2次预应力简支组合梁受力性能与技术经济分析

高速铁路预应力混凝土桥梁徐变上拱过大会影响桥上列车运行安全，为了控制预应力混凝土桥梁徐变上拱，将2次施加预应力新技术应用于预应力混凝土梁中，以箱梁为例，设计了4根不同预应力度的2次预应力简支组合梁，分析了其各施工受力阶段截面应力、强度和抗裂性，并进行了结构尺寸与配筋完全相同的常规预应力混凝土简支梁和2次预应力简支组合梁徐变上拱的对比计算分析。结果表明：2次预应力简支组合梁截面应力梯度小，受力合理，与常规预应力混凝土简支梁相比，徐变上拱减少约40％～60％；并可以降低梁的建筑高度，节约10％左右的预应力筋和一定数量的混凝土，具有明显技术经济优势。

Mechanical Behavior and Techno economic Analysis of Twice prestressed Simply Supported Composite Beam

Excessive creep camber of prestressed concrete bridge would result in risk on the traffic safety in high-speed railway. To control creep camber of presstressed concrete bridge, a new twice-prestressed technology was proposed to presstressed concrete beam. Four twice-prestressed simply supported box girders with different prestressed degrees were designed as an example. Its section stress, strength and crack resistance in different construction stages were analyzed. Compared the creep camber between conventional prestressed simply supported concrete beam and twice-prestressed simply supported composite beam with the same prestressed steels, it was shown that twice-prestressed composite beam has a smaller stress gradient. And the creep camber decreased approximately 40% to 60% with building height reduction, as well as some 10% energy saving and some amount of concrete.