Ultimate Capacity Of Reinforced Concrete Members Under Combined Loadings

There are rich research results on reinforced concrete structural members under single loading or two and three loading combination of tension, compression, bending, shear and torsion. However, there are few researches on four loading combination of tension/compression, bending, shear and torsion, especially for the axial force effects on the failure mechanism and bearing capacity of reinforced concrete members. Till now, there is not a unified failure model for reinforced concrete members under combined loading which has been commonly accepted worldwide. Many design codes for combined loading are consisted of test data fitting experience formulas. Therefore it is very important to focus research on the unified failure model of RC members under combined loadings.The dissertation studies failure mechanism and bearing capacity of the RC members under combined loadings through theoretical investigation, test data comparison and numerical analysis method.Firstly, the ultimate equilibrium theory is improved and used to study the influence of axial force to failure mode and ultimate capacity through the variation of the twist failure surface angles. Applying concrete failure criteria on the failure surface, the twist failure surface angles could be determined, and using the three dimensional ultimate equilibrium theory, the unified failure model and formulas for reinforced concrete structural members under the combined loadings could be deduced. The theoretical results are compared with the experimental results and the coordination of both is satisfied.Then, the numerical analysis method is used to broaden the research parameters, which could solve the test data lack problem. More attention is paid on the check of numerical modeling with the existed experimental results and numerical analysis results are compared with theoretical results.The dissertation suggests the unified failure model for reinforced concrete structural members under combined forces of tension, compression, bending, shear and torsion. The theoretical model fits well with the test data and the numerical analysis results. The research results could be used as references for concrete failure theory and design codes.