In order to satisfy adjustable span demand when 250 km/h passenger dedicated railway crosses some complicated control engineering projects, it is necessary to design adjustable-span beam with its span changed freely within 24 ~ 32 m. The adjustable-span beam with unchanged cross-section, distributed forms of steel cable and reinforcement control stresses can increase and decrease its span within the given limits. In this paper, some key techniques of general drawings of ballastless adjustable-span beam are studied to solve uncontrolled residual creep deformation when the span of adjustable-span beam with larger span is decreased. As far as ballastless adjustable-span beam on passenger dedicated lines with supporting frame and cast-in-site concrete is concerned, the beam is prestressed with lower initial stress level before the strength of concrete reaches its design strength while early creep deformation of concrete is also accelerated, which can decrease effectively later residual creep. Meanwhile, the supporting frame could be reused rapidly, which leads to quick construction and lower construction cost. The final prestressing of the beam is conducted immediately after the strength and modulus of concrete reach their design values, so as to shorten the loading age of concrete as much as possible, which could effectively decrease residual creep deformation although with increased total creep.%为满足时速250 km客运专线铁路跨越复杂控制工点调跨需要,设计满足24～ 32 m可以任意改变跨度的“调跨梁”通用图非常必要.“调跨梁”为桥梁截面尺寸不变、钢束布置形式不变、张拉控制应力不变,但可在某一跨度范围内任意伸长或缩短的简支箱梁.对无砟轨道调跨梁通用图设计中的关键技术进行研究.解决跨度较大的无砟轨道调跨梁当跨度缩小时,残余徐变变形很难控制的问题.支架现浇施工的客运专线无砟轨道调跨梁,混凝土强度达到设计强度前采用低应力初张拉,通过加快混凝土早期徐变变形的方法可有效降低结构后期残余徐变.同时还能实现支架尽快倒用,加快施工进度,节省施工临时设施费用,降低工程总造价.混凝土强度及弹模达到设计值后立刻进行终张拉,尽可能降低混凝土加载龄期,总徐变变形虽然增大但残余徐变变形可有效减小.同时,早张拉还可以加快施工进度.
展开▼
