Constitutive Relation Of Recycled Concrete And Numerical Simulation Of Seismic Behavior Of Structural Members

In recent years,with the further deepening of the concept of green development,the study on recycled concrete has been paid more and more attention and support by the country.Domestic and foreign scholars have done a lot of experimental research on the material properties of recycled concrete and the seismic performance of structural members,and have achieved many outstanding results.The constitutive relation of recycled concrete is an important basis for strength calculation,internal force analysis and finite element analysis of recycled concrete structures.At present,there are relatively few studies on the failure criteria of recycled concrete.It is necessary to further carry out related studies on general constitutive models applicable to constrained and unconstrained recycled concrete to provide a basis for numerical simulation.This paper proposes a universal recycled concrete constitutive model based on the failure criterion of recycled concrete,and applies this model to the numerical simulation of recycled concrete.The main work and conclusions of this paper are divided into the following three aspects:(1)Based on the experimental data of 30 stirrups confined recycled concrete circular short columns and 24 stirrups confined recycled concrete square short columns under axial compression completed by the research group,a comparative analysis is made by using Willam-Warkne five-parameter failure criterion,Zhao Guofan-Song Yupu failure criterion,Ottosen failure criterion,Guo Zhenhai-Wang Chuanzhi failure criterion and Jiang Jianjing four-parameter failure criterion.On the basis of Willam-Warkne five-parameter failure criterion,the failure criteria of recycled concrete under two different recycled aggregate replacement rates are fitted.Five kinds of ordinary concrete failure criteria,Zhang Jiaxing-He Zhenjun recycled concrete failure criterion,Wang Yumei-Deng Zhiheng recycled concrete failure criterion and the fitted recycled concrete failure criterion are compared.it is verified that the proposed failure criterion of recycled concrete can accurately predict the compressive strength of recycled concrete confined by stirrups.(2)Based on the constitutive model of recycled concrete confined by stirrups proposed earlier by the research group,combined with the aforementioned failure criterion of recycled concrete,a modified constitutive model of recycled concrete is proposed.Through the full curve tests of 5 C30 strength and 10 C40 strength recycled concrete blocks,the applicability of the modified recycled concrete constitutive model to plain recycled concrete is verified.(3)The modified constitutive model of recycled concrete is combined with Yassin hysteretic rule to form a hysteretic constitutive model of recycled concrete.Based on the Open Sees framework,the constitutive model is compiled into Concrete R,a recycled concrete material controlled by 5 parameters,through 15 functional functions.Based on Open Sees software,the newly developed recycled concrete material Concrete R is used to simulate the low cyclic loading tests of 6 recycled concrete frame columns and 6 recycled concrete short beams carried out by the research group.the results show that the Concrete R material simulation can accurately reflect the seismic performance of recycled concrete members,and the developed Concrete R material can be applied to the numerical simulation of recycled concrete members.