Analysis of Loading Conditions of Bridge Consisting of Extra-Large Steel Trusses Erected by Crawler-Type Incremental Launching System and Sliders
The main bridge of Weihe River Bridge carrying a section of the Xi'an Metro Line 10 is a bridge with superstructure consisting of extra-large steel trusses,stiffened by two continuous spans of upper arch chords and inclined rigid suspenders.The bridge has two levels of decks accommodating road and light rail traffic,respectively.During the construction,the steel trusses were erected ahead of the stiffening upper arch chords.The steel trusses were erected by a crawler-type incremental launching system from the north and south banks towards the center,assisted by sliders.The construction process of the full bridge was numerically simulated in MIDAS Gen to ensure the loading safety of the main bridge structure and the temporary supporting structures by activating and deactivating elements during analysis.Multiple factors were analyzed and checked,including the load bearing behaviors of steel trusses,reaction forces of bearings,truss lowering deformation adjustment at closing stage,thermal effects at closing stage,asymmetry in incremental launching,and the loading bearing capacity of the incremental launching system under gusts.It is shown that the load bearing capacity of the steel truss girder bridge and the load bearing capacity of the incremental launching system met the code requirements.The maximum reaction force of bearings at each pier was 24 000 kN.The truss lowering deformation adjusting values for the south W05 pier and the north L08 temporary pier were-60 mm and-40 mm,respectively,aiming to eradicate the down warping of tips of cantilevers at the closure gap.The closing of the superstructure would not be hindered,as the integral temperature rise is less than 10 ℃,considering a reference ambient temperature at 20 ℃,and the temperature gradients of the upper and lower chords are within 10 ℃.The transverse and longitudinal instantaneous asymmetric displacements during incremental launching were controlled within the ranges of 5 mm and 20 mm,respectively.
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