Simulation By Software Mfpa For The Whole Fracturing Process Of Reinforced Concrete Structures

In recent years, with the rapid development of civil engineering, hydroelectic engineering and railway tunnel engineering, the reinforced concrete structure has become more widely used, the researches on reinforced concrete structure become more and more. These researches mainly concentrated on the deformation and limit strength of reinforced concrete, but rarely studied the whole failure process of reinforced concrete structure. At present, there are some researches on the failure of reinforced concrete structure at home and abroad. However, the complication of mechanics property of reinforced concrete structure and the limitations of tests and measures made it difficult to obtain all property data from the tests. Therefore, tests combined with other methods are required to analyze the mechanics property of structure. In the meantime of the tests, the numerical simulation research emerged. In 1960's, American scholars introduced the finite element method to the numerical simulation analysis of reinforced concrete structure, started the numerical research on reinforced concrete structure and gained a certain achievements. But the method for finite element model still had some deficiency. The structure calculation of numerical simulation method based on the finite element theory required that the deformation is continuous and harmonious, but for the uncontinuous medium mechanics existing between the reinforcing bar and the concrete, it is hard to use the finite element method to solve the problem.The whole failure process analysis system of composite material-MFPA2D developed by Centre for Rock Instability and Seismicity Research, Northeasten University provided a feasible method of studying the failure of reinforced concrete structure. The numerical model of the MFPA system utilizes elastic damage constitutive model with residual strength, and introduced statistical distribution function, reflected the concrete heterogeneity. It showed that when the unit stress reached the point of failure, the failure produced, and the failure unit was treated to soften the rigidity, thus the physical uncontinuous medium problem can be solved by the continuous medium mechanics.By the MFPA2D numerical simulation system, the numerical simulation of the whole failure process of reinforced concrete structure was conducted. The research and conclusions contain the following three aspects: First, numerical simulation of reinforced concrete beam. The test model was selected from the reference documents, and the numerical simulation of four point-bend loading mode of the reinforced concrete beam subjecting symmetrical concentrated load was performed. The simulation results mainly included the variation of stresses and displacement, the failure mode, and the energy and times of Acoustic Emission hardly obtained from test, etc. By comparing the results of numerical simulation with those of corresponding tests, it was found that, to certain extent, there is a good agreement between the results of numerical simulation and those of the corresponding tests,. During the numerical simulation, the 500MPa high-strength reinforced bar from the reference document was selected as the loaded bar. Meanwhile, the numerical simulation of regular reinforced bar HRB335 was also carried out. Through comparing the results from the two numerical simulations, it indicated that the failure process of loading feature, deformation pattern and crack development of the 500MPa high-strength reinforced bar was basically identical to that of regular reinforced bar. Thereby, it provided a certain reference for the research on the reinforced concrete beam with high-strength reinforced bar.Second, Numerical simulation of reinforced concrete column. The simulation mainly considered two cases-large eccentric loading and small eccentric loading. The simulation results included stress, displacement and the energy of Acoustic Emission, etc. The simulation also chose the corresponding test model as the numerical simulation model in order to make it convenient for comparing with the results of the corresponding test. By comparing the results between the two eccentric loading cases, it showed that the respective loading, deformation and failure feature of the large eccentric loading and small eccentric loading are basically identical to those of test.Third, Numerical simulation of reinforced concrete frame. It simulated the deformation and failure of single reinforced concrete frame. It offered a certain reference for the research on the frame structure.By the numerical simulation research on the three aspects above, the certain referense of the numerical simulation-MFPA2D was verified, therefore, it provided a new method for the research on reinforced concrete beam, column and frame.