导管架海洋平台失效路径分析及连续倒塌机制

针对突发事件下导管架平台"局部破坏"可能引发的连续倒塌现象,建立一种针对导管架平台结构的失效路径搜索及概率评估流程,采用逐步施加增量载荷的方法,并结合广义承力比准则,充分考虑失效过程中单元内应力的变化及候选失效单元的不确定性和外部载荷的随机性,并通过模拟示例获得平台可能发生的事故树,从而确定最可能发生的失效顺序。针对具体失效路径,引入备用荷载路径方法(ALP方法),研究倒塌过程中平台结构的力学分布特性和状态变化规律,分析构件失效后的平台剩余系统的动力效应和内力重分布规律,从而揭示平台结构的连续倒塌机制。结果表明:某桩腿单元突发失效后,失效单元上方的水平撑杆通过塑性铰机制成为新的竖向传力路径;相邻桩腿由于严重的内力重分布现象成为薄弱环节,易发生屈曲失效。

Failure paths identification and progressive collapse mechanism analysis of offshore jacket platforms

In order to analyze the progressive collapse problem of jacket platforms resulted from "local failure", a failure path searching method was presented, and a failure probability calculating process was developed by using incremental loading method, in which the uncertainty of candidate failure components and the stochasticity of external loads were considered. Through simulation, all possible failure paths were sought out, and the most likely failure sequence was identified. Then, considering a specific failure spreading path, the dynamic effects of damaged platform and the rule of internal force redistribution were studied using alternative load path (ALP) method, and the progressive collapse mechanism was revealed. The analysis results indicate that:when a leg member fails, the above horizontal brace will become the new vertical load path through the plastic hinge mechanism, and then the adjacent leg member will become a weak point due to severe internal force redistribution phenomenon, therefore the platforms are prone to buckling failure.