Research On Assembliing U-shaped Splint To Reinforce Hollow-slab Bridge And UHPC Hinge Joint

The assembly-type reinforced concrete or prestressed concrete hollow-slab girder bridge has been widely used in the construction of highway or urban middle and small span bridges in recent decades because of its advantages such as standardized design,integrated production,prefabricated construction,low construction cost,small building height,overall aesthetics effect and clear structural behavior,etc.But the detection found that the in-service hollow slab bridge may often suffer from many diseases,particularly hinge joint cracking disease.If left untreated,these diseases will lead to single plate bearing phenomenon and the overall bearing capacity reduction of the bridge,thus threatening traffic safety,affecting the normal operation of highway and urban road transportation.These consequent problems will cause the citizen's life property to have the security threat,even causes the bridge collapse accident to occur.Take 2011 bridge approach collapse accident of Hangzhou Qiantang Third Bridge as an example,it was because the hinge joint crack disease was not timely cured that the heavy vehicle overload finally became the last straw that crushed the bridge.Small hinged hollow slabs have been replaced by large hinged hollow slabs since 2004,so the hinge joint disease is improved greatly,after 3-5 years of operation however,such typical disease still occurs.Although gradually replaced by the short T-section beam in the construction of highway bridge in ZheJiang Province,the hollow-slab is still used in urban bridge construction because of its low building height,convenient construction and graceful outline.In addition,those large number of hollow slab bridge built previously are still in service.So it is of practical significance and engineering application value to carry out hollow slab bridge research from the aspects of reinforcement and prevention with the expection that occurrence or deteriorationof this disease would be controlled.Based on the engineering background of the hollow-slab bridge selected from 2008 general drawing of highway bridge with a span of 16 meters,a bridge deck width of 10 meters and a skew angle of 0 degree,the calculation and analysis are carried out by ABAQUS finite element software and the main research results are as follows:(1)The preliminary strengthening scheme of assembling U-shaped splint to reinforce hollow-slab bridge is put forward and the calculation method of transverse load distribution coefficient of hollow-slab and its corresponding reinforcement theory are expounded against the hinge joint disease of hollow-slab bridge.The three-dimensional solid model of simply-supported hollow-slab bridge is established by finite element software ABAQUS,and based on the verification of the model calculation results,the following conclusions are drawn:1)The analysis of the joint stress difference of hinge joint damage state,reinforcement state and original bridge state shows that the corresponding hinge joints can restore some transverse connection ability after reinforcement;2)The concept of uniformity coefficient of load transverse distribution is used to characterize the ability to distribute lateral load of hollow slab.The uniformity coefficient difference of the three states mentioned above is analyzed to verifiy the reinforcement effect of assembling U-shaped splint and evaluate it quantitatively;3)Analysis and comparison of the reinforcement effect of hollow-slab bridge under different influence parameters show that with the increase of the bridge length or the decrease of the bridge width,the reinforcement effect is obviously increasing;and 3 sets of assembling U-shaped splint are suitable for the reinforcement of the hollow-slab bridge with small and medium span.When the span is 16 m,the longitudinal spacing of each U-shaped splint is 7m,and the whole center line of the device is coincident with the cross section of the bridge;(2)Considering the design level measures to prevent or end hinge joint cracking,a design scheme of UHPC used as hinge joint filler in the construction of hollow-slab bridge is proposed to prevent or reduce the occurrence of joint diseases.Through the study on the mechanical performance of the hollow-slab bridge with the UHPC hinge joints and the common C50 concrete hinge joints,the conclusions are drawn as follows:1)The force state of C50 hinge joints is analyzed and the position of vehicles when the hinge joints are most unfavorable is given accurately by introducing the concept of nominal vehicle and nominal lane;2)The mechanical properties of bonding interface of UHPC hinge joints and C50 hinge joints,the hinge joints of their own,reinforcement bars,the hollow-slab and the paving layer are analyzed and studied.Results show that the working performance of the UHPC hinge joints hollow-slab bridge is better than that of the C50 hinge joints.When there are overloads on the hollow slab bridge,the UHPC hinge joints have better anti overloading ability than the C50 hinge joints,and the overload proportion has a great improvement.