川藏铁路常用跨度预应力混凝土简支梁的耐久性设计对策

Durability Design Countermeasures for Common Span Simply Supported Beam in Sichuan-Tibet Railway

为减少川藏铁路运营期内的养护维修工作,结合高原及寒区铁路简支梁桥的现状调查,分析常用跨度混凝土简支梁桥的服役环境及面临的挑战,提出有利于保障结构耐久性的设计对策。(1)常用跨度混凝土简支梁应优先采用预制工艺,宜优先选用箱梁;(2)梁体应采用高性能混凝土和高强度钢绞线,管道压浆应选用高性能灌浆料;(3)梁体配筋设计除考虑碳化环境外兼顾考虑风蚀及雨雪冻融的影响;(4)选用耐低温、抗紫外线强的防水材料,泄水管及梁端止水带可选用不锈钢材料,防水保护层混凝土宜设置钢筋网;(5)可根据海拔高度、风场环境、昼夜温度变化等因素,选择将混凝土浇筑作业置于全封闭厂棚内;(6)根据沿线地区气候环境与景观要求合理选用栏杆类型,力求简单、经济、耐用。

In order to reduce maintenance workload during the operation of Sichuan-Tibet Railway,this paper analyzes the service environment and challenges of the simply supported beam bridge with common span,and proposes the design countermeasures to ensure the durability of structures based on the investigation on the current situations of the simply supported railway beam bridge in plateau and cold areas.(1)The simply supported beam with common span should prioritize prefabrication technology and box beam.(2)High-performance concrete and high strength steel strand should be applied to the beam,and high-performance grouting material should be used in pipeline grouting.(3)The reinforcement design of beam should consider not only the carbonation environment but also the influence of wind erosion and freeze thaw due to the rain and snow weather.(4)The waterproof material which can resist low temperature and ultraviolet should be applied,stainless steel should be used in drain pipes and water-stop belt at beam end,and mesh reinforcement should be used in the concrete of waterproof protection layer.(5)Concrete pouring should be performed in a fully enclosed plant shed,depending on such factors as altitude,wind field conditions and temperature variation between the day and the night.(6)Railing type should be selected reasonably according to climatic environment and landscape requirements of the areas along the route,and railings should be simple,economic and durable.