| China is one of the earthquake frequently happened countries,so it has high requirements on seismic performances for building structures.As the most important member in reinforced concrete(RC)frame structures,which is one of the most common structural systems,the research on seismic performance of the beam-column joint has been becoming the hot point and emphasis.Shape memory alloy(SMA)has the excellent shape memory effect,good super-elasticity,high corrosion resistance,high damping,high resistance and other characteristics.The super-elasticity effects have unique characteristics of hysteretic energy dissipation and self-resilience capacity,which can consume a large amount of energy without generating residual strain or with a small deformation.The hysteretic energy dissipation and self-resilience capacity has broad application prospects in disaster prevention and mitigation in the future.In this dissertation,multi-story and high-rise frame structures are used as the background to study the self-resilience performance of beam-column joints.A comprehensive method of theoretical analysis and numerical simulation as well as experimental validation is used for the aim of proposing an SMA-based beam-column joint and establishing a self-resilience based seismic analysis method.The main research contents are included as following.(1)Three kinds of SMA-Steel-Concrete material constitutive relationships are established and programmed.Based on the Boyd and Lagoudas models,an SMA constitutive relationship model is set up.Two kinds of constitutive relationship model for steel rebar and concrete are compiled into the program.The stress-strain relationships of the three material constitutive equations are concise and accurate.(2)The self-resilience properties of iron-base alloy beam-column joints are investigated using pseudo-static experimental method.Four reinforced concrete beam-column joints are designed and fabricated.One of them is a common reinforced concrete beam-column joint and the other three are SMA-based beam-column interior joints.The design overview,loading system and test process of the beam-column joint test are introduced in detail in the experimental part,and the destruction phenomenon of the test pieces at each test step is observed.The influences of the SMA reinforcement ratio and the ratio of the stirrup on seismic properties such as the bearing capacity,residual deformation ratio and restoring force ratio at the balance position,and stiffness and strength degradation of the specimens are analyzed.(3)Finite element analysis(FEA)of iron-base alloy beam-column joints is performed using the ABAQUS platform.The super-elastic SMA rebars are embedded into the concrete beam-column joints as main tendons,and the common beam-column joint with the same size and the same reinforcement ratio is used as a reference.These specimens are numerically tested by using the FEA under pseudo-static loading on the beam end,companying a constant vertical compressive load on the column end.The seismic performances such as the hysteretic behavior,bearing capacity,self-resilience capability of the specimens are analyzed.(4)The self-resilience performance of Ni-Ti based beam-column joints is analyzed using the ABAQUS platform.For investigating the influence of different SMA material on the seismic performance,the different pre-strain levels and reinforcement ratio on the hysteresis curves and skeleton curves of the beam-column joint are analyzed.Based on this,the residual deformation ratio and the self-restoring force ratio at the balance position are analyzed.Both of experimental and FEA results show that:the super-elastic SMA based beam-column joints have better self-resilience performance than that of ordinary beam-column joints.With the increase of SMA reinforcement ratio,the residual deformation and the self-restoring force ratio of the beam-column joints at the balance position can be reduced,and this performance can improve the self-resilience performance of the beam-column joint. |
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