Study On Dynamic Response Of Freeze-thaw Cycle Reinforced Concrete Beam Members Under Explosion Load

The buildings in the northern regions of China and the high cold area were subjected to various environmental effects,among which the damage to the buildings was obvious due to the freeze-thaw cycle,but the dynamic response of the structures under the blast load after the freeze-thaw cycle was less studied.The beam is an important component in the structure.It is necessary to study the dynamic response of the beam component under blast load after freeze-thaw cycle.In this paper,the dynamic response of reinforced concrete beam members under blast load after freeze-thaw cycle is studied by combining numerical simulation and experiment.The main research contents are as follows:1.The dynamic response of beam members under explosion load was analyzed and the empirical formula used to calculate the peak overpressure of explosion load was summarized.Different empirical formulas were used to calculate and analyze the peak value of overpressure under blast load when the proportion distance is between 0.1 and 2.0m·kg^-1/3,which provides theoretical support for the dynamic response analysis of post-freeze-thaw cycle reinforced concrete beam members under blast load.2.The experimental simulation research on dynamic response of beam members under TNT explosion in free air domain and explosion load was carried out.A simulation model was established according to the parameters of finite element model in previous explosion simulation.Seven working conditions of explosion distance of 0.4m and explosive equivalent W of 0.2kg,0.4kg,0.6kg,0.8kg,1.0kg,1.5kg and 2.0kg were set in free air domain explosion simulation research conditions.The explosion distance and explosive equivalent were converted into proportional distance analysis.The results show that there were different degrees of error between the explosion simulation and the explosion overpressure peak calculated by the empirical formula.The simulation results were in good agreement with the Henrych and Baker empirical formulas.3.The small free air explosion test of C30 reinforced concrete beam members with freeze-thaw cycles of 50 and 100 times was carried out.In the test,the dimensions of the failure zone of the blast facing surface and the back explosion surface,the overpressure time history curve and the mid-span maximum displacement of the member were measured.By comparing the experimental results with the simulation results,the error of both results is less than 15%,and the simulation results were good,which proves the rationality of using simulation methods to study the dynamic response of reinforced concrete beams under explosion load.4.The differences of stress,displacement,reinforcement displacement of concrete beams without freeze-thaw and freeze-thaw cycles of 50 times under the action of explosion load were analyzed,and the time history curves and peak values of the displacement,velocity and acceleration of the members of freeze-thaw reinforced concrete beams under different freeze-thaw cycles,explosive equivalent,explosion distance and concrete strength were analyzed.The influence of different factors on dynamic response of beam members under blast load after freeze-thaw cycle was studied.In this paper,the dynamic response rules of beam members under different influencing factors were obtained,which provides the foundation support for the dynamic response analysis of freeze-thaw reinforced concrete beam members under blast load.