Session: 02-11-02 Fatigue and Fracture Reliability 2

Paper Number: 105144

105144 - Damage Analysis of Oc4 Jacket Under Fatigue Loading by Peridynamic Approach 

Offshore structures are prone to damage by cyclic loading generated by environmental conditions. The cumulative damage approach is widely utilized for predicting structural life. The percentage of damage from individual stress cycles, i.e., the ratio of the number of applied load cycles to allowable load cycles, are summed up to obtain total damage without considering cracks in the structure. And in the fracture mechanics approach, the number of load cycles for an initial crack to grow up to its fracture length is evaluated for fatigue analysis. However, the latter method sounds realistic since structural life is assessed based on crack propagation. Still, due to the mathematical model of the classical approach, crack initiation cannot be evaluated. The present study adopts a peridynamic approach for evaluating the structural life of jacket structure under fatigue loading by considering crack initiation and propagation. In peridynamic theory, the classical mathematical model is modified by replacing spatial differential with integrals by introducing nonlocality in structural analysis. The internal force at each point is assumed to be influenced by neighboring points within the horizon through bond interaction. The damage is incorporated within the governing equation, treating it as an integral part of the structure. Silling and Askari (2014) developed a peridynamic fatigue model based on the cumulative damage of individual bonds at every load cycle through a remaining life parameter. This model is evaluated by performing fatigue analysis in two-dimensional structures. The present study attempts to perform fatigue analysis in jacket structures modeled in a peridynamic framework. The jacket is modeled as a combination of three-dimensional beams. A cyclic bond-strain approach obtains damage initiation in the structure and load cycles required for the jacket to get fractured.

Presenting Author: Pranitha Bachimanchi Indian Institute of Technology

Presenting Author Biography: A Ph.D. student in the Department of Ocean engineering, IIT Madras.

Authors:

Pranitha Bachimanchi Indian Institute of Technology
Nilanjan Saha Indian Institute of Technology