Study On Reinforcement Technology With Transverse Prestressed CFRP Plate For Existing Hollow Slab Girder Bridges

Because of the advantages of simple structure,convenient construction,strong adaptability and low building height,hollow slab girder bridge has become one of the preferred bridge types for small and medium span bridges.However,due to the reasons of design,construction and maintenance,the existing hollow slab girder bridges in China have suffered grouted joints cracking during the service period,which seriously affect the safety and durability of bridges.At present,the widely used reinforcement measures are passive,which cannot take the initiative to improve the stress in joints,and the joint diseases cannot be effectively controlled for a long time.As an active reinforcement technology,transverse prestressed reinforcement technology can effectively limit the lateral relative displacement between adjacent beams,restore the lateral compression of the joints concrete,and improve the shearing ability of the joints to a certain extent,which can effectively eliminate the disease of the grouted joints by rational design.Therefore,this paper combining the reinforcement technology with prestressed CFRP plates which has the advantage that construction process is rapid without interrupting the traffic,makes a detailed study on the reinforcement principles,practical calculation methods and reinforcement design schemes of reinforcement technology with transverse prestressed CFRP plates for existing hollow slab girder bridge through the ANSYS finite element software.The finite element method is used to calculate the influence lines of load distribution in the transverse direction of the hollow slab girder bridge,and the results are compared with the theoretical calculation results.The results show that the influence lines of load distribution in the transverse direction calculated by the hinge-connected slab method is different from the results by finite element method,especially for the hollow slab girder bridges with large size joint,and the hinge-connected slab method cannot accurately calculate the transverse distribution of the hollow slab girder bridge with large size joints.Through the analysis of the stress of joints,it is found that the actual stress situation in joints is more complex than that assumed in present design method.The local structure makes the hollow slab girder bridge not as uniform and continuous transfer lateral force as the whole slab,the larger transverse tensile stress is generated at the bottom edge of the joints,and with the increase of the width of bridge,the transverse tensile stress is getting bigger and bigger and become the leading factor of the joint diseases.On the basis of the research results of the mechanism of joint diseases,damage degree of every grouted joint is classified.According to the improvement of stress injoints and the mid span deflection of the reinforced hollow slab girder bridge,the influence factors of reinforcement effect are analyzed under the most unfavorable load condition,including the layout position of transverse prestressing,the spacing of transverse prestressing,the tension force of transverse prestressing,the anchorage position of transverse prestressing,the bridge width,the thickness of the concrete pavement,the grade and location of load,the damage degree of joints and so on.Based on the study of the reinforcement effect with transverse prestressing,the transverse prestress should be arranged in full span in order to ensure the reinforcement effect of each cross section under the most unfavorable vehicle loads.The reinforcement principles of strengthening the existing hollow slab girder bridges with transverse prestressed CFRP plate are proposed.A simple method for estimating the numerical value of the transverse prestress when the spacing is determined and a practical calculation method for the load distribution in the transverse direction after reinforcement are given.Specifically for the hollow slab girder bridges with different bridge width of the span of 10 meters,13 meters,16 meters and 20 meters in the 1.0 meter width hollow slab standard drawing,the design schemes of transverse prestressing reinforcement are proposed,and the size of CFRP plates are selected according to the different schemes.The proposed reinforcement schemes are proved applicable for the 1.25 meters width hollow slab model with large size joints and the 1.0 meter width hollow slab model with small size joints.Finally,according to the experimental data,the design of transverse prestressing reinforcement is carried out for a real bridge,and the relevant construction technology and precautions in construction are introduced combined with the reinforcement scheme.