Study On Constitutive Model Of Concrete Materials Under Freeze-thaw Cycles Based On The Damage Theory

With the increase of the service life for concrete structures,the problems on the durability of concrete materials are non-negligible.Especially,the damage degree of concrete structures due to freezing and thawing is more prominent for the cold regions in northern China.In this paper,based on the fro st-resistant durability of concrete materials,the constitutive models of concrete materials subjected to freezing and thawing cycles are investigated.In order to investigate the evolution law of concrete freeze-thaw damage,the constitutive model of concrete material under the effect of freeze-thaw cycles was studied.The main research contents are as following:1.According to the basic force characteristics of concrete materials,the elasto-plastic damage constitutive models of concrete are investigated based on the Lee-Fenvas yield criterion.The modified method of the cohesive force function for yield criterion is proposed.Besides,UMAT material subroutine is established and numerical calculation is conducted by the finite element software ABAQUS platform.The effectiveness of constitutive model is validated through comparison with test results and dereferencing method of modified parameters is obtained.2.Through the statistical analysis of the actual freezing and thawing test results for the concrete structures,a model for the degradation of the mechanical properties for the concrete materials under freezing and thawing cycles is established.Besides,a constitutive model of the concrete materials under the freeze-thaw cycles is proposed based on the materials degradation model.The effectiveness of constitutive model is validated through analyzing the comparison results between tests and numerical simulations.3.Based on the elasto-plastic damage constitutive model for concrete materials of the materials degradation model under the action of freeze-thaw cycle,the seismic performance simulations of reinforced concrete column members under freezing and thawing cycles are carried out.The feasibility of constitutive models is validated through analyzing the comparison results between tests and numerical simulations and numerical simulations which considering the freezing-thawing degradation constitutive model,respectively.