Non Linear Seismic Pile Soil Structure Interaction Analysis of Piles in Offshore Platforms

2004 ◽  
Author(s):  
Mehrdad Kimiaei ◽  
Mohsen Ali Shayanfar ◽  
M. Hesham El Naggar ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Soil Structure ◽  
Seismic Analysis ◽  
Interaction Analysis ◽  
Site Response ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Model Parameters ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Structure Interaction

Pile supported offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. It is often required to perform nonlinear seismic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviours of the piles. In this study a BNWF (Beam on Nonlinear Winkler Foundation) model is incorporated into a finite element program (ANSYS) and it is used to compute the lateral response of piles subjected to seismic loading. The soil stiffness is established using the P-Y curve. The results of equivalent linear earthquake free field ground motion analyses are used as the input excitations at support nodes of the model. The components and advantages of this practical ANSYS model in seismic pile soil structure interaction analyses are discussed and addressed in detail. Computed responses compared well with the experimental test results. Sensitivity of the results to model parameters and site response calculations are evaluated.

Generalized dynamic Winkler model for nonlinear soil–structure interaction analysis

2008 ◽  
Vol 45 (4) ◽  
pp. 560-573 ◽  
Author(s):  
Nii Allotey ◽  
M. Hesham El Naggar
Keyword(s):  
Soil Structure ◽  
Interaction Analysis ◽  
Soil Structure Interaction ◽  
Winkler Foundation ◽  
Deep Foundations ◽  
Structure Interaction ◽  
Design Engineers ◽  
Winkler Model ◽  
Centrifuge Tests ◽  
Cyclic Degradation

The beam on nonlinear Winkler foundation (BNWF) model is widely used in soil–structure interaction (SSI) analysis owing to its relative simplicity. This paper focuses on the development of a versatile dynamic BNWF model for the analysis of shallow and deep foundations. The model is developed as a stand-alone module to be incorporated in commercial nonlinear structural analysis software. The features of the model discussed are the loading and unloading rules, slack zone development, the modeling of cyclic degradation and radiation damping. The model is shown to be capable of representing various response features observed in SSI experiments. In addition, the predictions of the model for centrifuge tests of piles in weakening and partially weakening soil are shown to be in good agreement with the experimental results. This agreement demonstrates the potential of the model as a useful tool for design engineers involved in seismic design, especially performance-based design.

Nonlinear Seismic Soil-Pile-Structure Interaction Analysis of Fixed Offshore Platforms

2009 ◽  
Author(s):  
Ehssan Zargar ◽  
Ali Akbar Aghakouchak ◽  
Maziar Gholami
Keyword(s):  
Seismic Analysis ◽  
Interaction Analysis ◽  
Site Response ◽  
Geometrical Nonlinearity ◽  
Radiation Damping ◽  
Response Analysis ◽  
Offshore Platforms ◽  
Soil Layers ◽  
Structure Interaction ◽  
Nonlinear Site Response

A nonlinear seismic soil-pile-structure interaction (SSPSI) analysis of fixed offshore platforms constructed on pile foundations including both vertical and battered piles is presented. The analysis is carried out in time domain and the effects of soil nonlinearity, discontinuity at pile soil interfaces, energy dissipation through soil radiation damping, formation of soil layers on bed rock, structural material nonlinearity and geometrical nonlinearity are considered. A combination of FEM approach and BNWF approach is used in modeling pile (substructure), platform structure (superstructure) and soil media. Gapping in clay is modeled by a special connector configuration. To find out the ground motion of soil layers caused by earthquake excitations at bed rock, a nonlinear site response analysis is performed. The effects of soil-pile-structure interaction on nonlinear seismic analysis of offshore platforms are discussed. A comparison of SSPSI model and pile stub modeling is investigated and it is generally concluded that considering soil-pile-structure interaction causes higher deflections and lower stresses in the platform elements due to soil flexibility, nonlinearity and radiation damping and leads to a more feasible and realistic platform design. The sequence of generation of plastic zones in the structure and their distribution are also investigated. Results show that this nonlinear behavior is started at brace elements and then propagated to leg elements as earthquake last.

scholarly journals Critical Soil-Structure Interaction Analysis Considerations for Seismic Qualification of Safety Equipment

2004 ◽  
Author(s):  
Quazi A. Hossain
Keyword(s):  
Soil Structure ◽  
Seismic Analysis ◽  
Interaction Analysis ◽  
Soil Structure Interaction ◽  
Building Structure ◽  
Safety Equipment ◽  
Foundation Soil ◽  
Structure Interaction ◽  
Inappropriate Treatment ◽  
Analysis Models

While developing seismic analysis models for buildings that support safety-related equipment, a number of issues should be considered to ensure that the input motions for performing seismic qualification of safety-related equipment are properly defined. These considerations are listed and discussed here with special attention to the effect and importance of the interaction among the foundation soil, the building structure, the equipment anchors, and the equipment structure. Typical industry practices are critically examined to assess their adequacy for determining the input motions for equipment seismic qualification. The features that are considered essential in a soil-structure interaction (SSI) model are described. Also, the effects of inappropriate treatment or representation of these features are discussed.

State-of-the-Art Techniques for Seismic Soil-Structure Interaction Analysis of Steel Gravity Structures

2014 ◽  
Author(s):  
Frederick Tajirian ◽  
Mansour Tabatabaie ◽  
Basilio Sumodobila ◽  
Stephen Paulson ◽  
Bill Davies
Keyword(s):  
Soil Structure ◽  
State Of The Art ◽  
Interaction Analysis ◽  
Layered Soil ◽  
Soil Structure Interaction ◽  
Soil System ◽  
Cyclonic Storm ◽  
Structure Interaction ◽  
Analysis Methods ◽  
Moderate Seismicity

The design of steel jacket fixed offshore structures in zones of moderate seismicity is typically governed by Metocean loads. In contrast the steel gravity structure (SGS) presented in this paper, is a heavy and stiff structure. The large mass results in foundation forces from seismic events that may exceed those created by extreme cyclonic storm events. When computing the earthquake response of such structures it is essential to account for soil-structure interaction (SSI) effects. Seismic SSI analysis of the SGS platform was performed using state-of-the-art SSI software, which analyzed a detailed three-dimensional model of the SGS supported on layered soil system. The results of this analysis were then compared with those using industry standard impedance methods whereby the layered soil is replaced by equivalent foundation springs (K) and damping (C). Differences in calculated results resulting from the different ways by which K and C are implemented in different software are presented. The base shear, overturning moment, critical member forces and maximum accelerations were compared for each of the analysis methods. SSI resulted in significant reduction in seismic demands. While it was possible to get reasonable alignment using the different standard industry analysis methods, this was only possible after calibrating the KC foundation model with software that rigorously implements SSI effects. Lessons learned and recommendations for the various methods of analysis are summarized in the paper.

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