已建大跨径PC梁桥长期下挠的加固对策研究

以某高速公路1座运营超过12年、严重下挠的(65+100+65) m PC连续梁桥为工程实例,首先尽可能准确地识别该桥现有的结构状态,针对其结构状态,提出相应的加固目标,并提出3种加固方案,即:增设体外预应力束、增设斜拉索以及截断跨中更换钢梁.从应力、线形、内力改善情况及施工工艺方面对3种加固方案的加固效率进行比较,结果表明:对于跨径100 m级的在役预应力混凝土连续梁桥,3种加固方案均可使其基本满足加固设计和规范要求.综合考虑施工风险、工期、费用、交通组织和社会影响等,最终选用增设体外预应力束加固方案,并结合桥面铺装减载的方法,可明显提高加固效率.

Study of Strengthening Measures for Long-Term Deflection of a Long Span Prestressed Concrete Girder Bridge in Service

For a expressway prestressed concrete (PC) continuous girder bridge with span arrangement (65+100+65) m that has been in service over 12 years and that has severe deflection deterioration, the existing structural conditions of the bridge were firstly identified as exactly as possible. In the light of the structural conditions, the corresponding strengthening goal was set and three kinds of the strengthening schemes, that is, adding of the external prestressing tendons, adding of the stay cables and replacement by the steel girder blocks at midspan, were prepared. The efficiency of the three strengthening schemes were compared in aspect of the improvement of the stress, geometric shape and internal force and the construction technology. The results of the comparison showed that for the in-service PC continuous girder bridges with span length of 100 m, the three schemes could all basically satisfy the requirements in the strengthening design and specifications, however in comprehensive consideration of the construction risk, schedule, cost, traffic control and public influence, the scheme of adding of the external prestressing tendons was finally chosen and in addition to the utilization of the load reduction method of deck surfacing, the strengthening efficiency of the bridge could be significantly improved.