Study On The Bending And Torsional Load Capacity Of Curved Folded Steel Webs Bridges Considering Creep Effect

In the current development of China’s urban rail infrastructure transportation,in order to meet the needs of various terrain conditions and road planning and construction in small,medium and large cities,curved bridges are used in large numbers in engineering construction.As a new type of bridge structure,folded steel webs and steel bottom plate box girder bridges are also gradually applied by engineers in the construction of curved bridge projects.However,compared to traditional linear bridge structures,the effect of bending and torsional coupling on curved folded steel webs and steel bottom plate box girder bridges is more obvious and has its own characteristics;if the bridge is designed according to the conventional linear bridge design code,the effect of bending and torsional load bearing capacity on the whole bridge structure will not be taken into account,thus causing the curve of curved folded steel webs and steel bottom plate box girder bridges to be ignored.After the bridge is completed,it is usually in an overload condition based on the national conditions,along with the increase in the age of the concrete the creep effect of the reinforced concrete structure will act directly on the whole bridge structure and stress redistribution will occur,affecting the bridge stress state,compared with the straight line bridge,the ultimate bearing capacity of the curved folded steel webs steel bottom plate box girder bridge is very different,for the safety of the whole bridge should also be fully considered.The safety of the whole bridge should also be considered comprehensively.In view of the above,the main tasks of this paper are.(1)To propose a method for calculating the creep of folded steel webs and steel bottom slab reinforced concrete box girder structures by analysing the methods and mechanisms of creep calculation for folded steel webs and steel bottom slab bridges.(2)By means of finite element simulation analysis of folded steel webs and steel bottom slab box girder bridges,the mechanical properties and force mechanism of the concrete top slab subjected to the effect of creep are derived.(3)To derive the formulae for calculating the load carrying capacity of a curved folded steel webs steel bottom plate box girder structure under combined bending and torsional action and pure torsional action,and to plot the bending and torsional ratio curves of a curved folded steel webs steel bottom plate box girder under different bending moments and torsional actions using the curved folded steel webs steel bottom plate box girder diagonal bending damage model.(4)To establish an ABAQUS finite element model of a curved folded steel webs steel bottom plate box girder bridge to investigate how the concrete top slab cracks develop under bending and torsional loading to investigate its stress mechanism under combined bending and torsional action.(5)By simulating the finite element model of the curved folded steel webs and steel bottom plate box girder bridge of a city T3 building,the curvature of the whole bridge,the bending and torsion ratio,the crack development of the concrete top slab,the thickness of the folded steel webs,and the reinforcement ratio of the longitudinal reinforcement and hoop reinforcement of the top slab,and the effect of creep are analysed as parameters to analyse their respective effects on the bending and torsional mechanical properties of the curved folded steel webs and steel bottom plate box girder.The full bridge torsional ultimate load capacity equation under the effect of creep is derived,and the data are fitted by finite element parametric analysis to derive the curve of torsional correlation of curved folded steel webss and steel bottom plate box girders.