Dynamic performance of integral buckle arrestors for offshore pipelines. Part II: Analysis

A design methodology for integral buckle arrestors for deepwater pipelines was presented in a previous study (Park TD, and Kyriakides S., International Journal of Mechanical Sciences 1997;39:643–69). It was based on experiments and analyses in which buckles engaged the arrestors quasi-statically. In this two-part paper series, the performance of the same arrestors is reevaluated under the more realistic dynamic buckle propagation conditions encountered in the sea. The experimental program described in Part I involves tubes with D/t=27.9 and arrestors with L_a /D=0.5. The quasi-static arresting efficiency of buckle arrestors is first established experimentally as a function of the arrestor thickness. The same arrestor designs are then tested again in constant pressure environments where buckles propagate at velocities of 400–1100 ft/s. Experiments are conducted using both water and air as pressurizing media. A typical test specimen involves a relatively long upstream section of tube welded to an arrestor and to a downstream tube. The buckle is initiated in the upstream tube, accelerates to steady-state propagation, engages the arrestor and is either arrested or crosses over. For each arrestor design several such tests are required in order to bracket the dynamic crossover pressure. For all cases considered, the dynamic crossover pressure was found to exceed the corresponding quasi-static value. The reasons for this enhancement in performance are discussed in Part II in the light of results from numerical simulations of this process.