Study On Seismic Performance Of RC And R/ECC Short-leg Shear Walls

Short-limb shear walls are favored by a wide range of structural engineers for their flexibility in structural arrangement,ease of meeting building functions,low cost of construction,and energy efficiency.However,the application and development of traditional Reinforced concrete(RC)short-limb shear walls in large seismic zones,especially in high-intensity areas,is limited by their short limbs and poor seismic performance,especially their susceptibility to cracking,ductility,and lack of structural energy dissipation.Therefore,it is of great practical importance to improve the seismic performance of RC short-limb shear walls,to expand the application of short-limb shear walls in seismic zones,and to improve the corresponding design methods.In this paper,based on the experimental study of RC short-limb shear walls carried out by the group,the data from the experimental study was extended by means of finite element analysis,and numerical simulations of the seismic performance of R/ECC(Reinforced ECC)short-limb shear walls were carried out to compare and analyze the differences in the seismic performance of the two types of structures,and to provide a reference for the improvement of the seismic capacity of RC short-limb shear walls and the application and promotion of ECC in short-limb shear walls.The study is intended to provide a reference for the improvement of the seismic capacity of RC short-limb shear walls and the application and promotion of ECC in short-limb shear walls.The following research elements and conclusions are mainly addressed:(1)A brief overview of modelling methods and material models for the finite element analysis of short-limb shear walls is presented,and the uniaxial tensile/compression principal structure relationships between concrete and ECC materials are investigated.The correctness of the material parameter definitions and the mesh insensitivity of the numerical simulation results were verified through the simulation of individual cells with different mesh divisions;the numerical simulation of the 1:2 large-scale frame structure was then compared with the test results to verify the reliability of the implementation process of the finite numerical model and to provide a guarantee for the reliable conduct of the numerical simulation work in the subsequent sections.(2)Six tests on RC short-limb shear walls at 1/2 scale were carried out.The results show that the bending damage mode is dominant in short-limb shear walls of the RC-L section,with longitudinal tendons at the end of the flangeless web buckling,hoop tendons yielding in tension,concrete crushing at the end of the flangeless web and severe seismic damage in the plastic hinge zone at the bottom of the wall.The energy dissipation capacity and ductility of the members at high axial pressure ratios are relatively good,but the ductility of the members at higher axial pressure ratios deteriorates with decreasing shear-to-span ratios.Based on this,an RC short limb shear wall model(L500-1)was developed using ABAQUS software and compared with test results to verify the reliability of the numerical model.By simulating the RC short-limb shear wall model with an axial pressure ratio between 0.1 and 0.6,the analysis results found that the seismic performance of RC short-limb shear walls is better at axial pressure ratios between 0.1 and 0.3.(3)The geometric model,boundary and loading conditions of the RC short-limb shear wall were kept unchanged.ECC materials were adopted and their compressive strength was equal to the concrete strength of the RC short-limb shear wall.The seismic performance of the R/ECC short-limb shear wall were simulated,and the simulation conditions were completely same with to the RC short-limb shear wall members as described.The analysis results show that the R/ECC short-limb shear wall has good ductility performance and energy dissipation capacity ranging from the axial pressure ratio 0.1 to 0.5.Whereas,the bearing capacity decreased at the axial pressure ratio of 0.6.(4)Numerical simulation results of RC and R/ECC short-limb shear walls with axial pressure ratios from 0.1 to 0.6 were compared and analyzed,with emphasis on the difference in seismic performance between the two types of structures in the range of 0.3-0.5 for axial pressure ratios.The results show that ECC applied to short-limb shear walls exhibit better ductility and energy dissipation capacity,which significantly improves the seismic performance compared to RC shortlimb shear walls.Taking the axial compression ratio of 0.3 as an example,the bearing capacity of R/ECC short-limb shear walls was increased by 22% and 18.1%,the corresponding deformation displacement was increased by 32.5% and 21%,and the energy dissipation capacity was increased by 16.36% and 25.71%,respectively,compared with that of RC short-limb shear walls.(5)By extracting the characteristic data(yield load and its deformation,peak load,and its deformation,breaking load and its deformation)from the simulation of R/ECC short-limb shear walls under different axial compression ratios,a restoring force model for short-limb shear walls was established by means of mathematical model description,which mainly involves the determination and verification of the skeleton curve and stiffness degradation law.The restoring force model can be used as a reference basis for structural damage and safety assessment.(6)The multi-vertical truss element model considering the influence of normal stress to shear stiffness,which is achieved by the combination of axial stiffness with shear stiffness.The new multi-vertical truss shear wall member model is proposed to take account for the shear-lag and cumulative damage effect.The high simulation accuracy of the proposed model was confirmed by comparing between the tests date and the simulations.