叠合梁斜拉桥中跨辅助合龙施工技术

Auxiliary Techniques for Midspan Closure of Composite Girder Cable-Stayed Bridge

灌河大桥为主跨400m的叠合梁斜拉桥,主梁为双工字型边主梁。为使该桥顺利安全合龙,中跨采取温度合龙,并采用临时长圆孔拼接板为过渡性约束措施的辅助合龙技术,即首先以临时长圆孔拼接板固定合龙口状态,在预测温度变化范围内解除塔梁临时约束,然后根据实测螺栓孔距加工永久拼接板,最后由永久拼接板替换工具板,完成合龙。中跨合龙前,提前2个梁段观测扩大合龙口的状态,通过计算确定合龙段下料长度及长圆孔工具拼接板螺栓孔尺寸;为满足温度±5℃变化范围施工要求,工具拼接板长圆孔尺寸定为ф33mm×93mm,工具拼接板外形尺寸与永久拼接板相同,工具拼接板长圆孔高强度螺栓按80个设计。实践表明,采用该方法进行合龙减小了温度变化对合龙施工的影响,提高了合龙施工工效和可靠性。

The Guanhe River Bridge is a composite girder cable-stayed bridge with a main span of 400 m and the main girder of the bridge are composed of the twin I-shaped edge beams. To en- sure the safe and smooth closure of the bridge, the midspan adopts the temperature closure tech- nique assisted by the auxiliary closure technique of using temporary splice plates with long round holes as the transitional constraining measures. Firstly, the temporary splice plates with long round holes were used to fix the closure gap and the temporary constraints between the pylon and the beam were dismantled within the predicted temperature variation range. Then the permanent splice plates were manufactured according to the measured locations of the bolt holes. Finally, the temporary splice plates were replaced by the permanent splice plates and the closure was complete. Before the closure of the midspan, the condition of the closure gap that was gradually expanding should be monitored ahead of the construction of two beam sections. The material spreading length of the closure section and the dimension of the bolt holes in the splice plates with long round holes were determined via calculation. To meet the construction requirements of keeping the temperature variation within the range of ± 5 ℃, the long round holes in the temporary splice plates were designed with the dimension of 433 mm × 93 mm, and the shape and size of the temporary splice plates were the same to the permanent one. There were 80 high-strength bolts on each temporary splice plate. The engineering practice proves that the method used reduces the influence of temper- ature variation on the closure construction, improving the efficiency and reliability of the closure construction.