Fatigue design procedure for welded hollow section joints

Floating fish cages provide the main production utilities for salmon farming. However, despite their pivotal role in production safety as well as in protection of the environment, there is still much room for improvement in relation to verified structural design procedures and computerized tools for structural analysis. To a large extent they can be regarded as not being in accordance with the state-of-the-art of structural analysis and design for more traditional types of marine structures. In this paper a study of fatigue design for floating fish farms is presented. The study is based on a structure which is being applied by the Norwegian fish farming industry today. The floater is made of steel cylinders which are configured as a square. The formulation for the wave loading is based on a combination of potential theory and horizontal drag forces on the floater. Horizontal and vertical drag forces on the netpen are also accounted for. A fatigue design procedure for floating fish farms in steel is suggested. The procedure is based on a time domain analysis of the structure in irregular waves. For each seastate half an hour (real time) analysis is performed and the stress history for an assumed critical location is computed. Based on the stress histories, the fatigue damage is estimated by application of rain flow counting and a given SN curve. The scatter diagram for the seastates at a given location is generated from the associated wind speed distribution.

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Fatigue Under Wide Band Random Stresses Using the Rain-Flow Method

Journal of Engineering Materials and Technology ◽

10.1115/1.3443520 ◽

1977 ◽

Vol 99 (3) ◽

pp. 205-211 ◽

Cited By ~ 64

Author(s):

P. H. Wirsching ◽

A. Mohsen Shehata

Keyword(s):

Fatigue Behavior ◽

Design Procedure ◽

Random Variable ◽

Wide Band ◽

Stress Process ◽

Structural Elements ◽

Constant Amplitude ◽

Design Algorithm ◽

Flow Method ◽

Fatigue Design

A fatigue design procedure is proposed for the structural elements subjected to a stress process, modeled as stationary wide-band gaussian. This procedure, restricted to high cycle fatigue design, uses available constant amplitude material fatigue data and a modified, probability based, Palmgren-Miner (PM) rule. Statistical uncertainty in fatigue behavior and nonstatistical uncertainty in the PM rule are implicitly accounted for by treating the PM index at failure as a random variable. The rain flow method of counting stress cycles is used. The fatigue design algorithm requires only that the RMS and irregularity factor of the stress process be specified in addition to the constant amplitude S-N curve for the material.

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Critical Analysis of the New High Cycle Fatigue Assessment Procedure From ASME B31.3—Appendix W

Journal of Pressure Vessel Technology ◽

10.1115/1.4050320 ◽

2021 ◽

Vol 143 (5) ◽

Author(s):

Nikola Jaćimović ◽

Sondre Luca Helgesen

Keyword(s):

High Cycle Fatigue ◽

Design Procedure ◽

Piping System ◽

Assessment Procedure ◽

Stress Range ◽

Cycle Fatigue ◽

Fatigue Design ◽

Process Piping ◽

Piping Systems ◽

Fatigue Evaluation

Abstract ASME B31.3, the leading process piping system design code, has included in its 2018 edition a new procedure for evaluation of high cycle fatigue in process piping systems. As stated in the Appendix W of ASME B31.3-2018, this new procedure is applicable to any load resulting in the stress range in excess of 20.7 MPa (3.0 ksi) and with the total number of cycles exceeding 100,000. However, this new procedure is based on the stress range calculation typical to ASME B31 codes which underestimates the realistic expansion stress range by a factor of ∼2. While the allowable stress range used typically for fatigue evaluation of piping systems is adjusted to take into consideration this fact, the new fatigue design curves seem not to take it into account. Moreover, the applicability of the new design procedure (i.e., welded joint fatigue design curves) to the components which tend to fail away from the bends is questionable. Two examples are presented at the end of the paper in order to substantiate the indicated inconsistencies in the verification philosophy.

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Rectangular hollow section webs under transverse compression

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2018-0485 ◽

2019 ◽

Vol 46 (9) ◽

pp. 810-827 ◽

Cited By ~ 2

Author(s):

Jens Kuhn ◽

Jeffrey A. Packer ◽

YuJing Fan

Keyword(s):

Finite Element ◽

Design Procedure ◽

Experimental Tests ◽

Full Width ◽

Transverse Compression ◽

Hollow Section ◽

Wide Range ◽

Current Design ◽

Stress Ratios ◽

Design Recommendation

An investigation is presented into full-width, rectangular hollow section (RHS) X-connections subject to transverse compression, including the effect of a compressive or tensile chord preload. A re-evaluation of world-wide experimental tests on full-width X-connections revealed considerable inaccuracy with current design recommendations, as well as significant discrepancies between them. A finite element study was hence conducted to further investigate the behaviour of such connections. A critical value of the bearing length-to-chord height ratio was found, where yielding failure of the chord webs turns into buckling failure, and this has been implemented in the subsequent design recommendation. The proposed design procedure is based on 350 finite element results, covering a wide range of chord sidewall slenderness values, bearing length values and chord stress ratios, as well as against a screened database of 125 experimental tests. The proposal is shown to offer excellent predictions and incorporates a simple reliability analysis.

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Simplified Fatigue Design Procedure For Offshore Structures

10.4043/5331-ms ◽

1986 ◽

Cited By ~ 1

Author(s):

J.F. Geyer ◽

B. Stahl

Keyword(s):

Design Procedure ◽

Offshore Structures ◽

Fatigue Design

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Assessment of Fatigue Damage of Floating Fish Cages Due to Wave Induced Response

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4003699 ◽

2011 ◽

Vol 134 (1) ◽

Cited By ~ 6

Author(s):

Paul E. Thomassen ◽

Bernt J. Leira

Keyword(s):

Structural Analysis ◽

Fatigue Damage ◽

Design Procedure ◽

Irregular Waves ◽

Induced Response ◽

Fish Farms ◽

Analysis And Design ◽

Drag Forces ◽

Fatigue Design ◽

Fish Cages

Floating fish cages provide the main production utilities for salmon farming. However, despite their pivotal role in production safety as well as in protection of the environment, there is still much room for improvement in relation to verified structural design procedures and computerized tools for structural analysis. To a large extent, they can be regarded as not being in accordance with the state-of-the-art of structural analysis and design for more traditional types of marine structures. In this paper, a study of fatigue design for floating fish farms is presented. This study is based on a structure that is being applied by the Norwegian fish farming industry today. The floater is made of steel cylinders that are configured as a square. The formulation for the wave loading is based on a combination of potential theory and horizontal drag forces on the floater. Horizontal and vertical drag forces on the netpen are also accounted for. A fatigue design procedure for floating fish farms in steel is suggested. The procedure is based on a time domain analysis of the structure in irregular waves. For each seastate, 1/2 h (real time) analysis is performed and the stress history for an assumed critical location is computed. Based on the stress histories, the fatigue damage is estimated by application of rain flow counting and a given SN curve. The scatter diagram for the seastates at a given location is generated from the associated wind speed distribution.

Download Full-text