Study On Shear And Torsion Of Single Box Multi-cell Girder Bridge With Corrugated Steel Webs

With the advancement of bridge design technology and the accumulation of engineering experience,the composite box girder bridge with corrugated steel webs presents three major development trends of “large span”,“wide bridge deck” and “new construction technology”.In recent years,the multi-cell single-box composite box girder bridge with corrugated steel webs has been widely used in the construction of large-span bridges in China.In addition,the asynchronous pouring construction fully combines the structural characteristics of the composite box girder bridge with corrugated steel webs and it has some advantages,such as the short construction period,high safety and good economy,etc.Therefor,it has a good application prospect in the large-span composite box girder bridge with corrugated steel webs.However,the shear and torsion effects of multi-cell single-box composite box girder bridges with corrugated steel webs are significant,and the structural stress during the asynchronous pouring construction period is complicated.The existing research is mainly for single-cell single-box girder,but the researches on multi-cell single-box girder are not fully addressed.By model test,theoretical analysis and numerical simulation,a series of research on the shear and torsion performance of large-span multi-cell single-box girder bridges with corrugated steel webs and the key technical problems in asynchronous pouring construction are studied in this paper.And then the design calculation method and structural optimization measures are proposed.The main contents of this paper are as follows.(1)Based on the double cantilever beam model tests,the mechanical characteristics of conventional cantilever pouring construction and asynchronous pouring construction of multi-cell single-box girder with corrugated steel webs are studied in the first time.The failure modes,shear and torsion of the main girder under the two construction methods are compared and analyzed.Then,the the torsional resistance and design suggestions for keycomponents of asynchronous pouring construction are provided.(2)For shearing mechanism and the uneven distribution of web shear stress of multi-cell single-box girder with corrugated steel webs,a simplified calculation formula of shear stress for the variable section girder is presented based on the equivalent shear stiffness and bending moment equivalent action principle and the recommended value of the shear stress non-uniformity coefficient of the actual bridge design is proposed by numerical analysis.The applicability of the calculation formulas for the local shear buckling,integral shear buckling and related shear buckling of corrugated steel webs was comprehensively evaluated,and the shear design process and accurate calculation method of multi-cell single-box girder bridges with corrugated steel webs are proposed.(3)Based on the thin-walled box girder theory,the constrained torsional differential equations of multi-cell single-box girder with corrugated steel webs are derived and solved.The distortion differential equations of multi-cell single-box girder with corrugated steel webs are solved by the elastic foundation beam comparison method and Newmark numerical method.And the applicability of the theory of torsion and distortion is verified by model tests.(4)The effects of lining concrete on the shear and torsion properties of composite box girder with corrugated steel web were studied through the model tests,and the variation law of the shear force ratio of the lining concrete with the load was revealed.The influence of the layout and geometric parameters of the lining concrete on the mechanical properties of multi-cell single-box girder bridges with corrugated steel webs are analyzed by the finite element model,and the design proposal of the concrete lining concrete structure is given.