practicality and feasibility of this method were verified by examples. |
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