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VERY LARGE FLOATING STRUCTURES:
APPLICATIONS, ANALYSIS AND DESIGN
E. Watanabe1, C.M. Wang2, T. Utsunomiya1 and T. Moan3
1Department of Civil and Earth Resources Engineering, Kyoto University
Kyoto 606-8501, Japan
2Centre for Offshore Research and Engineering, Department of Civil Engineering
National University of Singapore, Kent Ridge 119260, Singapore
3Centre for Ships and Ocean Structures, the Norwegian University of Science and
Technology, NO-7491, Trondheim, Norway
Abstract – In this report, structural and civil engineers are introduced to the world of very
large floating structures (VLFS) that have been gradually appearing in the waters off
developed coastal cities (and countries with coastlines). Their presence is largely due to a
severe shortage of land and the sky-rocketing land costs in recent times. After providing a
description of a VLFS and highlighting its advantages (under certain conditions) over the
traditional land reclamation in creating space from the sea, the authors bring to attention the
early, the present and future applications of VLFS. The input design data, hydroelastic
analysis and design considerations for very large floating structures are discussed, albeit in
the most basic forms.
1. INTRODUCTION
As population and urban development expand in land-scare island countries (or countries
with long coastlines), city planners and engineers resort to land reclamation to ease the
pressure on existing heavily-used land and underground spaces. Using fill materials from
seabed, hills, deep underground excavations, and even construction debris, engineers are
able to create relatively vast and valuable land from the sea. Countries such as the
Netherlands, Singapore and Japan, have expanded their land areas significantly through
aggressive land reclamation programmes. Probably the first large scale and systematic land
reclamation work was carried out by Kiyomori Taira off Kobe’s coastal waters in the 12th
Century. However, land reclamation has its limitation. It is suitable when the water depth is
shallow (less than 20 m). When the water depth is large and the seabed is extremely soft,
land reclamation is no longer cost effective or even feasible. Moreover, land reclamation
destroys the marine habitat and may even lead to the disturbance of toxic sediments. When
faced with these natural conditions and environmental consequences, very large floating
structures may offer an attractive alternative solution for birthing land from the sea.
There are basically two types of very large floating structures (VLFSs), namely the semisubmersible-
type and the pontoon-type. Semi-submersible type floating structures are raised
above the sea level using column tubes or ballast structural elements to minimize the effects
of waves while maintaining a constant buoyancy force. Thus they can reduce the waveinduced
motions and are therefore suitably deployed in high seas with large waves. Floating
oil drilling...

source: http://www.eng.nus.edu.sg/core/Report%20200402.pdf