Analysis On Operation Safety And Causes Of Longitudinal Cracks On Vertical Walls Of Trough Girders

The prestressed concrete trough girder bridge,with the characteristics of low building height,decreasing the line elevation,increasing the headroom under the bridge,reducing the earthwork of subgrade,small noise pollution and preventing the derailment vehicles from overturning,is widely used in rail traffic recently.However,as a through-type bridge with upper opening and non-closed,the prestressed concrete trough girder bridge has several problems on matching the layout of structures and materials,for example,closely spaced rebar,high requirements for construction technology,low torsion stiffness,and the area of the tension zone is much larger than the compression zone.As a result,the various beam cracks and safety during operation stage have been paid more attention to.In order to study the operational safety and the reasons for longitudinal horizontal cracks on the vertical wall of the trough girder,the field test and numerical simulation analysis have been carried out on a railway prestressed concrete trough girder bridge in this paper.The main contents of this paper are as follows:(1)The structural features,mechanical properties and crack characteristics of the prestressed concrete trough girder bridge were introduced in details.And the causes of cracks in the prestressed concrete bridge were described.In addition,the crack tests under operational loads in the field have been carried out,and the reasons for longitudinal horizontal cracks on the vertical wall of trough girder bridge have been analyzed combining with experimental data.(2)A finite element model of prestressed concrete trough girder was established.By the numerical simulation calculation method,the maximum principal stress and the crack location have been studied under three working conditions.And the results of numerical simulation and test have been compared.The comparison results indicate that concrete pouring in lifts is the key factor of longitudinal horizontal cracks on the vertical wall of the trough girder bridge.(3)Considering the influence of existed cracks to the operation safety of prestressed concrete trough girder bridge,the field static loads test and dynamic loads test of the trough girder bridge has been carried out based upon the field test method of bridges.Meanwhile,the evaluation parameters related to the operational safety have been obtained with the comparison of the numerical simulation and test results.Moreover,the operational safety of the prestressed concrete trough girder bridge has been evaluated by combining with the specifications.