Toward Limit State Design of Ships and Offshore Structures Under Impact Pressure Actions: A State-of-the-Art Review

2006 ◽  
Vol 43 (03) ◽  
pp. 135-145
Author(s):  
Jeom Kee Paik
Keyword(s):  
Limit State ◽  
Structural Response ◽  
Time History ◽  
Rate Sensitivity ◽  
Offshore Structures ◽  
Impact Pressure ◽  
Green Water ◽  
Limit State Design ◽  
Structural Capacity ◽  
Pressure Time

In design of ships and ship-shaped offshore units, issues related to impact pressure actions arising from sloshing, slamming, green water, or explosion are of particular concern. The structural response under impact pressure actions is quite different from that under static or quasistatic actions. It has been recognized that the limit state approach is a more rational basis for structural design and safety assessment where both "demand" (loads) and "capacity" (strength) must be accurately defined. For impact pressure action cases, the demand is associated with hydrodynamics areas, taking into account the characteristics of impact pressure-time history, and the structural capacity is associated with structural mechanics areas, considering geometric and material nonlinearities together with strain rate sensitivity. This paper reviews recent advances and trends toward future limit state design of ships and offshore structures under impact pressure actions.

Numerical Prediction of Sloshing Loads in Ship Tanks

2008 ◽  
Author(s):  
Sanjay P. Singh ◽  
Anant Lal ◽  
Sharad S. Dhavalikar
Keyword(s):  
Structural Response ◽  
Time History ◽  
Ship Motions ◽  
Flow Solver ◽  
Structural Rules ◽  
Ansys Cfx ◽  
Pressure Time ◽  
Fill Level ◽  
Common Structural Rules ◽  
Oil Tankers

The present work is about the estimation of sloshing loads in partially filled tanks of a ship for design purpose. Two oil tankers of different dimensions were taken for this study. Ship motions for several wave-heading angles were computed using potential flow solver. Relevant period for sloshing was determined based on the seakeeping analysis. Critical fill levels of the tanks (with respect to sloshing) were identified from all possible set of motions. The numerical simulation of tank fluid motions for critical fill level was performed, using general fluid flow solver, ANSYS CFX. Prior to applying the method to ship tanks a validation study was carried out. The method was validated against the experimental results obtained by Hinatsu et al. (2001). Pressures at various locations of the tank were computed and were compared with the Common Structural Rules for Oil Tankers (CSR). Pressure time history obtained from computational fluid dynamics (CFD) simulations was applied on the tank bulkhead to get the structural response, using ANSYS Mechanical.

Experimental Investigation of Invar Edge Effect in Membrane LNG Tanks

2010 ◽  
Author(s):  
Mateusz Graczyk ◽  
Kjetil Berget ◽  
Joachim Allers
Keyword(s):  
Fluid Motion ◽  
Structural Response ◽  
Time History ◽  
Pressure Profile ◽  
Pressure Effects ◽  
Local Pressure ◽  
Temporal And Spatial Distribution ◽  
Containment System ◽  
Pressure Time ◽  
Time Histories

Sloshing, a violent fluid motion in tanks is of current interest for many branches of the industry, among them gas shipping. Although different methods are commonly combined for analyzing sloshing in LNG carriers, time histories of the pressure in the tanks are most reliably obtained by experiments. Very localized pressures may be important for the structural response of the tank containment system. Moreover, the typical pressure time history duration is similar to the structural natural frequency. Therefore, pressure measurements need to be performed with due account for temporal and spatial distribution. This requires a high sampling resolution both in time and space. Fine spatial resolution becomes especially important when local pressure effects are of interest, such as pressure profile passing a membrane corrugation of Mark III containment or Invar edge of No.96 containment. In this paper experimental approach applied by MARIN-TEK for analyzing sloshing phenomenon is presented. The focus is put on investigating effects of Invar edges. A transverse 2D model of a typical LNG carrier is used. Local pressure effects are investigated based on low filling level tests with different wall surfaces: smooth and with horizontal protrusions representing the surface similar to the No.96 containment system.

scholarly journals Assessment of Buckling Behaviour on an FPSO Deck Panel

2020 ◽  
Vol 27 (3) ◽  
pp. 50-58 ◽  
Author(s):  
Ozgur Ozguc
Keyword(s):  
Finite Element ◽  
Limit State ◽  
Practical Interest ◽  
Structural Response ◽  
Ultimate Limit State ◽  
Imperfection Sensitivity ◽  
Stiffened Panels ◽  
Structural Capacity ◽  
Response Subject ◽  
Ultimate Limit

AbstractStiffened plates are the main structural building block in ship and offshore hulls and their structural response subject to loads is a topic of significant practical interest in ship and offshore structural design. To investigate the structural capacity for design and evaluation purposes, it is becoming an efficient and reliable practice to carry out non-linear finite element (FE) analysis. The present study is to assess the buckling strength of a stiffened deck panel on an FPSO vessel using the nonlinear finite element code ADVANCE ABAQUS, where imperfection sensitivity work is also accounted for. The cases studied correspond to in-plane bi-axial compression in the two orthogonal directions. The findings are compared with the DNVGL PULS (Panel Ultimate Limit State) buckling code for the stiffened panels. It is found that the strength values from the ADVANCE ABAQUS and DNVGL PULS code are very close. The results and insights developed from the present work are discussed in detail.

Structural Response of a Multi-Hinged Articulated Offshore Tower Under Seismic Excitation

2009 ◽  
Author(s):  
Syed Danish Hasan ◽  
Nazrul Islam ◽  
Khalid Moin
Keyword(s):  
Water Depth ◽  
Vertical Component ◽  
Structural Response ◽  
Vertical Direction ◽  
Time History ◽  
Equation Of Motion ◽  
Offshore Structures ◽  
Rotational Degree ◽  
Energy Potential ◽  
Sea Bed

Articulated towers are the compliant offshore structures that are designed with high degree of compliancy in horizontal direction and to remain relatively stiff in vertical direction. The nonlinear effects due to large displacements, large rotations and high environmental forces are of prime importance in the analysis. This paper investigates the structural response of a 580 m high multi-hinged articulated tower under different seismic sea environment in a water depth of 545 m. The articulated tower is represented as an upright flexible pendulum supported on the sea-bed by a mass-less rotational spring of zero stiffness while the top of it rigidly supports a deck in the air; a concentrated mass above still water level (SWL). For computation of seismic loads, the tower is idealized as a “stick” model of finite elements with masses lumped at the nodes. The earthquake response is carried out by time history analysis using real sets of Californian earthquakes. Disturbed water particle kinematics due to seismic shaking of sea bed is taken into consideration. Nonlinear dynamic equation of motion is formulated using Lagrangian approach. The approach is based on energy principle that relates the kinetic energy, potential energy and work of the system in terms of rotational degree-of-freedom. The solution to the equation of motion is obtained by Newmark-β scheme in the time domain that counters the nonlinearities associated with the system in an iterative fashion. It is observed that with the increase in water depth, additional hinges are required to compensate the increased bending moment due to additional earthquake loads. Analysis results are compared and presented in the form of time-histories and PSDFs of various responses along with combined responses due to horizontal and vertical component of ground motion using direct sum and SRSS method.

Development of geotechnical limit state design

1995 ◽  
Vol 32 (1) ◽  
pp. 128-136 ◽  
Author(s):  
Geoffrey G. Meyerhof
Keyword(s):  
Limit State ◽  
Offshore Structures ◽  
Soil Parameters ◽  
Ultimate Limit State ◽  
Offshore Structure ◽  
Limit States ◽  
Limit State Design ◽  
Earth Structures ◽  
Earth Retaining Structures ◽  
Operational Constraints

The historical development of limit state design in geotechnical engineering is reviewed. Total and partial factors of safety used for the design of land–based and offshore structures are compared. It is found that the factors of safety in different codes for the ultimate and serviceability limit states design of earthworks, earth retaining structures, and land-based and offshore foundations are very similar. Partial factors in the ultimate limit state design are linked to the variability of the loads and soil parameters, the design approximations, and construction tolerances. They influence the nominal probability of failure of the type of structure considered and the seriousness of failure, which differ for land-based and offshore structures. These probabilities are compared with human fatality risks of common experiences. The serviceability limit states are governed by structural and operational constraints and the intended service life of the land-based or offshore structure. The corresponding partial factors are generally taken as unity. Key words : codes, earth structures, foundations, human risks, limit states design, probability of failures, factors of safety.

scholarly journals Structural response of corrugated plates under blast loading: The influence of the pressure-time history

Structures ◽  
2021 ◽  
Vol 30 ◽  
pp. 531-545
Author(s):  
A. Caçoilo ◽  
R. Mourão ◽  
F. Teixeira-Dias ◽  
D. Lecompte ◽  
D. Rush
Keyword(s):  
Structural Response ◽  
Time History ◽  
Blast Loading ◽  
Pressure Time ◽  
Corrugated Plates
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