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The fastening bolt is one of the important parts of the stacked structure proton exchange membrane electrolyzer (PEMEC), and the bolt tightening behavior has a significant impact on the electrochemical performance of the PEMEC. In this paper, we use a transparent visualization system to explore the effect of tightening bolt behavior on the performance of PEMEC. Pressure sensitive paper was used to record the contact pressure distribution map of PEMEC under different bolt tightening methods, and a high-speed camera was used to record the state of gas-liquid two-phase flow inside PEMEC under different bolt tightening methods. Both of them are used to verify the effect of bolt tightening behavior on the performance of PEMEC. The experimental results show that the contact pressure of PEMEC increases with the increase of bolt torque, and the electrochemical performance first increases and then decreases with the increase of bolt torque. The optimum bolt torque is 3.5 N m for a square PEMEC with an end plate size of 100 mm × 100 mm and a membrane size of 50 mm × 50 mm × 0.17 mm. The PEMEC performance increases with the increase of bolt tightening steps, and the optimal tightening step for the system is three steps. In addition, symmetrical tightening of bolts is beneficial for improving electrochemical performance, and there is an optimal tightening sequence in the system. This paper illustrates the relationship between tightened bolts and PEMEC electrochemical performance, showing the relationship between bolt tightening and the gas-liquid two-phase flow state inside PEMEC. The research results can provide a reference for optimizing the assembly and installation process of PEMEC. • A transparent visualization of PEMEC bolt tightening experimental method is proposed. • Minimum bolt torque for PEMEC installation is presented. • The optimal installation process for PEMEC is presented. [ABSTRACT FROM AUTHOR]

The detection of fastener defects is crucial for ensuring the safety and reliability of high-speed train operations. This paper proposes an intelligent algorithm named YOLO-Fastener for detecting fastener defects in ballastless track systems. The proposed YOLO-Fastener incorporates efficient channel and spatial attention mechanisms, enhancing the extraction of crucial features related to fastener defects. Decision regions of the model in identifying fastener defects are visualized through heatmaps. The model is trained and tested on a limited dataset of high-resolution fastener images collected by a ballastless track detection vehicle equipped with 3-D laser devices. The results show that the precision and recall of the proposed model on the test set are 98.33% and 99.15%, which are 1.63% and 4.81% higher than those of the advanced Faster R-CNN model. In terms of fastener detection efficiency, the proposed model is the fastest with an inference time of 10.4 ms, which is an 18.75% improvement over the result of the advanced YOLOv7 model. • The paper proposes an intelligent algorithm named YOLO-Fastener for detecting fastener defects. • A high-resolution dataset of fastener defects is collected by a ballastless track detection vehicle. • The ECSA module has been developed to extract more crucial fastener defect features. • The GhostConv and RepConv modules are employed to reduce model parameters and increase inference speed. [ABSTRACT FROM AUTHOR]

For the response of the train-track-bridge system under extreme environment, an increasing number of studies employ co-simulation strategies for detailed modeling and calculation of the structure. However, there is a lack of research on the module connectors, which significantly impact simulation accuracy and stability. In this paper, the theoretical differences between weak, moderate, and strong coupling methods in dealing with co-simulation module interface connectors are discussed. An explicit-implicit multi-timestep co-simulation platform is established using MATLAB and OPENSEES software. Taking China's CRTS II slab ballastless track, a simply supported beam bridge, and a train as examples, a three-dimensional train-track-bridge coupling model is created. The three coupling methods are then verified and compared. Finally, two coupling methods are used to model and calculate the train-track-bridge system under earthquake. It is concluded that when calculating the train-track-bridge under earthquake, using the fastener with less damage as the co-simulation partition boundary can avoid complex nonlinear calculation. On this basis, it is feasible to use weak, moderate and strong coupling methods to deal with fastener elements. Different co-simulation software can adopt different coupling methods according to the difficulty of modeling. In the MATLAB-OPENSEES multi-timestep explicit-implicit co-simulation platform, the weak and moderate methods can achieve better calculation accuracy, and can be used to calculate the response of train-track-bridge system under earthquake. • Fasteners aid module partitioning in train-rack-bridge co-simulation under seismic conditions. • In OPENSEES, fixed-spring-damping modifies only diagonal stiffness matrix elements. • Strong, moderate, and weak coupling methods enable diverse simulation strategies. • Moderate/weak coupling ensures consistent train-track-bridge seismic simulation. [ABSTRACT FROM AUTHOR]

The resilient fastener slab track (RFS track) has found extensive application in urban railways, effectively mitigating vibration and noise resulting from train operations. However, the structure elasticity of the RFS track is higher than the normal slab track (NS track), which can affect train running stability and cause abnormal vibration phenomenon. This paper explores the track structure elasticity on vehicle-track interaction and train running stability through experimental tests and numerical simulations. The vibrational properties of the RFS track and the NS track are obtained through field tests. A 3D metro vehicle-track coupled dynamics model is developed and utilized to simulate the dynamic performance of metro vehicles moving on different track structures. The impact of track structure parameters upon the vehicle-track interaction and train running stability are discussed. The findings indicate that the track structure elasticity can reduce train hunting stability and cause abnormal vibration phenomena in metro vehicles under certain conditions. The reasonable matching of the fastener lateral and vertical stiffness can not only accomplish vibration attenuation but also minimize the impact on train running stability. In addition, the rail surface wear and track gauge variation also exert influence on the running stability and dynamic performances of metro vehicles. • Track structure elasticity on vehicle-track interaction and train running stability was investigated. • Train hunting mechanism running on resilient fastener slab (RFS) track was revealed. • Vibrational properties of RFS track and normal slab track were tested on site. • The impact of track structure parameters upon vehicle dynamic performances was evaluated. • The track structure elasticity reduces hunting stability of metro vehicles. [ABSTRACT FROM AUTHOR]

Fasteners in assemblies are often subjected to multi-axial loading; however, the role of load angle and the assembly design/geometry on the failure of fasteners are not well understood. Existing experimental data often convolutes multiple sources of uncertainty. Thus, numerical modeling is needed to make accurate conclusions about the failure mechanisms of fasteners. This paper investigates the mechanics that controls the loading angle effects on the mechanical response of fasteners by using a simple finite element bolt model without threads. The material model of this model is calibrated against tensile testing data, which minimizes the contribution of the fixture to the bolt's response. The calibrated material model is then used to investigate the loading fixture effects (including the fixture gap, compliance, and double shear loading configuration) on the mechanical response of the fasteners. After identifying the fixture parameters that the fastener's response is most sensitive to, a model of a simplified fixture is validated against experimental results. This investigation reveals that the loading angle effects and most of the loading fixture effects on fasteners' mechanical response are attributed to the change of stress concentrations at the contact tips. The primary contributions of this paper are novel insights into the failure mechanisms of fasteners, and that a reduced model of a fastener can be used to predict its constitutive behavior accurately. • A simplified fastener-test fixture model is developed to investigate failure mechanisms under mixed shear and tensile loading • The model is validated against multiple sources of experimental data from the literature • The model is used to investigate the fixture's effects on the measured constitutive properties of a fastener • This work highlights the need to account for the test fixture design in extracting properties from fastener testing [ABSTRACT FROM AUTHOR]

Abstract Previous studies on stressed skin effect of industrial steel buildings showed discrepancies between the ECCS formulae and experimental results. To clarify the discrepancies full-scale experimental test program was planned and executed by the Budapest University of Technology and Economics, Department of Structural Engineering. The aims of the full-scale tests were to refine the stressed skin design method and to adjust it to the nonstandard cladding structural system applied by an industrial partner. During execution of the full-scale experiments the shear flexibility of those industrially applied nonstandard diaphragms were examined, where the application of seam fasteners were rejected. Next to the building section a loading frame was built, so that tension and compression force could be applied to each frame, in order to examine the in-plane shear flexibility of the whole nonstandard diaphragm assembly, including the shear flexibility of the portal frame. In the test series four purlin and two trapezoidal sheeting height configurations were combined in more than 100 tests. This paper, denoted as Part I shows the test setup and introduces the results derived from the ECCS formulae, underlining the importance of extending the applicability of the current design formulae to nonstandard cases, which are often applied in industrial practice all over Europe. A companion paper (Part II) presents the comparative results between the various cladding configurations, also the main conclusions regarding the stiffening effect of the applied diaphragm configurations, and reports the effect of change in section size to shear flexibility. Besides this in Part II the effect of different structural components in regards to shear flexibility is underlined. Highlights • A full scale experimental test series of a single bay steel cladded building was presented in this article. • As far as known, no international study was executed in order to examine the stiffening effect of nonstandard, steel diaphragm constructions. • This paper focuses on the details and results of the full-scale experiment. • The conclusions regarding to the effect of diaphragm height, fixing number, and the structural components on shear flexibility are presented in Part II of this two-part paper. • The principal aim of current research is to extend the current formulae to nonstandard cases, which are out-of-scope of the ECCS design methodology. [ABSTRACT FROM AUTHOR]

This paper presents a new self-clinching fastener to connect two sheets (or plates), made from similar or dissimilar materials, placed over one another by means of a mechanical form-closed joint that is hidden inside the sheets. The development of the fastener, the definition of its main design variables and the identification of its workability limits are carried out by means of a combined experimental and numerical simulation work based on finite elements. It is shown that self-clinching by pressing the two overlapped sheets against each other to displace material around the annular groove of the fastener shank and create undercuts in both sheets requires an appropriate choice of the design variables. Wrong values of the design variables resulting in lack or excess of material displaced by plastic flow gives rise to inappropriate lap joints that cannot be used in production. The new proposed fastener allows, for the first time ever, joining by forming with the use of auxiliary elements that are harder than the sheet materials to fabricate invisible joints with no material protrusions in applications requiring minimum installation space. [ABSTRACT FROM AUTHOR]

High wind uplift loads acting on the light gauge steel roofing systems during tropical cyclones and storms frequently cause premature failures of roof connections, which lead to extensive damage to roofing systems. Such roofing system damage was observed in recent cyclones due to premature failures of steel roof batten to rafter/truss connections. They were mostly observed to be due to a localised pull-through failure in the bottom flanges of roof battens. Hence a series of small scale and full scale tests of roof battens was first conducted to study their pull-through failures. To further enhance the understanding gained from the experimental study and to predict the pull-through capacities of a wide range of roof battens, finite element models were developed and analysed using a suitable failure criterion. This paper first presents the applicability of the failure criterion for different roof batten geometries and screw fastener head sizes. Then it provides the details of a numerical parametric study conducted to study the pull-through failures of roof battens in relation to influential parameters such as batten geometry and screw fastener head sizes. Finally, this paper proposes suitable design equations and capacity reduction factors for the calculation of the design pull-through capacities of thin-walled steel roof battens. [ABSTRACT FROM AUTHOR]

This paper concerns the short-term behaviour of innovative steel-timber composite (STC) floors comprising of cross-laminated timber panels connected to steel girders by various mechanical fasteners and/or glue. The results of four-point bending tests performed on full-scale STC beams are reported and the structural behaviour (the load-deflection response, short-term stiffness, peak load capacity, and failure modes) of the proposed STC system is studied. In addition, extensive non-linear 1D and 2D finite element (FE) analyses of STC beams are carried out and the numerical results are verified against the test results. It is shown that 1D and 2D FE models are adequate in capturing the structural response of the STC beams. Using the FE and experimental results, the composite efficiency of STC beams that can significantly influence their structural behaviour beams is determined and reported in the paper. [ABSTRACT FROM AUTHOR]

Predicting the mechanical response of components requires simplifications and idealizations that affect the fidelity of the results and introduce errors. Some errors correspond to the limited knowledge of intrinsic physical attributes while others are introduced by the modeling framework and mathematical approximations. This paper studies the dependence of the force-displacement response of threaded fasteners on modeling attributes such as geometry, material, and friction resistance using finite element simulations. A systematic comparison of 1 D , 2.5 D or 3 D computational models demonstrates the influence of model properties and the limitations of the methodologies. Finally, the paper discusses the sources of model inputs and model form errors for threaded fasteners. [ABSTRACT FROM AUTHOR]

It has been a desire to unify the models for structural and parametric analyses and design in the field of robotic mechanisms. This requires a mathematical tool that enables analytical description, formulation and operation possible for both finite and instantaneous motions. This paper presents a method to investigate the algebraic structures of finite screws represented in a quasi-vector form and instantaneous screws represented in a vector form. By revisiting algebraic operations of screw compositions, this paper examines associativity and derivative properties of the screw triangle product of finite screws and produces a vigorous proof that a derivative of a screw triangle product can be expressed as a linear combination of instantaneous screws. It is proved that the entire set of finite screws forms an algebraic structure as Lie group under the screw triangle product and its time derivative at the initial pose forms the corresponding Lie algebra under the screw cross product, allowing the algebraic structures of finite screws in quasi-vector form and instantaneous screws in vector form to be revealed. [ABSTRACT FROM AUTHOR]

An accurate and fast fasteners detection is of great significance for improving the inspection efficiency of railway tracks. However, the task is also challenging due to the limited memory and processing capacity of the embedded maintenance systems. To address these challenges, in this paper, we presents a solution that can be deployed on the high-speed operation vehicles, including You Only Look Once version 2 (YOLOv2) network and Field Programmable Gate Array (FPGA) HW-based acceleration strategy. The algorithm proposed in this paper is implemented completely on FPGA, and the hardware acceleration strategy such as loop pipelining, array partition and ping-pong buffer optimization is applied to get the highest performance. The hardware implementation results show that the improved YOLOv2 detection network and fastener detection system are superior to the existing embedded maintenance system in processing time and hardware resources. The proposed systems can detect a track image in 41 ms, which is much faster than the existing embedded maintenance system. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical and the hysteretic behaviour of steel-to-timber joints with annular-ringed shank nails in Cross-Laminated Timber (CLT). These fasteners are used to anchor typical metal connectors, such as hold-downs and angle brackets, to the CLT panels. The experimental programme presented in the paper was carried out at the Institute of Timber Engineering and Wood Technology, Graz University of Technology (Graz, Austria). Average and characteristic values of the experimental strength capacities are evaluated and compared to the analytical predictions determined according to current structural design codes and literature. Furthermore, to fulfil the requirements of the capacity-based design, the overstrength factor and the strength degradation factor are evaluated and conservative values are recommended. [ABSTRACT FROM AUTHOR]

Fastener hole cracks, resulting from stress concentration around the hole, are potential sources of failure in mechanical structures. Traditionally, inspection involves manually moving a single ultrasonic probe around the hole or using an eddy current probe to move through the hole. However, single ultrasonic probe inspection is time-consuming and needs skilful operators. Eddy current inspection requires the removal of the fastener in advance and does not allow easy crack sizing and visualization. This paper proposes a novel approach that combines a 2D phased array with a coupling block to enable complete fastener hole inspection from a single array position. A single full matrix capture (FMC) data set is collected, from which 3D volumetric images are formed. To obtain clear images of the geometry and potential defects, half-skip and multi-skip total focusing method imaging algorithms are investigated together with transmitter–receiver pairs selection methods to detect different target features. Experimental results demonstrate that the proposed inspection approach can eliminate dead zone problems and capture all target information from a single inspection position. These methods show great potential in enhancing the efficiency and reliability of fastener hole inspections. [ABSTRACT FROM AUTHOR]

• The EU-DEMO initiated an investigation into the development of a remote maintenance friendly solution for fastening and sealing of the vacuum vessel port closure plates. • The initial design of a quick and convenient port closure plate fastening mechanism was created. • A preliminary analysis and modelling of a welded seal were conducted. • The goal is to engage the industry in the early stages of development to foster future participation. The EU-DEMO project, which has been in the Concept Design phase since 2021, is already focusing on the integration of the main system components but is also analysing variants to simplify this process. One of these is the fastening and sealing of vacuum vessel closures, known as port closure plates, in order to simplify the execution of the work with the aid of remote maintenance. Recognising the key role of industry, the fusion programme roadmap foresees intensive industry involvement in specific tasks. To provide a starting point for such collaboration, the Fusion Technology Department (FTD) has developed an initial design for a mechanical fastening solution based on the design of ship bulkhead doors. This could be combined with a welded seal, also developed to an early stage in FTD, which could cope with all load cases without additional measures. This system of easy to use fastening and reliable welded seal could be a significant simplification compared to other established technical solutions to this function. This paper presents the above issues and describes the current state of development. It also outlines initial plans to involve experienced industrial partners in these tasks. [ABSTRACT FROM AUTHOR]

Abstract: Damage detection for thermal protection systems is crucial for hypersonic flight. Since fastener failure is a critical failure mode for many thermal protection systems, an efficient methodology that does not require a significant amount of experimental data collection and analysis for implementation is desired. In a coming paper, we develop a methodology for localizing fastener failure in a thermal protection system utilizing an experimentally validated finite element model. This paper focuses on validating the finite element model in its healthy state versus low-frequency experimental results obtained on the composite structure for future research in damage quantification. The experimental validation is implemented in three steps to individually account for the unknown composite material properties, insulation effects, and the assembly with the connecting brackets and backing structure. The inverse optimization problem implemented in the first level of experimental validation demonstrated excellent agreement between the finite element model and the experimental results. The overall assembly also demonstrated good agreement between the low-frequency dynamics of the experimental results and the finite element model. The validated finite element-model will then be used to simulate damage in the structure to investigate the effectiveness of vibration mode-based damage detection metrics. [Copyright &y& Elsevier]

Cold-formed steel (CFS) built-up members are formed by connecting several single members by fasteners. This paper presents experimental, numerical and analytical studies on the effect of fastener configurations on the flexural rigidity of built-up sections. In this research, two zinc-coated steel C-sections are connected back-to-back to form a double-web built-up I-section, which is subject to weak-axis bending. A closed-formed expression for the flexural rigidity of built-up sections as a function of fastener stiffness, number and position of fasteners, and section geometry is then derived. This is validated against the tests and finite element modelling, and can be adapted more generally to determine the stiffness and global strength of CFS built-up members in bending. • The study is about how fastener configurations affect the effective flexural rigidity of cold-formed steel built-up sections. • Tested fasteners are screws, bolts and welds. • The effective flexural rigidity is a function of fastener stiffness, number and position of fasteners, and section geometry. • Effective flexural rigidity affects stiffness and strength of built-up members in bending and members subject to buckling. [ABSTRACT FROM AUTHOR]

• An analytical calculation method for displacement and force at the transition. • Comparison on the derived calculation scheme for three different conditions. • Study on effects of the maximum temperature gradient ratio. • Study on effects of the maximum fastener resistance on longitudinal displacement. The rails at the transition between a bridge or subgrade and a tunnel tend to creep longitudinally because of a temperature gradient on the rail, which can cause irregularity in the track. The longitudinal temperature distribution along the rail and the longitudinal resistance of the fasteners are the main influences on rail creep. In this paper, the linear and nonlinear models of longitudinal temperature distribution on rails and the longitudinal resistance of fasteners are tested for their accuracy in predicting rail creep. By researching the rail at the temperature-transition zone, differential equations for the longitudinal displacement and force of the rail are established. To predict the changes that a rail will experience in a temperature-transition zone, expressions for the longitudinal displacement and force are derived from these differential equations. The derived calculation scheme is tested for three conditions: linear models of both rail temperature and longitudinal resistance, linear rail temperature and nonlinear resistance, and nonlinear models of both rail temperature and displacement. The maximum longitudinal rail displacement and the maximum longitudinal additional force in all three conditions are compared to reveal the influence of the maximum temperature force gradient multiple and the maximum fastener resistance on longitudinal displacement. [ABSTRACT FROM AUTHOR]

This paper presents a combined experimental and numerical study on bolted L-stub connections under simultaneous bending and axial excitation from a cyclic separating load, which has not been reported in the open literatures. The reduction of the clamping force is found from experiments. Additionally, the thread damage is analysed using an optical microscope, a white light interferometer, a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX). The effects of the eccentricity, the excitation level and the initial clamping force on the reduction of clamping force and the damage of threads are also studied in experiments. It is found from the experimental results that the degrees of the thread damage and self-loosening increase with the increases of the excitation level and the eccentricity, and they decrease with the increasing initial clamping force. A three-dimensional finite element model is created to analyse the contact stress and the relative slip between the threads of the bolt and the nut, and the finite element results agree with the experimental measurements. • This work is the first attempt to study the self-loosening of a bolted joint under simultaneous bending and axial excitation from a cyclic separating load. • The wear mechanisms of the thread surfaces were investigated. • Experimental observations were further explained using finite element method. [ABSTRACT FROM AUTHOR]

Abstract Pull-through failure of steel roof batten to rafter connections is one of the critical failures observed in cold-formed steel roofs during tropical cyclones. Although design equations are available for steel roof battens subject to static pull-through failures, no suitable design equations are available for fatigue pull-through failures. Currently, a Low-High-Low (LHL) cyclic test method based on expensive and time consuming large scale prototype tests is being used to design roof battens for fatigue pull-through failures. Therefore, this research study proposes suitable design equations based on both linear and nonlinear damage models to determine the fatigue life and capacity of steel roof battens by understanding the fatigue behaviour of steel roof battens subject to variable amplitude cyclic wind suction loading. This was achieved through a series of multi-level cyclic tests, including LHL cyclic tests, conducted on roof battens made of different steel grades and thicknesses and fastened with different screw fasteners. This paper presents the details of the experimental study and its results, and proposes suitable fatigue pull-through design equations based on linear and nonlinear fatigue damage models. Highlights • Investigated the fatigue pull-through failure of roof battens under variable amplitude cyclic loading. • Examined the use of linear damage model for the fatigue pull-through failure of roof battens. • Investigated the sequence effect using multi-level cyclic tests. • Proposed a nonlinear damage model for the fatigue pull-through capacity by including sequence effect. • Investigated the suitability of linear and nonlinear damage models to replace the LHL cyclic test. [ABSTRACT FROM AUTHOR]

Abstract The railway track fasteners play a critical role in fixing the track on the ballast bed. Achieving full automation of the fastener defect detection is significant in terms of ensuring track safety, and reducing maintains cost. In this paper, innovative and intelligent methods using image processing technologies and deep learning networks are proposed. In the first part, the traditional fastener positioning method based on image processing is reconsidered. In addition, a novel fastener defect detection and identification method using Dense-SIFT features is proposed which can achieve a better performance than the methods available in the literature. In the second part, VGG16 is trained for fastener defect detection and recognition. The result demonstrates that it is possible to carry out the defect detection of fasteners with CNN. Finally, Faster R-CNN is used for fastener defect detection to advance detection rate and efficiency. The fastener positioning and recognition can be carried out simultaneously. The time for the defect detection and classification is only one-tenth of the other methods mentioned above. Highlights • The Dense-SIFT, spatial pyramid decomposition and BOVW techniques are applied to the classification and this method achieves classification accuracy of 99.26%. • The DCNN method uses only one network for fastener defects detection and achieves a sound classification accuracy of 97.14%. • Faster R-CNN based method realizes the positioning and classification of the fasteners simultaneously and the time spent by Faster R-CNN is only about 10% of the time spent by the other methods. [ABSTRACT FROM AUTHOR]

Abstract Environmentally induced degradation is a serious issue governing the use of titanium alloy fasteners for marine applications. The workhorse alloy Ti6Al4V which has been the most used titanium alloy till date as fastener material has its limitations and search has been on for improved titanium-based materials. This paper deals with researches aimed at evaluating the metastable beta titanium alloy Ti15V3Cr3Al3Sn (Ti15-3) in solution annealed condition as a fastener material for medium strength applications. A variety of tests was carried out to rate the resistance of the alloy in this condition to seawater environments slow strain rate testing (SSRT), crevice corrosion testing, potentiodynamic polarization studies, and immersion testing. Limited SSRT was also done on Ti6Al4V for the sake of comparison. Analysis of test results shows that solution annealed Ti15-3 offers itself as a good candidate material for medium strength fastener applications in marine environments. Highlights • Slow strain rate testing indicates that alloy Ti15-3 shows excellent resistance to sea environment. • The alloy Ti15-3 in solution annealed condition shows excellent resistance to crevice corrosion. • Lower corrosion rates of Ti15-3 in 3.5% NaCl compared to Ti6Al4V. [ABSTRACT FROM AUTHOR]

Abstract: Dowel-type fastener connections perpendicular to grain may fail in either a ductile or a brittle fashion. Whether the failure mechanism should be classified as ductile, depends on the definition of ductility utilized. Generally, the load–slip response is considered as a means of ductility quantification. In this respect, the elastic potential energy is calculated (being the area underneath the load–slip response) or the ratio of the ultimate slip and the slip at the onset of yielding is used, amongst others. Another approach relates to the European Yield Model which is commonly adopted in design standards to calculate the load-bearing capacity of dowel-type fastener connections. In this respect, ductility may be considered to be associated with plastic deformation of the steel fasteners solely since the deformation ability of connections with dowel-type fasteners at yield is much larger compared to situations with non-yielding fasteners. In the case of connections with rigid dowel-type fasteners, it therefore may be suggested that less ductility is exhibited although it is recognized that timber in compression perpendicular to grain exhibits plastic capabilities as well. Whether these connections behave either brittle or ductile is related to the spacing requirements as well. In this paper, first an overview of potential fracture and failure mechanisms of dowel-type fastener connections is provided. Experimental results of a variety of connections and corresponding failure mechanisms are presented. Based on mechanical models to predict the load-bearing capacity, classification of these connections in terms of ductility is provided, and the governing parameters involved are distinguished. This paper does not intend to provide a quantification procedure of ductility. Yet, an extensive overview of failure mechanisms and an analytical analysis of parameters involved are given providing expressions to calculate the failure mechanism being governing. [Copyright &y& Elsevier]

Abstract: Embedding strength is recognized as a very important property in any dowel type timber joints since it affects bearing performance, load carrying capacity and failure mode of the joint. In this paper, using an inverse modelling technique effective flat nail embedding strengths of double-sided nail plate joints were predicted based on single-tooth 3-D finite element models. In those models, timber was treated as an orthotropic elasto-perfect plastic material, and steel nail as a rigid body. The predicted embedding strengths were compared with experimental ones and good correlation was obtained. Using the predicted embedding strength, the overall joint behaviour was simulated and validated against the corresponding experimental results. This paper presents a new approach to obtain embedding strength of double-sided nail plate joints. [ABSTRACT FROM AUTHOR]

Roof wind design consist of three parts: determination of wind loads, evaluation of wind uplift resistance and correlating the resistance with the design load such that the resistance is higher than the load requirement. Wind uplift resistance of a system with its respective components is evaluated in laboratory testing. This paper presents a novel approach to estimate wind uplift resistance when components are substituted during field application. Wind dynamics, on a mechanically attached single-ply roofing assembly, lift the membrane and cause fluttering, introducing stresses at the attachment locations. In such assemblies, the fastener–deck interface is a critical design factor. First, by taking steel deck as a component this paper systematically characterizes the various steel decks that are commonly used in low slope application. Second component, namely the fasteners and its engagement strength with deck have been quantified for variations of its design, size and sources. Based on this component characterization, fastener pullout resistance (FPR) is identified as a verification factor for system wind resistance estimation. When variations occur in the fastener–deck interface between the proposed and the existing configurations, the present research through case studies has proved that: “as long as the FPR of the proposed configuration is higher than the existing configuration then wind uplift ratings can be maintained”. This is valid as long as both the configurations have all the remaining roofing components similar with comparable layout. Based on this verification, the study recommends that the testing lab should report the FPR along with the wind uplift resistance such that FPR can be used as a verification factor to accept design/field alternatives. [Copyright &y& Elsevier]

Abstract: A mechanically attached roof system has flexible membranes that are exposed to environmental elements to achieve the waterproofing function. Wind induced loads can lift the roof membrane between attachment locations and cause fluttering. The membrane under tension induced by wind forces transfers stresses through fasteners at the attachment locations. By characterizing the membrane deformation with its slope and using a force-vector diagram, one can predict the critical forces on fasteners. This paper presents the use of a three-dimensional finite element (3D-FE) model for predicting membrane deformation. To validate the model, a series of benchmark experiments have been performed at the Dynamic Roofing Facility of the National Research Council of Canada. The experimental data are also used to evaluate the validity of a mechanical model. From this comparative exercise between the existing model and the newly developed one, the paper offers the designer the limitations at which the simplified mechanical model can be used. [Copyright &y& Elsevier]

Abstract: The analytical model for reinforced concrete beams strengthened using mechanically-fastened fiber reinforced polymer (MF-FRP) pultruded strips is discussed in this paper. In this method, FRP strips, reinforced with a combination of carbon and E-glass unidirectional fibers and continuous strand mats, are fastened to the concrete with steel powder-actuated (PA) fasteners and expansion anchors (EA). The model predicts the ultimate strength and failure modes of MF-FRP strengthened beams and was developed based on results of tests on over 75 RC beams of many different sizes using the MF-FRP method, that have been conducted over the last five years. These tests have explored numerous different failure modes and factors affecting the behavior of MF-FRP strengthened beams. The analytical model can be used to proportion the strengthening system for an RC beam so as to cause the beam to fail in a unique ductile failure mode. This procedure was used to proportion strengthening systems for large-scale beams (7.3m long by 51cm×51cm) that were used to verify the analytical procedure. The strengthened RC beams were designed to fail in a ductile manner. In the test results presented in this paper, the strengthened beams showed increases in yield and ultimate moments of up to 25% and 58%, respectively over an unstrengthened beam. All strengthened beams failed, as intended, in a ductile manner with the ultimate failure mode due to concrete compression failure at large deflections with the FRP strip still firmly attached. Comparisons between the analytical predictions and the experimental results show good agreement. [Copyright &y& Elsevier]

The Lie product involves two screws, namely, a driver screw (so-called screwer in this paper) and a driven screw (termed screwen in this paper). Thus, in a spatial motion, the screwer performs a displacement of the screwen. Under this context, the Lie product represents the change of the screwen due to the infinitesimal motion performed by the screwer. To this end, this paper sets forth an integrated formulation that brings together a general geometric interpretation of the Lie product and a novel and simple derivation of the Lie product in terms of the involved screws. Moreover, since the formulation is purely geometric, a great deal of physical insight into the description of the motion problem is gained. As a result, the screw partial derivatives, in terms of the involved Lie products, are obtained for three frequently encountered types of kinematic joints, namely, helical, revolute and prismatic. Since the derivation of the Lie product is completely general, this derivation should provide a sound foundation for further applications of the Lie product. [Copyright &y& Elsevier]

[Display omitted] • A type of bolt fasten wedge (BFW) active joint is developed. • Loading tests are conducted on four full-scale specimens. • Load-displacement curves, load–strain curves, moment-rotation curves and failure modes of BFW joints are obtained. • The field test is carried out and compared with the commonly used steel wedge active joint. In this paper, the bearing capacities and failure behaviors of bolt-fastened wedge active joints used in prestressed internal supports are studied. A thorough exploration of the design of the bolt-fastened wedge active joint is elaborated, and an overview, working mechanism, stiffness analysis, parameters, and strength checking are provided. Then, loading tests are conducted on four full-scale specimens. One test is an axial compression test, while the other three tests are performed to analyze the long-axis (Y-axis) eccentricity, short-axis (X-axis) eccentricity, and biaxial (XY-axis) eccentricity. The load–displacement curve, load–strain curve, bending moment-rotation curve, and failure mode of each specimen are obtained. The experimental results show that the samples have good compressive properties and bending resistance. The impact of the X-axis and Y-axis eccentricities on the compressive ultimate bearing capacity is investigated, revealing a significant reduction in the former, while the latter has a minimal effect. Under bidirectional eccentricity, the weakening of the axial bending performance is most apparent. Bidirectional eccentric loads lead to a reduction in the yield load and initial compression stiffness to approximately 90% of those observed under unidirectional eccentricity. Finally, a field test is carried out to compare the constructability and load-holding performances of bolt-fastened wedge active joints with those of commonly used steel wedge active joints. It is demonstrated that the bolt-fastened wedge active joint effectively maintains prestress through bolt fastening, substantially enhancing the safety of foundation pit excavation construction. [ABSTRACT FROM AUTHOR]

Damage to the roofing system during tropical windstorms often results in costly losses for industrial and commercial low-rise buildings. In this paper, finite element models are used to calculate the response of standing seam roofs to wind loading. The study is the first step in a comprehensive program, currently underway at FM Global Research, to develop mathematical models to estimate aggregate losses from severe windstorms. A three-dimensional static and dynamic analysis approach is developed, using ABAQUS, to incorporate details of the geometry and boundary conditions for the roof panels, seams, clips, fasteners and purlins. Only preliminary results are presented in this paper. Detailed validation of the model, using experiments conducted at the University of Western Ontario and at Mississippi State University are in progress. The validated model will be used to assess failure mechanisms of the roof components, fatigue demand, effectiveness of repair schemes and to supplement standard uniform static pressure tests. Additionally, the validated model will be used to construct the vulnerability curves for standing seam roofs. [Copyright &y& Elsevier]

The paper gives a bibliographical review of finite element methods applied for the analysis of fastening and joining from the theoretical as well as practical points of view. The bibliography at the end of the paper contains 726 references to papers and conference proceedings on the subject that were published between 1990 and 2002. These are classified in the following categories: pin joints; thread connections; bolted joints, screws, nuts; rivets; fittings; tubular joints; expansion joints; gaskets; and other types of fastening. [Copyright &y& Elsevier]

Most studies on composite joints focus on in-plane bearing mode, while little attention to fastener pull-through failure mode from out-of-plane loads. This paper presents a 3D continuum damage mechanics (CDM) model to investigate and assess the mechanical behaviors of carbon fiber-reinforced polymer (CFRP) laminates subjected to pull-through failure. The proposed model based on the use of intralaminar and interlaminar damage models is established and implemented by means of a user-defined subroutine VUMAT for Abaqus/Explicit. The novelty lies in the material model integrating the thresholds preset by the semianalytical approximation approach, which largely eliminates unnecessary fracture angle enumerations in Puck's IFF theory, coupled with the simple parabolic interpolation search (SPIS) technique for optimal fracture angle search, considerably reducing the computational burden. Moreover, the numerical results compare well with experiments, effectively replicating the load–displacement response, damage modes, failure behaviors and damaged areas. This study provides an accurate and efficient computational methodology to analyze pull-through failures, enhancing the damage modeling and predictive capabilities for composite joints under out-of-plane loads. [ABSTRACT FROM AUTHOR]

• The half-lap joint has an inclined lapped surface with screws as fasteners. • Four-point bending tests were conducted considering axial compressive forces. • Analytical models were developed for glulam components with half-lap joints. • Axial compressive force improved the capacity and stiffness of spliced components. • Axial compressive force enabled spliced components to fail in a more ductile manner. Glulam gridshells provide a preferred structural form for large-span structures due to their aesthetic appearance and structural efficiency. As the gridshell span becomes large, the length challenge of glulam members associated with the manufacturing and transportation limits needs to be well addressed. Attention should also be paid to the influence of spliced joints on the structural performance of large-span glulam gridshell structures. This paper studies the effect of a type of commonly used half-lap spliced joints on mechanical properties of structural components for large-span glulam gridshell structures. Experimental tests were conducted on a series of full-scale intact and spliced glulam components. Two boundary conditions (i.e., roller and hinge supports) were employed in the tests, investigating the influence of axial compressive forces on the mechanical performance of glulam components. The failure modes, moment-rotation responses, moment capacities, rotational stiffnesses, and ductility factors of the specimens were compared. The test results showed that the moment capacity and the initial rotational stiffness of the roller-supported spliced specimens respectively reached 43.0% and 55.6% of the capacity and stiffness of the intact specimens. Compared to the roller-supported spliced specimens, the axial reaction force provided by the hinge support suppressed the initiation and growth of cracks within the tension zones of the spliced specimens, enabling them to fail in a more ductile manner. Analytical models were then developed to predict the moment capacity of glulam components with half-lap joints. The models were validated by the test results and can serve as a convenient tool for designing such joints. [ABSTRACT FROM AUTHOR]

In many areas of the United States, corrosion is a common cause of steel bridge deterioration. This has caused some state agencies to use stainless steel for bridges in very corrosive environments. However, most steel bridges in the United States contain numerous slip-critical bolted connections, and stainless steel bolts have not historically been used in slip-critical connections. Therefore, there is limited or no guidance on the specified pretension to which stainless steel bolts can be installed. There is also limited or no guidance on the installation parameters, such as the nut rotation for the turn-of-nut method or initial torque and nut rotation for the combined method of installation. In this project, torqued tension tests were conducted on 128 ASTM A1082 UNS S32205 (2205) and 128 ASTM A1082 UNS S17400 Type 630 Condition H1150 (17–4-H1150) stainless steel fastener assemblies. All bolts tests were 7/8 in. in diameter and ranged from 2 to 5.5 in. in length. Multiple types of lubricants were used in the testing to evaluate their effectiveness. Test results were used to improve upon an existing method to determine the specified pretension and installation parameters of each fastener assembly type, depending on strength, ductility, and lubricant criteria. Analysis determined that 2205 fastener assemblies can be installed to a specified pretension of 80% of their ultimate strength while 17–4-H1150 fastener assemblies can be installed at their yield strength. Nut rotation values from snug for the turn-of-nut installation method and initial torque range and nut rotation values for the combined installation method are also provided in the paper. • Torqued tension testing of 2205 and 17–4 PH Condition H1150 stainless steel fastener assemblies. • Specified pretension values for 2205 and 17–4 PH Condition H1150 stainless fastener assemblies. • Turn-of-nut installation for 2205 and 17–4 PH Condition H1150 stainless fastener assemblies. • Combined installation method for 2205 and 17–4 PH Condition H1150 stainless fastener assemblies. [ABSTRACT FROM AUTHOR]

Abstract The method of fastening the trapezoidal sheeting to the supporting beams has a significant influence on their rotational restraint, and thus their buckling resistance. Commonly one fastener is placed in each trough of the sheeting. In this paper the arrangement of two fasteners located near the trapezoidal sheeting webs in every second trough was investigated. Such an arrangement, with the same number of fasteners along the purlin, increases the value of the rotational stiffness C D and in a consequence favorably affects the bending resistance of cold-formed Z-purlins. Such conclusions were based on the results from 28 experimental tests and the results from the corresponding numerical models built in the Abaqus software. The numerical investigation was also extended to the additional 8 models, which had not been tested experimentally. Finally, the buckling resistance of cold-formed Z-purlins restraint by the trapezoidal sheeting, according to Eurocode 3-1-3, for two of the most encountered static schemes of purlin were calculated with the use of rotational stiffness C D values obtained for two arrangements of the sheet-to-purlin fasteners. Highlights • Different arrangement of sheet-to-purlin fasteners was investigated. • New fastener arrangement increases the value of the rotational stiffness C D. • The bending resistance of cold-formed Z-purlins is favorably affected. • The non-linear FEA model was developed to simulate the standard test. • Experimental test results were in good agreement with numerical results. [ABSTRACT FROM AUTHOR]

Highlights • An equivalent model for the railway track behaviour in the lateral plane is built starting from the transmission modes of the inner forces. • Bending moment is transmitted without deforming sleeper and fasteners and is composed of two parts with fixed ratio. • Longitudinal and transversal shear forces are originated by two independent mechanisms. • The model constitutive properties are consistent with the real track behaviour since were derived by an averaging and limiting processes of the strain energies pertaining to the transferring modes, without any kinematical a priori assumption. • Two closed form corrective solutions are given to take into account the local effects due to applied loads and boundary conditions altering periodicity in track response. Graphical abstract Abstract This paper deals with a mechanical model for the analysis of the railway track behaviour built by exploiting the periodicity of the track-structure. The starting point of this study are the inner forces transferring modes. They have been determined by the unit principal vectors analysis of the base cell transfer matrix. The main outcome on bending moments is that they are transferred through the track without deforming the sleepers and fasteners and are composed of two parts: the first one, referred as primary bending moment, is generated by the couple of axial forces acting on each nodal section while the second is due to the curvature changes of the rails. Shear forces are engendered by two independent mechanisms that are associated respectively with the unit changes of the total and primary bending moments. The constitutive properties of the equivalent medium are derived by an averaging and limiting process of the transferring modes strain energies, avoiding any a priori assumption on the kinematics of the substitute medium. Finally, the equilibrium equations are achieved by the virtual work principle. The proposed model is able to reproduce accurately the track behaviour in transferring its inner forces. However, solutions that are equilibrated but not kinematically admissible are obtained from it when transversal loads are applied. In additions, only boundary conditions compatibles with the track transferring modes can be satisfied. This inconsistency is eliminated by superposition of some corrective deformed shapes. These are derived by the eigenvectors of the transfer matrix pertaining to self-equilibrated systems of bending moments decaying along the track. The application field of the proposed track model is also discussed, and the results of a validation study carried out by F.E. analysis are finally presented. [ABSTRACT FROM AUTHOR]

One of the most popular Timber-Concrete connection types is the dowel type fastener, due to many factors, such as for example, simplicity, low cost and adequate performance in most conditions. This connection type was traditionally used in timber structures and was adopted for composite structures from the early ages. The basic phenomena governing the mechanical behavior of timber-timber and timber-concrete connections with dowel type fasteners are similar, however, the last show some relevant specificities due largely to the presence of concrete. Such specificities have a non-negligible influence in the performance and consequently in modelling and design. In this paper such specificities are discussed, as well as, their consequences in the modelling. Based on this analysis proposals are made for models to estimate the connections’ load carrying capacity and slip modulus. Additional the existing knowledge about the performance of notched connections is summarized. Therefore, also values for important design parameters such as minimum values for the geometry, values for the slip modulus and possible failure modes of a notched connection are given. [ABSTRACT FROM AUTHOR]

Transition zones in railway tracks are the locations with considerable variation in the vertical stiffness of supporting structures. Typically, they are located near engineering structures, such as bridges, culverts, tunnels and level crossings. In such locations, the variation of the vertical stiffness and the differential track settlement result in amplification of the dynamic forces acting on the track. This amplification contributes to the degradation process of ballast and subgrade, ultimately resulting in the increase of maintenance costs. The paper studies a corrective countermeasure that can mitigate the track degradation in transition zones when differential settlement appears. The countermeasure is the adjustable rail fastener and its working principle is to eliminate the gap under hanging sleepers by adjusting the shims (height of the fastener). The adjustable fasteners are first tested on three transition zones, wherein the adjusted heights of fasteners (accumulated voiding) are recorded after the 2-month and 5-month operation. The test results show the adjustable fasteners are effective to mitigate the track degradation in the transition zones. The effect of the adjustable fasteners on the dynamic behaviour of transition zones is analysed using the FE method. The results show that the adjustable fasteners are effective to reduce the amplification of wheel forces, achieve a better stress distribution in ballast, and decrease the normal stresses in rails in transition zones. Parametric studies are also performed to study the applicability of the adjustable fasteners. [ABSTRACT FROM AUTHOR]

Recent laboratory experiments have demonstrated the superior performance (high stiffness, load-carrying capacity and ductility) of bolt shear connectors embedded in the pockets of cementitious grout compared to conventional fasteners (e.g. screws) for developing composite action between steel beams and timber slabs. Accordingly, this paper investigates the structural behaviour of steel-timber composite (STC) joints with bolt connectors embedded in grout pockets (BCGP) using 3-D continuum-based finite element (FE) models. Following validation of the FE models against available push-out test data, they are used to conduct a parametric study that elucidates the influences of the compressive strength of the grout, the yield strength and size of the bolt shear connectors, the size of the grout pockets and the thickness of the steel profile flange on the load-slip behaviour, service stiffness, peak load-carrying capacity and failure modes of STC joints with BCGP. Simple formulae for the stiffness and load-carrying capacity of the STC joints with BCGP are derived from linear regression of the results of the parametric study. [ABSTRACT FROM AUTHOR]

This paper focuses mainly on the mechanical behaviour of unclassified cross-laminated timber walls under lateral loading (seismic and wind loads). Unclassified wooden planks were used to construct the wall unit with an odd number of layers (three) for each wall, with the planks in each layer in a perpendicular relative orientation. In this research, an experimental study of large-scale timber walls was carried out with a view to determining the lateral load resistance. Diagonal struts, under tension and compression were employed on the cross-laminated walls to investigate the effects of these elements on the lateral resistance of the wall. A theoretical approach has been developed to describe the overall behaviour of the cross-laminated wall and to investigate the internal forces on the fasteners. The present work is then compared to Oriented Strand Board (OSB) panel designs. Based on the data and results obtained from the experimental tests, this study confirms, firstly, that cross-laminated walls without a diagonal strut have approximately double the horizontal strength of (OSB) panels, secondly, that diagonal strut significantly increases the lateral load resistance of cross-laminated walls, particularly under compression conditions, and thirdly, the proposed theoretical approach shows similar performance to the average experimental test up to 100 mm of overall lateral displacement of cross-laminated timber wall. [ABSTRACT FROM AUTHOR]

Variabilities in geometrical and material properties occur systematically after manufacturing and joining operations on different parts of an assembly. The behaviour and structural performance of composite/composite or composite/metal fastened joints are particularly sensitive to some of these variabilities. Controlling the effect of variabilities by tolerancing uncertain parameters is therefore crucial to avoid the failure of the structure. However, performing a variability study is generally costly because a large number of configurations need to be evaluated, especially when the behaviour model of the system is a numerical one. This paper presents an approach for tolerance synthesis of uncertain parameters in fastened metal-composite joints. The low time-cost of the approach is ensured by using a reduced finite element model of the joints and a strategy to reduce the number of calculations. Both probabilistic and worst-case approaches for the propagation of uncertainties can be applied through the proposed tolerancing synthesis. An allowable tolerance value for an uncertain parameter can then be easily calculated by identifying an analytical law which links tolerance to a structural performance criterion. The robustness of the proposed approach is illustrated by its application to a 4-bolt metal-composite single-lap joint where several sources of variability are introduced (i.e. hole-location error, pin/hole clearance, fastener preload). [ABSTRACT FROM AUTHOR]

With tremendous weight saving potential, magnesium alloy high pressure die casting components have been widely used for automotive applications. Magnesium fastening technology is thus becoming increasingly important to design engineers. Joining as-cast holes of magnesium high pressure die casting components with thread forming fasteners provides significant advantages for the assembly process, overall cost benefit and joint integrity. This type of joint is thus preferred for structural applications. Designing the thread forming fasteners with as-cast holes follows the general rules for designing for the machined holes, including carefully designing the variables such as the assembly torque range, the length of thread engagement, the hole diameter and required failure mode. In addition, special attention needs to be paid to the draft angles of the magnesium cast components that are required for the die casting process. In this paper, the effects of above key factors, individually and combined, on the joint performance of thread forming fasteners with as-cast blind holes of AM60B magnesium components are studied. A joint design philosophy was proposed to optimize both joint performance (the prevailing torque, the failure torque and the failure mode) and manufacturing easiness (the hole diameter and corresponding draft angle). The detailed design considerations for as-cast holes of magnesium HPDC are discussed and explained through a hypothetical example. [ABSTRACT FROM AUTHOR]

Light gauge steel roofing systems of low rise buildings are made of high strength steel roof cladding, battens and purlins/rafters/trusses and fastened with self-drilling screws. Localised failures occurring at these screw connections under wind uplift loading often lead to catastrophic losses of steel roofing systems during severe storm events. Pull-out failures occurring at the two bottom flanges of roof batten to purlin/rafter screw connections is one of them. Multiple screw fasteners connecting the bottom flanges of roof battens to purlins/rafters pull out prematurely from the light gauge steel purlins/rafters. Since the structural behaviour of multiple screw connections differs significantly from the behaviour of single screw connections, the pull-out capacity of multiple screw connections cannot be calculated directly based on the number of screw fasteners. Hence a series of 80 small scale pull-out tests was conducted to investigate the pull-out capacities of two and four-screw fastener connections in roof battens. The pull-out failure loads from the tests were first compared with the pull-out capacities predicted using the design equations in the current cold-formed steel design standards. Suitable design modifications were then proposed to accurately calculate the pull-out capacities of roof battens with two and four-screw connections. This paper describes the details and the results of this study. [ABSTRACT FROM AUTHOR]

Cold-formed steel hollow flange beams have been commonly used as flexural members in buildings due to their structural efficiency. The rivet fastened Rectangular Hollow Flange Channel Beam (RHFCB) is a new type of cold-formed steel section, characterized by two torsionally rigid hollow flanges connected to a web element. The RHFCB takes advantage of an intermittent fastening method using self-pierce riveting. Buckling analyses have shown that the moment capacity of short-span RHFCB is governed by local buckling while intermediate span RHFCB is governed by the unique lateral distortional buckling. An experimental investigation of RHFCB flexural members was carried out based on a quarter point loading method to investigate their lateral distortional buckling behaviour and moment capacities. It considered the effects of intermittent rivet spacing on the member moment capacity of RHFCBs. The results from the experiments were compared with the member moment capacities predicted using the Australian cold-formed steel structures standard. Following the experimental study, finite element models of tested RHFCBs were developed to simulate the experiments. The developed finite element models were validated by comparison of ultimate moment capacities, applied moment versus deflection curves and failure modes. This paper presents the details of the experimental investigation, the development of finite element models of RHFCBs subject to lateral distortional buckling effects, and the results. [ABSTRACT FROM AUTHOR]

Premature failure of cable bolts due to stress corrosion cracking (SCC) is a phenomenon that has reported to occur in underground environments. This paper presents an experimental study to determine the impacts of environmental factors on SCC in high-carbon steel cable bolts used in ground support system. The service life of the wire strands was measured under a range of accelerated SCC conditions using three- and four-point loading jigs. Fractographic analyses of the fracture surfaces of the failed wires displayed typical features indicating that hydrogen embrittlement was involved in SCC in these tests. It was shown that the presence of hydrogen sulphide is more critical than its concentration in SCC. The pH and level of applied stress were determined to have a direct impact on the occurrence of SCC. The deflection angle of the crack path was observed to be an inverse polynomial function of the applied stress level in the wire. This demonstrated the significance of the stress level on the fracture mechanism of cable bolts. Furthermore, the use of a protective galvanised coating on cable bolts was found to be a promising countermeasure against SCC. The results of this study provide detailed insight into the environmental factors involved in SCC of high-carbon steel wires and can be further used for setting guidelines for assessment of environments which cause susceptibility to SCC. [ABSTRACT FROM AUTHOR]

In this paper, the compound strip method is applied to the stability analysis of cold-formed steel built-up sections. A beam element with adjustable stiffness properties is adopted to represent the utilised fastener and the associated stiffnesses of the connection elements are incorporated in the global stiffness matrix of the built-up sections. The presented method allows for modelling arbitrarily-located discrete fasteners in the context of the semi-analytical finite strip method. The proposed numerical technique is verified against finite element solutions through various numerical examples and shown to be both accurate and versatile. Some typical and also complex built-up sections with various fastener configuration and end boundary conditions are analysed to evaluate the influence of fastener spacing. The extent of composite behaviour in built-up sections is determined by investigating the enhancement of buckling capacity and changes in the corresponding buckling modes. The simplicity of the proposed technique expedites extensive parametric studies of cold-formed built-up sections and facilitates the search for optimal placement of fasteners and choice of section geometry. [ABSTRACT FROM AUTHOR]

Predicting the mechanical behaviour and the failure mechanism of timber joints with dowel-type fasteners requires consideration of several factors, including the geometrical and mechanical properties of the metal fastener, the physical properties of timber and the interaction between such elements. This paper proposes a numerical model where a joint is schematized as an elasto-plastic beam in a non-linear medium with a compression-only behaviour. Unlike the differential approach adopted by most of the hysteresis models published in literature, this model predicts the load-displacement response using simple mechanical relationships and basic input parameters. Furthermore, the model is capable of reproducing the effect of the cavity formed around the fastener by timber crushing, and simulates the hysteretic behaviour and the energy dissipation under cyclic conditions. Shear tests are reproduced on nailed steel-to-timber joints in Cross-Laminated Timber and results are compared to the experimental test data obtained on similar single fastener joints. Simulations lead to accurate predictions of both the mechanical behaviour (initial stiffness, maximum load-carrying capacity, global shape of the loading curve and of the hysteresis cycles) and the total energy dissipation observed in the tests. [ABSTRACT FROM AUTHOR]

Steel roofing is widely used for non-residential facilities. However, it is vulnerable to high winds. This paper addresses a damage estimation framework that incorporates wind loading correlation and wind directionality effects for steel roofing. In this framework, external pressures were measured from wind tunnel testing. At positions where pressure measurements are not available, a proper orthogonal decomposition (POD) method is introduced to interpolate external wind pressures. Internal pressures due to openings in the building envelope are taken into account by simulation. Then, the internal forces on fasteners distributed on the steel roof are evaluated by the influence-surface-based method, with corresponding peak values estimated by a Gumbel conversion approach. Furthermore, the failure probability of a single cladding element and the damage ratio for the whole roof are determined based on Monte Carlo simulation (MCS), where the correlation among internal forces of fasteners is incorporated by a Nataf transformation. Finally, wind directionality effects are integrated in order to provide a comprehensive damage assessment for the roofing. Although the proposed framework works for existing buildings, it may potentially benefit the performance-based design for new low-rise buildings. [ABSTRACT FROM AUTHOR]

• The failure mechanism of elastic strip fracture is studied by resonance response and fatigue failure. • A wheelset-rail-cologne-egg fastener system in corrugated section is built. • Elastic strip failure can be controlled by grinding and changing fastener damping. • The elastic strip model, installation state and constraint conditions are verified. Rail corrugation is a typical problem on rail surface, and its high-prevalence section is often accompanied by the fracture of fastener elastic strip. The present paper focuses on the fracture mechanism and control method of the Cologne-egg fastener elastic strip in the high-prevalence section of rail corrugation. Firstly, the numerical simulation model of wheel-rail-fastener system considering the key components of Cologne-egg fastener is completely constructed. Then, the fracture mechanism of Cologne-egg fastener is explored by comprehensively considering the resonance response and fatigue failure of the fastener elastic strip. Finally, the corresponding control methods are proposed by the passive control of rail grinding and active adjustment of fastener structure. Analysis results show that the intensified wheel-rail friction coupling vibration in the corrugation zone leads to the resonance response of the Cologne-egg fastener elastic strip, which intensifies the vibration response of elastic strip. Then, the aggravation of vibration response of the Cologne-egg fastener elastic strip leads the fatigue of the elastic strip, and the outer elastic strip is easier to fracture than the inner elastic strip on the low rail of small-radius curve. Controlling the corrugation depth before 0.16 mm or adjusting the elastic modulus of the damping rubber to be 2.20 MPa and 9.40 MPa can increase the service life of Cologne-egg fastener elastic strip. [ABSTRACT FROM AUTHOR]