有效预应力对PC连续刚构桥挠度的影响

以涪陵区聚云大道沙溪沟大桥工程为背景，运用有限元软件对其进行仿真模拟计算，分析了PC混凝土连续刚构桥顶板和底板的纵向预应力筋有效性的降低分别对关键截面（零号块根部截面、L／4截面、跨中截面）处挠度的影响，从而找出了一种对挠度影响最不利的纵向预应力的损失情况，即最不利组合。计算结果表明，主梁纵向预应力有效性的逐渐降低是PC混凝土连续刚构桥梁后期挠度下挠过大的主要原因之一，且当顶板纵向预应力失效50％，同时底板纵向预应力失效30％的时候，对挠度的影响最不利。文章给出了相应的控制预应力有效性降低的措施。

Effect of valid prestress to the deflection of PC continuous frame bridge

According to the project of Shaxi Gou Bridge across the Juyun Avenue in Fuling District, Chongqing City, the calculation was made with finite element software, to analyzes the effect of valid prestress in the longitudinal tendons at the top and the bottom of box - section of continuous frame bridge to the deflection of key sections （ i. e. , the root of Section No. 0, the quarter - span, and the mid - span ） , respectively, thus finding a case of losses in longitudinal prestress to exerting the most unfavorable influence on the deflection, i. e. , the most unfavorable combination. The calculated results shown that the lowering gradually of valid prestress in the longitudinal tendons are one of main factors causing the final - period over - deflection, and would be the most adverse to the deflection when the losses comes up to 50 percent at the top slabs while 30 percent at the bot- tom. This paper presents measures for controlling the lowering valid prestress.