The Research Of Prestressed Carbon Fiber Reinforcement Method And Anchorage Performance Of Simply Supported Hollow Slab Bridge

With the rapid development of economy in China,more and more bridges are faced with the dilemma of insufficient bearing capacity.Some bridges that are still in service are also facing demolition because they do not meet the actual needs.For example,some bridges are being demolished and rebuilt because of the needs of urban development,which is undoubtedly a huge waste of resources.Based on one demolition and reuse project of Jianzhou Bridge in Chengdu,the protective demolition method was studied,and the reuse scheme of the demolished bridge after reinforcement was deeply studied.The main research contents and achievements are as follows :(1)The feasibility of reusing 30 m simply supported hollow slab beam after dismantling was studied.The bridge location for reinforcement and reuse was determined.The bearing capacity of the dismantled hollow slab was evaluated.The calculation results show that the bending and shear bearing capacity of the beam were insufficient,so it is necessary to reinforce it.The reinforcement scheme of enlarging section and sticking steel plate was studied.The results show that the reinforcement effect of C50 concrete scheme with 5 cm thick roof was not ideal.The scheme of bonding steel plate at the bottom of beam was feasible,but the construction was complicated and the durability was poor.(2)The reinforcement method of 30 m simply supported hollow slab with prestressed carbon fiber plate was studied.Three carbon fiber plates with thickness of 1.4mm,width of100 mm and tensile strength of 2400 MPa were used for reinforcement.After reinforcement,the bending capacity increased by 10.07%,the crack resistance was improved,and the maximum tensile stress at the bottom of the mid-span beam was reduced from 1.55 MPa to0.32 MPa.(3)The spatial finite element model was established by ABAQUS,and the stress state of carbon fiber plate anchorage system was studied.In the limit state,the maximum stress of the tensioning device was 693.4MPa,and the maximum stress of the anchoring device was389.4MPa.The concrete stress was influenced by the space of anchorage device.When the arrangement spacing increased from 1m to 1.5m,the tensile stress of concrete decreased by12.42% and the compressive stress decreased by 17.22%,but the tensile damage factor of concrete reached 0.80.(4)Combined with the demand of shear reinforcement and the demand of concrete stress during anchorage,the optimization scheme of anchorage system was studied.U-shaped steel plate at the beam end was used to reinforce and the prestressed carbon fiber plate anchorage was welded on the U-shaped steel plate,which improves the anchorage performance.Compared with direct anchor scheme,when the spacing of U-shaped anchors was 400 mm,the compressive stress,tensile stress and tensile damage factor of concrete decreased by 62.83%,70.61% and 0.04.