Fastener Failure Research Articles

Research on track vibration characteristics and rail corrugation based on fastener failure

Based on the measured rail corrugation data on the curve, a rigid-flexible coupling vehicle-track system dynamic model is established. The stiffness and damping of the fasteners were changed to simulate the failure behavior of the track structure, and the influence of fastener failure on the vibration characteristics of the system was studied to determine the causes of rail corrugation. The research results show that: (1) The number of peaks on wheel-rail vibration significantly increases after fastener failure, which increases the probability of wheel-rail resonance. The fastener failure causes more frequent wheel-rail resonance, leading to severe system vibration and increased wheel-rail wear. (2) The simulated wavelength of 57 mm on the slight radius curve with the highest proportion of corrugation is similar to the measured wavelength of 55 mm. The fastener failure is related to the generation of rail corrugation, which verifies the existence of rail corrugation on site. (3) The smaller the curve radius, the greater the lateral and longitudinal creep forces and wear number, indicating that the degree of rail corrugation on slight radius curve is more severe. When the slight radius curve and fastener failure are satisfied together, the lateral and longitudinal creep forces and wear number reach their maximum values, which further accelerates the generation of rail corrugation.

Identification Methods for Modal Parameters of Track Structures and Their Application Status and Prospects

Rail transit’s wheel–rail system periodically encounters defects such as wheel polygons, rail corrugation, and rail fastener failure, which are intricately linked to the modal parameters of track structures. Identifying these modal parameters is essential for refining wheel–rail dynamics models, understanding track defect mechanisms, and defect detection. This study reviews the current methodologies for identifying track structure modal parameters, emphasizing their significance in track engineering. It categorizes various identification techniques, examines their development, and highlights their application in updating track dynamics theoretical models. The relationship between track modal parameters and wheel–rail defects is discussed, alongside a summary of modal parameter-based defect remediation strategies globally. The paper also evaluates the current state of defect identification research utilizing track modal parameters. In the “prospects” section, three forward-looking research avenues are proposed. These approaches are poised to streamline and improve the efficiency of modal parameter extraction, marking potential breakthroughs in the field.

Behavior of steel liner tray walls under external blast: Experimental testing and numerical simulations

Explosions produced in urban or industrial areas due to accidental or intentional detonation of explosives are low-probability but high-impact events. If standoff distance from buildings or other constructions is small, explosions can cause structural failures and serious injuries or deaths of occupants. Although heavy/stiff enclosure systems were long considered appropriate to protect buildings against explosive threats, lighter and flexible steel-based systems, which are increasingly used for modern buildings, may also provide satisfactory performance. The study presents the results of full-scale blast tests on liner tray walls attached to a steel frame building. Walls were tested against increasing blast charges until failure. Due to very high peak pressures and very short durations, the loading regime could be classified as impulsive. The ultimate strength is given by the failure of the end fasteners, after large bolt hole elongations coupled with the pull-through of the end fasteners. If the insulation and outer cladding are lost, the liner trays are directly exposed to blast and the seaming fasteners at overlapping sheets are prematurely lost. As a result, the wall panels work mostly independently, as one-way elements. On the contrary, if the outer cladding protects the seaming fasteners, the overlapping provides additional capacity due to membrane effect (two-way behavior). Numerical models were calibrated using test data and were further used to obtain more information about liner tray behavior under blast.

Research on Vibration Characteristics of a Flexible Vehicle-Ladder Track System

As a means of vibration reduction, the ladder track has seen broad implementation in urban rail transit. However, issues such as increased vibration noise, rail corrugation, and fastener failure have been observed in certain sections of the ladder track during later operation. To investigate the mechanisms behind these phenomena and provide comprehensive insights into the system's response to various operational conditions, this study employed vehicle-track coupled dynamic theory to establish a three-dimensional finite element model of the flexible vehicle-ladder track system. The vibration transmission and dynamic response characteristics of the vehicle-ladder track system were analyzed. The findings revealed that the vehicle-track resonance and anti-resonance phenomena were more prominent in the medium- to low-frequency range. At specific frequencies, the wheelset exhibited various vibration modes, and the fastener force was found to closely correlate with the ladder vibration mode. Furthermore, the influence of speed on diverse components of the vehicle-ladder track system, in terms of maximum vibration and the dominant vibration frequency range, differed considerably. This study provides a more comprehensive and reasonable exploration of the modeling and dynamic behavior of vehicle-ladder track systems.

Failure mechanisms and load paths in a standing seam metal roof under extreme wind loads

In this paper, the failure sequence and load sharing for standing seam metal roofs (SSMR), up to the limit state, were investigated using full-scale experiments. The tested SSMR system had full-scale dimensions and boundary conditions, which provided the opportunity to investigate the performance of SSMR systems under realistic conditions. The results show that there is a linear relationship between the wind pressure and clip reaction under low wind pressure (less than 500 Pa). Load redistribution happens along with the deformation of roof panels with greater load transfer to the ridge and eaves of the roof at higher pressure. Near the corner of the roof, between 27 and 46 % of the applied load is transferred to edges of the eaves and gable end. Away from the roof corner, between 17 and 23 % of the applied load is transferred to eave edge. Global buckling of panels occurs before connection failures and the initial location of global buckling is near the seam and in the middle of two adjacent clips. Two failure modes for the connections, clip slippage and fastener failure, were observed during the tests. However, the failure modes vary with the clip arrangement and boundary conditions.

Experimental testing of liner tray walls subjected to near field blast

AbstractExplosions produced in urban or industrial areas due to accidental or intentional detonation of high energy explosives (e.g., improvised explosive devices IED) are low‐probability but high‐impact events. If standoff distance from buildings or other constructions is small, explosions can cause structural failures and serious injuries or deaths of people. Preventing buildings from collapse is essential to minimizing casualties among occupants. However, experience has shown that even if the collapse is prevented, high number of injuries can result from fragments and flying debris generated by the non‐structural components or building envelopes. This risk could be minimized through appropriate design and selection of construction materials for most exposed elements (i.e., building envelopes). Although heavy/stiff systems were long considered appropriate to protect buildings against explosive threats, lighter and flexible systems are increasingly used for modern buildings. By allowing damage (but not fragmentation), the envelope system can provide predictable response, with minimal injuries in case of an explosion.The study presents the results of full‐scale blast tests on liner tray walls attached to a steel frame building. Walls are tested against increasing blast charges until complete failure. The ultimate strength is given by the failure of the end fasteners, after large bolt hole elongations coupled with the pull‐through of the end fasteners.

Probabilistic analysis of derrick frame in a formwork support system

The fastener is the core component of the formwork support system, and its working characteristics have a significant influence on the bearing capacity of the system. The non-intrusive stochastic finite element analysis of the formwork support system was conducted using the Python script process driving the ABAQUS main progress based on the Monte Carlo simulation. The influence of random occurrence of fastener failure with different numbers at any position on the reliability of the system was obtained. The analysis results showed that the increase of the failure probability of the fastener would lead to a significant increase in the magnitude and probability of the decrease of the bearing capacity. The above results also illustrated that the deterministic analysis of the formwork support system based on the integrity of all fasteners is not practical and unsafe.

Identification method for subgrade settlement of ballastless track based on vehicle vibration signals and machine learning

High-frequency train loads and complex environmental factors over a long period will inevitably cause subgrade settlement, an issue that adversely affects line smoothness. The existing monitoring methods are inefficient, manpower consuming and small in scope. This paper takes the subgrade settlement disease of the double-block ballastless track as the research object and proposes a subgrade settlement identification method based on vehicle vibration signals. In addition, it establishes a vehicle-track-subgrade vertical coupling model that combines feature extraction with algorithms such as support vector machines (SVMs) and convolutional neural networks (CNNs) to accurately identify subgrade settlement diseases on ballastless tracks. The results show: I) the subgrade settlement is far more impactful than fastener failure and debonding of the supporting layer on the vehicle vibration, with the main frequency band concentrated in 0 to 10 Hz, and the vertical vibration acceleration of the vehicle body and bogie can be used as a sensitive feature to identify ballastless track subgrade settlement, II) both the particle swarm optimization (PSO)-SVM and CNN-SVM algorithms can effectively determine the existence of subgrade settlement and the values of the settlement wavelength and amplitude. Both algorithms run a 100 % identification of subgrade settlement, with the lowest identification rates of settlement wavelength being 97.56 % and 100 %, respectively and the lowest identification rates of amplitude being 84.78 % and 97.56 %, respectively. In general, the overall accuracy of the CNN-SVM always outperforms PSO-SVM, and III) changes to the vehicle passing speed will create a more obvious interference effect on the identification of the settlement amplitude. For the PSO-SVM algorithm, the identification rate for the amplitude has a difference of up to 8.70 %, while this is 2.44 % for the CNN-SVM algorithm, indicating the CNN-SVM algorithm is more robust than the PSO-SVM algorithm.

Failure mode of interlayer connection of longitudinally-connected ballastless track-bridge system under uneven pier settlement

• Proposing the characterization model of uneven pier settlement and interlayer connection failure in LBTBS. • Analysing the generation mechanism and development law of interlayer connection failure caused by uneven pier settlement. • Describing the evolution law of interlayer contact behavior of each layer of track caused by uneven pier settlement considering the existing interlayer connection failure. The generation and mechanical balance mechanisms and the deformation compatibility relationship of interlayer connection failure (ICF) of a longitudinally-connected ballastless track-bridge system (LBTBS) caused by uneven pier settlement is analyzed in this paper. The characterization model of the uneven pier settlement and the ICF of the LBTBS was derived based on Castigliano's Second Theorem, Linear Superposition principle, Heaviside function, and Tension-free Winkler beam. The characterization model was further verified by the field measured data and finite element model results. Finally, the development law of the ICF of the LBTBS caused by uneven pier settlement based on the characterization model was analyzed. The results show that the calculated results of the characterization model agree well with the field measured data and finite element model results, which verifies the correctness of the characterization model. Under uneven pier settlement, a void beneath the slab first appeared between the base slab and bridge, and then mortar debonding occurred between the CA mortar and track/base slab when settlement value is 193.48 mm. The maximum height of void beneath the slab developed away from the beam gap, and when the settlement value was less than 8.434 mm, the void beneath the slab length in the left area of the settlement pier was greater than that of the adjacent pier. With the increase in mileage, the height of the void beneath the slab and mortar debonding increased first and then decreased. In practical engineering, mortar debonding is not easy to notice, and the void beneath the slab between the base slab and the bridge should be inspected regularly. The existing fastener failure had little influence on developing a void beneath the slab caused by the uneven pier settlement. The existing mortar void aggravated the occurrence of mortar debonding. When the existing mortar void length exceeded 5 m, the mortar debonding length at both ends of the adjacent pier was about 1/2 of the existing mortar void length. When the length of the existing mortar void was less than 1 m, there was little effect on the length of the void beneath the slab.

Influence of Fastener Failure on Dynamic Performance of Subway Vehicle

The track fasteners may be damaged by fatigue and impact load during long-term subway operation, resulting in the failure of the connecting components between the rail and the track plate, and the spacing of rail support becomes larger, resulting in an increase in its dynamic deformation, affecting the subway vehicle’s running performance, and, in severe cases, endangering the vehicle’s running safety. A vehicle-subway track system model was created to study the running performance of subway vehicles when fasteners failed. A multi-rigid, body spring damping system is used to describe the vehicle system. The model for the track system is created using the finite element method (FEM), and the vehicle dynamic performances under various fastener failure scenarios are calculated, as well as the vehicle’s running comfort and safety in various scenarios. The findings show that fastener failure has little impact on the vehicle’s running comfort but it has a significant impact on the vehicle’s wheel unloading ratio.

A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

PurposeThis study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approachThe track and substructure are decomposed into the rail subsystem and substructure subsystem, in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener. The rail is treated as a continuous beam with elastic discrete point supports, and spring-damping elements are used to simulate the constraints between rail and fastener. Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system, while the external load is used to deal with the reverse effect. The fastener failure is simulated with the methods that cancel the forced vibration transmission, namely take no account of the substructure–rail interaction at that position.FindingsThe dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method. Local fastener failure will slightly affect the vibration of substructure and carbody, but it will significantly intensify the vibration response between wheel and rail. The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value, respectively, under the train speed of 350 km·h−1. At the same time, the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%, respectively, from the normal value.Originality/valueThis method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

Evaluating the Effect of Rail Fastener Failure on Dynamic Responses of Train-Ballasted Track-Subgrade Coupling System for Smart Track Condition Assessment.

Rail fasteners are among the key components of ballasted track of high-speed railway due to their functionality of fixing rails to sleepers. The failure of rail fastening system hinders the transmission of train loads to underlying track substructure and therefore endangers the operation safety and longevity of ballasted track. This paper first established a three-dimensional (3D) numerical model of the train-ballasted track-subgrade coupling system by integrating multibody dynamics (MBD) and finite element method (FEM). Numerical simulations were then performed to investigate the effects of different patterns of rail fastener failure (i.e., consecutive single-side, alternate single-side, and consecutive double-side) on critical dynamic responses of track structures, train running stability, and operation safety. The results show that the resulting influences of different patterns of rail fastener failure descend in the order of consecutive double-side failure, consecutive single-side failure, and alternate single-side failure. As the number of failed fasteners increases, the range where dynamic responses of track structures are influenced extends, and the failure of two consecutive single-side fasteners exerts a similar influence as that of four alternate single-side fasteners. The failure of single-side fasteners affects dynamic responses of the intact side of track structures relatively insignificantly. The influence of rail fastener failure on track structures exhibits hysteresis, thus indicating that special attention needs to be paid to locations behind failed fasteners during track inspection and maintenance. The occurrence of the failure of two or more consecutive fasteners demands timely maintenance work in order to prevent aggravated deterioration of track structures. The findings of this study could provide useful reference and guidance to smart track condition assessment and condition-based track maintenance.

Fatigue life estimation of preloaded Aluminium (Al2024-T6) aircraft fasteners using finite element method

The fatigue failure of the aircraft fasteners during service conditions are unavoidable. Most of the published research works related to fatigue life estimation of threaded fasteners have neglected the effect of bolt preloading. The present work mainly aims to determine the effect of bolt preload on fatigue life of the aircraft fasteners. High cycle fatigue analysis was carried out using FE based software on aluminium bolts of Al2024-T4 material with same dimensions under two different conditions (with and without the presence of crack). The preload of the bolt was varied based on the limiting stress value of the bolt material. In addition to the bolt preloading, cyclic load was applied to the bolt in order to determine the effect of synergetic loading on fatigue life. 3D finite element model of the bolt under the presence of crack was modelled and the crack region was meshed with singular elements. During meshing, singular nature of stresses and strains at the crack tip was considered and thus 20 node quadratic brick element was used. The static analysis of the bolt was carried out using Abaqus finite element code and the fatigue life of the bolt was determined after applying the cyclic load using Fe-safe software. The residual life of the bolt was determined for various preloads. From the numerical results, it was noted that as the magnitude of the preload increases, fatigue life of the bolt also increases significantly. This is due to the ‘spring action’ provided by the initial preload on the bolt. It is also observed that, the presence of crack at the root region significantly reduces the fatigue life of the bolt.

Study on Wheel Polygonal Wear of Metro Trains Caused by Frictional Self-Excited Oscillation

This article aims to study the special phenomenon of wheel wear occurring on trains operating on a metro line in which the wheel polygonal wear rate of the right wheel is higher than that of the left wheel. Based on the perspective that frictional self-excited oscillation causes wheel polygonal wear, a flexible wheelset–rails system was built and, using complex feature value analysis, the unstable vibrations of this system were investigated. Moreover, the factors influencing wheel polygonal wear were studied. The simulation results show that when a subway train runs on a tightly curved track at 50 km/h, saturated creep forces upon two wheels of the leading wheelset are created. These forces can lead to unstable vibrations at frequencies of about 51, 60, and 69 Hz that are capable of inducing ninth-order wheel polygonal wear. Based on modal analysis and transient analysis, it is found that the unstable vibration intensity of the inner wheel–rail system is greater than that of the outer wheel–rail system, which leads to more uneven wear on the inner wheel. The length difference between the right and left curved tracks is the main reason for the different polygonal wear rates between the right and left wheels. The addition of damping material to the surface in the middle part of the wheelset axle has a small effect on the inhibition of wheel corrugation caused by the unstable vibrations. Fastener failure can lead to a stronger tendency toward wheel polygonal wear.

Sheathing-fastener connection strength based design method for sheathed CFS point-symmetric wall frame studs

Cold-formed steel (CFS) in construction delivers cost effectiveness and design flexibility. The instability failures of CFS Structural members significantly influences the failures of sheathing boards attached as an external cover. Therefore, present study experimentally examines the structural behavior of sheathing fastener connection in cold-formed steel wall frame. As a first attempt, strength and stiffness of the sheathing fastener connection is determined against the failure modes of point symmetric CFS wall frame studs. A new test setup has been developed to investigate the individual sheathing fastener failure modes. Parameters investigated include sheathing board types (varying thickness) and different dimensions of point-symmetric CFS studs. A total of forty-one individual fastener connection tests were carried out. The experimental investigation revealed that the fastener connection strength varies depending on the geometric dimensions of CFS stud and material composition of sheathing board. The result indicated that the bracing effect provided by plain gypsum board (fiber less) is insignificant and should not be considered for design. For sheathing boards with fiber composition, a generic parameter [ratio to design moment (Mx or My) to CFS stud depth (h)] is introduced to consider the structural bracing effect in CFS wall panel design. The limitations to consider the bracing effect of sheathing in the design of CFS wall frame studs are suggested for minor axis buckling and major axis buckling.

‘Rope effect’ mechanism of self-tapping screws as reinforcement on dowel-type connections

The ‘rope effect’ is a positive effect caused by the failure of fasteners of dowel-type connections. A similar mechanism can be found in connections with screw reinforcement. For self-tapping screws used as reinforcement for connections, bending of the self-tapping screws tends to close developed cracks. Utilising the withdrawal resistance provided by the threads on the pointed end of the screw and the pull-through resistance from the screw head, screw reinforcement enhances the embedment strength and splitting resistance of the wood and increases the ductility of the connection. The influence of different thread lengths and locations on reinforcement effectiveness regarding the embedment strength of the timber was investigated in this study. For cases with threads located only on the pointed end, the splitting resistance increased with longer thread length, indicating that the rope effect was progressively enhanced. It was also found that screws with halved thread length demonstrated similar reinforcement effectiveness to fully threaded screws while the partial threads reduced the risk of damaging the screw during installation. A calculation method to predict the load-carrying capacity of screw-reinforced dowel-type connections was also formulated.

Typhoon risk and climate-change impact assessment for cultural heritage asset roofs

Recent catastrophic events in Southeast Asia have emphasized that roofs made of wood/steel frames and lightweight metal roofing sheets are the most vulnerable component in the building envelope when subjected to typhoon-induced wind uplift. This also applies to aging cultural heritage (CH) assets, which deserve special consideration because of their intangible value for local communities, and their essential role for inclusive and sustainable socio-economic development through cultural tourism.This paper introduces a simulation-based framework for fragility analysis and typhoon risk assessment of CH-asset roofs. Fastener pullout and roof-panel pullover are explicitly considered in the proposed framework to model the progressive failure of the roof system. A simplified roof geometry is assumed, requiring limited information about the structure under investigation and low computational resources. Such a low computational burden allows modeling wind-induced demands and component capacities probabilistically as well as considering the effects of load redistributions due to fastener failure and fastener/roof-panel corrosion. Variance-based sensitivity analysis (i.e., Sobol’ indices) based on polynomial chaos expansions of the limit state function is also performed, highlighting the parameters most affecting typhoon-fragility variance and then requiring special attention during data collection. Climate-change impact on the typhoon risk estimates is finally investigated through the use of various scenarios and a time-dependent function modifying the wind hazard profile of the site where the assets of interest are located.The proposed framework is applied to 25 CH assets in Iloilo City, Philippines. The required input data was collected through rapid visual surveying combined with new technologies, such as drones. It is shown that the proposed framework can be adopted in practice for both risk prioritization at a building-portfolio level and simplified risk assessment at a building-specific level.

Railway Fastener Fault Diagnosis Based on Generative Adversarial Network and Residual Network Model

The present work aimed at the problems of less negative samples and more positive samples in rail fastener fault diagnosis and low detection accuracy of heavy manual patrol inspection tasks. Exploiting the capacity of a Convolution Neural Network (CNN) to process unbalanced data to solve tedious and inefficient manual processing, a fault diagnosis method based on a Generative Adversarial Network (GAN) and a Residual Network (ResNet) was developed. First, GAN was used to track the distribution of rail fastener failure data. To study the noise distribution, the mapping relationship between image data was established. Additional real fault samples were then generated to balance and extend the existing data sets, and these data sets were used as input to ResNet for recognition and detection training. Finally, the average accuracy of multiple experiments was used as the evaluation index. The experimental results revealed that the fault diagnosis of rail fastener based on GAN and ResNet could improve the fault detection accuracy in the case of a serious shortage of fault data.

Numerical analysis and experiment of sandwich T-joint structure reinforced by composite fasteners

This study presents an investigation into the failure mechanism and strength improvement of a sandwich composite T-joint bonded and reinforced by fasteners made of thermoplastic composite. The T-joint subjected to pulling load was analysed by numerical simulation and experiment methods. Cohesive zone model (CZM) and Hashin damage model were used in the FE analysis to simulate the crack propagation and composite fastener damage. According to the results, the composite joint reinforcement is mainly attributed to the resistance of composite fasteners to shear failure of the bonded interface. Following the interface delamination and crack propagation in mode II failure, fracture of the composite fasteners occurred in transverse shear mode. The results show nearly 19% increase of bonding strength for the T-joint reinforced by composite fasteners of 5 mm diameter compared to the T-joint without fasteners. After the interface delamination, pull-out failure of fasteners was also observed and correlated to the numerical model considering material property reduction due to the sparse fibre tows in the fastener head forming and T-joint assembly. The investigation was extended to a parametric study of diameter and fibre orientation of the composite fasteners. The results show that the T-joint reinforced by composite fasteners of 6.28 mm diameter and ±354s lay-up can achieve the same strength and 44% weight saving compared to a titanium fastener opponent of 5 mm diameter.

Wind-uplift fragility analysis of roof sheathing for cultural heritage assets in the Philippines

Recent catastrophic events in the Philippines (e.g., the 2013 Typhoon Haiyan) have highlighted that ageing cultural heritage (CH) assets are especially vulnerable to typhoon-induced extreme wind. Non-engineered CH roofs have been recognized as the most vulnerable component in the building envelope due to wind uplift, often resulting in large economic losses and disruption for those assets. Effective prioritization of high-vulnerable structures is a key to effective risk mitigation and resilience-increasing strategies.This paper introduces a simulation-based approach for non-engineered CH roof fragility analysis (i.e., to assess the likelihood of different levels of roof damage over a range of wind hazard intensities) and risk assessment. In the proposed approach, two common failure modes are considered, corresponding to (first) roof-fastener pullout and roof-panel pullover. The overall aim is to identify the highest-risk candidate assets and prioritize more detailed data collection campaigns and structural assessment procedures (e.g., properly accounting for load redistribution and fastener failure progression), and ultimately to plan further repair/strengthening measures.An illustrative application of the proposed procedure is presented with reference to eight priority CH assets in Bohol, the Philippines. The analysis results indicate that, especially for roof panels supported by wood-type purlins, pullout fragility/risk can be significantly high, while the pullover one is generally lower.