Research On The Reconstruction Methods Of Hinged Cantilever Plates Of Reinforced Concrete Ribbed Girder Bridges

Before 2003,the hinged cantilever plate of reinforced concrete ribbed girder bridges was very common.The wing plates of the two main beams were connected by hinged joints that did not bear bending moments.However,the total thickness of the bridge deck plate when hinged joints were used was smaller than that of the rigid connection.The amount of reinforcement and cast-in-place concrete was less,and the force transmission performance was poor.Accordingly,the stress on the main beam would be increased,which seriously threatened the safety of the bridge structure.At present,the existing reinforced concrete ribbed girder bridges in our country cannot meet the basic requirements of highway operation due to insufficient bearing capacity or structural surface cracks,concrete peeling and other diseases caused by the increasing traffic volume.Therefore,the reconstruction of these bridges is an important task of safe operation management.This thesis firstly summarizes and analyzes the research status of hinged cantilever plate at home and abroad,centers on two reconstruction methods of steel plate reinforcement and replacement of one-way plate reinforcement,and makes a basic theoretical analysis of the three transverse connections involved--hinged,rigid,semi-rigid and semi-hinged connection.Refer to the standard drawings and specifications,design specimens and carry out the static loading tests.The test results show that the improvement of bearing capacity by steel plate reinforcement and replacement of one-way plate reinforcement is 41.48% and 29.22% respectively.However,the steel plate reinforcement still does not solve the problem of large cantilever root stress.The replacement of one-way plate does not have this hidden danger and the stress is typical,but the overall performance is reduced by secondary pouring.Based on the bearing capacity formula of the normal section of reinforced concrete flexural members strengthened by pasting steel plates,the bending bearing capacity formula of hinged cantilever plates strengthened by steel plates is derived,and the failure mechanism under the ultimate state is analyzed.The finite element analysis software ABAQUS is used to verify the numerical results and carry out expansion analysis.The results show that the test values are close to the simulation values,and the load-displacement curve is roughly consistent.The expansion analysis is carried out by changing the size of the steel plates and the position of the bolts,the result show that the bearing capacity of 70cm×10cm×1cm steel plate is greater than that of 90cm×10cm×1cm steel plate adopted in the test,and the amount and cost of steel plates are saved to the greatest extent.For the actual engineering reconstruction,the length of the reinforced steel plate should account for43.75% of the main beam spacing,and the width can be determined according to the construction conditions.The bolt position is 2.5cm away from the end of the steel plate,and the rest of the bolts can be uniformly arranged according to the length of the steel plate on the premise that there is a certain safety distance from the adjacent reinforcement.Based on the test data and simulation data,the bending stiffness formula of hinged cantilever plate strengthened by steel plate is derived.Taking the fabricated reinforced concrete T-shaped girder bridge with span of20 m and deck width of net-7+2×0.75 m as an example,the economic and social benefits of the two reconstruction methods are analyzed.The results show that the economic benefits of steel plate reinforcement are higher,and the social benefits of replacing one-way plate reinforcement are higher.From the perspective of upgrading and reconstruction of old bridges,the vehicle load after replacement of one-way plate reinforcement has been increased from the original highway-Grade II to 90% of highway-Grade I,while the vehicle load after steel plate reinforcement has been increased from the original highway-Grade II to 98.57% of highway-Grade I,almost reaching the highway-Grade I standard.Therefore,the upgrading and reconstruction of old bridges strengthened with steel plates is relatively successful.Finally,the advantages and disadvantages of the two reconstruction methods are comprehensively analyzed,and the conclusion is proposed to provide some reference for the bridge maintenance and construction departments: steel plate reinforcement can be selected under the condition of saving costs and greatly improving the bridge bearing capacity,and replacement of one-way plate reinforcement can be selected if more attention is paid to social benefits.