scholarly journals A Paradigm for the Analysis of Preloaded Bolted Joints

2019 ◽  
Vol 69 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Michael Welch
Keyword(s):  
Structural Integrity ◽  
Bolted Joints ◽  
Classical Analysis ◽  
Validation Process ◽  
Design Standards ◽  
Analysis Process ◽  
Practical Design ◽  
Out Of Plane ◽  
Joint Interpretation ◽  
External Loads

AbstractThe purpose of this paper is to present a paradigm, or guide, to the analysis of preloaded bolted joints made using multiple bolts. Classical analysis methods are applied to the interaction of the joint elements subjected to combinations of both in-plane and out-of-plane loads and moments. The distribution of the external loads and moments within the preloaded joint is determined in relationship to individual bolts. An analysis of loads and stresses in individual bolts and dowels along with flange bending and thread shear in tapped or threaded holes is developed. The article brings together a number of concepts and links them into a practical design analysis process that is applicable for many cases of preloaded bolted joints and are adequate to demonstrate the structural integrity of each element of the joint. Interpretation of results, within the context of design standards, is provided. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process.

scholarly journals Preloaded Bolted Joint Made with a Single Row of Fasteners

2020 ◽  
Vol 70 (1) ◽  
pp. 143-146
Author(s):  
Welch Michael
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Technical Note ◽  
Bolted Joint ◽  
Classical Analysis ◽  
Validation Process ◽  
Single Row ◽  
Analysis Process ◽  
Practical Design ◽  
Out Of Plane

AbstractThe purpose of this technical note is to present a method of analysis of a joint made using a single row of bolts, typical of a bolts around the edge of a closure plat or a simple bracket. Classical analysis methods are applied to the joint subjected to combinations of both in-plane and out-of-plane loads and moments. An analysis of loads and stresses in a single bolt is developed. The note brings together a number of concepts and links them into a practical design analysis process that is applicable for many cases of joints made with a single bolt or a single line of bolts and are adequate to demonstrate the structural integrity of the joint. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process.

Classical analysis of preloaded bolted joint load distributions

2018 ◽  
Vol 9 (4) ◽  
pp. 455-464
Author(s):  
Michael Welch
Keyword(s):  
Structural Integrity ◽  
Design Analysis ◽  
Bolted Joints ◽  
Stress Range ◽  
Design Standards ◽  
Content Type ◽  
Analysis Process ◽  
Load Distributions ◽  
Joint Load ◽  
External Loads

Purpose The purpose of this paper is to develop the understanding of how external loads are reacted through preloaded bolted joints and the interaction of the joint elements. The paper develops ideas from how to do an analysis to understanding the implications of the results. Design/methodology/approach Classical methods of analysis are applied to preloaded bolted joints, made with multiple bolts. The paper considers both the detailed analysis of bolts stresses, fatigue analysis and load-based design analysis, to demonstrate the structural integrity of preloaded bolted joints. Findings In preloaded joints the external tensile axial load and moments are mainly supported by changes in contact pressure at the faying surface. Only a small proportion of the external loads produce changes in bolt tensile stress. The bolts have a significant mean stress but experience a low working stress range. This low stress range is a factor in explaning why preloaded bolted joints have good fatigue performance. Practical implications In many cases the methods presented are adequate to demonstrate the structural integrity of joints. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process. Originality/value The paper brings together a number of concepts and links them into a practical design analysis process for preloaded bolted joints. Interpretation of results, within the context of design standards, is provided.

scholarly journals Analysis of Bolt Bending in Preloaded Bolted Joints

2018 ◽  
Vol 68 (3) ◽  
pp. 183-194
Author(s):  
Michael Welch
Keyword(s):  
Shear Strain ◽  
Structural Integrity ◽  
Bolted Joints ◽  
Bending Moments ◽  
Classical Analysis ◽  
Analysis Methods ◽  
Bolt Preload ◽  
Small Footprint

AbstractClassical analysis methods are applied to show how flexural deflections due to shear strain in the flange pack produce bending moments and tensile loads on bolts within preloaded bolted joints. It was found that in joints made with long bolts these loads can be significant. The loads can cause yielding of the bolt, reducing bolt preload. The methods presented are adequate to demonstrate the structural integrity of joints made with long bolts or with a small footprint.

Accurate Evaluation of Bolt and Clamped Members Stiffnesses Of Bolted Joints

2021 ◽  
Author(s):  
Rashique Iftekhar Rousseau ◽  
Abdel-Hakim Bouzid ◽  
Zijian Zhao
Keyword(s):  
Finite Element ◽  
Joint Stiffness ◽  
Element Model ◽  
Fe Analysis ◽  
Bolted Joints ◽  
Analytical Models ◽  
Fe Modeling ◽  
Bolted Joint ◽  
A New Technique ◽  
External Loads

Abstract The axial stiffnesses of the bolt and clamped members of bolted joints are of great importance when considering their integrity and capacity to withstand external loads and resist relaxation due to creep. There are many techniques to calculate the stiffnesses of the joint elements using finite element (FE) modeling, but most of them are based on the displacement of nodes that are selected arbitrarily; therefore, leading to inaccurate values of joint stiffness. This work suggests a new method to estimate the stiffnesses of the bolt and clamped members using FE analysis and compares the results with the FE methods developed earlier and also with the existing analytical models. A new methodology including an axisymmetric finite element model of the bolted joint is proposed in which the bolts of different sizes ranging from M6 to M36 are considered for the analysis to generalize the proposed approach. The equivalent bolt length that includes the contribution of the thickness of the bolt head and the bolt nominal diameter to the bolt stiffness is carefully investigated. An equivalent bolt length that accounts for the flexibility of the bolt head is proposed in the calculation of the bolt stiffness and a new technique to accurately determine the stiffness of clamped members are detailed.

scholarly journals Integrity Management of Marine Structures; With Emphasis on Design for Structural Robustness

2018 ◽  
Author(s):  
Torgeir Moan
Keyword(s):  
Structural Damage ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Design Standards ◽  
Limit States ◽  
Fabrication Errors ◽  
Integrity Management ◽  
Operational Errors ◽  
And Control

Based on relevant accident experiences with oil and gas platforms, a brief overview of structural integrity management of offshore structures is given; including an account of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. The focus is on developing research based design standards for Accidental Collapse Limit States to ensure robustness or damage tolerance in view damage caused by accidental loads due to operational errors and to some extent abnormal structural damage due to fabrication errors. Moreover, it is suggested to provide robustness in cases where the structural performance is sensitive to uncertain parameters. The use of risk assessment to aid decisions in lieu of uncertainties affecting the performance of novel and existing offshore structures, is briefly addressed.

On the Design of Contact Member Surface Shape of Bolted Joints to Minimize Clamping Load Loss

2018 ◽  
Author(s):  
Linbo Zhu ◽  
Yifei Hou ◽  
Abdel-Hakim Bouzid ◽  
Jun Hong
Keyword(s):  
Contact Surface ◽  
High Performance ◽  
Thermal Loading ◽  
Structural Integrity ◽  
Bolted Joints ◽  
Surface Shape ◽  
Geometrical Shape ◽  
Joint Surfaces ◽  
Joint Contact ◽  
The Stability

Metal to metal contact between joint surfaces is widely used in bolted joints to obtain a rigid and a high performance connection. However, a significant amount of clamping load is lost when the joint is subjected to mechanical and thermal loading including creep and fatigue. In practice, to prevent bolt loosening, additional parts such as spring washers, double nut, spring lock washers, Nyloc nut and so on are used. Those methods are costly and influence the stability of the joint and affect its structural integrity. It is well established that a small compression displacement in clamping parts leads to a big clamping load loss in stiff joints. This paper discusses the relationship between connection stiffness and clamping load and presents a method that improves clamping load retention during operation by a careful design of the member contact surface shape. A single bolted joint with two clamping parts is modeled using finite element method (FEM). A method is proposed to obtain a specific stiffness by an optimized geometrical shape of the joint contact surfaces. The result shows that the contact surface shape based on a gradually varying gap can improve the retention of the initial clamping load. Furthermore, a formula of the connection stiffness based on the curve fitting technique is proposed to predict residual clamping load under different external load and loosening.

Large-Scale Resonant Fatigue Testing of Welded Tubular X-Joints for Offshore Jacket Foundations

2019 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Philippe Thibaux ◽  
Maarten Van Poucke
Keyword(s):  
Large Scale ◽  
Fatigue Testing ◽  
Water Pressure ◽  
Limit State ◽  
Fatigue Tests ◽  
Offshore Wind ◽  
Design Standards ◽  
Initiation Phase ◽  
Out Of Plane ◽  
Jacket Structures

Abstract Offshore wind turbines are being installed in deeper water and with more powerful generators resulting in more severe loading conditions on its foundations such as jacket structures. Because the main loading is due to wind and currents, the dominant design limit state is fatigue. The fatigue performance of the tubular joints used in jacket structures has been assessed several decades ago based on test results with limited component dimensions (diameter and wall thickness). In addition, improvements of welding methods and evolution of steel grades are not considered in the current design standards. To provide experimental fatigue-life data on large-scale structures a test program has been carried out on 4 welded tubular X-joints. Each X-joint consists of two horizontal braces with a diameter of 711 mm welded to a central vertical tubular member with 806 mm diameter. The X-joint has a total length of 7.5 m and has two identical welds that are fatigue tested. The fatigue tests are carried out on an innovative resonant bending fatigue test rig that allows to load the specimen in in- and out-of-plane direction at a different amplitude to obtain an even stress distribution over the circumference of the welds. The tests are carried out at a speed close to the resonance frequency of the X-joint. During the test, hotspot strains are measured using strain gauges and a limited amount of water pressure is used to detect through-thickness cracks. The tests are carried out in two phases. During the crack initiation phase, the sample is loaded in both the in- and out-of-plane mode. Once cracks are detected, the test is continued in the crack propagation phase with loading in the plane where cracks had been initiated until through-thickness cracking appeared. During this phase the beach marking technique has been used to mark the shape of the fracture surface at different moments during the fatigue tests. The testing program is part of the RFCS project JABACO that aims to reduce offshore wind cost by incrementing prefabrication of the jacket substructure.

scholarly journals EFFECT OF OUT-OF-PLANE STIFFNESS AND STRENGTH ON BUCKLING STRENGTH OF HSS BRACE WITH SINGLE-SHEAR BOLTED JOINTS

2018 ◽  
Vol 83 (744) ◽  
pp. 309-319
Author(s):  
Hayato ASADA ◽  
Taichiro OKAZAKI ◽  
Tsuyoshi TANAKA ◽  
Saya NAKAI ◽  
Shogo HASHIOKA
Keyword(s):  
Bolted Joints ◽  
Buckling Strength ◽  
Out Of Plane ◽  
Single Shear

New Standard for Assessment of Structural Integrity for Existing Load-Bearing Structures-Norsok N-006

2009 ◽  
Author(s):  
Gunnar Solland ◽  
Inge Lotsberg ◽  
Lars G. Bjo̸rheim ◽  
Gerhard Ersdal ◽  
Vidar-Andre´ Gjerstad ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Regulatory System ◽  
Life Extension ◽  
Design Standards ◽  
Load Bearing ◽  
Fatigue Design ◽  
Design Life ◽  
Advanced Analysis ◽  
The Cost ◽  
Existing Structure

An increasing number of platforms in the Norwegian continental shelf are reaching their design life. For various reasons these platforms will require an assessment of their structural integrity. When performing these assessments the engineer is faced with tasks where little guidance is found in design standards, for several reasons. The two most important being: 1) The analyses that is performed in a typical assessment of existing structure is often applying very advanced techniques and methodology that seldom is used in design of new structures, as the cost of doing advanced analysis is relatively low compared to replacement of an existing structure, but relatively high compared to moderate additions of e.g. steel in the design of a new structure. 2) Design standards are based on theories, methods and experience for structures in a given design life (e.g. fatigue design and corrosion protection design). When this design life is extended, sound methods for ensuring that the structures are still sufficient safe is needed. Such methods will normally be “condition based design”, where inspection, maintenance and repairs are included in the assessment in integrated way. Such methods are not given in normal design standards. For these reasons a new NORSOK standard is developed that gives recommendation on how to deal with the specific aspects that engineers meet when performing assessments of structures in general, but also specifically for assessment for life extension. The standard is named “Standard for Assessment of Structural Integrity for Existing Load-bearing Structures” and is issued as a NORSOK standard and given the number N-006 [1]. The topics that are covered in the standard include: Shut down and unmanning criteria for platforms not meeting ordinary requirements, specific issues for determination of ultimate capacities by use of non-linear methods, cyclic capacity checks, fatigue life extension, requirements to in-service inspection etc. The paper describes the background and the content of the new standard and it presents examples of recommendations given. The role of the new standard in the Norwegian regulatory system is shown.

The Tightening of Bolts to Yield and Their Performance Under Load

1986 ◽  
Vol 108 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Ian Chapman ◽  
John Newnham ◽  
Paul Wallace
Keyword(s):  
Fatigue Strength ◽  
Stress Distribution ◽  
Yield Point ◽  
Dynamic Strength ◽  
Bolted Joints ◽  
Bolt Preload ◽  
High Fatigue ◽  
External Loads

The mechanism of tightening bolted joints and the stress distribution in the bolt are analyzed. Measurements were made of static and dynamic strength of joints. It is shown that all bolts behave elastically when external loads are applied to the joint even when the fastener was tightened to its torque-tension yield point. It is shown that joints generally fail when the external loads are sufficient to overcome the bolt preload. Fatigue reesults show that joint fatigue strength increases with preload, and that high fatigue bolts gave an improvement over standard fasteners at all preloads.

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