Numerical Simulation Of Dynamic Mechanical Behavior Of Two-gradation Random Distribution Coarse Aggregate Concrete

Concrete is widely used in civil,industry and safety protection buildings,which has high compressive strength,simple preparation,better corrosion and tolerance resistance.Concrete structures are often subjected to quasi-static load changing slowly,but sometimes need to bear the role of anti shock and anti explosion dynamic load,therefore,it is necessary to study the dynamic properties of concrete.From the macroscopic point of view,the concrete is an isotropic material,but in the microscopic aspect,we can regard the concrete as a two-phase composite material consisting of coarse aggregate and cement mortar.In this paper,finite element analysis software ANSYS/LS-DYNA is used to analyze the dynamic mechanical properties of two size of two-gradation concrete,the specific researches are as follows.(1)Coarse aggregate distribution.Firstly using Fuller gradation and Varaven plane transformation formula turns the three-dimensional problem into a two-dimensional problem.The Varaven plane transformation formula is to calculate the plane area of required content of coarse aggregate.The paper prepared for random distribution of coarse aggregate by area control program using the ANSYS/LS-DYNA APDL language,which means coarse aggregate randomly distribution by controlling the content of coarse aggregate in the area of the plane.(2)On the basis of coarse aggregate randomly distribution,the influence of coarse aggregate volume content,the maximum size of coarse aggregate and the middle size of coarse aggregate which are changed on the peak stress of two-gradation concrete are studied,then extract the relevant stress-strain curve.Analysis shows that:?With the increase of volume content of coarse aggregate,two-gradation concrete peak stress in the coarse aggregate volume content of 40%is maximum.?With the increase of maximum size of coarse aggregate,the peak stress of two-gradation concrete declines.?With the enhancement of the middle size of coarse aggregate,the peak stress of two-gradation concrete increase firstly,and then declines.?The peak stress of two-gradation concrete has obviously size effect.?The impact of low speed leads to low impact energy and few macro cracks;The impact of high speed leads to high impact energy,more macro cracks and numbers of smaller fragments.