Numerical Simulation Study On Seismic Performance Of Reactive Powder Concrete Coupling Beams With Small Span And Height Ratio

Coupling beams are important parts of shear-wall structures and frame-shear-wall structures.In design of building structures,it is expected that coupling beams are yield before shear walls.Plastic hinges will be formed at both ends of coupling beams,which can reduce the damage induced of earthquakes.Coupling beams with small span-to-depth ratio are refer to the coupling beams whose span-to-depth ratio are less than 2.5.Shearing forces of coupling beams with small values of span-to-depth ratios are very high under earthquakes,but bending moments are very small.Coupling beams with small span-to-depth ratios are mainly destroyed by shearing deformation.The beams are lack of ductilities.New ways of reinforcement mode,new types of section and concrete material are commonly used methods to improve the seismic behaviors of coupling beams with small span-to-depth ratios.RPC(Reactive Powder Concrete,RPC)is a new type of concrete material.The strength and durability of RPC are better than ordinary concrete.Using RPC in buildings can improve its strength and seismic behavior.In order to study and improve the seismic behavior of coupling beams with small span-to-depth ratios,this thesis studied RPC coupling beams with small span-to-depth ratios by numerical simulation method.The main work and conclusions of this thesis are as follows:1.The research status of coupling beams with small span-to-depth ratio and constitutive relation of RPC are introduced firstly.A briefly summary is given in the thesis.2.The constitutive relation model of concrete,reinforcement and nonlinear spring in ABAQUS war discussed in this thesis.According to previous studies and calibration test method,those parameters and data of constitutive relation are put forward.3.In order to study the failure process,load capacity,deflection capacity,energy consumption,stiffness degradation of reactive powder concrete coupling beams with different span-to-depth ratio,4 pieces of RPC coupling beams with different span-to-depth ratio models are established through ABAUQS.The analysis results for the seismic behavior of RPC coupling beams with small span-to-depth ratio are obviously affected by the ratios.With the larger spanto-depth ratios,coupling beams have smaller load capacity,better deflection capacity,energy dissipation and stiffness degradation.The RPC coupling beam with span-to-depth ratio of 0.8will be damaged under “shear baroclinic failure”.Owing to lack of ductility,the failure process is very fast.With the increase of span-to-depth ratio of coupling beams,“shear bending failure”are occurred,the characteristics of bending failure appeared gradually,but the ultimate failure is still dominated by shear deformation.4.To study the seismic behavior of reactive powder concrete coupling beams with different span-to-depth ratio,stirrup spacing and reinforcement mode,an orthogonal numerical simulation experiment of three factors and three levels is designed in this thesis.The experiment analysis shows that for three different factors,the span-to-depth ratio has the most obvious effect on seismic behavior of reactive powder concrete coupling beams.With the larger span-to-depth ratio,reactive powder concrete coupling beams have better ductility.In the design of reactive powder concrete coupling beams with small span-to-depth ratio,the span-to-depth ratio should be kept above 1.25,the reactive powder concrete coupling beam has slightly better ductility.The seismic behavior of reactive powder concrete coupling beams with rhombic bars and diagonal bars is better than that of ordinary coupling beams.The stirrup spacing has little effect on seismic behavior of reactive powder concrete coupling beams.It is suggested that the stirrup spacing should not be less than 75 mm.Using rhombic bars and diagonal bars could reduce the stirrup consumption.