Research On Long-span Continuous Beam Construction Control In Passenger Dedicated Line And Parameters’ Sensitivity Analysis

Combining with the actual engineering of the bridge of the Lanzhou-Xinjiang second-tier cross the Lanzhou-Xinjiang existing Line, this paper conducts simulation analysis to this bridge through the large-scale finite element software-MIDAS CIVIL. The main bridge of this bridge uses the existing railway with continuous beam; the span is48m+80m+48m. Adopting pouring Construction crafts of cantilever, the beam structure need successively experience the following process:Pier beam consolidation, consolidating pier beam, Pouring cantilever, folding side span, tensioning the steel beam through the roof and the bottom of the sidespan, folding middle span, tensioning part of the steel beam through the roof and the bottom of the midspan, removing temporary consolidation, tensioning the other part of the steel beam through the roof and the bottom of the midspan, bridge built, loading in the second phase of constant. The results of simulation calculation on construction control have guidance on actual construction process and provide basic guarantee and theoretical basis for the whole bridge folding smoothly.Continuous beam linear control of effect factors has many, this select has on linear effect larger of concrete capacity heavy, and prestressed, and concrete elastic modulus, and main beam closure order, and temperature, and concrete contraction creep, six a effect factors on continuous beam linear of effect for sensitivity analysis, master its in construction process in the of changes law, to guarantee into bridge linear and design linear of consistent, and effective reduced all effect factors on late deflection deformation of effect. Following conclusions can be drawn from the sensitivity analysis on the impact of each factors on the linear control of the continuous beam:(1) The greater of the density of the concrete, the smaller the creep of the later deflection Linear control is easier. The use of high-grade concrete, is more favorable to the alignment control of the continuous beam bridge.(2) The smaller of the control stress under anchor, the smaller of the later deflection of shrinkage and creep, the easier of the linear control, selecting the appropriate control of stress of pre-stressed steel beam under anchor, is of great significance to the linear control of continuous beams.(3) The greater of the modulus of elasticity of concrete, the smaller of the later deflection of shrinkage and creep, the easier of the linear control, the modulus of elasticity of concrete impact on the continuous beam alignment control significantly.(4) The later deflection of shrinkage and creep by the way of folding the side span firstly and then folding the middle span is much smaller than the results by the way of folding the middle span firstly and then folding the side span. The former is much easier to the linear control of continuous beam. So selecting the appropriate way of folding of the continuous beam is particularly important to the linear control of Continuous beam.(5) The computational analysis on the Upper Box by using two kinds of rules and regulations of temperature effect shows that:under the same characteristics, the largest vertical displacement of node which is calculated according to the working condition one of is smaller than the results of the working condition two.(6) Through the comparative analysis on the later deflection value of shrinkage and creep by three influencing factors of the concrete structure, which is relative humidity of the environment, the first loading age of the concrete structure, extension of constant load in phase ii, to master the influencing law, can effectively reduce the later deflection value of shrinkage and creep of the concrete.â‘ While the relative humidity of environment where Bridge lies is larger, conversely, the relative humidity of environment where Bridge lies is smaller, the later deflection value of shrinkage and creep of the concrete is smaller. So calculation value of the relative humidity should be based on the value of actual average relative humidity of the geographical location in the design of the Bridges.â‘¡The shorter of the age of concrete of the first pre-stressed loading, the larger of the later deflection value of shrinkage and creep, conversely, the longer of the age of concrete of the first pre-stressed loading, the smaller of the later deflection value of shrinkage and creep. So in order to reduce the later deflection value of shrinkage and creep, should try to extend the age of concrete of the first pre-stressed loading after the completion of the concrete structure in the casting. While applying the constant load in Phase ii, the longer of the constant load in Phase ii is delayed, the smaller of the later deflection value of shrinkage and creep of the concrete. Conversely, the shorter of the constant load in Phase ii is delayed, the larger is the later deflection value of shrinkage and creep of the concrete.â‘¢But excessive extension of the constant load in phase ii will influence the bridge construction, so we should consider comprehensive accounts of various factors, to choose the extension time of the constant load in phase ii appropriately.