邻近既有桥梁不平衡受力条件下钢管桩围堰支撑结构冗余度分析

REDUNDANCY ANALYSIS OF STEEL PIPE PILE COFFERDAM SUPPORT STRUCTURE OF ADJACENT EXISTING BRIDGE UNDER UNBALANCED LOAD CONDITION

京台高速公路齐河至济南段改扩建工程主桥P3号墩深基坑处于黄河岸边,具有下游回水冲刷较大、距离已有桥墩基础非常近、承受不平衡水土压力作用的特点,为防止复杂地质条件下支撑结构冗余度不足而导致局部支撑结构破坏,从而引起整个支护结构连续坍塌等安全问题的发生,本研究以冗余度理论为指导,基于拆除杆件法,共设立3组冗余度研究方案,分析了不平衡受力条件下,斜撑、纵撑、支撑杆件等局部失效下剩余支撑结构抵抗支护结构连续破坏的能力。针对工程特点,提出了邻近既有桥梁沉降冗余度表达式,最终计算并分析了各方案的钢管桩围堰刚度冗余度、邻近既有桥梁沉降冗余度,可为各类深水桥梁承台围堰施工支撑结构设计提供参考。

Located on the bank of the Yellow River,the deep foundation pit of the Pier P3 of the main bridge in the reconstruction and expansion project of the Qihe-Ji'nan section of Beijing-Taiwan Expressway is very close to the existing pier foundation and subjected to downstream backwater erosion and unbalanced water and earth pressure.In order to prevent local support failure arising from insufficient redundancy under complex geological conditions,as well as other safety hazards such as the continuous collapse of the entire support structure,three redundancy research schemes were developed based on the redundancy theory and member demolition method,and the resistance of remaining support structures to continuous support damage in case of local failure of diagonal braces,longitudinal braces and support bars was analyzed under unbalanced load conditions.According to the engineering characteristics,a formula was proposed for calculation of the settlement redundancy of adjacent existing bridges,and eventually the stiffness redundancy of steel pipe pile cofferdams in each scheme and the settlement redundancy of adjacent existing bridges were calculated and analyzed,to provide a reference for the support structure design of deep-water bridge cap cofferdams.