Numerical Simulation Of Reinforced Concrete Columns With A Two-scale Model

As concrete structure has been applied widely in modern engineering structures,it is increasingly important to study the mechanical properties of concrete.In this paper,the two-scale modelling approach is developed to study the behavior of concrete columns.In meso-scale model,concrete is composited by aggregate,mortar and interface transition zone.A numeircal concrete generating program is developed using MATLAB to generate a three-phase concrete with circular and pilybonal aggregates,which is used to study the properties consideing mesoscopic parameters.It is showed that the change in the position of the aggregates leads to crack location change,but it has little influence on the stress-strain curve before the peak under the tensile load.Besides,the tensile cracks are mainly distributed in the direction perpendicular to the direction of applied load and initiate along with the interface,but different crack propagation pathes cause variation in post peak behavior of concrete.The variation of aggregate shape has little effect on the stress-strain curves before the peak load.In the strain-softening period,circular aggregate has lower softened strength than polygonal ones for the uniform radian of its surface is beneficial to the propogation of crack.The interface transition zone has a great effect on reducing the strength of concrete.While the element division is larger than the thickness of interface transition zone,the weighted homogenization equivalent method in this paper can take the influence of thin interface transition zone into consideration and has a better computed results.In macro-scale model,in order to simulate the behavior of reinforced concrete column under rapid cycling load,a two-scale model with three dimensional(3D)fiber beam elements and solid elements is developed.The simulated behavior is compared with the test results and the results show that the developed two-scale model using the developed subroutines simulate the load-carrying capacity and the dynamic hysteretic performance of the RC column with acceptable accuracy.The stress of the steel and concrete and the damage development of the concrete are similar to the model using solid element.The two-scale model is efficientive in simulating the global behavior of the RC columns and in describing the local failure pattern with acceptable computing time.