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

Research on Impact Energy and Damage of Subsea Protection Structures by Trawling board
Zheng Huang1, Honghong Wang2, Wei Zhang1 ,Rongqi Chen3, Yanbo Liu1*
1 College of Shipbuilding Engineering, Harbin Engineering University, Harbin, China
2 CNOOC Research Institute, Beijing, China
3Offshore Oil Engineering CO. LTD, Tianjin, China

pipe deformation and impact force of trawling board. In the researches
conducted by DNVGL, a calculation method based on maximum
deformations theory is proposed to calculate the impact of energy andpipeline damages.

ABSTRACT
Panels with frames have been applied as protection structures of subsea
production systems for reducing the damages caused by dropping objects
and trawling boards. However, current standards do not provide
calculation methods for the impact energy of trawling board anddamages of protection structures in specific region. For investigating theimpact process in specific regions, data statistics based on AIS andmultivariable simulations are conducted in this paper. Simulations
suggest that pile-soil interaction has a good inhibitory effect on structuralvibrations and panel depressions. The simulation results also show that
protective structure with FRP panel has less overall displacement but
greater depression than structures with steel panels.

In researches with numerical simulation, Zhou (2015) conducted a threedimensional simulation in ANSYS/Explicit for investigating thedynamics response of underwater protection structure impacted byjumper tube. The stress and deformation of protection structures during
the impacting process is in agreement with the results calculated byengineering empirical calculation method. Ralph (2012) proposed angeometric model of underwater protection structures and conductedfinite element analyses based on the geometric model to investigate theimpact between protection structures and glacier. The impact energy andstructural deformation in the maximum plastic strain state of theprotection structures are analyzed in the simulations conducted by Ralph.
For investigating the stability and bearing capacity of the protection
structures, Tauqeer (2016) conducted FEA simulation of protection
structures with square, triangular and semi-circular glass fiber reinforced
plastic panels.

KEY WORDS: Subsea Protective Structures; AIS Data; Multivariable
analysis; Pile-Soil Interaction; FRPINTRODUCTION
Bottom trawling is one of the most common operation methods used byfishing vessels. During bottom trawling operations, the trawling board
may impact subsea equipment, which seriously threatens the safety ofthe underwater production system. Therefore, protection structures havebeen apllied to prevent the damages from impact of trawling board. Mostprotection structures are fabricated with steel pipes and plates. In some
protective structures, fiber reinforced polymer (FRP) is also used as thepanel material.

However, previous researches on impact process between fishing gears
and protection strutures usually do not focus on the information offishing vessels in the target sea area. Thus, for investigating the impact
process between the protection structures and trawling board based ontarget areas, FEA analysis based on vessel information from AIS data isconducted in this paper. The data statistics of AIS information include
the size, weight, and operating speed of the fishing vessels. The impact
energy and the weight of the trawling boards is calculated based on theseparameters. For accurately predicting the impact process, the impacting
velocity of the trawling board is also calculated based on the impact
energy and wight of trawling board. The overall displacement and thepanel depression of the protection structures is extacted to investigatedthe damage of protection strutures. The influence of pile-soil interactions
and material properties are investigated respectively.

Previous researches usually adopted the extended theory and damage
models of researches about impacting process of subsea pipelines toanalyze the impact energy and structural damage of the protection
structures. Ellinas (1995) proposed a semi-empirical formula to calculate
the impact forces and the pipeline depressions, which are in good
agreement with the experimental results and have widely used in thesubsequent damage analysis. Bai (1993) used nonlinear spring theory toanalyze the impact between trawling board and circular pipes, a massspring formula for calculating the impact force on subsea pipes
summarized in his research for integrating the impact force along thepath of the pipe depression to solve the impact energy. Based on
experimental data, DNVGL (2017) improved the calculation formula ofIMPACT ENERGY CALCULATION
Fishing Vessel Information by AIS Data3297