scholarly journals Ultimate Strength of Fixed Offshore Platforms Subjected to Near-Fault Earthquake Ground Vibration

2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Hesam Sharifian ◽  
Khosro Bargi ◽  
Mohamad Zarrin
Keyword(s):  
Ultimate Strength ◽  
Pile Foundation ◽  
Fragility Curves ◽  
Nonlinear Behavior ◽  
Ground Vibration ◽  
Offshore Platforms ◽  
Near Fault ◽  
Key Factor ◽  
The Persian Gulf ◽  
Proportional Distribution

The pile foundation nonlinearity and its influence on the ultimate capacity of fixed platforms have not comprehensively been covered by previous researchers. In this study, the seismic behavior and capacity of a newly designed and installed Jacket Type Offshore Platform (JTOP) located in the Persian Gulf is investigated by conducting Incremental Dynamic Analysis (IDA) using a suit of near-fault ground motions. Additionally, two modified models of the original platform are created by slightly increasing the diameter of the pile foundation and also softening the jacket part for evaluating the importance of the pile foundation and seismic soil-pile structure interaction on the dynamic characteristics of the JTOPs. Valuable discussions are provided to explore various aspects of the dynamic behavior of JTOPs by presenting individual and multirecords IDA curves using effective Engineering Demand Parameters (EDPs). Comparing the results of the three platform collapse fragility curves, it is concluded that the pile foundation plays a very important role in the dynamic response of offshore platforms and can drastically alter the ultimate strength of the platform together with its collapse capacity. It is observed that the proportional distribution of nonlinear behavior in the pile foundation and jacket part is the key factor in the enhancement of the ultimate strength of JTOPs. On the basis of the results derived from this paper, it is recommended that some basic requirements should be developed in order to ensure that the coupling ductility of pile foundation and jacket part is optimized during the design process. Furthermore, according to the findings from this study, some practice recommendations are presented to be devised within the design step.

From detente to containment: the emergence of Iran's new Saudi strategy

2021 ◽  
Author(s):  
Hassan Ahmadian ◽  
Payam Mohseni
Keyword(s):  
Decision Making ◽  
Saudi Arabia ◽  
Middle East ◽  
Strategic Decision ◽  
Key Factors ◽  
Peace And Conflict ◽  
Key Factor ◽  
Decision Making Factors ◽  
Containment Strategy ◽  
The Persian Gulf

Abstract Iran's strategy with respect to Saudi Arabia is a key factor in the complex balance of power of the Middle East as the Iranian–Saudi rivalry impacts the dynamics of peace and conflict across the region from Yemen to Syria, Lebanon, Iraq and Bahrain. What is Iranian strategic thinking on Saudi Arabia? And what have been the key factors driving the evolution of Iranian strategy towards the Kingdom? In what marks a substantive shift from its previous detente policy, we argue that Tehran has developed a new containment strategy in response to the perceived threat posed by an increasingly prox-active Saudi Arabia in the post-Arab Spring period. Incorporating rich fieldwork and interviews in the Middle East, this article delineates the theoretical contours of Iranian containment and contextualizes it within the framework of the Persian Gulf security architecture, demonstrating how rational geopolitical decision-making factors based on a containment strategy, rather than the primacy of sectarianism or domestic political orientations, shape Iran's Saudi strategy. Accordingly, the article traces Iranian strategic decision-making towards the Kingdom since the Islamic Revolution of 1979 and examines three cases of Iran's current use of containment against Saudi Arabia in Syria, Yemen and Qatar.

The Experiment Study on Parameters of Duncan-Chang Model for Silt Based on Different Water Content

2014 ◽  
Vol 665 ◽  
pp. 213-216
Author(s):  
Xun Zhong Zhang ◽  
Ru Heng Wang ◽  
Bin Jia
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Triaxial Test ◽  
Nonlinear Behavior ◽  
Optimum Moisture Content ◽  
Experiment Study ◽  
Optimal State ◽  
Test Parameters ◽  
Key Factor ◽  
Chang Model

Duncan-Chang model can reflect soil’s nonlinear behavior much better, its’ concept is clear and easy to understand. In this paper, through triaxial test, parameters of Duncan-Chang model were gained by analyzing characteristics of Silt’s stress-strain Cures. A key factor, effecting silt’s stability, is the moisture content; there is a optimum moisture content in silt, in this moisture content, silt’s parameters of Duncan-Chang model can reach to the optimal state.

Rehabilitation of jacket offshore platforms using friction damper device and buckling restrained braces under extreme loads

2017 ◽  
Vol 233 (1) ◽  
pp. 209-217
Author(s):  
Mohammad Reza Tabeshpour ◽  
Younes Komachi
Keyword(s):  
High Efficiency ◽  
Point Of View ◽  
Offshore Platforms ◽  
Friction Damper ◽  
Economic Point ◽  
Extreme Loads ◽  
Buckling Restrained Braces ◽  
The Persian Gulf ◽  
Near Fault Earthquakes ◽  
Far Fault

Some existing platforms may have some problems with probable extreme future loads such as earthquake. From economic point of view, it is preferable to retrofit and continue using of existing jackets in many cases, in comparison to a new installation. Two efficient rehabilitation methods of friction damper device and buckling restrained braces are presented and investigated numerically for seismic loads from far-fault and near-fault earthquakes. As an example, an existing four-leg service platform placed in the Persian Gulf (Ressalat) is considered and the results are presented. Because of low redundancy in jacket platforms (after buckling of compression members), it is important to investigate the effect of friction damper device on the structural behavior. Buckling restrained braces solves the law redundancy because of no buckling and no decrease in strength. The results show the high efficiency of both methods in reducing structural responses and increasing seismic performance level. Such studies are very useful for many existing jacket platforms that their lifetime is to be extended.

Determination of Required Reserved Strength Ratio in Ultimate Strength Limit for Assessment of Existing Offshore Platforms in the Persian Gulf

2008 ◽  
Author(s):  
M. M. Amiri ◽  
B. Asgarian
Keyword(s):  
Persian Gulf ◽  
Statistical Data ◽  
Oil And Gas Industry ◽  
Offshore Structures ◽  
Wind Loading ◽  
Offshore Platforms ◽  
Strength Ratio ◽  
Effective Parameters ◽  
Original Design ◽  
The Persian Gulf

The offshore infrastructures are used by the oil and gas industry to meet over twenty percent of the world’s demand for the hydrocarbon productions. Offshore platforms are subjected to various environmental, operational and accidental loads. Environmental loads include wave, current, wind earthquake and ice loads. Considering the reuse of old platforms, design criteria for offshore structures have changed significantly over the post decades. Most of existing structures have been designed based on the previous codes. Many of these structures are now called upon for extended service beyond their original design life. This makes the need to assess the platforms under different environmental conditions such as wave, current and wind loading. Since the proposed amounts of Reserve Strength Ratio (RSR) in the guidelines are for the special geographical zones (i.e. Gulf of Mexico and other parts of US), and also since the methodologies used for estimation of RSR have not been determined explicitly, this study aims to explain more the effective parameters for the assessment of existing offshore platforms. Because the calculation of these parameters is based on statistical data for specific regions, to achieve the RSR ratio related to the Persian Gulf, we utilize the environmental statistical data for this region. And consequently a relevant RSR is proposed. Ultimately, the reserved strength of three sample platforms located in this zone will be assessed according to proposed criterion.

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 Mechanism of Localized Corrosion of Steel Pipe Pile Foundation for Offshore Wind Turbines and Corrosive Action

2016 ◽  
Vol 10 (1) ◽  
pp. 685-694
Author(s):  
Kui Wang ◽  
Zhanqiang Li ◽  
Mingjie Zhao
Keyword(s):  
Wind Turbine ◽  
Ultimate Strength ◽  
Pile Foundation ◽  
Local Corrosion ◽  
Steel Pipe ◽  
Corrosion Mechanism ◽  
General Corrosion ◽  
Splash Zone ◽  
Pipe Pile ◽  
Steel Pipe Pile

The wind turbine foundation serves as a permanent construction in the harsh marine corrosive environment, its anti-corrosion design is essential to the safe use of the wind turbine structure. At present, there is a significant controversy over the local corrosion mechanism (such as pitting corrosion, and crevice corrosion) and its diffusion mechanism in the academic circle. In the paper, the Faraday electrochemistry formula was used to compute the local corrosion degree of the steel pipe pile for the wind turbine and obtain the general corrosion equivalent. The local corrosion effect of the offshore steel pipe pile for the wind turbine was converted into homogeneous corrosion thickness loss of certain length, and then the ultimate strength of the offshore steel pipe pile foundation for the wind turbine was analyzed under the conditions of local corrosion. The result indicates that the maximum ultimate strength reductionof the steel pipe pile for the wind turbine induced by the local corrosion in the splash zone is 80.8% of the non-corrosive ultimate strength. The maximum ultimate strength reduction of the steel pipe pile for the wind turbine induced by the local corrosion in the continuous immersion zone is 63% of the non-corrosive ultimate strength. Once the local corrosion rate in the splash zone exceeds 10%, the ultimate strength of the steel pipe pile for the wind turbine will exhibit a negative exponential decrease. The local corrosion in the continuous immersion zone has a huge effect on its ultimate strength. There are no significant signs of the structural strength loss. The areas prone to local corrosion should be prioritized in anti-corrosion design of the steel pipe pile for the wind turbine.

Dimensionless fragility curves for rocking response to near-fault excitations

2015 ◽  
Vol 44 (12) ◽  
pp. 2015-2033 ◽  
Author(s):  
Elias G. Dimitrakopoulos ◽  
Themelina S. Paraskeva
Keyword(s):  
Fragility Curves ◽  
Near Fault ◽  
Rocking Response

Nonlinear Analysis of Jacket-Type Offshore Platforms Using Fiber Elements

2006 ◽  
Vol 128 (3) ◽  
pp. 224-232 ◽  
Author(s):  
B. Asgarian ◽  
A. A. Aghakouchak ◽  
R. G. Bea
Keyword(s):  
Lateral Displacement ◽  
Nonlinear Behavior ◽  
Offshore Structures ◽  
Buckling Load ◽  
Hysteretic Behavior ◽  
Analytical Models ◽  
Offshore Platforms ◽  
Nonlinear Program ◽  
Post Buckling ◽  
Strength And Stiffness

A nonlinear fiber element for analysis of jacket type offshore structures is formulated and implemented in the nonlinear program DRAIN-3DX. This element can be used for modeling the nonlinear behavior of both strut and portal members. The element predicts buckling load and post buckling behavior of strut members accurately. It also produces fairly accurate results for yield load and post yield behavior of portal members. This element is verified using the experimental data for individual strut and portal members subjected to cyclic displacements. The element is then used to predict nonlinear behavior of two tested X-braced jackets made of tubular members under cyclic lateral displacement. The results are in good agreement with experiments and the results of other analytical models in terms of frame hysteretic behavior, energy dissipation, buckling load, load-deformation curve, strength and stiffness degradation.

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