Causes And Prevention Measures Of Longitudinal Cracks On The Slab Of Long Span Continuous Beam Bridge

Continuous bridge has been widely used in all kinds of bridge engineering because of its simple structure and convenient construction.In our country,the number of long-span continuous girder bridge that has been built is great.In recent years,due to some reasons associated with the design and construction process,the longitudinal cracks in the bottom of the continuous bridge are attracting great concern due to their great harm.In order to study the causes and preventive measures of longitudinal cracks in continuous beam floor,the following work was done in this paper:(1)According to the research status of continuous bridge slab longitudinal cracks,the related research conducted by domestic and foreign experts and scholars was introduced;Based on the analysis of the mechanical characteristics of the box girder,it was found that the transverse tensile stress of the bottom plate was the main reason for the longitudinal cracks in the bottom slab of the continuous bridge.the practical significance of the research related to the continuous beam slab longitudinal cracks on the safety of the project and the national economy was illustrated.(2)The simplified calculating formula of the lateral stress of the slab was derived by taking into account the effect of the pre-stressed force,the temperature,and the applied load.(3)Combining with the specific engineering background,the changes in the transverse stress of the bottom in the continuous beam was analyzed for different parameters.The finite element method was used to further validate the calculated results.Combining the simulated outcomes with some experimental data,it was found that variations in the concrete weight,the environmental gradient,and the height of the box section and other factors had little effect on the transverse stress of the bottom plate.however,the following reasons were responsible for the increase in the transverse tensile stress: increase in the coefficient and exponent of the parabolic equation for the bottom plate of the box girder bridge;decrease in the thickness of the bottom plate of the box girder;increase in the width of the bottom plate of the box girder;and the error of closure segment height and tendons positioning.At the same time,it was found that the variation of these parameters had a more prominent effect on the transverse stress of the bottom plate in the vicinity of the closure section.(4)According to the results derived by using finite element method,the transverse tensile stress of continuous beam floor induced by the action of shrinkage and creep will not significantly decreases after a long period of time.In order to avoid the longitudinal cracks in the bottom plate,great attention is needed to be paid to the maintenance and the standard usage of the bridge after its completion.(5)From the perspective of design and construction,some controlling measures and considerations needed to be taken into account were proposed to prevent the longitudinal cracks in the bottom slab of continuous beam bridge.