Journal article
Numerical evaluation of long term monopile head behavior for ocean energy converters under sustained low amplitude lateral loading
International journal of civil and structural engineering, Vol.3(4), pp.669-684
2013
Abstract
The study presented in this paper is motivated from the increased interest in recent years to explore use of Ocean Energy Converters (OEC's) to generate electricity from the ocean. Typically OEC's generate electricity from tidal action, wave action, or marine current. A key challenge for OEC's is the need to decrease the initial cost of OEC's where their foundation systems can represent up to about 35% of the initial installation cost. Common OEC foundation systems are monopiles, however they may experience gradual accumulation of pile head deformations under the ocean induced cyclic loading. Under some conditions monopile head deformations could exceed OEC serviceability limits. This design consideration is important since OEC foundation systems are often subjected to more than 108 low amplitude dynamic load cycles during a normal 30 year design life. Experimental research on single model piles installed in sand have shown important gradual accumulation of pile head deformations for some piles subjected to over 104 low amplitude lateral load cycles. This gradual development of pile head deformations is largely related to progressive accumulation of plastic strains in soil zones in the vicinity of the monopile. Analytical methodologies based on conventional p-y curves typically cannot predict the observed accumulation of pile head rotations and displacements. Even 3D dynamic finite element analyses (FEA) may not capture this response for some conventionally used soil constitutive models. This manuscript presents predictions of monopile head deflections under sustained cyclic loading using p-y based methods as well as 3D dynamic FEA. The different numerical predictions are compared to available experimental data. Results from this study show that API p-y curves used for offshore piles do not adequately predict the gradual pile head displacements observed experimentally. Modified p-y curves, developed for pseudo-static cyclic loading, do a better job than the API p-y curves, but still greatly under-predict deformations. In contrast, the 3D FEA were found to capture reasonably well the general observed trends of gradual accumulation of pile head rotation and lateral deformation with increasing constant amplitude lateral load cycles.
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Details
- Title
- Numerical evaluation of long term monopile head behavior for ocean energy converters under sustained low amplitude lateral loading
- Creators
- Deepak PappusettyMiguel A Pando
- Publication Details
- International journal of civil and structural engineering, Vol.3(4), pp.669-684
- Publisher
- Integrated Publishing Association
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Civil, Architectural, and Environmental Engineering
- Identifiers
- 991020575096804721