Research On Freeze-thaw Damage Model And Numerical Simulation Of Concrete In High Cold Area

In alpine regions,it will be affected by a variety of unfavorable factors,resulting in frequent freezing and thawing of concrete structures,such as high altitude,low temperature,etc.,resulting in structural damage,restricting its life,and even threatening the safety of buildings in severe cases.In order to improve its frost resistance and durability,predict the life of alpine concrete,quickly and accurately judge the change of mechanical properties and failure mechanism of alpine concrete in freeze-thaw cycle.Through the physical and mechanical test and freeze-thaw cycle test of concrete mixed with different admixtures in alpine region,the working performance,mechanical properties and frost resistance of concrete in alpine region are studied.The existing concrete damage models are analyzed.Considering the influence of special environment in alpine region on concrete,a three-parameter Weibull distribution model is constructed by introducing frost resistance factor into the two-parameter Weibull distribution model.The 28-day-old compressive strength of the four is simulated by the ABAQUS application.The temperature field,temperature stress distribution and mechanical properties of alpine air-entraining and waterreducing concrete during freeze-thaw cycle were simulated by sequential coupling thermal-stress analysis.This results in:（1）Among the 4 middle and high cold concretes,from the perspective of mechanical characteristics,the ordinary type is stronger than the air-entraining type,and both the airentraining water-reducing type and the water-reducing type are enhanced,and the four can meet the design standards in terms of pressure resistance and folding resistance.The air-entrained water-reduced type has the best frost resistance and durability.（2）The freeze-thaw damage of alpine concrete should be regarded as random fatigue damage.Considering the influence of special environment on concrete in alpine region,the twoparameter Weibull distribution model is optimized and the three-parameter Weibull distribution model constructed by introducing antifreeze factors can calculate the degree of freeze-thaw damage of concrete in alpine region and predict the life of concrete,so that the accuracy of solving the amount of freeze-thaw damage of concrete is further improved.（3）The external temperature of alpine concrete changes more greatly than the internal temperature during the freeze-thaw cycle,coupled with the relatively high temperature stress,it is the first to be damaged.The changes of flexural strength and dynamic elastic modulus obtained by simulation are consistent with the experimental values.It reflects the possibility and reliability of ABAQUS software to simulate the failure mechanism and mechanical properties change of alpine concrete during freeze-thaw cycles.