Summary
After a brief review of the main problems and the most common analysis methods for offshore structures, a method of analysis for offshore towers submerged in water and subjected to strong earthquake motions is proposed. Nonlinear drag effects as well as random non-stationary seismic excitations are considered by means of a linearization technique based on a particular step-by-step procedure. Using a discrete lumped-mass model, the standard deviations of nodal displacements and velocities are evaluated. The probability of not exceeding a defined threshold of nodal displacements is also computed.
Keywords
Mechanical Engineer Civil Engineer Tempo Strong Earthquake Nodal DisplacementSommario
Dopo una breve panoramica sui problemi e le soluzioni esistenti per le strutture offshore, si valuta la risposta di una struttura a torre immersa in acqua sotto eccitazioni sismiche di tipo non stazionario. Si prendono in considerazione le non linearità insite in tali sistemi utilizzando tecniche di linearizzazione equivalente mediante un procedimento di calcolo al passo nel dominio dei tempi.
Si valutano le deviazioni standard degli spostamenti e delle velocità nodali, per uno schema a masse concentrate ai vari livelli ed operati alcuni confronti attraverso valutazioni numeriche, si calcolano le probabilità di non eccedenza rispetto a prestabiliti valori di soglia.
Preview
Unable to display preview. Download preview PDF.
References
- [1]Marshall P.W.,Fixed Pile-Supported Steel Offshore Platforms, Journal of the Structural Division, Vol. 107, No. ST6, ASCE, June 1981.Google Scholar
- [2]Vugts J.H.,Hayes D.J.,Dynamic analysis of fixed offshore structures: a review of some basic aspects of the problem, Eng. Struct., Vol. 1, April 1979.Google Scholar
- [3]Anagnostopoulos S.A.,Dynamic response of offshore platforms to extreme waves including fluid-structure interaction, Eng. Struct., Vol. 4, July, 1982.Google Scholar
- [4]Fish P.R.,Dean R.B.,Heaf N.J.,Fluid-structure interaction in Morison's equation for the design of offshore structures, Eng. Struct., Vol. 2, Jan. 1980.Google Scholar
- [5]Tajimi H.,A statistical method of determining the maximum response of a building structure during an earthquake, Proceeding of the II World Conference on Earth. Eng., Tokio, 1960, pp. 781–797.Google Scholar
- [6]Malhotra A.K.,Penzien J.,Nondeterministic analysis of an offshore structures, Journ. of the Eng. Mech. Div., EM 6, Dec. 1970.Google Scholar
- [7]Spidsöe N.,Sigbjörnsson R.,On the reliability of standard wave spectra in structural response analysis. Eng. Struct., Vol. 2, April, 1980.Google Scholar
- [8]Cerami A.,Analisi aleatoria non stazionaria di strutture offshore, VI Congresso AIMETA, Sez. V, 23, Genova, Ott. 1982.Google Scholar
- [9]Foster E.T.,Model for nonlinear dynamics of offshore towers, Jour., of the Eng. Mech. Div., EM 1, Feb., 1970.Google Scholar
- [10]Singh R.P.,Dynamic behaviour of offshore jacket platform, International Journal of Structures, No. 32 IJS, Vol. 3, No. 2, April 1983.Google Scholar
- [11]Api Recomended Practice for Planning Designing, and Constructing Fixed offshore Platforms, American Petroleum Institute Washington, D.C. Thirteenth Edn., Jan. 1982.Google Scholar
- [12]Tanaka, Y., Hamamoto T., Konno K.,Earthquake response analysis of shell-type fixed offshore towers by matrix progression method, Proceeding of VII World Conf. on Earth. Eng. Istanbul, Vol. 5, 1980, pp. 245–252.Google Scholar
- [13]Clough W.,Effects of earthquake on underwater structures, Proceeding of II World Conf. on Earth. Eng., Tokio 1960, pp. 815–831.Google Scholar
- [14]Kaul M.K.,Penzien J.,Stochastie seismic analysis of yielding offshore towers, Jour. of the Engg. Mech. Div. EM 5, V. 6, Oct. 1974.Google Scholar
- [15]Di Paola M.,Ioppolo M.,Lanza M.,Nonstationary non white seismic input and response, 7 Symp. on Earth. Eng., Roorkee, (India), Vol. I, 1982.Google Scholar
- [16]Di Paola M.,Ioppolo M.,Muscolino G.,Earthquake response analysis of multidegree of freedom systems, to appear in Eng. Struct.Google Scholar