Failure Analysis of Cast Iron Trunk Main in Cleveland, Ohio
Failure Analysis of Cast Iron Trunk Main in Cleveland, Ohio
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俄亥俄州克利夫兰铸铁主干管失效分析
DOI：
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发表时间：
2012
影响因子：
1.2
通讯作者：
Alex Margevicius
中科院分区：
文献类型：
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作者：
B. Rajani;J. Lewandowski;Alex Margevicius
本文介绍了2008年3月在俄亥俄州克利夫兰发生的直径为30”的铸铁主管道在钟形接头处突然失效的失效分析。自1880年安装以来，主管道基本上没有出现任何问题。使用先前开发的三个模型分析失效，每个模型考虑特定的失效机制候选者，即（a）操作载荷或静态分析，（B）由于地面移动（沉降）引起的接头失效，以及（c）疲劳失效。运行荷载分析清楚地表明，虽然2002年在管道上方安装了混凝土拱顶，安全系数大大降低，但安全裕度仍然足以使主管道安全运行。对连接管道的地面移动分析表明，在30”铸铁主管道连接处上方的混凝土拱顶施工使连接处发生旋转，这可能最终使钟形件破裂，导致故障。在这种情况下，可能出现两种失效情况：即，（a）额外的旋转足够大，导致钟形件开裂，或（B）额外的旋转足以在钟形件中引起轻微裂纹，但疲劳（重复）加载导致裂纹随时间增长，直到裂纹长度和载荷的组合足以导致钟形件最终开裂。沿着断裂表面的颜色差异表明断裂发生在两个不同的阶段。这一观察结果表明，第二种情况比第一种情况更合理。
This article describes the failure analyses of a 30”-diameter cast iron main that failed suddenly at the bell–spigot joint in Cleveland, Ohio in March 2008. The main had been operating largely without problems since its installation in 1880. The failure was analyzed using three models developed previously, each of which considered a specific failure mechanism candidate, namely (a) operational load or static analysis, (b) joint failure due to ground movement (settlement), and (c) fatigue failure. Operational load analysis clearly showed that while the factor of safety was significantly reduced in the presence of a concrete vault installed in 2002 just above the pipe, the margin of safety was still sufficient for the main to have performed safely. Ground movement analysis of the jointed pipe showed that the construction of the concrete vault above the joint of the 30”-cast iron main subjected the joint to rotation, which might have ultimately cracked the bell leading to failure. Under this circumstance, two failure scenarios are possible: namely, (a) additional rotation was large enough to cause the bell to split, or (b) additional rotation was sufficient to induce a minor crack in the bell but fatigue (repeated) loading caused the crack to grow over time until the combination of crack length and loading was sufficient to cause the bell to eventually split. The color differences along the fracture surfaces indicated that the fracture occurred in two distinct stages. This observation suggests that the second scenario is more plausible than the first.