大跨度桥梁承载能力鉴定研究

Study on Identification of Load Bearing Capacity of Long Span Bridge

针对现行桥梁承载能力鉴定方法运用于大跨度桥梁时的局限性,以湖北6座主跨超过600m的长江大桥成桥荷载试验为基础,总结大跨度桥梁承载能力鉴定的经验,并参考《公路桥梁承载能力检测评定规程》(JTG/T J21-2011)和《公路桥梁荷载试验规程》(JTG/T J21-01-2015),针对测试项目、加载工况及加载效率、结构校验系数等提出合理建议。建议对大跨度桥梁进行承载能力鉴定时,除遵循规范规定外,增加温度、支座位移、伸缩缝位移、特殊构造应力及结构重点部位观测等测试项目,增加主梁最大挠度、中塔扭转效应及偏心加载等工况,降低部分工况的加载效率控制值,对规范中主梁挠度、桥塔偏位及结构应力等主要参数的结构校验系数的合理取值范围进行修正。

In regard of the limitations of the current identification method for the load bearing capacity of the bridge, the experience of the identification of the bearing capacity of the long span bridges was summarized based on the loading tests of six completed Changjiang River Bridges with the main spans exceeding 600 m in Hubei. Then, following the Specification for Inspection and Evaluation of Load Bearing Capacity of High-tray Bridges （JTG/T J21 2011） and Load Test Methods for Highway Bridge （JTG/T J21 01 2015）, reasonable suggestions were proposed for the testing projects, loading conditions, loading efficiency and structural verification coefficients. It is suggested that when the bearing capacity of the long span bridges is identified, the testing projects including the temperature, displacement of the bearings, displacement of expansion joints, stress of the special structure and observation on key parts of structure should be added in addition to following the code requirements. Meanwhile, the loading cases such as the maximum deflection of the main girder, twist effect of the middle pylon and eccentric loading conditions should be added, and the controlling values of the loading efficiency of partial loading cases should be reduced. The reasonable ranges of the structural verification coefficients of the main parameters including the deflection of the main girder, offsetting of the pylons and structural stress in the codes are revised.