Study of Crack Initiation and Fracture in OC4 Jacket Structure Under Cyclic Loading by Peridynamic Approach

Abstract

Abstract The offshore structures are frequently subjected to the cyclic loads generated by environmental conditions leading to structural damage. The analysis of such damage that manifest as cracks become non-trivial due to mathematical abstraction of their classical governing equations in the presence of structural discontinuities. In this study, we employ peridynamic theory [1] that modifies the classical mathematical model by replacing spatial derivatives with integrals through non-local bond interactions between material points. This approach helps us model the breakage of bonds pertaining to structural cracks. In the peridynamic fatigue model [2], the breakage of bonds is evaluated through the remaining life parameter that accounts for the cumulative damage at every load cycle caused by in-plane cyclic deformation in a 2D plate. In this work, we model OC4 jackets with peridynamic beam formulation [3], where the fatigue model considers the bond’s cyclic in-plane, shear, bending, and torsional deformation. We successfully identify the critical locations for crack initiation in the jacket under constant amplitude cyclic point loading. We further evaluate the number of load cycles required for crack initiation and fracture under different maximum load magnitudes of cyclic loading.