Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Numerical analysis of welded dislocation structure of jacket wall based on multi-scale modeling
Ning Liu1,Lu-yang Zhang1,*,Qian Chen1,Jie,Fan1
1 College of Shipbuilding Engineering,Harbin Engineering University.
Harbin,Heilongjiang,China

An Z (2010)analyzed the dislocation stress of welded structure in thecomplex structure of jacket. He used ANSYS to carry out finite element
analysis of different points in the dislocation structure, and evaluated theapplicability of common formulas. Wen Xiong et al(2019). usedABAQUS to establish different dislocation pipe pile models andanalyzed the influence of dislocation quantity on the structural strengthof pipe pile, providing reference for practical engineering applications.
Lotsberg I(2009)verified the correctness of Lotsberg's formula undersmall dislocations, which was also adopted by DNV specification.
However, the nowadays researches on the stress concentration factor of
welding dislocation are mainly for the structures with small dislocation,and the researches on the stress concentration of the jacket wall
dislocation welding or large dislocation are relatively few. For the wholepipe jacket wall basic structure, pipe wall welding dislocation is aparticle incident. Therefore, this paper adopts the idea of multi-scalemodeling, combines a jacket construction example, and simulates
welding dislocation by reducing the thickness of plate element in the rod
system model to study the relationship between plate element modelingand actual dislocation. Based on the refined modeling of solid element,
the structural stress response was analyzed when the welding dislocation
was large, and the applicability of the formula was verified by comparing
it with the code.

ABSTRACTWith the massive development and utilization of offshore wind energy,
offshore wind turbine has become an important marine engineering
structure. In the process of construction, due to the limitation of working
environment and welding process, the welded parts of the pipe wall willappear structural dislocation, which will result in structural stressconcentration, and resulting in great safety hidden danger. Based on theidea of multi-scale modeling, this paper adopts different modelingmethods to simulate welding dislocation with plate element and solid
element respectively. In this paper, the structural response is analyzed bynumerical calculation, and the stress concentration factor under different
modeling methods is obtained.On the basis of the above research, thestructural response under different degrees of dislocation is calculated,
and the stress concentration factor is compared with the standard value,which further improves the calculation and treatment method of thestress concentration factor in the code, and puts forward the correction
formula of the stress concentration factor under the large amount ofdislocation.

KEY WORDS: Jacket platform, Multiscale modeling, Welding
dislocation, Stress concentration factor (SCF), Finite element
analysis

JACKET WALL DISLOCATION BASIC SETTINGINTRODUCTION

Jacket Structure Description

As a simple, safe and reliable basic structure, jacket is widely used inmarine development. In the construction process, the connection
between the pipe is usually in the form of welding(Yang J,2013), due tothe limitation of working environment and welding technology, it isunavoidable to appear the welding dislocation of pipe wall. Under theaction of alternating loads, such as wave, tide and current, the structural
structure of ducted frame is in the sea for a long time. The stressconcentration will occur at the local dislocation and fatigue will easily
occur, damage the integrity of the whole structure(ARGYRIADISK,2017; Han C,2013), bring great economic losses and even staff safety
problems.

Three legs jacket in the process of building this usually takes the form ofblock, first carries on the socket, block, transition section and othersubsidiary of precast structure, and then under the catheter closed phases
through the rack section, and transition section installation segmentgroup, jacket overall consists of two sections, respectively was built after
the inspection, the folded under paragraphs and paragraphs. This isshown in the Figure 1.

720