Study Of The Nonlinear Creep Properties Of Concrete Based On The Flexibility Tensor Equivalence

Non-linear creep is manifested when the external sustained load of concrete is high.The nonlinear creep of concrete will have a very serious impact on concrete structures subjected to continuous loading for a long time.Since concrete itself is a composite material with complex mechanical properties,most of the current studies on nonlinear creep in concrete have been conducted by macroscopic fitting,which does not reveal the mechanism of nonlinear creep in concrete.Therefore,in this paper,concrete creep tests under long-term high loads were carried out,and the mechanical properties of concrete under high sustained loading and the evolution of damage with strain energy were researched.The connection between the damage evolution of concrete under uniaxial and creep loads were we carried out,and concrete nonlinear creep model based on the principle of flexibility tensor equivalence was propsed.The main research aspects of this paper are as follows.(1)Using uniaxial compressive creep tests with high sustained loads of concrete,the strain evolution relationship with time,strain rate evolution relationship with time,damage evolution relationship with time,and damage evolution relationship with strain under the effect of creep are analyzed.The evolution of damage with strain energy was analyzed by considering evolution of microcrack propagation and the strain energy accumulation of concrete under creep.(2)By studying the damage evolution law of concrete uniaxial compression test,the damage evolution equivalence relationship between uniaxial and creep loading of concrete is investigated,a nonlinear concrete creep model based on the flexibility tensor equivalence is established,and a new concrete nonlinear creep calculation method is proposed.The test values are compared to explain the mechanism of concrete damage evolution under high sustained load uniaxial compression condition.(3)The model proposed in this paper is used to study the relationship between the tertiary creep damage time,damage strain under different loading magnitude of concrete.The relationship between damage strain and total strain of concrete under high sustained load is investigated,and the mechanism of creep damage of concrete under high sustained load is elucidated.