| The proportion of concrete bridges is very large in the bridges built in China 's transportation network.As an important part,the cover beam is affected by various factors such as design,construction and abnormal use,and there are cracks and reinforcement leakage.From the design level,when the design is unreasonable,the amount of reinforcement is too small or too much,resulting in the production of cover beam diseases or waste of materials.Since the concept of stress disturbance zone which does not conform to the plane section assumption has been proposed,a large number of domestic and foreign scholars have studied this area and achieved fruitful results.However,the main research objects are open deep beam,prestressed tooth block anchorage zone,corbel and other parts,and the research on cover beam is less.The research results of domestic and foreign scholars show that the reinforcement design effect of the component based on the conclusion of the tension and compression bar model analysis is better.Therefore,this paper takes the strut-and-tie model as the research method.From the design level,ABAQUS finite element software is used to analyze the transition pier cap beam,and the strut-and-tie model is constructed.According to the strut-and-tie model,the reinforcement optimization design and stress analysis of the cap beam are carried out.The work of this paper is as follows :1.Through the topological optimization analysis of the cover beam,it is concluded that when the model deletion rate is greater than 60 %,the shape of the model is basically unchanged.The model shape with the deletion rate of 70 % is taken as the basic shape of the strut-and-tie model according to the relationship between the deletion rate and the strain energy.The fmincon function is used to determine the position of each node of the model with the minimum strain energy of the model,and the overall vertical strut-and-tie model of the cover beam is constructed.2.The stress and deformation of the cover beam when the prestressed reinforcement is only arranged in the upper and lower parts are compared and analyzed,and it is determined that the range of the prestressed reinforcement only arranged in the upper position and the length L as the section height h of the anchorage point is zone D.According to the stress trace diagram obtained by finite element analysis,the basic shape of the tension and compression rod model is constructed,and the stress integration of the section is carried out to determine the joint force position of the splitting tensile stress and the compressive stress under the anchor.According to the node balance,the vertical and longitudinal tension and compression rod models of the prestressed anchorage end are constructed.3.Reinforcement design and model checking of cover beam are carried out according to strut-and-tie model.The concrete stress,steel stress,cover beam deformation and material usage of cover beams with different reinforcement methods under different load conditions are compared.The results show that when the cover beam is reinforced by the tension and compression bar model method,the tensile and compressive stress under the concrete anchor and the Mises stress of the steel bar are smaller than those of the original design.Although the tensile stress of the top concrete,the Mises stress of the prestressed reinforcement and the deflection at both ends of the cover beam are slightly larger than those of the original design,they are also far less than the requirements of the specification,and the amount of material is also reduced.In other words,the strut-and-tie model is also applicable to the transition pier cap beam with a distance of about 1.2 times from the vertical load point to the horizontal distance of the pier column,and the design results obtained by this method are good,while the original design is relatively conservative. |
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