Analysis On Axial Compressive Behavior Of Reinforced Concrete Short Columns After Freeze-thaw Cycles

At present,freeze-thaw damage has become an important reason to affect the normal use of reinforced concrete structures.Many scholars at home and abroad have carried out research on the failure mechanism,mechanical properties,constitutive model and other aspects of concrete after freeze-thaw cycles,and made some progress.However,due to the complexity of freeze-thaw action and the diversity of concrete structures,there is still room for research and development in this field.In the existing research results,the research on the mechanical properties of reinforced concrete compressive members after freeze-thaw cycles is still not perfect.In view of the above situation,this paper studies the axial compressive behavior of reinforced concrete short columns after freeze-thaw cycles by method of finite element analysis.The specific work is as follows:(1)Using the stress-strain curve equation in the code as the basic model equation,the stress-strain curves of C40 and C70 concrete under different freeze-thaw cycles were constructed according to the uniaxial compressive test results of prisms after freeze-thaw cycles.Based on the plastic damage theory,the Concrete Damaged Plasticity Model after freeze-thaw cycles in ABAQUS was further established.(2)Using the concrete constitutive model after freeze-thaw cycles constructed in this paper,the finite element analysis of concrete prism axial compressive strength and cube compressive strength after freeze-thaw cycles was carried out by ABAQUS software.By comparing the results of finite element analysis with the test results,the applicability of the concrete constitutive model after freeze-thaw cycles established in this paper is verified.In addition,according to the finite element analysis results of the concrete cube compressive strength after freeze-thaw cycles,the transformation relationship between the cube compressive strength and the axial compressive strength under different freeze-thaw cycles of C40 concrete was established.(3)Using the concrete constitutive model and strength transformation relationship after freeze-thaw cycles constructed in this paper,the finite element analysis of reinforced concrete short columns’ axial compression after freeze-thaw cycles was carried out by ABAQUS software.According to the results of finite element analysis,the mechanical properties such as failure modes,peak loads,load-strain curves of reinforced concrete short columns after freeze-thaw cycles are obtained.(4)The analysis of axial bearing capacities of reinforced concrete short columns after freeze-thaw cycle was carried out,and ultimate bearing capacities of specimens with different reinforcement ratios after freeze-thaw cycles were fitted,the parameters of them were analyzed.The results show that it is feasible to describe the constitutive relationship of concrete after freeze-thaw cycles by using the stress-strain curve of ordinary concrete given in the concrete code;Under the same reinforcement ratio,with the increase of the number of freeze-thaw cycles,the ultimate bearing capacities of the specimens decrease gradually,the peak strains increase gradually,and the load-strain curves gradually become flat;With the increase of the number of freeze-thaw cycles,the increasing degree of short column specimens’ ultimate bearing capacities decrease gradually with the increase of the longitudinal reinforcement ratio,and the cooperative performances between concrete and reinforcement decrease gradually.