scholarly journals On Characteristics of Ice Ridges and Icebergs for Design of Ship Hulls in Polar Regions Based on Environmental Design Contours

2021 ◽  
Vol 11 (12) ◽  
pp. 5749
Author(s):  
Bernt J. Leira ◽  
Wei Chai ◽  
Gowtham Radhakrishnan
Keyword(s):  
Probabilistic Models ◽  
Limit State ◽  
Relevant Information ◽  
Interaction Process ◽  
Contour Method ◽  
Design Parameters ◽  
Ultimate Limit State ◽  
Polar Regions ◽  
Ship Hulls ◽  
Structural Resistance

Ice ridges and icebergs generally pose a major threat to both ships and offshore facilities that operate in Polar regions. In many cases these features will govern the structural design loads associated with the Ultimate Limit State (ULS) and the Accidental Limit State (ALS). In general, a large number of load cases must be considered in order to ascertain an adequate structural resistance. Alternatively, conservatively high values of the relevant design parameters can be applied, which implies cost penalties. Accordingly, it is natural to consider methods that can serve to reduce the number of relevant load cases. Based on relevant information about the statistical properties of the parameters that characterize ice ridges and icebergs, the most likely combinations of these parameters for design purposes are highly relevant. On this background, the so-called environmental contour method is applied. Probabilistic models of the key parameters that govern the ship and ice interaction process are introduced. Subsequently, the procedure referred to as inverse reliability methods (IFORM) is applied for identification of the environmental contour. Different forms (i.e., dimensions) of environmental contours are generated to reflect the characteristics of the interaction process. Furthermore, the effect of an increasing correlation between the basic parameters is studied. In addition, the increase of the design parameter values for increasing encounter frequencies is illustrated.

Theoretical and Experimental Study on the Ultimate Strength of Corrugated Bulkheads

1997 ◽  
Vol 41 (04) ◽  
pp. 301-317
Author(s):  
Jeom K. Paik ◽  
Anil K. Thayamballi ◽  
Min S. Chun
Keyword(s):  
Ultimate Strength ◽  
Lateral Pressure ◽  
Limit State ◽  
Plate Thickness ◽  
Experimental Information ◽  
Design Guidelines ◽  
Design Parameters ◽  
Collapse Mechanism ◽  
Ultimate Limit State ◽  
Analytical Formulation

The objectives of the present study are to obtain experimental data on collapse strength of steel corrugated bulkhead models and also to develop a simple analytical formulation for ultimate strength useful in the design of corrugated bulkheads under static lateral pressure. Collapse tests on nine mild steel corrugated bulkhead models having five bays of corrugations are carried out, varying the corrugation angle, the plate thickness and the type of loading (axial compression and/or lateral pressure). Using the test data, the characteristics of the collapse mechanism for corrugated bulkheads are investigated. For purposes of rapid first cut estimates of strength, a new and simple analytical formulation for predicting the ultimate strength of corrugated bulkheads under hydrostatic pressure is derived based on an assumed stress distribution over the corrugation cross section at the ultimate limit state. The modeling error associated with the new formulation is established by comparing its predictions with the experimental results. The development of ultimate strength based design guidelines and the effect of design parameters such as the corrugation angle on ultimate strength of a corrugated bulkhead are then discussed. All experimental information and strength data are tabulated, which is a benefit in itself.

A Guide for the Ultimate Longitudinal Strength Assessment of Ships

2004 ◽  
Vol 41 (03) ◽  
pp. 122-139
Author(s):  
Jeom Kee Paik
Keyword(s):  
Progressive Collapse ◽  
Limit State ◽  
Bending Moment ◽  
Ship Hull ◽  
Safety Measure ◽  
Ultimate Limit State ◽  
Ship Hulls ◽  
Collapse Analysis ◽  
Longitudinal Strength ◽  
Progressive Collapse Analysis

The aim of the present paper is to establish a practical guide for the ultimate longitudinal strength assessment of ships. The ultimate hull girder strength of a ship hull can be calculated using either the progressive collapse analysis method or closed-form design formulas. In the present paper, both the progressive collapse analysis method and the design formulas are presented. A comparison between the progressive collapse analysis results and the design formula solutions for merchant cargo ship hulls is undertaken. The total design (extreme) bending moment of a ship hull is estimated as the sum of the still-water and wave-induced bending moment components as usual. The safety measure of a ship hull is then defined as a ratio of the ultimate longitudinal strength to the total design bending moment. The developed guidelines are applied to safety measure calculations of merchant ship hulls with respect to hull girder collapse. It is concluded that the guidance and insights developed from the present study will be very useful for the ultimate limit state design of newly built ships as well as the safety measure calculations of existing ship hulls. The essence of the proposed guide shall form ISO code 18072-2: Ships and Marine Technology— Ship Structures—Part 2: Requirements of Their Ultimate Limit State Assessment.

PROBABILISTIC OPTIMIZATION OF PARTIAL SAFETY FACTORS FOR THE DESIGN OF INDUSTRIAL BUILDINGS

2008 ◽  
Vol 15 (05) ◽  
pp. 411-424 ◽  
Author(s):  
ZOLTÁN SADOVSKÝ ◽  
DUŠAN PÁLEŠ
Keyword(s):  
Probabilistic Models ◽  
Limit State ◽  
Optimization Procedure ◽  
Ultimate Limit State ◽  
Safety Factors ◽  
Probabilistic Optimization ◽  
Industrial Buildings ◽  
Reliability Method ◽  
Partial Safety Factors ◽  
Ultimate Limit State Design

By probabilistic optimization of partial safety factors for a class of structures a more uniform reliability of practical design of individual cases within the class is aimed at. The paper deals with an ultimate limit state design of a class of low rise industrial buildings subject to climatic loads and permanent loads. The optimization is carried out on selected representative structures, the reliability of which is calculated by the level II reliability method FORM. Probabilistic models of cross section resistance and of climatic loads pertinent to a continental climate are based on measurements. Peculiarities of the optimization procedure, particularly optimization stages in conjunction with the choice and possible differentiation of partial factors are discussed.

Extreme Response Analysis of an End-Anchored Floating Bridge

2019 ◽  
Author(s):  
Zhengshun Cheng ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Axial Force ◽  
Limit State ◽  
Bending Moment ◽  
Contour Method ◽  
Response Analysis ◽  
Ultimate Limit State ◽  
Extreme Response ◽  
Structural Responses ◽  
Floating Bridge ◽  
Extreme Responses

Abstract During the design of a floating bridge, extreme structural responses are required to be properly evaluated for ultimate limit state (ULS) design check. This study addresses the estimation of extreme structural responses for an end-anchored curved floating bridge. The floating bridge, about 4600 m, consists of a cable-stayed high bridge part and a pontoon-supported low bridge part. The long-term extreme responses are approximated by using a engineering approach, i.e., the environmental contour method. The sea state with 100-year environmental conditions is considered, and a 90% fractile is used to calculate the short-term extreme responses by using the Gumbel method and the mean up-crossing rate (MUR) method based on 100 1-hour simulations with different seeds. The extreme responses are expressed as μ + κσ, where μ and σ are the ensemble mean and standard deviation, and κ is a multiplying factor. Numerical results show that structural responses are close to Gaussian distributed. κ of axial force and strong axis bending moment along the bridge girder estimated by both the Gumbel and MUR methods vary in the vicinity of 4. κ estimated by the two method deviates, especially for axial force. Moreover, for both methods the estimated κ deviates more significantly if fewer ensembles are used.

Application of the Global Optimization Method to the Preliminary Design of Tension Leg Platforms

2016 ◽  
Author(s):  
Jeong-Du Kim ◽  
Beom-Seon Jang
Keyword(s):  
Global Optimization ◽  
Limit State ◽  
Optimization Method ◽  
Total Weight ◽  
Design Parameters ◽  
Ultimate Limit State ◽  
Wave Loads ◽  
Hull Form ◽  
Optimization System ◽  
Design Requirements

The TLP requires a complicated and time-consuming design process. Principal dimension of hull form and tendons should be carefully determined with the consideration of many design requirements which dominantly affect the safety of the platform. In this paper, a global optimization system for both the hull-form and tendon system is developed. The maximum heave response and total weight of hull and tendons are formulated as an objective function with the several constraints related to the safety of platform. In order to find a technically and economically feasible design, a modelling and assessment processes are fully automated, which enables the algorithm can controls the modelling and analysis process while varying a set of design parameters until it figures out an optimum design. Major design requirements related to the safety of platform is assessed by ultimate limit state (ULS) and fatigue limit state (FLS) approach to ensure the accuracy of analysis. In the ULS approaches, every safety requirement is checked on the basis of the most unfavorable environments. FLS approach is conducted for all tendons since they suffer cyclic deformation for their service life, which results in collapse of mooring system with the relatively small wave loads. In the optimization module, a better set of design parameters is investigated by using a simulated annealing (SA) algorithm. Throughout the optimization system, both the heave responses and total weight of hull and tendons are improved while satisfying the all constraints related to the design requirements.

scholarly journals Fragility curves for Italian URM buildings based on a hybrid method

2021 ◽  
Author(s):  
A. Sandoli ◽  
G. P. Lignola ◽  
B. Calderoni ◽  
A. Prota
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Limit State ◽  
Ultimate Limit State ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Building Stock ◽  
Ground Acceleration ◽  
Damage Scenario

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

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