| The hollow slab bridge has the advantages of low section height,economical material index and convenient construction,this type of bridge is often used in small and medium span bridges in China..With the increase of the service life of the bridge and the influence of heavy load traffic and other factors,a large number of hollow slab Bridges have been damaged,especially the construction of older hollow slab Bridges with low carrying capacity,small resistance reserves,poor durability of the structure,and some diseases even endanger the safety of the bridge.For some hollow slab Bridges with diseases,how to restore the original bridge to its normal service condition and extend its service life through effective reinforcement measures becomes urgent and important.Bridge disease analysis is the premise of bridge reinforcement,By investigating the hollow slab bridge in ten highways in guangdong province,this paper summarizes the common diseases of the upper structure of the hollow slab,For example: deck pavement damage,girder crack,steel bar disease,hinge joint disease.That is to say: the main cause of the disease of bridge deck pavement is the lack of consideration in the design stage and the lack of calculation theory.During the construction,the concrete is not evenly poured,which leads to the uneven thickness of the pavement layer,the spacing of the steel mesh and the thickness of the protective layer of the pavement layer.So that the deck pavement layer and hollow board between the formation of a complete force integral.The vertical crack in hollow slab is mainly caused by the thin bottom plate,insufficient protective layer and uneven local vibration of concrete.The main causes of transverse cracks are improper proportion of concrete,poor health maintenance,improper operation in the process of prefabrication,storage and hoisting,and overload etc.The main causes of steel diseases are: unreasonable mix ratio of concrete and carbonation of concrete;The chlorine ion content in environment is too high;Insufficient structural protective layer;Health and construction quality control is not strict.The main causes of the disease of hinge joints are: the theory of check calculation of hinge joints is not perfect,and the size design of hinge joints is not reasonable;Quality control is not in place during construction;Overload,rain and other factors.The example of strengthening a 3-16 m prestressed hollow slab bridge in the Shuangxixi Expressway is the research object.The first span of the left frame with relatively large number of original bridges is selected as the research object,and the static load is applied to the bridge.test.Considering that the scheme suitable for the reinforcement of the upper structure of the bridge is a method of bonding steel plate and bonding carbon fiber cloth,the hollow plate of the bridge adopts a pretensioning structure,the bottom plate is thin,and the prestressed steel strand is close to the lower layer of the bottom plate.The method of sticking steel plate requires drilling and burying bolts on the bottom plate,so the steel strands may be damaged and endanger the safety of the bridge.Considering the construction difficulty and reinforcement effect,it is decided to strengthen the hollow slab by the method of bonding carbon fiber cloth.The effect of the carbon fiber cloth reinforcement was simulated by the non-linear structural analysis software MADIS FEA.The effect of the one-layer,two-layer and three-layer carbon fiber cloth and the measured data of the dynamic and static load test were carried out under the same working conditions as the dynamic and static load test.Compared.It was found that the adhesion effect of the three-layer carbon fiber cloth was the best,and the deflection,strain,structural fundamental frequency and structural durability of the original bridge structure were improved by the carbon fiber reinforcement measures.Provide reference for the maintenance and reinforcement of the later hollow slab bridge. |
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