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 the Application of Digital Twin Technology in the Structural Safety Assessmentof Deep-water Semi-submersible Platforms
Bo Wua,b, Yufeng Koua, Jun Liua, Xin Lia,b*aState Key Laboratory of Ocean Engineering, Shanghai Jiao tong University.

Shanghai, ChinabSJTU Yazhou Bay Institute of Deepsea Technology.

Sanya, Hainan, China

and has been developed in three stages.

ABSTRACT:Formation Period (before 2010): The term "digital twin" has not been
formed, but the basic ideas have been produced, which is expressed in"Mirrored Spaces Model" and "Information Mirroring Model". In 1969,
NASA used the concept of "twins" in the Apollo program to mirror theconditions of vehicle in space (Boschert & Rosen, 2016). In 2002,Grieves (Grieves, 2017) proposed the concept of “Conceptual Ideal for
Product Lifecycle Management (PLM)”, which did have the elements of
the Digital Twin: real space, virtual space, link for data flow between
real and virtual space. Later, he referred this concept to “Mirrored SpacesModel” (Grieves, 2005) and “Information Mirroring Model” (Grieves,2006, 2009), the virtual and real system are connected at the four phasesof creation, production operation and disposal.

Concerning the potential risk of a semi-submersible structure, the Digital
Twin technology was widely considered for the structural safetyassessment. Directly measurement of the stress responses could be
mostly accurate but quite difficult for installation of the sensors, due tothe complexity of the structure and environment loads. In this paper, amethod was introduced for structural safety assessment of a deep-watersemi-submersible platform. Combining the field measurement andnumerical simulation of the structural stress on specific locations,corrections of the stress response transition operator (RTO) on two
locations can be found. We could then modify the numerical model byintegrating correction coefficients from field measurement. To
demonstrate the proposed method, a semi-submersible platform in theSouth China Sea was applied. The stress on 5 locations were measured
with a duration of 15 days. To extend sample of sea states, 1428 shortterm cases were obtained by using time-stepping approach. It is foundthat the RTOs between measured points have approximately stable
relationships. The relative error between calculated result and measured
value is less than 10%, indicating the strong potential for the digital twin
application.

Definition Period (2010~2015): The term "digital twin" emerged andwas gradually clarified, which was mainly used for prognostics anddiagnostics activities in the aerospace field. The beginning of this stage
is marked by the draft released by NASA for technology area 11 (Shaftoet al., 2010), and the definition of digital twin appears for the first time:“A digital twin is an integrated multi-physics, multi-scale, probabilistic
simulation of a vehicle or system that uses the best available physicalmodels, sensor updates, fleet history, etc., to mirror the life of its flyingtwin.” Subsequently, Tuegel et al. (2011) proposed a conceptual model
for predicting the life of aircraft structure and assuring the structural
integrity by using digital twin. The digital twin was described as "anultrahigh fidelity model". One year later, at the work in cooperation withGockel (2012), they extracted the “Airframe Digital Twin” as submoduleof “Aircraft Digital Twin” and envisioned it “to be an ultra-realistic,
cradle-to-grave computer model of an aircraft structure that is used toassess the aircraft’s ability to meet mission requirements.” Later,
Reifsnider (2013) proposed a multidisciplinary physics-based
methodology to mirror the life of a flying physical twin, which could begreatly helpful for ultra-high fidelity simulation.

KEY WORDS: Digital Twin; Structural safety assessment; Filedmeasurement; Numerical simulation; Data exchange; Stress response

INTRODUCTION
The structural safety assessment of offshore platform has always been
the focus of the industry, and numerical simulation is the main
calculation method. With the development of measuring technology anddata transmission technology, it is very possible to use digital twin
technology to evaluate the structural safety of offshore platforms. At
present, there is no unified definition of digital twin. An acceptabledefinition is “to make full use of data such as physical model, sensor
update and operation history, integrate multi-disciplinary, multi physicalquantity, multi-scale and multi probability simulation process, andcomplete mapping in virtual space, so as to reflect the whole life cycle
process of corresponding physical equipment.” The concept of digitaltwin originated during the period of Apollo program in the United States

Development Period (2015 to present): "Digital twin" has graduallyextended to the whole manufacturing field, and the whole life cycle
process cover design, manufacturing, and service, which is closely
combined with smart manufacturing strategy such as "industry 4.0", andis gradually extended to medical, urban construction and spatialcommunication. The start of this stage is marked by the work of Ríos

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