Elastic-Plastic Analysis of the Interaction between Ice and Offshore Structures

2009 ◽  
Vol 417-418 ◽  
pp. 897-900
Author(s):  
Tao Yu ◽  
Wei Yang ◽  
Li Qiang Tang
Keyword(s):  
Mechanical Properties ◽  
Constitutive Equation ◽  
Stress Field ◽  
Offshore Structures ◽  
Offshore Platforms ◽  
Pressure Sensitivity ◽  
Strength Ratio ◽  
Structure Interaction ◽  
Plastic Analysis ◽  
Distribution Of Stress

In this paper, the mechanical properties of ice, which are affected by the existence of cavities and the different tensile-compression strength ratio, are analyzed in micromechanics view. Then the constitutive equation is established, and the distribution of stress field caused by the ice-structure interaction is constructed with the constitutive equation. Finally, the ultimate bearing capacity of ice is also discussed with different values of pressure sensitivity parameter and the tension-compression ratio. Thus, this paper provides the theoretical reference for offshore platforms design.

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.

Collapse comparison of offshore platforms before and after fire using plastic analysis and genetic algorithm

2020 ◽  
Vol 11 (3) ◽  
pp. 325-345
Author(s):  
Mohammad Mehdi Pouria ◽  
Abbas Akbarpour ◽  
Hassan Ahmadi ◽  
Mohammad Reza Tavassoli ◽  
Amir Saedi Daryan
Keyword(s):  
Genetic Algorithm ◽  
Failure Modes ◽  
Offshore Structures ◽  
Load Factor ◽  
Offshore Platforms ◽  
Content Type ◽  
Collapse Mode ◽  
Plastic Analysis ◽  
Before And After ◽  
Comparison Of The Results

Purpose Offshore structures are among the structures exposed to fire more often. Most of these structures are likely to be associated with flammable materials. In this research, some of the structures constructed on top of marine decks have been studied. Design/methodology/approach For this purpose, the upper-bound theory of plastic analysis has been used to investigate its collapse behavior. In this way, genetic algorithm has been used for application of the combination of elementary mechanisms in the classic plastic analysis problem. Findings The studied structures are optimized by plastic analysis theory before and after the fire and their failure modes are compared with each other. The comparison of the results indicates significant changes in the load factor value, as well as the critical collapse mode of the structure before and after the fire. Originality/value Results indicate that the combination of plastic analysis and a genetic algorithm can predict the collapse mode of the structure before and after the fire accurately.

A method of technical diagnostics for offshore structures

1994 ◽  
Vol 16 (2) ◽  
pp. 43-48
Author(s):  
Do Son
Keyword(s):  
Diagnostic Method ◽  
Joint Venture ◽  
Oil And Gas ◽  
Residual Life ◽  
Life Time ◽  
Offshore Structures ◽  
Technical Diagnostics ◽  
Offshore Platforms ◽  
South Vietnam ◽  
Local Destruction

This paper describes the results of measurements and analysis of the parameters, characterizing technical state of offshore platforms in Vietnam Sea. Based on decreasing in time material characteristics because of corrosion and local destruction assessment on residual life time of platforms is given and variants for its repair are recommended. The results allowed to confirm advantage of proposed technical diagnostic method in comparison with others and have been used for oil and gas platform of Joint Venture "Vietsovpetro" in South Vietnam.

Parameter Sensitivity in Numerical Modelling of Ice-Structure Interaction With Cohesive Element Method

2016 ◽  
Author(s):  
Dianshi Feng ◽  
Sze Dai Pang ◽  
Jin Zhang
Keyword(s):  
Element Model ◽  
Offshore Structures ◽  
Parameter Sensitivity ◽  
The Arctic ◽  
Cohesive Element ◽  
Structure Interaction ◽  
Marine Structure ◽  
Ice Loads ◽  
The Stability ◽  
Element Method

The increasing marine activities in the Arctic has resulted in a growing demand for reliable structural designs in this region. Ice loads are a major concern to the designer of a marine structure in the arctic, and are often the principal factor that governs the structural design [Palmer and Croasdale, 2013]. With the rapid advancement in computational power, numerical method is becoming a useful tool for design of offshore structures subjected to ice actions. Cohesive element method (CEM), a method which has been widely utilized to simulate fracture in various materials ranging from metals to ceramics and composites as well as bi-material systems, has been recently applied to predict ice-structure interactions. Although it shows promising future for further applications, there are also some challenging issues like high mesh dependency, large variation in cohesive properties etc., yet to be resolved. In this study, a 3D finite element model with the use of CEM was developed in LS-DYNA for simulating ice-structure interaction. The stability of the model was investigated and a parameter sensitivity analysis was carried out for a better understanding of how each material parameter affects the simulation results.

Damage Analysis of Concrete Subjected to Freeze-Thaw Cycles and Chloride Ion Erosion

2011 ◽  
Vol 488-489 ◽  
pp. 464-467
Author(s):  
Ji Ze Mao ◽  
Zhi Yuan Zhang ◽  
Zong Min Liu ◽  
Chao Sun
Keyword(s):  
Constitutive Equation ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Chloride Ion ◽  
Offshore Structures ◽  
Damage Evolution Equation ◽  
Freeze Thaw ◽  
Concrete Materials ◽  
Ion Erosion

With the development of damage mechanics, many researchers have used it to analyze the constitutive equation of concrete. Since the special environment in the cold marine regions, the offshore structures are common to subject to the comprehensive effects of freeze-thaw action and chloride erosion. This might cause concrete materials degradation and reduce the mechanical performance of concrete seriously. In this paper, based on the analysis and mechanical experiments of concrete materials under the comprehensive effects of freeze-thaw action and chloride ion erosion, the damage evolution equation of concrete elastic modulus along with the freeze-thaw cycles and chloride ion contents was established. The effects of chloride ion were investigated during the process of concrete degradation. According to the damage evolution equation, a new constitutive equation of concrete under freeze-thaw action and chloride erosion was established. And then, by means of the element simulation analysis of concrete beams when subjected to the comprehensive actions, the feasibility and applicability of the equation was examined and discussed. In this equation, both the freeze-thaw action and chloride ion erosion were considered together. It will be more suitable for analyzing the durability of concrete structures in the real cold marine regions. It will also provide some references for concrete constitutive theory.

FLAC3D Simulation for Dynamic Response of the Western Slope in Buzhaoba under Explosion

2013 ◽  
Vol 275-277 ◽  
pp. 1393-1397 ◽  
Author(s):  
Jian Qiang Xiao ◽  
Long Fa Luan ◽  
Jian Guo Wang
Keyword(s):  
Stress Field ◽  
Dynamic Response ◽  
Compressive Stress ◽  
Particle Velocity ◽  
The Self ◽  
Western Slope ◽  
Stress Increase ◽  
Amplification Effect ◽  
Distribution Of Stress ◽  
Response Rule

To study the dynamic response rule of the western slope in Buzhaoba under explosion, a vibrational wave was imposed on the slope. The FLAC3D program was utilized to simulate the rule. The distribution of stress field and the response of velocity were analyzed after blasting. The simulation result shows that the compressive stress increase step by step with the increase of the depth of slope, and as the elevation increases, the particle velocity appears an amplification effect, and the slope is mainly affected by the self-weight stress, and the blasting has little effect on the slope.

A Three-Dimensional Model for Ice Rubble Pile-Ice Sheet-Conical Structure Interaction at the Piers of Confederation Bridge, Canada

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Chee K. Wong ◽  
Thomas G. Brown
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Offshore Structures ◽  
Flexural Behavior ◽  
Small Scale ◽  
Structure Interaction ◽  
Flexural Failure ◽  
Modes Of Failure ◽  
Conical Structure ◽  
Rubble Pile

Offshore structures constructed in waters where ice cover is prevalent for several months a year are subjected to ice loading. Some of these structures are conical or sloped-faced in shape, where flexural failure becomes the dominant mode of failure for the ice sheet. The flexural failure mode reduces the magnitude of ice-structure interaction loads in comparison to other modes of failure. Various researchers have devised flexural failure models for ice-conical structure interactions. Each model shares the same principle of the ice sheet being modeled as a beam on an elastic foundation, but each model has different limitations in precisely simulating the interaction. Some models do not incorporate the ice rubble pile, while other models make oversimplified assumptions for three-dimensional behavior. The proposed three-dimensional (3D) model aims to reduce some of these limitations with the following features: (1) modeling the geometry of the ice rubble pile around the conical pier using the results of small-scale tests, (2) modeling the loads exerted by the ice rubble pile on the conical structure and ice sheet with a rigorous method of slices, (3) adding driving forces in keeping the rubble pile intact and in upward motion during the interaction, (4) accounting for eccentric offsetting moments at the ice-structure contacts, and (5) modeling the flexural behavior of the ice sheet subject to ice rubble loads using finite element method. The proposed model is used to analyze the interaction events recorded at the conical piers of the Confederation Bridge over a period of 11 years.

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