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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.

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.

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.

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.

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.

This paper seeks to deal with a new modelization method which aims at fatigue sizing of preloaded bolted joints. Industrial design offices indeed need new models which, on the one hand, take bending of the bolts and geometrical non‐linearity into account and, on the other hand, run fast enough to be used for preliminary design stages. Usual sizing procedures derive from VDI recommendations, which makes them inaccurate. On the contrary, classical finite element methods are revealed to be very costly.

The first task lies in reducing the physical problem down and model the structure using axisymmetrical elements. Then, the core of the method lies in modifying the stiffness matrix of a tube element, in order to modify the axial compression stiffness to the one used by preloaded assembly classical computations. Eventually, a 2D finite element model is programmed which takes advantage of the modified element. A mounting was built to reproduce the typical loading of a slewing bearing. Experimental tests were carried out in order to help analyse the problem and to check finite element simulation results.

Sample experimental results are presented which confirm the need for new models and validate the 2D model that was developed.

The new finite element, as well as the set of hypotheses that are used, appear to be usable for other bolted joints.

A software was produced for the industrial partners, which is usable by non FE‐specialists.

This work may serve as a basis for building fast and accurate finite element models of other types of bolted joints.

Bolted joints are the most common type of mechanical connections, and improving the anti-loosening performance of bolts for the reliable performance of mechanical and building structures is highly significant.

Because of the lack of sufficient theoretical basis for the evaluation and design of anti-loosening bolts, a quantitative evaluation model exhibiting the following two evaluation criteria for anti-loosening bolts is introduced: bolt rotation angular acceleration criterion and critical transverse load criterion. Based on the relationship among bolt tension, transverse load and bolt rotation angular acceleration, a critical transverse load calculation model is put forward, and the mechanism by which the critical transverse load increases with the increase of bolt tension is revealed.

Based on the above model, a new type of anti-loosening bolt is designed, which generates additional bolt tension when the transverse load increases, and then improves the critical transverse load of the bolt. The effectiveness of the new type of anti-loosening bolt is verified by theoretical calculations and experiments.

The proposed model and method set a preliminary theoretical foundation for the evaluation of bolt anti-loosening performance and the design of a new anti-loosening bolt.

In the last decades, the demand and use of renewable energies have been increasing. The increase in renewable energies, particularly wind energy, leads to the development and innovation of powerful wind energy converters as well as increased production requirements. Hence, a higher supporting structure is required to achieve higher wind speed with less turbulence. To date, the onshore wind towers with tubular connections are the most used. The maximum diameter of this type of tower is limited by transportation logistics. The purpose of this paper is to propose an alternative wind turbine lattice structure based on half-pipe steel connections.

In this study, a new concept of steel hybrid tower has been proposed. The focus of this work is the development of a lattice structure. Therefore, the geometry of the lattice part of the tower is assessed to decrease the number of joints and bolts. The sections used in the lattice structure are constructed in a polygonal shape. The elements are obtained by cold forming and bolted along the length. The members are connected by gusset plates and preloaded bolts. A numerical investigation of joints is carried out using the finite element (FE) software ABAQUS.

Based on the proposed study, the six “legs” solution with K braces under 45° angle and height/spread ratio of 4/1 and 5/1 provides the most suitable balance between the weight of the supporting structure, number of bolts in joints and reaction forces in the foundations, when compared with four “legs” solution.

In this investigation, the failure modes of elements and joints of an alternative wind turbine lattice structures, as well as the rotation stiffness of the joints, are determined. The FE results show good agreement with the analytical calculation proposed by EC3-1-8 standard.

This is the continuation of the article by Gerhard H. Junker, of the European Research and Engineering Standard Pressed Steel Co, Unbrako. The first part, which appeared in October, covered the mechanism of self loosening. The E‐F‐N curves, surface integrity and test programme will be covered in the final part of this feature.

A UNIQUE TEST method and apparatus now make it possible to reproduce conditions of vibration that are not only certain to loosen bolted joints but which also closely simulate actual conditions. It can be shown that properly preloaded fasteners loosen as a result of rotation as soon as relative motion occurs between the mating threads and between the bearing surfaces of the fastener and the clamped material.

This is the final part of the article by Gerhard H. Junker of the European Research and Engineering Standard Pressed Steel Co, Unbrako. Previous parts have covered mechanism of self loosening, design to prevent self‐loosening and test methods.

The use of flexible connections throughout the steel structures provides a high level of stiffness compared to that of fully welded connections. Flexible connections allow for rotation to an extent, which make them perform better during earthquake than welded connections. In hanger connections, the applied load produces tension in the bolts and bolts are designed for tensile forces. When the deformation of the flange plate is equal to that of the bolts, a plastic hinge is formed in the flange plate at the weld line and the bolts are pulled to failure. If the attached plate is allowed to deform, additional tensile forces called prying forces are developed in the bolts. The paper aims to discuss these issues.

This paper includes the results of investigation on prying force in T-stub connection fabricated with normal grade bolts and high strength friction grip (HSFG) bolts. Finite element analysis has been carried out by creating models and analyzing the effect of external tensile force and bolt force. For different grades of bolt (4.6, 8.8, 10.9, 12.9), the prying force is calculated.

It is found that prying force is increasing with the change in grade of bolt used from normal to HSFG. The results obtained from analysis using IS 800:2007 codal provision are also included. It is observed that HSFG bolts do not allow for any slip between the elements connected and hence rigidity is increased.

The prying force mainly depends on geometrical parameter of the connection. In this research work, the variation of prying force was studied based on the variation in dimensions of T-stub angle section and bolt grade (4.6, 8.8, 10.9, 12.9). The method of obtaining prying force from bolt load and applied load is a unique approach. The results of FE analysis is validated with the analytical calculation as per IS 800:2007 code provisions, which shows the originality of the research.

The purpose is to predict the distribution of the residual pretightening force of the bolt group under the action of any initial pretightening force, and to achieve the final residual pretightening force as the target to solve the initial pretightening force value to be applied.

Based on the finite element method and the elastic interaction theory between bolt group, this paper establishes a prediction model for the residual pretightening force distribution of bolt group for one-step pretightening and multi-step pretightening of gasketless flange connection systems. In addition, using the general modeling method given in this paper, the prediction model of residual pretightening force of long plate bolt connection system is established, and compared with reference, which fully proves the effectiveness and universality of the general prediction model of residual pretightening force of bolt group.

The appropriate pretightening sequence, increasing the number of pretightening steps and variable amplitude loading can effectively reduce the influence of elastic interaction and improve the uniformity of residual pretightening force of the bolt group. And the selection of material, number of bolts and connected thickness of bolt connection system also has a great influence on the distribution of residual pretightening force of bolt groups.

The general prediction model for the residual pretightening force of bolt group of connecting structural components considering elastic interaction given in this paper can provide a reference for the design and optimization of the bolt assembly process of the rotor system and the casing system in aero-engine and the prediction of the performance of the connecting system.

The purpose of this paper is to achieve the optimal system design of a four-wheel mobile robot on transmission line maintenance, as the authors know transmission line mobile robot is a kind of special robot which runs on high-voltage cable to replace or assist manual power maintenance operation. In the process of live working, the manipulator, working end effector and the working environment are located in the narrow space and with heterogeneous shapes, the robot collision-free obstacle avoidance movement is the premise to complete the operation task. In the simultaneous operation, the mechanical properties between the manipulator effector and the operation object are the key to improve the operation reliability. These put forward higher requirements for the mechanical configuration and dynamic characteristics of the robot, and this is the purpose of the manuscript.

Based on the above, aiming at the task of tightening the tension clamp for the four-split transmission lines, the paper proposed a four-wheel mobile robot mechanism configuration and its terminal tool which can adapt to the walking and operation on multi-split transmission lines. In the study, the dynamic models of the rigid robot and flexible transmission line are established, respectively, and the dynamic model of rigid-flexible coupling system is established on this basis, the working space and dynamic characteristics of the robot have been simulated in ADAMS and MATLAB.

The research results show that the mechanical configuration of this robot can complete the tightening operation of the four-split tension clamp bolts and the motion of robot each joint meets the requirements of driving torque in the operation process, which avoids the operation failure of the robot system caused by the insufficient or excessive driving force of the robot joint torque.

Finally, the engineering practicability of the mechanical configuration and dynamic model proposed in the paper has been verified by the physical prototype. The originality value of the research is that it has double important theoretical significance and practical application value for the optimization of mechanical structure parameters and electrical control parameters of transmission line mobile robots.