Mesoscopic Simulation Of Mechanical Properties Of Reinforced Concrete

With the development of computing technology, in recent years numerical methods have been widely used in high-rise, large-scale structural design. Because of the advantages on simulating the generation and propagation of cracks in concrete, as well as on prediction of crack width, the Rigid Body Spring Model (RBSM) has become a kind of important numerical method on the structural design and durability analysis. In this paper RBSM is used to simulate the behavior of concrete and reinforced concrete under static loading in terms of the mechanical properties and cracking characteristics. Through comparing the simulation results with experimental data, the RBSM has been confirmed to be effective and feasible for simulating the behavior of reinforced concrete. The major contents are summarized as follows:1. An improved method of generating random convex aggregates in two-dimensional area is proposed with help of the area index and convex polygon criteria. The methods of extending the aggregate or locating the special points are improved on the basis of previous findings. The new methods are able to accelerate the generation process of random polygon aggregates and subsequently improve the computational efficiency. Examples of uniaxially loading specimen are presented in the paper with the purpose to show that the mesoscopic simulation method can provide us with effective information to understand the effect of concrete performance of aggregates with different shapes. The calculated results illustrate that the concrete sample with circular aggregates has slightly higher strength and than that with polygon aggregates, which also indicates that shape of aggregate has little effect on the compressive and tensile mechanical properties of concrete in terms of the numerical simulation technique.2. By using different kinds of softening relationship (i.e., no softening branch, bilinear softening relationship and linear softening relationship), in this paper the mechanical properties of concrete specimens is simulated on the basis of RBSM. The results show that, since concrete is not a pure brittle material, by choosing an appropriate softening relationship the failure procedure of concrete can be simulated well to match the actual situation. It is concluded that the bilinear softening relationship can simulate the failure of concrete well when the parameters are set appropriately.3. Finally, this thesis proposes an improved method to analyze the failure of reinforced concrete structures by numerical simulation. In this method, concrete is represented by the RBSM, which can randomly mesh the spcimen. Reinforcing bars are modeled by beam elements. Link-springs are used to simulate the reaction between reinforcement and concrete. By means of the analysis of two-dimensional reinforced concrete specimens under three points bending load, the cracking process and distribution of cracks, as well as the load-deformation curve are investigated and compared with come available experimental results. The computed results give a good agreement with test findings.