Finite Element Analysis Of Composite Constrained High-strength Manufactured Sand Concrete Shear Wall And Study On Its Limits Of Stiffness Degradation Index

Reinforced concrete shear walls are widely used as anti-lateral components in high-rise buildings.However,its application is limited when the building reaches a certain height.Steel-concrete composite shear walls have received increasing attention due to their superior mechanical properties and remarkable economic benefits.It can effectively reduce the section area and the weight of the structure and increase the area of use of the building when applying high-strength concrete to the concrete-filled steel-concrete shear wall.However,China's code has limitted the use of high-strength concrete in seismic shear walls due to its brittleness.On the other hand,with obvious disadvantages of the increasing scarcity and excessive exploitationof natural river sand resources,it is particularly important to seek alternative sand sources for natural river sands.The use of machine-made sand instead of natural river sand for the preparation of high-strength concrete is a feasible solution.However,the brittleness of high-strength machine-made sand concrete is much more obvious.To this end,our group has designed a new type of composite shear wall component that is compositely restrained by steel tubes and hoop stirrups.Through the restraint of the steel pipe and the parted confining high-strength stirrups,it effectively improves the ductilityof high-strength machine-made sand concrete and improves itsbearing capacity and deformability.By studying the effectiveness of the new composite shear wall,it provides an important basis for its application in complex high-rise and super high-rise building structures.The cyclic tests on four composite constrained high-strength manufactured sand concrete shear walls had been conducted by the team.In order to further study its theory and seismic performance,the ABAQUS program was used to establish a finite element model of composite constrained high-strength manufactured sand concrete shear wall,and the reliability of the finite element model was verified.On this basis,the seismic performance of the composite constrained high-strength manufactured sand concrete shear wallwas studied;Then the formula for the calculation of the bearing capacity of the shear wall is proposed and validated;The standard for the classification of the seismic performance of the new shear wall is established,and the threshold values of the stiffness degradation index for each performance level are proposed,which provides an important basis for the performance-based seismic design.The main research content arelisetd as follows:(1)The results of cyclic tests on 4 composite constrained high-strength manufactured sand concrete shear walls are compiled.The nonlinear finite element software ABAQUS is used to establish the composite constrained high-strength manufactured sand concrete shear wall model with the axial compression performance test of the high-strength machined sand-concrete concrete column,whose result is comparedwith the experimental results.(2)Based on the validated finite element model,through the secondary development of the ABAQUS software,a pre-processing script for the composite constrained high-strength mechanism sand concrete shear wall based on the Python language was built;According to the pre-processing model written by the script,a post-processing script that can be used to classify and extract strains of various materials and load-displacement curves of components is proposed.(3)ABAQUS software was used to establish a finite element model of 98 composite constrained high-strength manufactured sand concrete shear walls.The effects of several parameters,such as the axial compression ratio,concrete strength,steel strength,steel ratio,and stirrup spacing,on the seismic performanceof the composite constrained high-strength manufactured sand concrete shear wallwere studied.(4)With reference to the Code for Design of Concrete Structures(GB50010-2010)and the Technical Specification for Steel Reinforced Composite Structures(JGJ 138-2016),the calculation formula for the bearing capacity of the designed new type composite shear wall was proposed.The results were compared with the test results of the existing one-line type steel tube confined concrete shear wall and the four-piece composite constrained high-strength manufactured sand concrete shear wallin our group,whose reliability is verified.The N-M curve of the test component is studied and the demarcation point of large-small eccentricity failure is determined.(5)Referring to the code,,the criteriabased on the material deformation and combined with the stress state and load displacement curve of the components for the four performance levels of basically complete,slightly broken,medium damage,severe broken were established.(6)By changing axial compression ratio,concrete strength,steel strength,steel ratio and stirrup spacing,156 finite element models of composite constrained high-strength manufactured sand concrete shear walls was designed.The correlationbetween variation parameters and each performance level's stiffness degradation index is studied,and the key parameters are determine d through the T test.On this basis,a regression formula for the establishment of key parameters and each performance level's stiffness degradation index is established.Using the formula to expand the calculation of 2880 sample,a composite constraint high-strength mechanism sand concrete shear wall stiffness degradation index threshold value is proposed.