ON THE PERFORMANCE OF INTEGRAL BUCKLE ARRESTORS FOR OFFSHORE PIPELINES

This paper presents the results of a study on the effectiveness of int egral buckle arrestors for offshore pipelines. A series of full scale experiments were conducted where the pressure at which buckles propaga ting quasi-statically crossed arrestors of various lengths and thickne sses was established. The crossover pressures were used to establish t he parametric dependence of the arresting efficiency (as defined in Ky riakides and Babcock, ASME Journal of Pressure Vessel Technology 102 ( 1980) and Proceedings of Offshore Technology Conference (1979)) of suc h devices. Buckles penetrated the arrestor in two modes: the flattenin g mode, where the arrestor and downstream pipe collapse in the same ma nner as the incoming buckle and the flipped mode, where the sense of c ollapse of the downstream pipe is orthogonal to the incoming buckle. T he mode switch occurred in the neighborhood of efficiency of 0.7. The process of quasi-static engagement of an arrestor by a propagating buc kle, the temporary arrest of the buckle and the eventual crossing of t he arrestor were simulated through a finite element model. The model i s based on finite deformation kinematics, incorporates J(2)-type plast icity with isotropic hardening, and allows for contact of the walls of the collapsed section of pipe upstream of the arrestor. The model was verified by simulating each of the 15 physical experiments conducted using the actual geometric and material characteristics of the test sp ecimens. The crossover pressures of the simulations were within 5% fro m the measured values and the mode of crossover was predicted correctl y as well. The model was subsequently used to extend the experimental parametric study of arrestor efficiency. Some limiting values of the p arameters were established from the results and several design recomme ndations are made. Copyright (C) 1997 Elsevier Science Ltd.