Research On Splitting Tensile Behavior Of New-to-old Concrete Interfaces Under Different Loading Rates

New-to-old concrete interfaces widely exist in concrete structures,such as the connections of precast components in assembled monolithic concrete structures through post-cast concrete,the installation of post-groove belts for long and large concrete structures,and the refilling of concrete when repairing partially damaged concrete components.The interface of new-to-old concrete formed by pouring at different times are usually the weak links of the structure.During their service period,they are not only subjected to static loads,but also may be subjected to dynamic loads such as waves,earthquakes,explosions,and impacts.Therefore,it is necessary to study the mechanical properties of the new-to-old concrete interface under dynamic load.Tensile cracking is one of the typical cracking failure modes of new-to-old concrete interface.Concrete is a rate-sensitive material,and its tensile strength increases with increasing strain rate.Then,whether and how the tensile cracking performance of the joint surface composed of new-to-old concrete interface will be affected by the strain rate has become a problem worthy of attention in the study of the mechanical properties of the new-to-old concrete joint surface under dynamic loading.This paper firstly carried out the experimental study on the split tensile properties of the new-to-old concrete interface under static and dynamic loads,and studied the effects of strain rate,roughness and age on the tensile properties of the new-to-old concrete interface.The results show that as the strain rate increases,the splitting strength of the new-to-old concrete joints also increases accordingly,and the specimen exhibits severe crushing at the loading end;the changes in roughness and age in this test did not The splitting strength and failure mode of the new-to-old concrete interface have obvious influence.Based on the experimental research,the finite element software ABAQUS was used to numerically study the static and dynamic splitting performance of the new-to-old concrete interface.Firstly,the correctness of the numerical simulation model was verified according to the test results.Then,by observing the strain distribution of the specimen and its change with loading time in the numerical simulation results,the split-pull failure mechanism of the new-to-old concrete interface was analyzed.On this basis,the parameter analysis of the influence of strain rate and roughness on the splitting performance of the new-to-old concrete interface was carried out,and the relationship between the splitting strength of the new-to-old concrete interface and the strain rate and roughness under static and dynamic loads was given.