Study On The Shear Capacity Of RC Beams Without Web Reinforcement Based On Mechanical Analysis

Reinforced concrete structure,as one of the most widely used structural forms,plays an important role in modern architectures,and the beam is a vital component and one of the main stress members for the reinforced concrete structure system.Compared with the flexural failure of the members,shear failure has more influence factors and its mechanical principle is more complicated.Accordingly,there has not been a recognized theoretical model and calculation method up to now.Different national standards for design of concrete structures draw up their own calculation formulas of the shear capacity based on different shear failure models and experimental data,and then introducing the reliability index considering the actual situation of its country.Nevertheless,these calculation formulas are relatively conservative in predicting the shear capacity,and the results have large dispersion.Therefore,the research on the shear behavior of the beam without web reinforcement can provide an accurate shear calculation model and reliable design method for practical engineering,which has a certain theoretical significance and practical value in solving the shear failure problem in the subject of concrete structure basic theory.In this paper,based on the classical mechanical theory,the shear capacity of reinforced concrete beams without web reinforcement was investigated,and the error analysis of its prediction results was carried out.The main contents and conclusions are as follows:1.The current mainstream theoretical models of shear failure for reinforced concrete beams without web reinforcement were summarized,and different shear theoretical models were compared and analyzed.Meanwhile,the current research status of shear design calculation methods of the reinforced concrete beams without web reinforcement is expounded,and further research directions of the shear failure problems of beam members are pointed out.2.The calculation theory model and calculation formulas of shear capacity in the Chinese code for design of concrete structure GB 50010-2010,American building code requirements for structural concrete ACI 318-14,European general design rules for buildings EN 1994-1-1: 2004 and Japanese standard specification for concrete structures JSCE 2007 were outlined and summarized.The main influencing factors considered in the shear capacity calculation formulas were discussed,and the influence of different factors on the shear strength of beams without web reinforcement was disclosed.Furthermore,the test data of 615 beams without web reinforcement was collected and sorted out.On the basis of the experimental results,the accuracy and stability of the calculation model are analyzed and the errors of each calculation model are evaluated.3.Based on the mechanical analysis method,the stress on the critical diagonal shear failure section of reinforced concrete beams without web reinforcement was analyzed.According to the classical mechanical principle,the calculation formula of the shear capacity based on the mechanical analysis method was derived.And the parameters in the calculation formula were determined.In accordance with the database of 615 reinforced concrete beams without web reinforcement established in Chapter two and the experiment results of 209 FRP-reinforced concrete beams without web reinforcement collected here,the rationality and stability of the mechanical analysis method and other bearing capacity calculation methods in predicting the shear capacity were comparatively evaluated by using the statistical evaluation methods(e.g.,statistical eigenvalue method,defect point method and prediction accuracy evaluation index method).The result verifies that the mechanical analysis method can reflect the shear failure mechanism well,and its calculation formula can ensure a high accuracy and the discreteness is very small when predicting the shear capacity.4.On the basis of the theoretical analysis,a monotonic loading experiment study of 9 beams without web reinforcement of 3 different shear span length was carried out.The failure process,failure mode,members performance,the ultimate load and the displacement were analyzed.Moreover,the shear capacity of the specimens was obtained,and the shear strength was compared with the predicted values of the mechanical analysis,different countries’ codes and the Zsutty calculation formula.The influence of different parameters on the shear strength was discussed.5.The models of the experimental specimens were established in the ABAQUS software to analyze the behavior of the specimens.The mechanical results of the specimens(e.g.,the failure deformation characteristics,and ultimate shear capacity)were obtained.The finite element analysis results were compared with the experiment values and the shear strength obtained by the mechanical analysis method.The result shows that the nonlinear finite element analysis can accurately reflect the actual stress and deformation of the specimens,which reveals the failure mechanism and predicts the shear capacity of the member well.The related work performed in this paper can further enrich the experiment data of reinforced concrete beams without web reinforcement,and provide the test basis for the revision of standards for the design and calculation of shear capacity,which can help further understand and analyze the shear performance of reinforced concrete beams without web reinforcement and the feasibility of mechanical analysis calculation method.It is of great significance to guide the actual engineering practice and promote the analysis of calculation of reinforced concrete beams.