Study On Construction Control Of Asymmetrical Side Span Suspension Bridge

With the rapid development of highway construction in China,more and more bridges and tunnels are constantly building in areas with complex terrain.Due to the complex terrain of the mountainous areas,most of them are deep trenches,and bridges need to span a relatively large distance.In addition,in some areas,the topographic condition has a large limitation on the span of the bridge.It is also necessary to consider the navigable conditions and economic problems.In order to adapt to these special terrain conditions,some asymmetrical suspension bridges are built.This article is based on the construction of the Xijiang Grand Bridge which is building.The side spans and anchor types of the Xijiang Grand Bridge are asymmetric.During the lifting of the stiffening beam,the main feature is that the pre deviation of the two main cable saddles is inconsistent and the slip law is different.It is necessary to analyze the lifting sequence of the stiffening beam to determine the lifting sequence of the stiffening beam suitable for the asymmetrical side span suspension bridge.In addition,calculate and analyze the channel anchor of the Xijiang Grand Bridge.The main work of this article is as follows:(1)Introduce the classification of asymmetrical suspension bridges,including unequal height support for main cable,asymmetry of anchor type,asymmetry of side spans,high asymmetry of main towers and asymmetric suspension bridges without towers.The common lifting sequence of the stiffening beam and the temporary connection between the beam sections in the lifting process are briefly described.(2)Combining the characteristics of the asymmetrical side spans of the Xijiang Grand Bridge,the finite element model of the Xijiang Grand Bridge is established using Midas Civil.Perform initial equilibrium analysis to obtain a reasonable bridge state.In combination with design parameters,the unstressed length of the main cable at the main cable saddle and the cable saddle is corrected.Calculate the unstressed length of the main cable and sling,and the empty cable shape of the main cable.Comparing the calculation results with the design documents,the correctness of the calculation model and the calculation results are explained.(3)Considering the different forward direction of the beam section and the symmetrical and asymmetrical lifting about the middle and side spans,four kinds of stiffening beam lifting schemes are formulated.Midas Civil is used to simulate and analyze the four kinds of stiffening beam lifting schemes.The changes and characteristics of the parameters such as the suspension force,main cable and temporary connection internal force,main cable shape,stiffening beam line shape,main cable saddle horizontal displacement during the lifting process of the stiffened beam are calculated and analyzed.The results show that the Xijiang Grand Bridge should adopt the asymmetric lifting scheme from the center to the tower,which four beam sections are hoisted symmetrically at the mid-span each time,and one beam section is hoisted at the north side.(4)Introduce the structural features of the channel anchor of the Xijiang Grand Bridge.The stability theory is used to check the foundation bearing capacity,overall anti-slip and anti-overturning stability of channel anchor.And check the oblique section of the anchor block and the unfavorable shear section of the base side wall.The results meet the requirements of standard safety,and the rationality of the channel anchor structure in space layout is proved.(5)The finite element model of the channel anchor is established by using Midas Fea.The stress distribution of each component of the channel anchor is analyzed,and the hydration heat analysis model for the construction stage of channel anchor is established to analyze the hydration heat of the concrete during the construction stage.The results show that the stress in some areas exceeds the standard.