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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Classification of Bolt Corrosion Levels Combining Deep Learning and Multi-Feature Segmentation</title>
      <link>https://trid.trb.org/View/2712017</link>
      <description><![CDATA[Many bolts are installed in subway tunnels, making manual inspection prohibitively costly, and deep learning models face difficulties in segmenting extremely small corroded regions, which results in low detection efficiency. To address these challenges, this study proposes a corrosion grade classification algorithm for subway tunnel bolts based on deep learning and multi-feature segmentation, which directly outputs the corrosion grade of each bolt to enhance maintenance efficiency. First, the YOLOv8 framework is improved using multi-scale channel group shuffle convolution (MSCGSC) and focal loss (FL) to develop the YOLO-MF (MSCGSC + FL) model for preliminary detection of corroded bolts. Second, the VGG16 network is employed as the backbone of U-Net, and channel shuffle is applied after the encoder–decoder concatenation to eliminate background noise of bolts using the VGG + channel shuffle (VCS)-Net model. Finally, the fusion of segmentation features, spatial features, and clustering features enables the accurate segmentation and grading of tiny corroded areas. Experiment results demonstrate that YOLO-MF and VCS-Net achieve higher accuracy in corroded-bolt detection and background noise removal. Compared with other segmentation approaches, the multi-feature fusion segmentation method improves the intersection over union by 0.1623. The corrosion grade results are directly printed on the images, facilitating maintenance operations, reducing the workload of tunnel maintenance personnel, and improving tunnel maintenance efficiency.]]></description>
      <pubDate>Wed, 10 Jun 2026 09:06:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2712017</guid>
    </item>
    <item>
      <title>Enhanced CAE Methodology to Predict Bolt Shear Failure Using Multi-Layer Approach</title>
      <link>https://trid.trb.org/View/2692122</link>
      <description><![CDATA[Automotive seat system is one of the most complex systems in vehicle for its technical and functional requirements. Seat is designed to meet all regulatory requirements subjecting it to multiple tests with loading patterns which caters to the occupant safety. Varied loading and load path for different test requirements cause seat bolts to experience tensile, compressive, bending moments and shear loading. Shearing along bolt length is one of the common failure modes observed during design validation by physical tests.In the world of CAE, there is an industry approach to find the bolt failures at nut and head for all kind of loads. But shear failures along varied bolt lengths are not accurately predictable as multiple sheet metal parts will transfer loads unevenly onto bolt length and it becomes challenge to find which component is leading to shear failure. Hence by adding multiple rupture layers across the bolt length shear and its location could be predicted. Further, to resolve the bolt shear issues, engineers generally try to modify the component design for better energy absorption, but our research found that, only by increasing the clearance around bolt hole will resolve the bolt shear issues.During one of such failures, a new approach of adding multiple rupture layers along bolt length was used which predicted the shear failure modes and location of shear as observed in physical tests. The CAE bolt model thus updated with new procedure for all such future bolt shear failure prediction in seat structure models.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692122</guid>
    </item>
    <item>
      <title>Analyzing Fastened Joints in Hydraulic Dampers Using Simulation and Experimental Methods</title>
      <link>https://trid.trb.org/View/2692056</link>
      <description><![CDATA[The main purpose of this study is to develop and validate an accurate calculation model for a hydraulic damper piston valve joint, enabling reliable torque specification and clamp behavior without full prototype iteration. Joint stiffness is a primary interest point. The joint features a bolted interface with a laminated shim stack of many thin disks with varying outer diameters. Analysis of such joints are uncommon in literature, making it challenging to quantify the effects of load distribution, truncation, and surface contact effects between members. The proposed models discussed in this paper are based on frustum load distribution combined with annular-plate bending and elastic-foundation effects to capture the effects of washer cupping. Concrete outputs of the calculator include member load distribution, bolt and member stiffnesses, torque-to-preload relationships, and an external-load simulation that predicts when individual members lose clamp load. Detailed internal hydraulic flow through piston valve orifices and shim hydrodynamics are outside the present scope. For model correlation, axisymmetric finite-element analyses of contact pressure and joint compression were conducted, and a 30-sample torque-to-failure study quantified general joint behavior and friction characteristics. The proposed virtual development method allows early selection of joint geometry and torque specification prior to physical builds. The performance characteristics of a representative joint are presented, with simulation and experimental results that show improved preload prediction.]]></description>
      <pubDate>Tue, 14 Apr 2026 15:11:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2692056</guid>
    </item>
    <item>
      <title>Reliability Analysis of Anchor-Reinforced Slopes Based on Nonlinear Mohr-Coulomb Failure Criterion</title>
      <link>https://trid.trb.org/View/2675949</link>
      <description><![CDATA[Slope stability is crucial to engineering safety, and traditional single safety factor design methods fail to account for parameter variability and nonlinear strength characteristics. This study employs the nonlinear Mohr-Coulomb (M-C) failure criterion to establish safety factor and reliability index constrained optimization models for searching potential slip surfaces. It also proposes a theoretical analysis method for reinforcing slopes with anchor bolts based on reliability theory. The study reveals that potential slip surfaces vary under different failure criteria, with those derived from the nonlinear M-C failure criterion exhibiting deeper slip surfaces. The nonlinearity of strength parameters and their variability significantly impact anchoring force calculations, resulting in notable discrepancies between anchoring forces determined through reliability theory analysis and traditional deterministic analysis. Incorporating the variability and nonlinearity of parameters is of importance for geotechnical engineering computations and design practices. When reinforcing slopes based on reliability theory, it is essential to search for slip surfaces corresponding to the minimum reliability index to ensure slope safety.]]></description>
      <pubDate>Wed, 25 Mar 2026 11:44:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/2675949</guid>
    </item>
    <item>
      <title>Optimizing Suspension Joint Reliability: Overcoming Bolt Loosening and Torque Variability in Automotive Production</title>
      <link>https://trid.trb.org/View/2663477</link>
      <description><![CDATA[In modern automotive manufacturing, ensuring the integrity of suspension joints under real-world driving conditions is a critical aspect of vehicle safety and performance. These joints endure substantial transverse loads and large vibrations due to irregular road surfaces, dynamic maneuvers, and varying environmental factors. As a result, bolt loosening becomes a significant concern, compromising joint integrity and overall vehicle reliability. This paper delves into the challenges associated with maintaining joint integrity, specifically focusing on pre-load determination, torque application, and production-related issues.The pre-load generated during torquing is the primary factor that ensures a suspension joint remains securely fastened under dynamic road conditions. This pre-load is derived using road load data acquisition (RLDA) inputs, which capture the forces acting on the joint during actual driving scenarios. RLDA inputs provide critical insights into the forces experienced by a joint, enabling engineers to calculate the optimal pre-load required to withstand real-world stressors. The torque applied during assembly is directly dependent on these calculated pre-load values, ensuring the joint remains secure during the vehicle's lifecycle.During production ramp-up, several concerns arise that impact the torque application process. Friction at the bolt and nut interface plays a significant role in achieving the desired pre-load. Variations in friction surfaces, such as presence of lubrication, debris, or surface roughness, can lead to major issues.These torque-related concerns have cascading effects on production efficiency and workplace safety. Additionally, the increased strain on assembly tools due to high torque demands reduces tool life and increases maintenance costs.Automotive suspension joints are subjected to significant challenges during production ramp-up due to the interplay of friction, torque, and pre-load parameters. Addressing these concerns is essential to ensure joint integrity, improve production efficiency, and create a safe workplace environment. By adopting advanced monitoring systems, enhancing friction control, and optimizing tool design, manufacturers can mitigate the risks associated with bolt loosening, breakage, and high torque issues, securing the reliability and safety of suspension joints in real-world driving conditions.]]></description>
      <pubDate>Mon, 02 Feb 2026 16:36:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663477</guid>
    </item>
    <item>
      <title>AI-Driven Predictive Methodology for Bolt Integrity in Vehicle Durability Testing</title>
      <link>https://trid.trb.org/View/2663378</link>
      <description><![CDATA[The application of AI/ML techniques to predict truck endgate bolt loosening represents a major innovation for the automotive industry, aligning with the principles of Industry 4.0. Traditional physical testing methods are both expensive and time-consuming, often identifying issues late in the development process and necessitating costly design changes and prototype builds. By harnessing AI/ML, manufacturers can now analyze endgate slam and bolt preload data to accurately forecast potential bolt loosening issues. This predictive capability not only enhances quality and safety standards but also significantly reduces the costs associated with tooling and builds. The AI/ML tool described in this paper can simulate a variety of load conditions and predict bolt loosening with over 90% accuracy, considering factors such as changes in loads, bolt diameters, washer sizes, and unexpected masses added to the endgate. It provides valuable design insights, such as recommending optimal bolt diameters and the use of high-friction washers to ensure strong and reliable connections. By enabling continuous monitoring and real-time adjustments, this tool helps maintain the integrity of bolted joints under diverse operational conditions. This methodology reduces dependence on physical testing along with considerable cost avoidance and accelerates the vehicle development process. It offers a more efficient and cost-effective approach to vehicle development. Through the integration of these advanced technologies, the automotive industry can fully embrace the concepts of Industry 4.0, leading to smarter manufacturing processes and improved product reliability.]]></description>
      <pubDate>Mon, 02 Feb 2026 16:36:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663378</guid>
    </item>
    <item>
      <title>A Rapid Evaluation Method for the Performance of Suspension Bolts in High-Speed Trains</title>
      <link>https://trid.trb.org/View/2616197</link>
      <description><![CDATA[To solve the problem of service performance evaluation efficiency of multiple types of hanging bolts of typical equipment, a rapid pre-evaluation method of service performance of hanging bolts is proposed. In this method, the hanging bolts on five types of equipment are taken as the research objects, including life prediction, evaluation index reconstruction, and service performance evaluation module. The life prediction module analyses the degradation law based on the equivalent cyclic stress calculation method, establishes the stress-life curve, and predicts the fatigue life with the help of Miner's theory, so as to realize the theoretical fatigue life of the hanging bolt. In the evaluation index reconstruction module, the main influencing factors of the service performance of hanging bolts are studied under the condition of a certain bolt selection, and the construction of three evaluation indexes of average mass, stress ratio and unit load strength is realized. Based on the multi-layer perceptron model and evaluation index, the service performance evaluation module realizes the rapid pre-evaluation of the service performance of hanging bolts. In order to verify the proposed rapid pre-evaluation method, an accelerated fatigue experiment was designed for verification. The experimental results show that the average errors of the pre-assessment results of the service life of the method and the actual results of the accelerated fatigue test are 5.04%, 6.20% and 3.52%, respectively, under the conditions of the load amplitudes of 0.075g, 0.1g and 0.325g. The experimental method verifies that the rapid pre-assessment method has high prediction accuracy and a certain degree of universality.]]></description>
      <pubDate>Mon, 26 Jan 2026 14:44:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/2616197</guid>
    </item>
    <item>
      <title>Bolt-loosening Fault Diagnosis in Rotor Systems with Nonlinear Vibration Transmissibility Function-based Features and Indexes</title>
      <link>https://trid.trb.org/View/2596640</link>
      <description><![CDATA[These methods that rely on features and indices derived from nonlinear vibration transmissibility functions (NVTFs) have found widespread success in detecting potential bolt-loosening faults within nonrotating systems such as bridges, railways, and satellites. To improve and extend existing NVTF-based methods for diagnosing bolt-loosening faults in rotor systems, a novel method is proposed with detailed theoretical analysis and experimental study in this paper. First, a general rotor dynamic model, considering bolt-loosening forces, radial unbalance forces, and nonlinear support forces, is built for the nonlinear rotor dynamic analysis and the definition of rotor-domain NVTFs. Importantly, by dividing the rotor system into a series of rotor subsystems and analyzing corresponding rotor dynamic submodels to be diagnosed only, relationships between NVTFs and bolt-loosening forces are summarized, and then three sensitive fault features are defined. Based on this, local diagnosis indexes are developed, and a novel method with detailed operating flowchart is proposed accordingly. Finally, results from experimental cases on a testing rotor system with single/multiple stage bolt-loosening faults and loosened pedestals verify and demonstrate the effectiveness of the novel method. The study in this article successfully improves and extends existing NVTF-based methods for nonrotating systems to diagnose potential bolt-loosening faults in rotor systems even with nonlinear supports such as loosened pedestals.]]></description>
      <pubDate>Tue, 06 Jan 2026 09:17:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/2596640</guid>
    </item>
    <item>
      <title>Three-Dimensional Direct Solution Method for the Elastoplastic Analysis of Deep-Buried Soft Rock Tunnels Considering the Volumetric Force of Anchor Rods</title>
      <link>https://trid.trb.org/View/2612957</link>
      <description><![CDATA[The theoretical analysis of deep-buried soft rock tunnels with anchor rod support in the past generally employed simplified methods such as strength superposition or dividing anchorage zones into n microelements, which resulted in a certain discrepancy between the theoretical solutions and the field measurements. In this study, based on the positioning of anchor rods in tunnel dynamic construction, the differential equation for the equilibrium of the anchorage elastic zone was regarded as a nonhomogeneous Euler equation. Combining this with the Taylor series to simplify the complex second-order differential equation, a direct solution method for three-dimensional excavation of surrounding rock in deep-buried soft rock tunnels with elastoplastic behavior was proposed. Subsequently, the feasibility of the theoretical analytical method was verified through numerical simulations. It was found that using grouting anchorage and increasing the length of anchor rods can significantly reduce the displacement of the surrounding rock and the deformation of the surrounding rock wall, and the support pressure is also reduced accordingly. The pretightening force of anchor rods can alleviate the deformation and support pressure of the surrounding rock and prevent anchor rod failure. The method of composing anchor rods and surrounding rock into a composite load-bearing structure by equivalently treating the strength of anchor rods as the strength of surrounding rock is excessively conservative and should not be utilized. The results of this study can provide theoretical guidance for the elastoplastic analysis of deep-buried soft rock tunnels with anchor rod support.]]></description>
      <pubDate>Mon, 29 Dec 2025 09:34:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/2612957</guid>
    </item>
    <item>
      <title>Novel Methodology for Assessment of Bolted Joints Under Vibration Fatigue</title>
      <link>https://trid.trb.org/View/2624015</link>
      <description><![CDATA[The smart industrial revolution in any organization brings faster product delivery to the market, which can meet customer expectations and full life requirements without failure. Failure per machine (FPM) is a very critical metric for any organization considering warranty cost and customer perception. One such area which needs a detailed evaluation is bolted joints. Bolts play a pivotal role when integrating a subassembly with the main structure. Often, it is challenging to address bolt failure issues due to vibration induced in structures.Current bolt virtual evaluation methods help to evaluate bolts in simple loading conditions such as axial and bending loads. But it is quite complicated to evaluate the bolts which are prone to vibration loading. Traditional methods of using gravity loads miss out on dynamic characteristics, hence it must be simulated using modal dynamic analysis. With the current vADV (virtual accelerated design verification) method it is not possible to capture correct physics as modal analysis converts all frictional contacts to bonded contact resulting in change of load path.Different methodologies to evaluate bolts under vibration fatigue. Both the methods have shown good correlation with field data and have been utilized in ongoing product development programs to address ADV (Accelerated Design Verification) failures. Pros and cons of these methods are understood and documented in this study.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:07:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2624015</guid>
    </item>
    <item>
      <title>Development of Test Methodology for Accelerated Fatigue Testing of Engine Pulley Bolt</title>
      <link>https://trid.trb.org/View/2623976</link>
      <description><![CDATA[Engine is the prime mover of an automobile. Tractor is also equipped with engine of higher capacity to meet the power requirement. Apart from powering the wheels, engine also runs different accessories such as water pump, alternator, AC pump, Oil pump and so on. The power from the engine is transferred to accessories via chain drive or belt drive through the crankshaft pulley. During field testing, in one of the tractors, engine pulley mounting bolt failure was reported. The failure resulted in immediate seizure of the engine making the tractor standstill in the field. The root cause of the failure was unknown. Hence, there was a need to develop a component or subsystem level test methodology to address the issue quickly. In the current scope, an attempt was made to develop a subsystem level laboratory test methodology to simulate the failure mode and to validate the design modifications in an accelerated manner. The failure mode was simulated in lab and different design iterations were also tested. On successful completion of testing and implementation of the improved design, this newly developed test methodology was added as a DVP requirement to all future projects.]]></description>
      <pubDate>Thu, 13 Nov 2025 16:07:15 GMT</pubDate>
      <guid>https://trid.trb.org/View/2623976</guid>
    </item>
    <item>
      <title>A comprehensive seismic resilience assessment of shield tunnel considering bolt preload loss with multistage functions</title>
      <link>https://trid.trb.org/View/2596840</link>
      <description><![CDATA[The segments of a shield tunnel are connected by preloaded bolts, which may experience significant preload loss under prolonged vehicle loading and other factors. This loss reduces structural stiffness and may exacerbate earthquake damage. However, the seismic resilience assessment of shield tunnels considering preload loss has been seldom addressed. This study proposes a comprehensive seismic resilience assessment method that spans the entire lifecycle of the shield tunnel, structured into four stages: pre-earthquake, earthquake, evolution, and recovery. Firstly, the pre-earthquake initial state functions of the shield tunnel are determined by incorporating preload loss. Then, the structural loss function during earthquakes is derived using fragility theory. A post-earthquake evolution function is established to capture r the tunnel's nonlinear self-recovery capability, followed by a restoration function based on the extent of earthquake damage. This method is applied to assess the seismic resilience of a typical shield tunnel under different preload loss cases. Key findings indicate a strong interdependence among the four stages. Preload loss in the pre-earthquake stage reduces structural performance during the earthquake stage, with a resilience index decreasing by up to 3.72 % at a peak ground acceleration (PGA) of 0.5 g. The evolution stage further amplifies the impact of preload loss, where neglecting this phase introduces an error of up to 12.841 % in resilience assessments. Residual deformation from the evolution stage serves as a critical input for the restoration stage, highlighting that preload loss affects resilience across all stages. A comparison of resilience indices reveals that models excluding the operation or evolution stages significantly overestimate resilience, emphasizing the need for a comprehensive lifecycle assessment approach.]]></description>
      <pubDate>Wed, 29 Oct 2025 09:11:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2596840</guid>
    </item>
    <item>
      <title>Testing and Evaluation of Slip Base Sign Supports</title>
      <link>https://trid.trb.org/View/2567175</link>
      <description><![CDATA[Under this project, several issues related to the performance of slip base sign supports were investigated. These issues include: the effect of bolt torque on the impact performance of slip base sign supports, the effect of sign panel size and configuration on the trajectory and impact performance of slip base sign supports, and an evaluation of methods for retrofitting slip base stubs that incorporate a lifting ramp or cone. A summary of the findings and conclusions resulting from these investigations is provided. Small slip-base sign supports with slip bolt torques in the range of 109 N·m (80 ft·lb) to 136 N·m (100 ft·lb) were determined to comply with National Cooperative Highway Research Program Report 350. A triangular-shaped, polycarbonate spacer cap was successfully tested as a retrofit option when repairing or upgrading existing sign supports with foundations that incorporate a lifting device. Test results indicate that slip base sign supports perform acceptably when used with conventional sign panels having an area of 0.84 m² (9 ft²) or greater. A test with a lightweight plastic sign with an area of 0.58 m² (6.25 ft²) was marginally acceptable.]]></description>
      <pubDate>Tue, 05 Aug 2025 11:40:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2567175</guid>
    </item>
    <item>
      <title>Temperature-Induced Cyclic Loading Effects on Rail Anchor Slip Force</title>
      <link>https://trid.trb.org/View/2573195</link>
      <description><![CDATA[Recently, continuous welded rail (CWR) systems have been widely adopted due to their enhanced ride quality, reduced maintenance requirements, and extended service life for both rails and rolling stock. However, the elimination of joints in CWR introduces challenges, particularly in managing thermal expansion, which can lead to track buckling. A critical factor in maintaining track stability is the Rail Neutral Temperature (RNT) — the temperature at which rails are free of thermal stress. Anchors, which resist longitudinal rail movement, play a key role in managing RNT and ensuring track integrity. While previous studies have largely focused on the static behavior of rail anchors, this research emphasizes the importance of cyclic longitudinal loading, which can simulate daily and seasonal temperature fluctuations. Unlike static loading, cyclic longitudinal loading on the rail-anchor under different temperatures can potentially lead to gradual degradation in anchor performance, slip initiation, or cumulative displacement over time. These effects may be more critical to track stability than static forces alone, especially under service operating conditions. This study will conduct full-scale laboratory testing to investigate the impact of cyclic temperature-induced longitudinal loading on slip force performance for various rail anchor types. By simulating temperature cycles and measuring anchor slip under controlled conditions — including different anchor geometries, installation tightness, and environmental parameters — this research aims to provide an understanding of the long-term reliability of rail anchoring systems under thermal cycling. Also, this study addresses the need to construct a 15-foot full-scale track segment on ballast and wood ties to replicate in-field conditions for the future studies to be performed for this project.]]></description>
      <pubDate>Mon, 14 Jul 2025 19:42:30 GMT</pubDate>
      <guid>https://trid.trb.org/View/2573195</guid>
    </item>
    <item>
      <title>Modeling Special Cases of Longitudinal Resistance in Continuously Welded Rail (CWR)</title>
      <link>https://trid.trb.org/View/2573194</link>
      <description><![CDATA[Continuously welded rail (CWR) is the standard for North American freight railroads due to its advantages in ride quality, fatigue life, and reduced maintenance costs, despite concerns about rail buckling and breaks. Longitudinal rail resistance is a critical parameter for re-establishing rail neutral temperature (RNT) after rail breaks and for mitigating potential rail failures caused by vehicle loading, temperature changes, and maintenance activities. This proposed research builds upon a previous year project and continues the effort to refine and enhance the Finite Element (FE) modeling of rail longitudinal resistance. Specifically, it aims to improve the representation of realistic rail and anchor conditions by integrating new experimental data into the FE models. The research will develop efficient 2D and 3D FE models in ABAQUS that incorporate rail-to-tie friction, anchor slip forces, and tie-to-ballast restraint, using both experimental results (e.g., anchor slip behavior under varying load conditions) and historical data (e.g., rail-sleeper friction and sleeper-ballast resistance). The models will accommodate various rail profiles, tie materials, and geometric configurations, and will be applicable to a wide range of track conditions including frozen ballast, frozen structures, turnouts, crossings, and loading scenarios from vehicles and maintenance activities. The proposed project will be executed through four key interconnected areas of research: (1) Effects of sleeper-ballast on models larger than 4-ft in length using FE modeling in ABAQUS, (2) experimental testing in the laboratory for anchor slippage with various anchor types, (3) sensitivity analysis, and (4) model analysis with various track conditions. ]]></description>
      <pubDate>Mon, 14 Jul 2025 19:49:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2573194</guid>
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