98
WAVE FORCES ON STRUCTURES
on the whole structure for the three cases: t/X <£ 1, t/X = 0.5, and f/X = 1. If
the net structural load is zéro for any of these cases, explain why the individual
wave loads on the legs can still be significant. Sketch possible leg deformation
patterns for each of these three cases.
4.8
Search the recent literature, such as the annual Proceedings of the Offshore Technology Conférence, to détermine whether diffraction coefficients such
as Ch, Cv, and Co hâve been measured for fixed objects other than vertical, right
circular cylinders.
4.9
For a deep water wave, show that équation (3.16) reduces to w2 — gk.
Then, for a vertical cylinder of diameter D and height h, express the diffraction
coefficients of équations (4.11) through (4.13) in terms of g, D, h, and « only.
4.10 Détermine an efficient analytical or numerical procedure to calculate
wave diffraction loads on a rigid, right circular conical monopod leg of an iceresistant offshore platform. Consult the classical référencés of Hogben (1976)
and also recent literature on the subject.
4.11 The legs of a jackup platform are cylinders of diameter 0.5 m. Each
leg is subjected to a single, simple wave, with each impact occurring separately
and at a different time. For each ratio X/H = 10, 15, and 20, détermine the
range of H for which the drag, inertia, and diffraction dominâtes.
4.12 Based on the data of Sarpkaya and Isaacson (1981), deduce the values
Cm and Cd for cylinders in the flow régime of subcritical Reynolds numbers,
where 10 < Kc < 40. That is, add typical flow coefficients to the left column of
Figure 4.5.
4.13 Calculate the explicit expressions for the Froude-Krylov force Fkz,
and the overturning moment
for the solid box caisson of Figure 4.2.
4.14 With the results of Example Problems 4-3 and ^.5, together with
Problem 4.13, complété the calculations for the three most important wave load
transfer functions on the box caisson: those for the total horizontal load, the
vertical load, and overturning moment. Use complex notation to describe G(w)
in each case; then calculate each value of |G(w)|2 .
REFERENCES
Berge, B., and Penzien, J., Three-Dimensional Stochastic Response of Offshore Towers to Wave Forces, OTC-2050, Proceedings of the Offshore Technology Conférence, 1974.
British Ship Research Association, A Critical Evaluation of Data on Wave Force
Coefficients, Report No. 278.12, August 1976.
Hogben, N., Wave Loads on Structures, Behavior of Offshore Structures (BOSS),
Norwegian Institute of Technology, Oslo, 1976.
gben, N., and Standing, R. G., Expérience in Computing Wave Loads on Large
Bodies, OTC-2189, Proceedings of the Offshore Technology Conférence, 1975.
WAVE FORCES ON STRUCTURES
on the whole structure for the three cases: t/X <£ 1, t/X = 0.5, and f/X = 1. If
the net structural load is zéro for any of these cases, explain why the individual
wave loads on the legs can still be significant. Sketch possible leg deformation
patterns for each of these three cases.
4.8
Search the recent literature, such as the annual Proceedings of the Offshore Technology Conférence, to détermine whether diffraction coefficients such
as Ch, Cv, and Co hâve been measured for fixed objects other than vertical, right
circular cylinders.
4.9
For a deep water wave, show that équation (3.16) reduces to w2 — gk.
Then, for a vertical cylinder of diameter D and height h, express the diffraction
coefficients of équations (4.11) through (4.13) in terms of g, D, h, and « only.
4.10 Détermine an efficient analytical or numerical procedure to calculate
wave diffraction loads on a rigid, right circular conical monopod leg of an iceresistant offshore platform. Consult the classical référencés of Hogben (1976)
and also recent literature on the subject.
4.11 The legs of a jackup platform are cylinders of diameter 0.5 m. Each
leg is subjected to a single, simple wave, with each impact occurring separately
and at a different time. For each ratio X/H = 10, 15, and 20, détermine the
range of H for which the drag, inertia, and diffraction dominâtes.
4.12 Based on the data of Sarpkaya and Isaacson (1981), deduce the values
Cm and Cd for cylinders in the flow régime of subcritical Reynolds numbers,
where 10 < Kc < 40. That is, add typical flow coefficients to the left column of
Figure 4.5.
4.13 Calculate the explicit expressions for the Froude-Krylov force Fkz,
and the overturning moment
for the solid box caisson of Figure 4.2.
4.14 With the results of Example Problems 4-3 and ^.5, together with
Problem 4.13, complété the calculations for the three most important wave load
transfer functions on the box caisson: those for the total horizontal load, the
vertical load, and overturning moment. Use complex notation to describe G(w)
in each case; then calculate each value of |G(w)|2 .
REFERENCES
Berge, B., and Penzien, J., Three-Dimensional Stochastic Response of Offshore Towers to Wave Forces, OTC-2050, Proceedings of the Offshore Technology Conférence, 1974.
British Ship Research Association, A Critical Evaluation of Data on Wave Force
Coefficients, Report No. 278.12, August 1976.
Hogben, N., Wave Loads on Structures, Behavior of Offshore Structures (BOSS),
Norwegian Institute of Technology, Oslo, 1976.
gben, N., and Standing, R. G., Expérience in Computing Wave Loads on Large
Bodies, OTC-2189, Proceedings of the Offshore Technology Conférence, 1975.