Applied Mathematics and Mechanics

, Volume 5, Issue 4, pp 1437–1447 | Cite as

Wave and earthquake effects on axisymmetric offshore structures

  • Michael Isaacson
  • Wu Song-ren
Article
Received:

Abstract

Vertical axisymmetric structures have found a variety of applications in offshore engineering, including oil storage tanks, production platforms and so on. The present paper describes an efficient calculation procedure for determining the interaction of such structures with the surrounding ocean. In particular, numerical calculations are explicated for:

  • - wave forces and runup for a fixed structure,

  • - added-mass and damping coefficients for an oscillating structure,

  • - earthquake loading in terms of base shear and overturning moment,

  • - motions of a floating structure.

The approach used is based on a boundary element method involving an axisymmetric Green's function, and exploits the structure's axisymmetry to provide a highly efficient computational procedure suitable for carrying out on a desk-top computer. Results are presented for surface-piercing conical structures under various loading conditions.

Keywords

Boundary Element Boundary Element Method Storage Tank Computational Procedure Efficient Calculation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notation

A

matrix coefficients, see eq. (2.14)

a

added-mass coefficients; cylinder or sphere radius

B

see eq. (2.13)

b

damping coefficients

C

matrix coefficients, see eq. (2.15)

d

still water depth

F

wave force

f

source strength distribution function

G

Green's function

g

gravitational constant

H

wave height

i

√−1

k

wave number

L

segment length

m

mass matrix coefficients

n

unit normal vector directed outward from body

R

runup

r

radial coordinate

Sb

equilibrium body surface

t

time

z

vertical coordinate measured upwards from still water level

α

see Fig. 1 and Fig. 4

βm

1 form=0.2im form≥1

ξ

z+d

θ

polar coordinate

ζ

amplitude of body motion

ρ

fluid density

ϕ

velocity potential

ω

wave angular frequency

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References

  1. (1).
    Fenton, J. D., Wave forces on vertical bodies of revolution, Journal of Fluid Mechanics, Vol. 85, (1978), 241–255.Google Scholar
  2. (2).
    Isaacson, M. de St. Q., Fixed and floating axisymmetric structures in wave, Journal of the Waterway, Port, Coastal and Ocean Division, ASCE, Vol. 108, No. WW2, (1982), 180–199.Google Scholar
  3. (3).
    Kim, W. D., On a free-floating ship in waves, Journal of Ship Research, Vol. 10, (1966), 182–191, 200.Google Scholar
  4. (4).
    Sarpkaya, T. and M. Isaacson, Mechanics of Wave Forces on Offshore Structures, Van Nostrand, Reinhold, New York, (1981).Google Scholar

Copyright information

© HUST Press 1984

Authors and Affiliations

  • Michael Isaacson
    • 1
  • Wu Song-ren
    • 2
  1. 1.Department of Civil EngineeringUniversity of British ColumbiaVancouverCanada
  2. 2.Chongging Jiaotong InstituteChongqing

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