Seismic Performance of Jacket Type Offshore Platforms Through Incremental Dynamic Analysis

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Behrouz Asgarian ◽  
Azadeh Ajamy
Keyword(s):  
Dynamic Analysis ◽  
Dynamic Behavior ◽  
Earthquake Engineering ◽  
Dynamic Instability ◽  
Ground Motions ◽  
Nonlinear Behavior ◽  
Incremental Dynamic Analysis ◽  
Offshore Platforms ◽  
Strong Ground Motions ◽  
Strong Ground

Fixed offshore platforms in seismic active areas may be subjected to strong ground motions, causing the platform to undergo deformation well into the inelastic range. In this paper, incremental dynamic analysis (IDA) of jacket type offshore platforms subjected to earthquake was performed in order to study the linear and nonlinear dynamic behavior of this type of structures. IDA is a parametric analysis method that has been recently presented to estimate structural performance under seismic loads. By using incremental dynamic analysis of jacket type offshore platforms, the assessment of demand and capacity can be carried out. The method was used to predict nonlinear behavior of three newly designed jacket type offshore platforms subjected to strong ground motions. The engineering demand parameters of the platforms in terms of story drifts and intermediate elevation maximum displacement for different records were compared. This method was used for the performance calculations (immediate occupancy, collapse prevention, and global dynamic instability) needed for performance-based earthquake engineering of the above mentioned platforms. Two different behaviors were observed for the third platform in the X and Y directions. Particular attention has to be paid for the seismic design of this kind of platform. The results of jacket type offshore platforms incremental dynamic analysis shows that the method is a valuable tool for studying dynamic behavior in a nonlinear range of deformation. Because of high uncertainty in the nonlinear behavior of this type of structures, it is recommended to use this method for the assessment and requalification of existing jacket type offshore platforms subjected to earthquake.

A Comparison Between Modal Push-Over and Nonlinear Dynamic Response of Jacket Type Offshore Platforms Subjected to Strong Ground Motions

2008 ◽  
Author(s):  
M. A. Roshandel Tavana ◽  
B. Asgarian
Keyword(s):  
Dynamic Analysis ◽  
Ground Motion ◽  
Earthquake Engineering ◽  
Nonlinear Dynamic ◽  
Strong Ground Motion ◽  
Ground Motions ◽  
Nonlinear Dynamic Analysis ◽  
Offshore Platforms ◽  
Modes Of Vibration ◽  
Strong Ground

Nonlinear dynamic analysis for offshore structures has been a major challenge in marine structures and earthquake engineering. Nonlinear Dynamic Analysis of the structures subjected to strong ground motions is the most reliable prediction method. This method is very complex and expensive. An alternative procedure that has found to be much applicable in recent years is the nonlinear static analysis called push-over analysis method. Many attempts have been made to improve the predictive capabilities of the push-over analysis, particularly by employing adaptive load patterns and accounting for higher modes of vibration effects through modal push-over. In this paper, modal push-over analysis (MPA) of jacket type offshore platforms considering soil-pile-structure interaction subjected to strong ground motion has been studied and the results have been compared with “exact” nonlinear response history analysis (NLRHA). A jacket type offshore platform includes of piles, jacket and deck with different behaviors during strong ground motion. In this paper, three-dimensional model of jacket and pile has been considered using a combination of finite element method (FEM) and beam on nonlinear winkler foundation (BNWF) approach in an integrated model. Both jacket and pile elements have been modeled using fiber sections. The model has been developed using Open System for Earthquake Engineering Simulation (OpenSEES) software. In this paper, nonlinear seismic analysis of a new designed jacket type offshore platform located in Persian Gulf subjected to different levels of earthquake has been performed and the results have been compared with MPA ones. It can be concluded that the error percentage in MPA procedure is negligible when more modes of vibration are participated in the evaluation of the structure behavior.

Incremental Dynamic Analysis Considering Pile-Soil-Structure Interaction for the Jacket Type Offshore Platforms

2008 ◽  
Author(s):  
Behrouz Asgarian ◽  
Alireza Fiouz ◽  
Ali Shakeri Talarposhti
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Response ◽  
Limit State ◽  
Nonlinear Behavior ◽  
Incremental Dynamic Analysis ◽  
Layered Soil ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Structure Interaction ◽  
Soil Deposits

Nonlinear response of piles is the most important source of potentially nonlinear behavior of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviors of the piles. Incremental dynamic analysis is an analysis method that has recently emerged as a promising tool for thoroughly evaluating the seismic performance of structures. It involves subjecting a structural model to a suite of ground motion records, each scaled to several intensities and recording the responses at each level to form IDA curves of response versus intensity. In this paper, jacket and soil-pile system is modeled and the effects of Soil-Pile-Structure Interaction (SPSI) are considered, and the Incremental Dynamic Analysis (IDA) is used to investigate nonlinear behavior of offshore platforms. An attempt is made to introduce a practical BNWF (Beam on Nonlinear Winkler Foundation) model for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. This model was incorporated into a Finite Element program (OpenSees). All the analyses are performed in two directions and the results are compared with each others. A computer program for Nonlinear Earthquake site Response Analyses of layered soil deposits (NERA) is used for analysis nonlinear response of soil layers. Limit state of the jacket is calculated from incremental dynamic analysis of the jacket using fiber elements for the nonlinear modeling of the system.

scholarly journals NZ society for earthquake engineering reconnaissance team to Seattle, USA

2001 ◽  
Vol 34 (4) ◽  
pp. 253-275
Author(s):  
Dick Beetham ◽  
Graeme Beattie ◽  
Barry Earl ◽  
Denzil Duncan
Keyword(s):  
New Zealand ◽  
Emergency Management ◽  
Earthquake Engineering ◽  
Ground Motions ◽  
Tectonic Setting ◽  
Community Response ◽  
Strong Ground Motions ◽  
Surrounding Areas ◽  
Ground Damage ◽  
Strong Ground

Our report describes the observations and assessments of the members of the reconnaissance team which visited Seattle, Tacoma, Olympia and surrounding areas a few days after the magnitude 6.8 Nisqually earthquake struck on 28 February, 2001. The report covers the tectonic setting and geology of the region, the source of the earthquake, its strong ground motions, ground damage - liquefaction and landslides, damage to buildings, bridges, lifelines, emergency management, community response, and lessons for New Zealand.

Bedrock Depth Effect Investigation in Seismic Response of Offshore Platforms Considering Soil-Pile-Structure Interaction

2007 ◽  
Author(s):  
B. Asgarian ◽  
M. A. Roshandel Tavana ◽  
R. H. Soltani
Keyword(s):  
Dynamic Analysis ◽  
Seismic Response ◽  
Ground Motion ◽  
Earthquake Engineering ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Structure Interaction ◽  
Strong Ground

Offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. In seismic design of offshore platforms, it is often necessary to perform a dynamic analysis that accounts for nonlinear soil-pile-structures interaction effects. Nonlinear dynamic analysis for offshore structures has been a major challenge in marine structural and earthquake engineering. In this paper, nonlinear dynamic analysis of jacket type offshore platforms considering soil-pile-structure interaction subjected to strong ground motion have been studied. A jacket type offshore platform is included of piles, jacket and topside with different behaviors in seismic loading. Both jacket and pile elements have been modeled using fiber cross-sections. In this paper, free field ground motion analysis with respect to bedrock excitations has been done using nonlinear stress-strain relations for soil. This model has been developed using Open System for Earthquake Engineering Simulation (OpenSEES) software. In this paper, nonlinear seismic response analysis of an existing sample offshore platform in Persian Gulf subjected to strong ground motions in different bedrock depths has been performed and the results in terms of lateral deflections of platform, soil layers displacement-time history and acceleration response spectra of pile head, top of jacket and deck have been presented.

Estimation of strong ground motions in meizoseismal region of the 1976 Tangshan, China, earthquake

1993 ◽  
Vol 83 (6) ◽  
pp. 1756-1777
Author(s):  
K. Dan ◽  
T. Ishii ◽  
M. Ebihara
Keyword(s):  
Earthquake Engineering ◽  
Ground Motions ◽  
Vertical Acceleration ◽  
Fault Models ◽  
Strong Ground Motions ◽  
Horizontal Acceleration ◽  
China Earthquake ◽  
Property Losses ◽  
Largest Aftershock ◽  
Strong Ground

Abstract The 1976 Tangshan, China, earthquake of MS 7.8 killed 242,000 persons, seriously injured 164,000 persons, and caused direct property losses totaling 8 billion Yuan Ren Min Bi (US $4.3 billion). Few investigations have been performed to estimate the characteristics of the strong ground motions in the meizoseismal region of this earthquake using either seismological or earthquake engineering approaches. In this paper, the observed far-field accelerograms of the mainshock are simulated by using the records of the second largest aftershock of MS 6.9 as Green's functions in order to obtain appropriate fault models for the mainshock. The strong ground motions in the meizoseismal region of the mainshock are then estimated by using these fault models and the records of several aftershocks with a magnitude of about 5 which were observed at temporary stations in the damaged area. The results indicate that large horizontal acceleration responses over 1000 cm/sec2 and vertical acceleration responses over 2000 cm/sec2 acted on the structures with natural periods shorter than 0.1 sec in the wide meizoseismal region having a length of 90 km.

Nonlinear Behavior of Single Piles in Jacket Type Offshore Platforms Using Incremental Dynamic Analysis

2008 ◽  
Author(s):  
Behrouz Asgarian ◽  
Mohammad Amin Assareh ◽  
Pejman Alanjari
Keyword(s):  
Dynamic Analysis ◽  
Site Response ◽  
Free Field ◽  
Nonlinear Behavior ◽  
Incremental Dynamic Analysis ◽  
Offshore Platforms ◽  
Limit States ◽  
Intensity Measures ◽  
Oil Exploitation ◽  
Single Piles

Offshore platforms are some of those structures which are built to withstand environmental and accidental loads during oil exploitation operation. One of the most usual types of these platforms is the Jacket Type Offshore Platform (JTOP) which can be divided into three important parts, which are Deck, Jacket, and piles. In order to increase the safety, particular attention should be paid to earthquake excitations which are directly applied to the piles of these structures. Nonlinearity in piles and buckling of the struts are important issues which have to be considered by the designers of offshore platforms. Incremental Dynamic Analysis (IDA) is a powerful tool to assess the capacity of a structure upon seismic loads. In this paper incremental dynamic analysis has been implemented on single piles considering soil-pile interactions and free field site response. The use of nonlinear materials and lateral load resisting elements in the incremental dynamic analysis done in this paper has made it possible to get promising insights for incorporation of appropriate limit states and applications of performance based engineering. Special Engineering Demand Parameters (EDP) and Intensity Measures (IM) have been introduced for the single pile dynamic analysis in jacket type offshore platforms.

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