Dynamic response of a compliant tower in wind and waves

Nonlinear Dynamic Response of a Compliant Tower Under the Effect of Steady and Unsteady Sea States

Volume 3A: Structures, Safety and Reliability ◽

10.1115/omae2017-62449 ◽

2017 ◽

Cited By ~ 1

Author(s):

Konstantinos Chatziioannou ◽

Vanessa Katsardi ◽

Apostolos Koukouselis ◽

Euripidis Mistakidis

Keyword(s):

Structural Analysis ◽

Dynamic Response ◽

Deep Water ◽

Nonlinear Dynamic ◽

Wave Theory ◽

Random Wave ◽

Wave Loading ◽

Nonlinear Dynamic Response ◽

Steady Wave ◽

Compliant Tower

The purpose of this work is to highlight the importance of considering the actual nonlinear dynamic response for the analysis and design of fixed deep water platforms. The paper highlights the necessity of applying dynamic analysis through the comparison with the results obtained by the authors by applying static nonlinear analysis on the structure under examination. The example treated in the context of the present paper is a compliant tower, set-up in deep water. Nonlinearities are considered both for the calculation of the wave loadings and the structural analysis. The wave loading is based on linear random wave theory and comparisons are provided with the steady wave theories, Airy and Stokes 5th. The former solution is based on the most probable shape of a large linear wave on a given sea-state; the auto-correlation function of the underlying spectrum. On the other hand, in the field of structural analysis, two cases are considered for comparison, static analysis and time history dynamic analysis. For both types of analysis, two sub-cases are considered, a case in which geometric nonlinearity and nonlinearities related to the modelling of the soil are considered and a case in which the corresponding linear theories are employed (reference cases). The structural calculations were performed using the well-known structural analysis software SAP2000, which was enhanced by a special programming interface that was developed to calculate the wave loading and to directly apply the generated loads on the structural members. The results show that the consideration of the particle velocities associated with the linear random wave theory in the wave loading lead to significant differences with respect to the steady wave theories in terms of the displacements and stresses of the structure. Moreover, irrespectively of the adopted wave theory, the nonlinear analyses lead to significant discrepancies with respect to the linear ones. This is mainly associated with the nonlinear properties of the soil. Another source of discrepancies between the results of static and dynamic analyses stems from the change of the effective natural frequency of the structure when nonlinearities are considered.

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Quickwave: An Impulse Algorithm to Calculate Preliminary Design Shear and Moment Envelopes for Compliant Towers

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.2827068 ◽

1995 ◽

Vol 117 (2) ◽

pp. 85-90 ◽

Cited By ~ 1

Author(s):

D. G. Morrison

Keyword(s):

Dynamic Response ◽

Closed Form Solution ◽

Form Solution ◽

Steel Grade ◽

Preliminary Design ◽

Wave Load ◽

Simple Method ◽

Compliant Tower ◽

Computer Analyses ◽

Water Depths

A novel, simple method to calculate compliant tower (CT) level shear and moment envelopes for preliminary design has been developed, and verified by comparing with rigorous 3-D tower analyses. The approach relies on a vast experience base to define important features influencing the dynamic response of CTs, and a new closed-form solution for the acceleration (needed to construct design envelopes) of the tower caused by an impulsive-type wave load. The main benefits of the approach are: 1) the designer can iterate and quickly converge on a working preliminary design without resorting to time-consuming computer analyses; 2) the designer can quickly evaluate configurations for different water depths, pile arrangements, payload, steel grade, reserve buoyancy, and well counts.

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Dynamic Response of the Baldpate Compliant Tower Platform to Major Hurricanes in Gulf of Mexico

10.4043/23045-ms ◽

2012 ◽

Cited By ~ 1

Author(s):

Ben C. Chang ◽

Bor-Feng Peng ◽

James Craig Edel ◽

Joe Kallaby

Keyword(s):

Dynamic Response ◽

Gulf Of Mexico ◽

Compliant Tower

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Optimal Cable Configurations for Passive Dynamic Control of Compliant Towers

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.3140691 ◽

1984 ◽

Vol 106 (4) ◽

pp. 311-318 ◽

Cited By ~ 3

Author(s):

J. F. Wilson ◽

G. Orgill

Keyword(s):

Dynamic Response ◽

Optimization Algorithm ◽

Nonlinear Dynamic ◽

Wind Wave ◽

Dynamic Control ◽

Nonlinear Dynamic Model ◽

Human Comfort ◽

Compatible System ◽

Compliant Tower ◽

The Ideal

Whether in storm or normal seas, the ideal offshore cable-stayed compliant tower moves in harmony with the wind and waves. A properly tuned cable configuration is the key to controlled dynamic response. Formulated here are a nonlinear dynamic model involving wind, wave, current, tower, and cable interactions and a cable optimization algorithm. The objective function, the rms tower rotation, is minimized subject to appropriate constraints involving compatible system geometries and loads, as well as bounds on the platform level accelerations needed for human comfort. Tower motion is limited to a plane.

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