大跨径PC梁桥长期下挠成因分析与加固对策研究

以某高速公路一座运营超过十二年、严重下挠的PC连续梁桥(65m+100m+65m)为工程实例,从桥面铺装厚度影响、施工误差影响、预应力度损失影响、混凝土收缩徐变影响、结构损伤的影响、开裂与结构长期效应的耦合作用以、温度影响以及结构承载能力及使用性能影响等方面进行了病害成因分析。对增设体外预应力束、增设斜拉索以及截断跨中更换钢梁等三种加固方案进行了研究。从线形恢复效果来看,斜拉索方案加固效率较高。但综合考虑施工风险、工期、费用、交通组织和社会影响等方面影响,最终采取桥面铺装采用LC40轻质砼减载和施加体外预应力相结合的主动加固方案。

Study on Causes and Strengthening of Long-term Deflection of Long-span Pre-stressed Concrete Girder Bridge

Based on an existing severe deflection of a certain expressway pre - stressed concrete girder bridge with the span of 65 ＋ 100 ＋65m and over 12 years service period, the causes of long - term deflection are discussed centered on such influence aspects as width of pavement, errors of construction control,losses of prestressing cables,creep and shinkage of concrete ,damage of structure ,coupling of cracks and long-term effect of concrete structure ,temperature ,structural hearing capacity , normal seviceablity performance and so forth. Several strengthening methods were compared, such as adding external pre - stressing tendons, increasing cantilever pre - stressing tendons in top plates, increasing height of girder, setting cable tower and replacing the segment at the middle of main span by steel - concrete composite beams. Setting cable tower method is better for shape recovery. Comprehensively taking into account of strengthening risk,time,cost,traffic control and public influence, adding external pre -stressing tendons plus reducing load of pavement method by LC40 light -weight aggregate concrete technique is the recommended retrofitting strategy.