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CONTENTS
Volume 16, Number 2, June 2026
 

Abstract
This research investigates seasonal variations in sediments of the swash zones at Alue Naga and Kuala Gigieng, Indonesia, by measuring mean grain size, sorting, skewness, kurtosis, slope of the beach, and height of waves. Sediment samples were collected during May and July 2022 using core sampling to a depth of 15 cm from the swash zones of Alue Naga and Kuala Gigieng. In May, mean grain size (Mz) values ranged from 0.89–1.99 o at Alue Naga and 1.40–2.16 o at Kuala Gigieng, both locations being dominated by medium and fine sands. In July, the sediments had changed to predominantly coarser sediments, the Mz values of both locations changed to 0.73–1.99 o for Alue Naga and 0.71–2.06 o for Kuala Gigieng; however, gravel content increased at both locations to 9.93% and 14.34%, respectively. It was found that the sorting had improved at Alue Naga (o = 0.35–0.88 o) while the sorting was highly variable at Kuala Gigieng (o = 0.08–2.06 o). Skewness was predominantly coarse skewed at both locations, indicating a predominance of strong hydrodynamic forcing at both study locations. Kurtosis values showed a range from very platykurtic (at 0.20 o) and later a very leptokurtic (at 2.43 o). Seasonal increases in wave energy, likely influenced by monsoon weather patterns, impact sediment structure and distribution. Regular observations of sediments in the swash zones provide important information to support coastal management in response to the impacts of natural processes and human activities that affect the coastline.

Key Words
coastal management; grain size; sediment; swash zone

Address
Ichsan Setiawan, Rafwan Hidayat, Syahrul Purnawan: Department of Marine Sciences, Universitas Syiah Kuala, Banda Aceh 23111, Indonesia
Syarifah Meurah Yuni: Department of Mathematics, Universitas Syiah Kuala, Banda Aceh 23111, Indonesia
Makwiyah A. Chaliluddin: Laboratory of Fishing Technology, Universitas Syiah Kuala, Banda Aceh 23111, Indonesia
Said Ali Akbar: Department of Aquaculture, Universitas Syiah Kuala, Banda Aceh 23111, Indonesia

Abstract
Line heating is a popular technique used in the ship building and related structures that involves bending of plates using a heat source, the path of which is determined by the final shape required. Numerical techniques such as Finite Element Analysis (FEA) is popularly used to investigate the various aspects of the process that significantly reduces the time and cost involved with the experimental analyses. Based on the numerical studies, a novel strategy of heating termed here as 'pulse heating strategy' is proposed primarily for thicker plates that is expected to reduce the overall production time. Furthermore, the effect of pulse amplitude in the residual deformation of the plate subjected to line heating as per the novel heating strategy is numerically investigated in the present study.

Key Words
finite element analysis; flame bending; line heating; numerical techniques; ship building; transient thermal analysis

Address
S.L. Arun Kumar, R. Sharma, S.K. Bhattacharyya: Design and Simulation Laboratory, Department of Ocean Engineering, IIT Madras,
Chennai (TN) - 600036, India

Abstract
There have been few analytical research studies to elucidate the effect of a low-permeability soil layer on the suction-induced seepage flow in the sand layer during the installation of suction caissons in multilayered soils. In this study, the influence of silt on penetration into the sand layer during suction caisson installation in multilayered sand and silt was investigated using a classical bearing capacity method. Since sand liquefaction tends to occur during suction installation, the relationship between suction and penetration was revealed in both preliquefaction and postliquefaction. The experimental results so far indicated that the unit shaft and base resistances of piles do not necessarily increase with depth, but instead reach maximum values at a certain critical depth. Thus, the friction reduction factors along the caisson skirt and the bearing capacity reduction factors at the caisson tip were presented for installation with both hardening and softening. Furthermore, an analytical procedure for punching shear failure in the silt layer overlying a sand layer during installation was proposed. For the relationships between suction and penetration during installation in multilayered sand and silt, a comparison between the results obtained from field and centrifuge tests and those predicted by the proposed method was carried out.

Key Words
bearing capacity; centrifuge tests; classical method; installation; sand and silt; suction caisson

Address
Hiroyoshi Hirai: Applied Geotechnical Institute, Inc., 1808, Oizumi, Hokuto, Yamanashi, 409-1502, Japan

Abstract
The global offshore oil and gas industry is facing rising decommissioning costs, which are expected to reach hundreds of billions of dollars. Decommissioning also creates significant environmental concerns. In this context, circular economy principles provide a useful direction. Repurposing decommissioned fixed steel jacket platforms for offshore renewable energy (ORE) systems can be seen as a practical alternative to full removal. This review evaluates the structural and economic feasibility of converting legacy platforms into renewable energy hubs. Findings indicate that reusing existing subsea foundations can reduce capital expenditure by 20–40% and lower the Levelised Cost of Energy. Structurally, many jackets retain substantial residual strength with utilisation ratios (UR) typically below critical thresholds after topside removal. However, transitioning to renewable applications introduces complex engineering challenges, requiring advanced Aero-Hydro-Servo-Elastic (AHSE) modelling to assess dynamic loading effects. Additionally, reliable evaluation of remaining useful life (RUL) must account for corrosion, fatigue degradation, inspection uncertainty and the as-is structural condition of ageing jackets. Beyond structural feasibility, this review highlights that repurposed offshore platforms should preferably support local offshore energy utilisation such as hydrogen or ammonia production, offshore refuelling, CO2 sequestration, enhanced oil recovery and platform self-powering rather than relying solely on long-distance electricity export to shore. The review also emphasises the need for non-destructive testing and sensor-assisted, AI-based structural health monitoring to support safe operation of normally unattended repurposed offshore stations.

Key Words
decommissioning; offshore platforms; offshore renewable energy; repurposing; structural integrity

Address
Joaanne Teoh, Jing-Shuo Leow, Hooi-Siang Kang: Marine Technology Center, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia,
81300 Johor Bahru, Malaysia
Yuanzhe Zhi, Yue Liu: China Construction Harbour and Channel Engineering Bureau Group Co., Ltd., Shanghai 200434, China
Xue Zhao: School of International Education, Zhejiang Polytechnic University of Mechanical and Electrical Engineering,
Hangzhou, Zhejiang, China, 310053, China
Xin Li: School of Ocean and Civil Engineering, State Key Laboratory of Ocean Engineering,
Shanghai Jiao Tong University, Shanghai, 200240, China


Abstract
In this study, we investigate transient responses of a floating bridge due to the sudden failure of a mooring line under seismic excitations. A straight 4,600-m-long discrete-pontoon floating bridge designed for Bjornafjord on West Coast of Norway and moored in a water depth of 300 m is employed. A mid-fidelity time-domain-numericalsimulation coupled dynamics model was built by using a commercial software OrcaFlex. Pre-generated site-specific multi-directional ground motion time-series were imposed at all anchors of mooring lines assuming simultaneous movement. Subsequent dynamic responses of pontoons, structural responses of girders, and fairlead mooring tensions are examined for three different scenarios (i) intact, (ii) 1-line pre-failure (iii) 1-line sudden-failure cases. From the numerical results and pertinent analyses, it has been observed that transient responses of the pontoons and girders in the sudden-failure case can be significant and the resulting dynamic quantities become larger than those of intact and pre-failure cases. In the case of a pre-failed line, the transient effects are absent, and it will lead to underestimation in girder's dynamic bending moments and maximum mooring tensions. The effects of the transient motions become appreciable especially for girder's transverse bending moments and adjacent mooring dynamic tensions. The maximum mooring tension is observed in the sudden-failure scenario at the neighboring lines of the failed line as a result of the transient effects.

Key Words
discrete pontoon; girder bending moment; mooring tension; seabed earthquakes; straight floating bridge; transient response

Address
Ikjae Lee, MooHyun Kim: Department of Ocean Engineering, Texas A&M University, College Station, TX 77843, USA

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