Study On Mechanical Properties And Energy Response Characteristics Of High-porosity Concrete Under Cyclic Loading And Unloading

“Sponge City” is a new model of urban construction in China.The core of its “sponge” function is the application of concrete materials with high porosity(high permeability)and high-pressure resistance.In the process of road operation,the typical cycle of vehicles such as vehicles adds and unloads,causing the structural damage in the road and the lower part of the road,severely weakening the "sponge" function of the road and its normal operation.Therefore,the mechanical properties of high porosity concrete under cyclic loading and unloading conditions are one of the key mechanical problems involved in the construction of “sponge cities”.In this paper,through the cyclic loading and unloading test,the mechanical properties of high porosity concrete and the energy dissipation during the failure process are studied.According to the theory of damage mechanics,the damage evolution characteristics of high-porosity concrete under cyclic loading and unloading are obtained,and the service life prediction of concrete is given.model.Mainly achieved the following conclusions:(1)Through the uniaxial compression test,the mechanical properties of four different high-porosity concretes were tested to obtain concrete stress-strain curves,elastic modulus,peak stress,peak strain,Poisson's ratio,energy dissipation with porosity.The law of change,determine the porosity of 15% of the concrete as a cyclic loading and unloading test object.(2)With the stress amplitude in the elastic phase,cyclic loading and unloading tests are performed on high-porosity concrete,the mechanical properties of the concrete after cyclic loading and unloading,and the cycle effects and stress amplitude effects of energy dissipation are systematically studied to clarify the cyclic loading and unloading effect.Underlying elastic modulus,unloading elastic modulus,peak strain and other mechanical characteristics with the number of cycles of the law,given the total absorption energy of the concrete,elastic energy and dissipated energy with the number of cycles and stress amplitude changes.(3)When the strain amplitude is in the stage of crack development,cyclic loading and unloading tests are performed on high-porosity concrete,and the effects of strain amplitude and number of cycles on the mechanical properties and energy dissipation of the concrete are systematically studied.The elastic modulus and unloading elasticity of the concrete are obtained.Modulus,peak stress,residual strain and total absorbed energy,elastic energy,dissipated energy as a function of strain amplitude and number of cycles.(4)Based on the damage mechanics theory of concrete,the damage evolution constitutive equation of concrete considering the stress amplitude effect is established respectively,and the experimental parameters of the equation are determined based on the stress-strain test data,and the running life of the high-porosity concrete road is predicted through calculation examples.The research conclusions can provide the basis for the selection of high porosity concrete materials in the construction of “sponge city” roads.