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    <title>Transport Research International Documentation (TRID)</title>
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    <language>en-us</language>
    <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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      <title>Live-bed contraction scour induced by bridge foundations on silty seabed in Hangzhou Bay</title>
      <link>https://trid.trb.org/View/2653015</link>
      <description><![CDATA[The construction of sea-crossing bridges in estuarine and bay areas may cause narrowing of the channel cross section, leading to the contraction scour between the bridge foundations. This study presents the first field investigation of live-bed contraction scour at Hangzhou Bay Bridge (HBB). Results show that as the contraction ratio (the ratio of net width with bridge to initial width without bridge) decreases from 0.97 to 0.88, the contraction effect is significantly enhanced, and the corresponding contraction scour depth increases largely from 1.8 m to 5.8 m. In addition, the HEC-18 and Nowroozpou methods for estimating the contraction scour are assessed against field measured data, revealing they significantly underestimate scour depth, with an RMSE (Root Mean Squared Error) over 3.0 m and a MPRE (Mean Percent Relative Error) over 80 %. Based on the theory of suspended sediment carrying capacity, a new prediction equation related to flow velocity, settling velocity and water depth is developed and shows good accuracy with an RMSE of 0.85m and a MPRE of 7 %.]]></description>
      <pubDate>Mon, 06 Apr 2026 08:50:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2653015</guid>
    </item>
    <item>
      <title>Time dependent deformations : state of art report</title>
      <link>https://trid.trb.org/View/2598592</link>
      <description><![CDATA[The study of shrinkage and creep in concrete, particularly in the presence of various supplementary cementitious materials (SCMs) and at different water to binder ratios, has shown a wide range of results in the existing literature. Contradictory findings have been observed, and it is crucial to address these discrepancies. Indeed, some SCMs have been found to reduce these phenomena, while others may increase them, adding another layer of complexity to the research landscape. To navigate these complexities, more comprehensive testing and data collection are imperative. A wider spectrum of experimental conditions, including different types and combinations of SCMs and a broader range of water to binder ratios, must be explored. This approach would help in uncovering the underlying mechanisms driving shrinkage and creep in these complex mixtures. Additionally, as modelling techniques have demonstrated limitations in accurately describing these intricate behaviours, model refinement is needed. Model enhancements that consider the synergistic effects of SCMs and their interactions with the water to binder ratio can provide more accurate predictions.]]></description>
      <pubDate>Fri, 12 Sep 2025 10:18:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2598592</guid>
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    <item>
      <title>Prestress losses in concrete structures : a pre-study</title>
      <link>https://trid.trb.org/View/2598591</link>
      <description><![CDATA[Many prestressed concrete structures were built several decades ago and they are now beginning to have issues with deflections and remaining prestressing forces. In this report, history, mechanisms, codes and some examples will be presented. There are approximately 2000 prestressed concrete bridges in Sweden, and most of them are managed by Trafikverket (1,686 in 2019.. A lot of progress was made regarding materials and construction of prestressed concrete bridges during the 70-ties. Prestressed concrete bridges built before 1980 may have a lower structural safety. In Sweden there are approximately 400 bridges built before 1980. Examples are given of time dependent prestress losses in prestressed concrete structures caused by friction, creep, shrinkage and relaxation. The total losses vary with time and is often between 10 to 25 % after 50 years. The variation of results between different assessment and monitoring methods is considerable and more work is needed.]]></description>
      <pubDate>Fri, 12 Sep 2025 10:18:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2598591</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>Investigation of Joint Transfer Characteristics in Rigid Airfield Pavements</title>
      <link>https://trid.trb.org/View/2562023</link>
      <description><![CDATA[The capability of a rigid pavement contraction joint to transfer stresses due to applied aircraft loads is one of the simplifying assumptions in the Department of Defense (DoD) rigid pavement design procedure. The design procedure assumes that 25% of the computed free edge stress on the loaded slab is shared by the adjacent unloaded slab, which may or may not be accurate depending on the joint construction technique. A study was undertaken to investigate joint behavior for two portland cement concrete pavements of different flexural strength and constructed thickness to gather data to inform actual joint transfer characteristics and to verify a more robust joint modeling approach. The proposed response model consists of two semi-infinite adherent plates connected by an elastic joint with both shear and moment transfer supported by a Pasternak foundation. The field data indicated that the joint load transfer behavior was sensitive to load intensity, as well as concrete flexural strength. Results showed that the response model provided reasonable agreement with the field collected data and could be used to improve the DoD rigid pavement design methodology.]]></description>
      <pubDate>Mon, 30 Jun 2025 11:21:47 GMT</pubDate>
      <guid>https://trid.trb.org/View/2562023</guid>
    </item>
    <item>
      <title>Evaluating thermal contraction behaviour of basalt mastic using micromechanical finite element modelling</title>
      <link>https://trid.trb.org/View/2556826</link>
      <description><![CDATA[Thermal contraction is a key factor in low-temperature cracking, contributing to internal stresses in the bitumen-aggregate composite. Most macromechanical models treat mastic as a continuous material, limiting an in-depth analysis of the component interactions, which is essential for improved material design. This study analyses the low-temperature behaviour of bitumen and mastic containing different basalt filler content using experimental testing and micromechanical finite element modelling (FEM). The model evaluates micromechanical interactions between bitumen and aggregates, with aggregates modelled as spherical particles in the bitumen. Thermal contraction coefficients are predicted via viscoelastic modelling and compared to experimental results. Findings show higher filler content lowers the thermal contraction coefficient while increasing stress concentrations due to the combined thermal properties of bitumen and filler. The micromechanical model aligns well with experimental data, confirming its reliability in predicting stress distribution and thermal behaviour. These insights enhance the understanding of bituminous materials in cold environments.]]></description>
      <pubDate>Thu, 26 Jun 2025 11:42:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2556826</guid>
    </item>
    <item>
      <title>Dowel Bar Placement and Displacement</title>
      <link>https://trid.trb.org/View/2534006</link>
      <description><![CDATA[This report describes research performed by the South Dakota Department of Transportation to investigate the problem of dowel bar misalignment in portland cement concrete (PCC) pavements. Over 400 dowel bars from three (3) construction projects were inspected and compared to the dowel bar alignment specifications. This study found that the dowel bars tended to conform to the alignment specifications even though, in the opinion of the researcher, the specifications were too rigid. It was noted that sawing of the contraction joint was the governing factor for the longitudinal displacements. Although no pavement distress was observed in areas containing dowel bar misalignments, it should be noted that only two (2) years had passed between project construction and the field survey. It is the opinion of the researcher that this is insufficient time for pavement distress to manifest itself since even undoweled PCC pavement may not show distress or faulting for 5 years or more.]]></description>
      <pubDate>Mon, 07 Apr 2025 18:37:29 GMT</pubDate>
      <guid>https://trid.trb.org/View/2534006</guid>
    </item>
    <item>
      <title>Development of Semi-integral Bridge Abutment Details for Texas Conditions</title>
      <link>https://trid.trb.org/View/2499022</link>
      <description><![CDATA[Semi-integral bridges constitute a promising alternative to conventional Texas Department of Transportation (TxDOT) bridges because they eliminate the need for deck expansion joints, which may significantly reduce bridge maintenance costs and potentially result in significant savings over the bridge service life. Adopting semi-integral bridges is particularly relevant to Districts with comparatively cold winters (e.g., Amarillo), where the use of deicing salts has resulted in significant joint maintenance problems. However, the elimination of expansion joints requires careful consideration because of the soil-structure interaction between the bridge structure and abutment backfill caused by the bridge’s daily and seasonal thermal expansion/contraction. In this research, the data collected from the monitoring of two pilot semi-integral bridges in Texas, USA, are presented and evaluated. In this study, the effect of daily and seasonal temperature changes on the displacement of various bridge components, changes in abutment earth pressure, foundation interaction, ratcheting, backfill settlement, etc., have been successfully captured. Among the findings are increased backfill lateral earth pressure due to ratcheting, continuous settlement of the backfill, loss of vertical support for the approach slabs, asymmetric expansion/contraction of the bridge, and slight displacement of the bridge superstructure toward one end of the bridge. In addition, it was found that the thermal expansion/contraction of the bridge deck results in cyclic lateral loading of the abutment caps and the bridge foundations despite a lack of rigid connection between the foundations and the superstructure.]]></description>
      <pubDate>Mon, 10 Feb 2025 09:32:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2499022</guid>
    </item>
    <item>
      <title>Effective optimization method of asphalt binders and asphalt mixtures based on the two-parameter of contraction and relaxation</title>
      <link>https://trid.trb.org/View/2438496</link>
      <description><![CDATA[Thermal cracking is one of the primary distresses of asphalt pavement which is a complex process. Evaluating the Low-temperature Performance (LTP) of asphalt mixtures accurately and conducting material optimization analysis is not only crucial for understanding the thermal cracking mechanism of asphalt mixtures but also serve as the basis for enhancing their thermal cracking resistance performance. However, current research has not sufficiently interpreted the mechanism of thermal cracking. It is segmentary that optimizes asphalt mixtures solely based on their ultimate strength, strain, and so on at certain low-temperature points. Therefore, this study closely integrated the thermal cracking mechanism and proposed a two-parameter optimization method. Firstly, clarifying the decisive role of the contraction and relaxation relationship in determining LTP through the Thermal Stress Restrained Specimen Test (TSRST), thermal contraction test, and low-temperature relaxation test. Secondly, quantizing the impact of the aggregates skeleton and then using a two-parameter method to analyze the comprehensive effects on LTP of asphalt mixtures. Finally, summarizing the material optimization method of asphalt binder-first, aggregates-second based on the multiple linear regression method. This paper simplified the evaluation method and provided a basis for material selection and design for improving the thermal cracking resistance of asphalt mixtures.]]></description>
      <pubDate>Tue, 22 Oct 2024 17:11:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/2438496</guid>
    </item>
    <item>
      <title>Revised Clear-Water and Live-Bed Contraction Scour Analysis



</title>
      <link>https://trid.trb.org/View/2441439</link>
      <description><![CDATA[Current guidance in Hydraulic Engineering Circular No. 18 (HEC-18), "Evaluating Scour at Bridges," (Arneson et al. 2012) provides equations for estimating contraction scour.  Existing equations are based on sediment transport theory using approaches developed by Laursen, 1960 (live-bed contraction scour) and Laursen, 1963 (clear-water contraction scour).  Both equations assume that the scour is due solely to the contraction effect and that local effects are negligible (i.e., that the contraction is hydraulically "long"). Depending on the ratio of the length of contraction L to the approach channel width b1, (L/b1) channel contractions are designated as long or short.  In a short contraction, local scour occurs throughout the contracted section as a result of large-scale turbulent flow structures created at the entrance to the contraction, and the total scour is the result of both the contraction and local effects. Analysis of existing laboratory data sets conducted under NCHRP Project 24-34, "Risk-Based Approach for Bridge Scour Prediction" revealed that the clear-water contraction scour equation does not envelope the observed data as a design equation.  Rather, it is a predictive equation which is seen to under predict observed scour relatively frequently compared to pier and abutment scour equations.  No laboratory data sets of live-bed contraction scour were identified during NCHRP Project 24-34. NCHRP Project 24-34 found that all of the previous studies suffered from a flaw in the experimental design, as none actually measured the depth of flow y0 in the contracted section before scour began to occur.  Therefore, this value had to be estimated in order to determine the depth of scour.  In addition, a number of laboratory studies did not directly measure the depth of scour using bed elevation measurements.  Instead, the assumption was made that y0 was equal to y1 (the depth of flow in the approach section upstream of the contraction).  This assumption ignores the hydraulic drawdown effect in the contraction which occurs during subcritical flow (particularly in a bridge reach). A contraction scour design approach for various bed materials is needed. Separating hydraulic erosion forces from the soil erosion resistance is needed to help determine a more realistic scour depth.
 
The objective of this research was to develop live-bed and clear-water contraction scour equations suitable for use in risk-based bridge design for a wide range of hydraulic conditions, contraction ratios, and bed material (cohesive, non-cohesive and rock–see Special Note H) and gradation uniformities. NCHRP Research Report 971: Revised Clear-Water and Live-Bed Contraction Scour Analysis and  NCHRP Web-Only Document 294: Revised Clear-Water and Live-Bed Contraction Scour Analysis Training Manual are available for immediate use. ]]></description>
      <pubDate>Mon, 14 Oct 2024 20:45:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/2441439</guid>
    </item>
    <item>
      <title>Thermal contraction coordination behavior between unbound aggregate layer and asphalt mixture overlay based on the finite difference and discrete element coupling method</title>
      <link>https://trid.trb.org/View/2401931</link>
      <description><![CDATA[The constraint action of the unbound aggregate base course plays an important role in affecting the temperature strains in the top asphalt layer. To understand thermal cracking, the authors investigate thermal contraction between the asphalt mixture and granular base layers. Experiments and simulations were conducted for thermal contraction tests. A mathematical model of virtual composite structures used wall-zone coupling based on the finite difference and discrete element method. The experimental composite structures containing three types of asphalt mixture overlays and five types of unbound aggregate base layers were developed for verification. The thermal contraction and restraint mechanism were revealed from both macro and microscopic scales. The proposed mathematical model shows a 94% high accuracy. The particle displacement vector and contact force chain could explain the thermal contraction behavior of composite structures. Smaller particle motion displacement or stronger contact force chain result in a higher restraint strain of the asphalt overlay. The thermal contraction behavior can be coordinated through the compaction and loosening of unbound aggregates. The material parameters and cooling temperature differences in the asphalt overlay have slight effects on the constraint action of a base layer, while the gradation and mechanical parameters of the unbound aggregate layer show significant impaction. The parameters, cohesion C and friction angle f, show a quadratic function with the restraint coefficient. This work has significant guidance on the selection of pavement structure and materials to improve the thermal cracking problem and lay the basis for the mechanical theoretical calculation to predict thermal cracking.]]></description>
      <pubDate>Mon, 09 Sep 2024 09:56:01 GMT</pubDate>
      <guid>https://trid.trb.org/View/2401931</guid>
    </item>
    <item>
      <title>Evaluating the low-temperature performance of asphalt mixtures based on the contraction and relaxation properties</title>
      <link>https://trid.trb.org/View/2320506</link>
      <description><![CDATA[The thermal cracking of asphalt pavement has been the focus of research in cold regions of the world. The contraction and relaxation properties of asphalt mixtures were crucial for investigating the thermal stress of asphalt pavement based on the thermal cracking mechanism. This paper proposed a novel evaluation index for characterizing the low-temperature performance of asphalt mixtures by considering their contraction and relaxation properties. Firstly, the rank during the evaluation indexes for low-temperature performance was determined by comparative analysis of method. Secondly, the thermal contraction coefficient was used to characterize contraction properties and cumulative stress at per unit strain rate (CSSR) was used to characterize relaxation properties in this paper. According to the cumulation process of thermal stress, a novel index was constructed based on the contraction and relaxation properties. Finally, considering the correlation between the failure temperature and the novel indexes, the prediction model of low-temperature performance consistent with the order of failure temperature was established based on the multiple linear regression method. Through the standardized analysis of the prediction model, the influence of novel indexes for the low-temperature performance of asphalt mixtures under different temperature conditions was clarified. A novel evaluation index provided a theoretical basis for unifying the evaluation indexes of asphalt mixtures.]]></description>
      <pubDate>Thu, 22 Feb 2024 09:06:19 GMT</pubDate>
      <guid>https://trid.trb.org/View/2320506</guid>
    </item>
    <item>
      <title>Contraction and Abutment Scour in Relief Bridges in a Flood Plain</title>
      <link>https://trid.trb.org/View/2270798</link>
      <description><![CDATA[The magnitude and duration of the Paraná river flood (Argentina) occurred in 1982/83, produced a very important increase in the discharge that flowed through the valley of the river. So, the flows that the relief bridges had to discharge, were much higher than the corresponding to the design section of the bridges. Then, very important scour occurred in these bridges, and many of them were destroyed by the flood. The field data measured during the flood, and their contrast with the computed erosion, gave the first evidences about the existing interrelation between the different types of erosion in relief bridees, and their bonds with the characteristic of the flow. Based on the field data, two sequences of laboratory experiments were carried out. The first sequence of experiments was developed in a mobile sand bed to evaluate the changes in the discharge distribution as a consequence of the occurrence of the abutment scour, and their influence on the contraction erosion. The second experiment sequence was designed to evaluate the influence of the width on the changes in the discharge distribution. The experimental study shows that the relief bridges in flood valleys, with a small width, require a special procedure to evaluate the total erosion, where the local scour must be computed before the contraction erosion. When the relief bridges have a large width, it is not necessary to use this sequence.]]></description>
      <pubDate>Wed, 14 Feb 2024 17:03:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/2270798</guid>
    </item>
    <item>
      <title>Local and Contraction Scour at Bridge Abutments</title>
      <link>https://trid.trb.org/View/2154511</link>
      <description><![CDATA[In most experimental studies on erosion at bridge piers and abutments, the value of the blockage ratio b/B between the transversal obstacle dimension and the flume width is kept as small as possible (typically b/B < 0.1) in order to avoid constriction and wall effects on the phenomenon. In many practical situations, though, b is not small compared to B so that the average acceleration due to contraction is expected to increase the scour effects of the local acceleration around the obstacle. Standard technical procedures propose to evaluate constriction and local scour depths separately and to sum up the two values, but no data are available to validate the correctness of such an assumption. In this work we present the results of several long duration (1.5→6 weeks) clear water scour laboratory tests around bridge abutments; the time evolution of the erosion process is analysed with respect to local and global characteristic values (maxima, volumes, hole shape). A series of experiments where all the main non-dimensional control parameters other than b/B are kept constant allows to enhance the effect of the constriction ratio alone. Results show that if standard models are used to evaluate contraction erosion, the simple addition of contraction and local effects may lead to a significant overestimation of the total scour.]]></description>
      <pubDate>Tue, 13 Feb 2024 16:34:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2154511</guid>
    </item>
    <item>
      <title>Storm Surge Scour at Coastal Bridges: Documenting the Effects of Hurricanes Bonnie and Floyd in North Carolina</title>
      <link>https://trid.trb.org/View/2154627</link>
      <description><![CDATA[Scour at bridges; over coastal waterways is caused by unsteady flows due to diurnal and semi-diurnal astronomical tides, storm surges (hurricanes, extratropical cyclones, and tsunamis), and combined riverine and tidal flows. Continuous rising: and failing, astronomical tides influence long-term trends of aggradation or degradation and produce some local scour around bridge piers and abutments. However, large amounts of contraction scour and severe local scour may be caused by storm surge that can exceed 23 ft (7 m) on the open coast. Storm surge can greatly increase water surface elevations and currents at coastal bridges, although durations of the increases are comparatively short, usually lasting no longer than several hours. Therefore, reliable estimates of water-level changes and currents under storm conditions are needed to account for roadway overtopping, hydrodynamic loads, and scour when planning and designing coastal bridges.]]></description>
      <pubDate>Mon, 12 Feb 2024 14:22:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/2154627</guid>
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