Research On Mesoscopic Modeling Methods Of Concrete Composites Based On Impact Simulation

As a dominant building material,concrete composites plays an important supporting role in civil engineering,geotechnical engineering,railway,highway and other construction.Previous studies on the mechanical properties of concrete is performed on a macroscopic scale,concrete composite is assumed homogenous.Along with the rapidly development of material science,experimental technologies and computational science,research perspective on concrete composites has been shifted from macro level to meso-and micro-levels.It was found that meso-scale model provides a more realistic representation of concrete material properties and yields more reliable simulations of concrete failure mechanisms and material properties than homogenous model under complicated working conditions,which is often hard to obtain by the common tests.Studies demonstrated the importance of considering the concrete heterogeneity in numerical simulations of concrete material behavior.Hence,to establish a numerical model which could really reflect the meso-scopic structure of concrete composite to the utmost extent is a very meaningful and valuable research.Now scholars mainly put forward meso-scale numerical model for plain concrete,models for the steel fiber reinforced concrete,especially in 3D,is not still too much.By introducing the impact simulation function of ANSYS/LS-DYNA software in the process of meso-scopic modeling,we successfully built the steel fiber reinforced concrete finite element model in 2D and 3D,.Main research contents are as follows:(1)The implementation process of random impact simulation of geometric body in the 2D and 3D on LS-DYNA has been studied.finite element,material model and contact type suitable for aggregate impact simulating is selected.Finally,the feasibility and effectiveness of introducing the impact simulation function of ANSYS/LS-DYNA software in the process of meso-scopic modeling was validated by an example.(2)The creating method of geometric models respective for the oval-shaped aggregates,random shape aggregates,hooked-end steel fiber and spiral steel fiber was proposed.(3)The random distribution of aggregates and steel fibers were performed by the process of random impact simulation using LS-DYNA(4)Based on the coordinates of keypoints obtained from the post-process in LSPREPOST,concrete meso-scopic numerical model respectively harbored oval aggregate,random shape gravel hooked-end steel fiber and spiral fiber was successfully reconstructed.(5)Considering the complex feature of aggregate's and steel fiber's shape,a discriminating method of material attributes of finite elements was proposed.Meso-scopic finite elements numerical model for steel fiber reinforced concrete in 2D and 3D was established based on background-mesh methods(6)Based on the proposed meso-scopic numerical model of steel fiber reinforced concrete,Characteristic parameters,orientation coefficient and dispersion coefficient,of steel fibers in the numerical specimens were qualitatively studied and quantitatively determined.Meanwhile,using the concrete damage model,a comparative study on the failure models,cracking model and after-cracking properties of plain concrete and steel fiber reinforced concrete under uniaxial tension was conducted.