Model Test Study On Fatigue With Crack And Crack Grouting Reinforcement Of PPC Cable-Stayed Bridge

As an indispensable part of highway construction,bridges have rich structural types and are widely used to cross rivers and valleys.As an important part of long-span bridges,with the continuous increase of their service time,most fully prestressed concrete cable-stayed bridges have concrete cracking due to the limitations of their design.In theory,the concrete cablestayed bridge with partial prestressed design can improve the limitations of the original fully prestressed concrete design,It is very meaningful to verify the feasibility of partially prestressed concrete cable-stayed bridge in practical engineering and study the reinforcement method after concrete cracking.The main work of this paper is as follows:(1)Based on the existing literature,the development process of cable-stayed bridges at home and abroad is summarized;The current research status of concrete fatigue and partially prestressed concrete structure fatigue is described;Summarize the existing reinforcement methods of concrete structures(2)The existing main concrete constitutive relations and concrete fatigue damage models are described,and summarizes the main research methods of concrete fatigue combined with the existing concrete fatigue research results.The research methods mainly include stiffness analysis,crack analysis and strain analysis,which paves the way for the model test data analysis and theoretical research of long-span partially prestressed concrete(PPC)cable-stayed bridge.(3)In order to study the fatigue performance of PPC cable-stayed bridge with cracks in the main beam,based on a double tower concrete cable-stayed bridge,a segment scale model is made according to the actual bridge parameters and the principle of geometric similarity and stiffness equivalence,and the scale of the model is 1/7.4.The cable force of the segment scale model and the prestress of the main beam are adjusted according to the results of finite element calculation and analysis.Adjust the stress of its main beam to the state of partial prestress.After preloading the segment scale model to a certain damage,carry out fatigue test research to study the working performance with cracks of PPC cable-stayed bridge under live load.The research results show that 250×104 under the condition of PPC,the stiffness of the cable system still meets the basic requirements of PPC under the condition of normal service load.(4)Carry out static load test on the PPC model after completing the fatigue test under different working conditions until the crack width of the main beam reaches 0.50mm;After the model is unloaded,the cracks in the main beam shall be grouted,and then the static load test shall be carried out until the crack width of the main beam reaches 0.5mm:CoMPare the displacement,crack development and cable force change of the main beam during the two static load tests.The test results show that the reinforcement of the main beam with large damage by crack grouting can effectively improve the structural stiffness to the stiffness in case of damage at the end of fatigue,and can alleviate the crack development speed to a certain extent.