| To further improve the seismic performance of reinforced concrete(RC)coupling beams and coupled shear walls,experimental and numerical studies on the application of engineered cementitious composites(ECC)in coupling beams and coupled shear walls are investigated in this thesis,and the main research achievements are as follows:(1)Numerical study on the seismic performance of RC coupling beams and coupled shear walls are carried out.Considering the buckling of diagonal bars in coupling beams,12 coupling beam specimens as well as 3 coupled shear wall specimens are simulated and the influences of slabs on the seismic performance of coupled shear walls are analyzed.Based on parametric analysis,suggestions of diagonal bar ratios and degrees of coupling are proposed.The real boundary conditions of coupling beams in the coupled shear walls are also revealed.(2)Experimental study on the seismic performance of 14 coupling beam specimens with different cement-based materials,reinforcement layouts and aspect ratios are carried out and the calculation method of the bearing capacity of ECC coupling beams is proposed.The failure mode,bearing capacity,ductility,energy dissipation capacity,shear deformation,degradation of stiffness and strength are thoroughly investigated.The axial force of coupling beams is monitored during the whole process of loading.Based on test data in this thesis as well as data reported by other scholars,the formula to calculate the shear strength of ECC coupling beams is proposed.Combining the flexural strength considering the axial compressive force in the coupling beams,the bearing capacity of ECC coupling beams can be accurately calculated.(3)A new two-dimensional(2D)fixed crack model for ECC is proposed and validated.The 2D fixed crack model considering confinement effect by stirrups,compression softening,tension strain-hardening,tension softening,pinching effect,compressive strength degradation due to the principle tensile strain and shear softening of ECC is proposed and implemented in the implicit solver provided in ABAQUS software.Calculation methods of model parameters are proposed based on material tests.Various ECC structural members including 19 coupling beams,6 shear walls and 5columns are simulated and comparison results demonstrate that the proposed ECC constitutive model has a wide application range with adequate accuracy.(4)The optimization analysis of applications of ECC in coupled shear walls are carried out.According to the parameter analysis of the seismic performance of coupling beams and shear walls,the suggested ECC tensile properties including tensile peak stress and strain are put forward.The parametric analysis of coupled shear walls with the use of ECC coupling beams are carried out,and the suggested diagonal bar ratio of ECC coupling beams is proposed.Based on the dynamic time history analysis of a practical coupled shear wall structure,the suggestions about the application range of ECC in the coupled shear wall is proposed.(5)A new macroscopic model for reinforced cement-based materials coupling beams is proposed and parametric analysis are carried out.A database consisting of 180 reinforced cement-based materials coupling beam test specimens is set up.The skeleton curve for the macroscopic model can be accurately predicted using the trained XGBoost machine learning models.A new hysteretic rule for the macroscopic model which can account for the pinching effect,strength and stiffness degradation is proposed and implemented in the implicit solver provided in ABAQUS software.The accuracy and applicability of the proposed model are validated according to 12 coupling beam specimens with different cement-based materials and reinforcement layouts,as well as a coupled shear wall specimen.Based on parametric analysis of the coupled shear wall system,effects of the main indexes of coupling beams on the seismic performance of the coupled shear walls are thoroughly investigated. |
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