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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]

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]

• 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]

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: 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 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]

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]

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]

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]

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]

Throughout the international railway community, there are many different designs of elastic fastening systems that have been developed to meet a variety of design specifications and performance expectations. Historically, in North America, the most common types of fastening systems used for concrete crossties are the Safelok I or e-clip systems. In recent years railroads have begun implementing the Skl-style (W) fastening system with concrete crossties in existing and new heavy haul freight railroad mainlines. The magnitude of lateral force applied to the Skl-style fastening system is important information for both design and application purposes. Despite this importance, the lateral force applied to the Skl-style fastening system in a heavy haul freight railroad environment has never been quantified to date. To better understand how the Skl-style system performs under the magnitude of lateral loads observed on heavy haul freight railroads, research was conducted by the Rail Transportation and Engineering Center (RailTEC) at the University of Illinois at Urbana-Champaign (UIUC). The focus of this paper is on laboratory characterization of the lateral load path through the Skl-style fastening system using novel instrumentation techniques that are subjected to heavy haul freight railroad loading conditions. The investigation of fastening system performance included an evaluation of lateral load distribution through the track superstructure, and a single fastening system. Laboratory experimentation concluded that lateral wheel load is primarily distributed to three crossties, the relationship between lateral wheel load and lateral force resisted by field side angled guide plate is non-linear, and that the design of the Skl-style fastening system allows lateral force to be transferred into the crosstie below the worst case concrete compressive fatigue strength. The observations from this study will assist the rail industry in improving fastening system design and developing mechanistic track structure design method. [ABSTRACT FROM AUTHOR]

The use of a running clamping technology enables clamping with a welding robot during laser welding in the body-in-white shop. Unlike common clamping fixtures, clamping is operated force-controlled. In this paper a FE-simulation method of the clamping process with the running clamping technology is presented. The method is applied to a clamping experiment with aluminum L-specimens. Objective of this simulation method is the prediction of the clamping force required to close the gap between sheet metal part flanges. A closed gap between flanges is necessary to achieve a proper weld seam. Furthermore, stresses and strains as well as potential plastic strains emerging during the clamping process can be identified using FE-simulation. In this contribution the simulation method is described in detail including assumptions and simplifications, due to the transfer from real experiment to virtual model, as well as important parameters of contact modeling. Comparison of simulation results to experimental investigations shows a reasonable correspondence. [ABSTRACT FROM AUTHOR]

In the present paper, the retrofitting of welded flange plate moment connections joined to double-I built-up columns is discussed by presenting the design method and details of construction retrofitting. Some of the usual construction problems of this connection include the defective complete joint penetration groove weld at the connection of the flange plate and the column, the large out-of-plane deformations of the column cover plate at the level of the beam-to-column connection, and as a result, its inappropriate seismic performance and the connection's partially restrained behavior. Thus, an attempt is made to evaluate the advantages of strengthening this defective connection with the help of lateral T-stiffeners using analytical and experimental studies. For this purpose, the experimental specimen and the high-fidelity finite element model are considered for both retrofitted and defective connections by evaluating the proposed design method, cyclic behavior of connection, collapse potential of weld fasteners, and failure modes. The results indicate that by using the proposed retrofitting method, the connection is classified in the group of fully restrained connections, while also having the necessary strength and ductility to accept the conditions of the special moment-resisting frames according to AISC seismic provisions. By performing a sensitivity analysis on the T-stiffener, changing its dimensions and examining the damage indices, the accuracy of the proposed design method is proven. The examinations indicate that the aforementioned retrofitting method is a proper method for the introduced defective connection. • Presenting the design method and detailing of retrofitting the WFP connections by T-stiffener • Retrofitting method meets the requirement of AISC seismic provision for SMFs • The possibility of using the T-stiffeners for the double-I columns based on experimental study • Reducing the stress demand in the existed defective welds by using the T-stiffener • Proving the optimality of presented geometry of the T-stiffeners through parametric studies [ABSTRACT FROM AUTHOR]

In the absence of external forces, the preload of the bolted joint will decrease due to self-loosening after the tightening process is completed. Self-loosening of a bolted joint will result in unstable contact between connected components, affecting the overall performance of mechanical equipment. This paper proposes a method for fastening reliability analysis of bolted joints considering the uncertainty of preload, friction coefficients, and material properties. The finite element method (FEM) is used to study the self-loosening behavior of a bolted joint under elastic conditions. The metamodel is constructed based on the proposed finite element model to improve computational efficiency. In addition, the fastening reliability of the bolted joint is calculated using the Monte Carlo simulation (MCS) method. Finally, the practical application of calculating the fastening reliability and a detailed analysis is presented to evaluate the proposed method's efficiency. The results show that the recovery of accumulated elastic deformation of a bolted joint generates self-loosening. In contrast, the torsional elastic deformation of the bolt rod causes relative rotation between the bolt and the nut. When the characteristic parameters obey the normal distribution, the probability distribution of preload reduction ratio approximately obeys the normal distribution. According to the proposed reliability calculation method, the reliability of bolted joint self-loosening is 99.7725% when the preload reduction ratio exceeding 0.026 is considered as self-loosening failure. • The self-loosening behavior of bolted joint without external load is studied. • A FEM-Kriging model based method is proposed to improve the efficiency of calculating the fastening reliability of bolted joint anti self-loosening. [ABSTRACT FROM AUTHOR]

Assembly is an important process of aerospace industry which involves significant number of fastening elements such as bolts, washers and nuts, etc. Presently, the identification of these elements is done manually by humans. Since human operators are prone to errors, any fault in the assembly line can have a major impact on the overall efficiency and safety of an aerospace vehicle. In this paper, we present a deep learning and image processing-based approach for identification of mechanical fixation/fastening elements used in the aerospace assembly line. We propose YOLO-v5 algorithm to classify the components based on their head and lateral shape. We also propose an image processing method to estimate the spatial dimensions of the assembly line components including thread pitch. Moreover, this study also features the development of an image acquisition platform with two cameras mounted and proper lighting mechanism to capture quality images. Despite the challenges associated with such systems, the proposed deep learning (YOLO-v5) algorithm has shown promising results with a mAP@0.5 of 0.996 for component classification. Whereas, the proposed image processing mechanism achieved an accuracy of 100% for standard size assignments with a maximum error of 0.05 mm for pitch calculation. [ABSTRACT FROM AUTHOR]

This paper proposes a new material efficient process for producing lightweight tubular screws and nuts. The process is built on the fundamentals of tube end forming and combines tube reduction, expansion, flaring and compression beading to establish two multi-stage cold forming sequences for producing hexagon head tubular screws and nuts. The methodology draws from the mechanical characterization of the material to the design and fabrication of an experimental apparatus consisting of several individual die sets. The investigation is supported by finite element modelling and it is aimed at evaluating the major process parameters, the overall feasibility of the process and the required forming loads. [ABSTRACT FROM AUTHOR]

• Wet condition can influence on FFU sleepers performance. • Two common screws used for FFU fastening system are studied. • Pulling out test is supported by DIC for crack opening and strains measurement. • Numerical modeling was developed to measure stress distribution on FFU specimens. • Wet condition may influence a lot on FFU sleeper fastening system performance. This paper studies the structural integrity of fastening systems used in fiber-reinforced foamed urethane (FFU) composite sleepers. 24 FFU specimens are studied with screw pull-out tests and digital image correlation (DIC) to investigate the effects of parameters such as wet conditions, the sleeper drilled hole diameter and the screw active length inside the sleeper. The pull-out test results reveal that a moisture content of 0.3% in FFU specimens can reduce the pull-out strength between the dry and water-absorbed specimens with 18 mm FFU hole and 80 mm screw active length in dry and wet states (18-AD &18-AW), 18 mm FFU hole and 90 mm screw active length in dry and wet states (18-BD & 18-BW), 20 mm FFU hole and 110 mm screw active length in dry and wet states (20-CD & 20-CW), and 20 mm FFU hole and 90 mm screw active length in dry and wet states (20-BD & 20-BW) by approximately 18%, 19%, 6% and 13%, respectively. Specimens with 20 cm holes have the highest pull-out loads of 71.9 kN and 68 kN in dry and water-absorbed states, respectively. When the active length of the screw decreases from 110 mm to 90 mm, the pulling strength decreases by approximately 14% and 16% in dry and water-absorbed states, respectively. Therefore, the experimental and FEM results show that a 20 mm FFU hole with a 110 mm active length and a 24 mm thick screw is the best option for an FFU sleeper fastening system, especially in wet conditions. [ABSTRACT FROM AUTHOR]

This paper examines the accuracy of a recently developed hygrothermal-corrosion model which predicts the corrosion of fasteners embedded in wood by comparing the results of the model to a one year field test. Steel and galvanized steel fasteners were embedded into untreated and preservative treated wood and exposed outdoors while weather data were collected. Qualitatively, the distribution of corrosion products along the length of the fastener were in agreement with the simulation results. Quantitatively, the combined hygrothermal-corrosion model predicted 20% less corrosion than measured in the exposure test for galvanized steel fasteners due to a lower simulated moisture content. [ABSTRACT FROM AUTHOR]

This paper describes the failure analysis of propeller blade fastening bolts made from martensitic stainless steel 0Cr16Ni5Mo, which was ruptured under service of cathode protection for 5 years. The general crack pattern of the bolts, fractographic features, hydrogen content determination and slow tensile test results are all exhibiting the characteristics of hydrogen embrittlement. Accordingly, hydrogen diffusion driven by hydrogen concentration gradient and stress concentration was identified by experiment and finite element analysis (FEA). The morphology of the crack was intergranular of initiation from bolt cap root surface, and quasi-cleavage of propagation. The hydrogen distribution indicated that the hydrogen concentration in the bolt was in gradient distribution, and the region farther away from the sea water contains less hydrogen content. This revealed that hydrogen entered the bolt top surface through sea water under cathodic protection, and diffused from top to cap. The hydrogen content of the cap where crack initiated was 7.0 ppm, which was much higher than that in bolt shaft with normal content of 1.1 ppm. Results of low tensile test together with fractographic observation showed that the brittleness of the bolt was enhanced by the effect of hydrogen. Stress distribution calculated by FEA analysis indicated that the maximal stress of the bolt was about 1016 MPa, located at cap root surface which was consistent with crack initiation sites. The stress drove hydrogen to accumulate at root surface until cracking occurred. In a sum, the failure was attributed to the hydrogen diffusion, local high stress, and the martensitic microstructure susceptible to hydrogen embrittlement. Remedial measures such as avoiding over protection potential, that increase tempering temperature were suggested. Methods to optimize stress distribution of the bolt were also suggested based on FEA calculation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present and to analyze the capabilities of a process named “springback-forming”, dedicated to stiffened panels such as airplane׳s fuselage panels. The principle of this forming process is to apply a tension on the stiffener, before the assembly stage with the sheet in a flat configuration using fasteners, adhesives, or a welding process, etc., the bending of the structure is then achieved by springback energy of the stiffener when its tension is released. Using an analytical and finite element models, we studied the capabilities of this process in terms of curvature limits in the case of a single-curved stiffened panel. The results of both models are in good agreement. Through a parametric study, numerical simulations show that when the structure is relatively slender the curvature radius obtained is uniform. Moreover, the value of this radius is independent of the structure׳s length and is mainly limited by the stiffener׳s height. The carried out experimental tests, using laser beam welding as a joining process, demonstrated the feasibility of the process. From the proposed modeling, it is possible to evaluate the range of achievable curvature radius and its uniformity for different values of both geometrical and mechanical parameters of the structure. [ABSTRACT FROM AUTHOR]

Applicability of currently available approaches to predict the fatigue life of riveted joints in aircraft structures is limited to cases when the actual joint, for which the predictions are made, and the reference joint, for which the prediction model has been tuned, differ only in the geometry. It is required that the riveting process should be similar for the actual and reference case, but the similarity criterion cannot be formulated in a precise way. In the prediction model developed by the authors and presented in this paper the influence of riveting on the fatigue life of a joint is unambiguously characterized by measurable quantities, namely rivet hole expansion and the load transfer distribution. Hence, the similarity of the riveting processes for the reference and actual joint is no longer required, which considerably extends the transferability of the reference results. A validation of the model is performed by comparing fatigue lives computed and observed in over 80 fatigue tests on aluminium alloy, lap joint specimens with three rivet rows, typical for aircraft fuselage skin connections in the longitudinal direction. Various combinations of production variables, such as sheet material and thickness, the squeeze stress and rivet type, were involved. A significant improvement in the present model prediction accuracy compared to a model which disregards the effect of riveting has been noted. Specifically, underestimates or overestimates of the fatigue life observed for the latter model in the case when hole expansion of the actual joint is larger or smaller respectively than for the reference joint are avoided with the present approach. [ABSTRACT FROM AUTHOR]

Reinforced concrete construction and steel construction are two of the most common contemporary construction methods. Both methods make use of composite decks as floor systems and diaphragms. During the design of composite decks, the interaction between the steel deck and concrete slab is typically disregarded when calculating the strength of the composite diaphragm due to lack of complete shear transfer, as existing practices such as stamping are not effective to provide substantial composite action. This conservative assumption essentially results in non-efficient use of material. This paper presents a method for ensuring shear transfer through the use of conventional sheet metal screws, driven through the corrugated steel deck and embedded in the fresh concrete. This method is proposed for use in the field between formed steel beams. Both experimental and analytical studies support an increase in strength with the addition of embedded fasteners. Further, experimental results indicate an additional increase in strength with the addition of synthetic reinforcing fibers. The increase in strength with the addition of the fasteners is on the order of 100%. When fasteners are already in use, the addition of synthetic reinforcing fibers can increase strength on the order of 10%. The ultimate deflection of enhanced deck is comparable to deck tested without fasteners, but the initial stiffness of enhanced deck is much higher. [ABSTRACT FROM AUTHOR]

This paper describes the results of a continuing study into a new class of multi-site damage problems, viz: the interaction between intergranular cracks and cracks that grow from small naturally occurring material discontinuities at a fastener hole, and extends the findings of the prior investigation by considering the effect of contact between opposing faces of the intergranular cracks. This study suggests that, for the particular problem analysed, the level of contact between the opposing surfaces of the intergranular cracks has little effect on crack growth and that intergranular cracks have little effect, i.e. less than approximately 11%, on crack growth. [ABSTRACT FROM AUTHOR]

In this paper, the influence of modeling the fastening with solid railpads on the vertical dynamics of railway tracks with monoblock sleepers is investigated. A 3D finite element (FE) model is presented with four different fastening representations: (1) commonly used spring-damper pair, (2) area covering spring-damper pairs, (3) solid railpad connected to the rail, and (4) solid railpad in frictional contact with the rail and fixed to the support by preloaded springs, which represent the clamps. The response of the four models to hammer excitation is simulated in the time domain, and the calculated response is transformed into the frequency domain to analyze how the models capture the seven main characteristics of tracks with monoblock sleepers. The numerical results show that the model with solid railpads and clamps reproduce the seven characteristics at a maximum frequency difference of 6%, while the conventional model with spring-damper pairs reaches only a 27%. In the improvement of the fit from multiple spring-damper railpad models to solid railpad models, the two key aspects identified are the Poisson׳s effect and the damping of the ballast. Additionally, the railpad type investigated showed a frequency-independent behavior, at least with acceptable error. In view of the close fit, the models with solid railpads can be used for track and fastening design and to derive track parameters to, for instance, study the deterioration of tracks. [ABSTRACT FROM AUTHOR]

• Experimental and numerical investigations have been done on four dimensions of anti-loosening bolt system. • The tested novel bolt system has shown superior capacities to withstand self-loosening, compared to the standard bolt-nut system, under equal conditions. • The new bolt locking system can be used in any joint or mechanical system where self-loosening is real or potential problem. In general, bolted connections are exposed to vibrations or repeated over-loads that could lead to self-loosening due to loss of preload. Pre-tensioned bolts in ring flanges are critical parts in Offshore Floating Wind Power Systems, and normally a certain percentage of the installed bolt connections are checked and re-tightened every year. This re-tightening is often done at a high cost and a short weather window due to strong winds and high waves. In this paper, three bolt dimensions (M20, M30 and M42) of the anti-loosening bolt system have been tested. The M30 and M42 bolt systems were preloaded and exposed to transverse oscillating loading, and the loss of preload as a function of load amplitude and number of cycles were measured and compared to standard bolts of HV type, exposed identically. The tested novel bolt system has shown superior capacities to withstand self-loosening, compared to standard bolts. [ABSTRACT FROM AUTHOR]

• Shear strengthening system using inserted fasteners is a very effective strengthening method for wide-shallow beams in shear. • The use of single steel plate to cover shear spans instead of steel angles increased the ultimate load and helps the specimens' exhibit much more ductile. • No significant effect for inclined fasteners on the specimen shear capacity compared with vertical fasteners. • The developed analytical formula gave reasonable values for the ultimate capacity that agreed with the experimental results for strengthening wide-shallow beams specimens. Wide-shallow beams are commonly used in bridges, and in most cases their collapse is governed by the shear failure. Accordingly, previous research was based on studying how to strengthen the wide beams in the shear, using different methods, most of which were internal modifications, whether in the stirrups or with special additives to the concrete used. This paper provides a new technique for shear strengthening of wide beams, and for this purpose, an experimental program with thirteen specimens is considered. The proposed technique relied mainly on the use of internal and external fasteners, whether vertical or inclined in the shear span zones of specimens. The effect of using a single steel plate instead of steel angles on the process of fixing fasteners was also studied. Cracking patterns, ultimate loads, failure mechanisms, load–deflection and load–strain relationships were investigated for the beam specimens. The results indicated that the proposed technique is a very effective strengthening method and enhances the shear capacity. In addition, a proposed analytical formula is suggested to calculate the effect of the new strengthening technique for wide-shallow beams and showed good agreement. [ABSTRACT FROM AUTHOR]

Fatigue is one of the most common failure modes of structures and components. The prediction of fatigue crack propagation in real structures must take into account realistic boundary conditions. The purpose of this paper is to describe a technique for modelling fasteners through FEM global structure modelling and using the model for stress state analyses and crack growth prediction. The consideration of fastener stiffness during stress analysis is an integral part of the damage tolerance philosophy. The FASTRAN retardation model with a load sequence simulating the real operational service of an aircraft structure was used for crack growth prediction. [ABSTRACT FROM AUTHOR]

Tensile failure is a primary failure mode in structures with multi-fastener joints specially for large bypass loads. Therefore, the precise prediction of the net-tension strength of these joints is essential for reliable design of many engineering structures. In this paper the analytical model presented by Kabeel et al. (2014) has been extended to predict the net-tension strength of double-lap joints under combined bearing-bypass loading conditions. Due to the ability of the cohesive law to predict the effect of the structure size on its strength, the present model is formulated based on the cohesive zone model. The effect of the bypass stresses on the joint net-tension strength has been studied. The present model is able to predict the optimum geometry of the joints and, consequently, its maximum nominal strength. A comparison of the obtained predictions with those of the available experimental work reveals good agreement. The obtained results can be used as design charts for the double-lap joints that are made of isotropic quasi-brittle materials. [ABSTRACT FROM AUTHOR]

In this paper, stress analysis of holed plates was implemented in order to estimate the fatigue life due to the combined effect of cold expansion and bolt tightening (clamping force). The fatigue life was divided into two phases of crack initiation life and fatigue crack growth life. The fatigue crack initiation and fatigue crack growth life estimations have been investigated numerically and the total estimated fatigue lives have been compared with the available experimental fatigue test results. To obtain the residual stress, pre-stress and strain distributions created by cold expansion and bolt clamping force, and also the stress and strain distributions under cyclic longitudinal loads, three-dimensional finite element models were employed using ANSYS software. The results obtained from the finite element analysis of cold expansion and bolt clamping were employed to predict the fatigue crack initiation life using Fatemi–Socie multiaxial fatigue criterion, and fatigue crack growth life using AFGROW computer code. The results show that there is a good agreement between the numerically predicted total fatigue life and experimental fatigue test results. [ABSTRACT FROM AUTHOR]

Composite and precast concrete structural systems are becoming the first choice for many construction designers. Headed fastenings are currently a relatively common technique to create joints in such types of structures. Performance of fastenings usually depends on load capacity of the concrete surrounding the fastening. The resistance of the fastening may be increased by using supplementary reinforcement designed in order to prevent concrete cone failure. The background of current design methods and experimental research is discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: The function of fuel channel fastener assembly is to keep enough clearance between fuel channels, allowing the insertion of control rod and fixing the channel on the fuel bundle. The assembly device is not safety related component, however, in case of the screw breaking, it may cause loose parts, which might adversely affect the normal operation of inserting and pulling fuel assemblies, and/or the movement of the control rods. In this paper, the possible loading conditions applied to the fuel channel fastener assembly are considered to analyze the stress state in screw. In order to assess the improper positioning of fuel channel, explicit finite element procedures is employed to simulate the complex contact/impact behaviors occurring between the fastener assembly and the neighboring fuel channel or the fuel rack, in which the effects of dynamic impact on the screw and initial contact speed are the main concern. The analysis results reveal that the reduced neck close to the screw head has the highest stress. If the external loads drive the stress up to the yielding limit, crack initiation will occur on the screw neck and thereby, under the tensile loadings and reactor core environment, initiating intergranular stress corrosion cracking (IGSCC) on the screw. [Copyright &y& Elsevier]