Study On Anti-crack Scheme And Spatial Mechanical Properties In Negative Moment Area Of The Case Of Skew-curved Composite Beam Bridge

For the traditional urban beam bridge,its structural form is mainly cast-in-place or precast concrete beam bridge,while skew-curved steel-mixed composite beam bridge is seldom used in beam bridge construction.The composite beam bridge has the characteristics of small mass,large stiffness and simple construction,while the skewcurved bridge has the characteristics of aesthetics,good environmental adaptability,good economic benefits and so on.However,due to the difference between the two materials of the composite beam bridge,the tensile failure of the bridge deck and the compression instability of the steel box girder may occur in the negative moment area,especially the cracking of concrete will significantly reduce the stiffness,bearing capacity and durability of the bridge.In addition,the continuous skew curved bridge will further lead to the spatial asymmetry of the composite beam bridge deck and steel box girder because of its plane alignment and the longitudinal axis of the bridge is not perpendicular to the support line.At present,there is little research and application on skew-curved composite beam bridge,so this paper studies the anti-crack measure scheme and spatial mechanical performance of skew-curved composite beam bridge deck based on the background of F ramp No.2 Bridge around Hangzhou Expressway.The main contents of this paper are as follows:(1)According to the existing engineering background and structural characteristics of the case bridge,aiming at the cracking problem of the bridge deck in the negative moment area,three different anti-crack schemes are put forward,and the whole bridge model of each scheme is established by using Midas Civil,focusing on the tensile stress of the bridge deck and the compressive stress distribution of the steel box girder in the negative moment area during the construction process,and the optimal anti-cracking scheme is determined by comparing and optimizing them at the same time.(2)Based on the final confirmed anti-crack scheme,according to the calculation principle of Midas composite beam structure,the overall mechanical performance of the case bridge in the key construction stage and operation stage is calculated,with emphasis on the spatial stress and stress distribution of the negative moment section bridge deck and steel box girder in each construction stage.(3)The local fine model of the negative moment section of the case bridge is established by using ABAQUS,and the mechanical behavior of the bridge deck in the negative moment area of the key construction stage and operation stage is calculated respectively,focusing on the spatial stress distribution and transfer of the bridge deck.At the same time,the influence of the longitudinal and transverse stress distribution of the case bridge on the overall stress is studied.Finally,the internal force calculation principle of the finite element section is compared with the Midas calculation results.The results show that:(1)For the skew-curved composite beam bridge,the combination of a variety of anti-crack measures can effectively improve the crack resistance of the bridge deck,and has a certain safety reserve and convenience.(2)The stress of steel box girder and bridge deck has a certain oblique distribution asymmetry in space,and the stress concentration area appears near the support.because of the large radius of the case bridge,the maximum principal stress of the bridge deck is mainly affected by the longitudinal stress.(3)The ABAQUS finite element calculation results of the case bridge are in good agreement with the Midas stress data,which has a certain reliability.