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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>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Generation of negative skin friction and drag load in near-offshore pile foundations: A numerical study addressing pile installation effects</title>
      <link>https://trid.trb.org/View/2627257</link>
      <description><![CDATA[Offshore and near-offshore infrastructures are primarily supported by pile foundations for transferring the super-structure load to the bearing stratum while bypassing the overlying soft consolidating medium. Apart from the characteristics of the surrounding consolidating soil medium, pile installation process can also significantly influence the development of negative skin friction on the installed piles for such applications. The present study elucidates the evolution of negative skin friction on both in-place and jacked pile with the aid of an updated Lagrangian-based 2D-axisymmetric finite-element simulation framework. A particular emphasis is given on the determination of optimum values of parameters like pile-tip cone angle, contact stiffness and mesh size etc., which becomes imperative for the simulation of pile penetration process exhibiting a large deformation phenomenon. Post installation of the pile, the surrounding soil is subjected to a surficial surcharge to induce consolidation settlement of soil strata. In contrary to the in-place pile, the squeezing effect induced by the penetration process of a jacked pile leads to the dissipation of higher excess pore-water pressure and subsequent marked increase in the effective radial stress. Consequently, it further leads to a higher negative skin friction and greater drag load on the jacked pile.]]></description>
      <pubDate>Tue, 03 Feb 2026 10:07:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627257</guid>
    </item>
    <item>
      <title>Downdrag Forces on Piles due to Embankment Fill near Bridge Abutments</title>
      <link>https://trid.trb.org/View/2452775</link>
      <description><![CDATA[Negative Skin Friction (NSF) is a crucial aspect of geotechnical pile design. Downdrag occurs when there are changes in the water table, driving piles through soft compressible soils, or settlement of soils. This leads to an increase in the vertical loads on piles, even though there is no change in geotechnical capacity. Calculating NSF is not straightforward, but various literature and code provisions provide guidelines for addressing downdrag. The additional downward forces generated by downdrag must be considered in the design of pile superstructures. This paper focuses on understanding downdrag forces and their impact on the geotechnical capacity of piles in soft clay, particularly when influenced by embankments near abutments. The study involved conducting immediate and consolidation ground settlement analyses using Settle 3 software, which were then validated with PLAXIS. The settlement curves obtained were used for downdrag calculations. The FHWA/AASHTO/US Army Corps methodologies were applied to compute downdrag. Undrained properties were considered for immediate settlement calculations, while drained parameters were used for consolidation settlement assessments. The study also analyzed the impact of water table levels on downdrag forces through finite element analysis and limit state equilibrium evaluation. Nonlinearity was accounted for in the consolidation settlement calculations using Settle 3 software to consider the effect of pre-consolidation pressure. Settlements were assessed in stages according to the construction sequence to avoid overestimating NSF. In conclusion, this paper provides a comprehensive exploration of the intricate concept of NSF in geotechnical pile design. It highlights the significant challenges posed by NSF, such as changing water tables, additional fill, and soil characteristics, utilizing advanced modeling techniques. By employing three different methods recommended by current standards, the study elucidates the complex phenomenon of downdrag forces and their implications for pile design, especially in soft clay undergoing consolidation due to embankments.]]></description>
      <pubDate>Sat, 30 Nov 2024 11:49:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2452775</guid>
    </item>
    <item>
      <title>Study on the Skin-Friction Drag Reduction by Air Injection Using Computational Fluid Dynamics-Based Simulations</title>
      <link>https://trid.trb.org/View/1974274</link>
      <description><![CDATA[The skin-friction drag reduction by air injection have been investigated numerically for the turbulent boundary layers first on the underside of flat horizontal surfaces and secondly on the bottom of a real LNG carrier using unstructured finite-volume CFD solver for the Reynolds averaged Navier-Stokes equations. In the present flow computations, two different multi-phase models, such as the volume of fluid (VOF) and the Eulerian multi-phase (EMP), are adopted to investigate their performances in resolving two-phase flow patterns and estimating skin-friction drag reductions. Both VOF and EMP models have similar capability and accuracy in capturing the topology of ventilated cavities, so called ‘air pockets and branches’. However, EMP model is superior to VOF model in predicting quantitatively the percentage of frictional drag reduction by air injection for the cases of both a flat-plate model and an actual ship.]]></description>
      <pubDate>Mon, 20 May 2024 14:02:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1974274</guid>
    </item>
    <item>
      <title>Effect of Roughness Shape Parameter of Painted Surface on Frictional Resistance</title>
      <link>https://trid.trb.org/View/1974266</link>
      <description><![CDATA[Regarding the effect on the skin friction resistance of the wavy roughness like a painted surface on the hull surface, the law for the sandy rough surface cannot be applied, and it is impossible to estimate the quantity of the frictional resistance change from the roughness parameter. In order to investigate the influence on the frictional resistance with the fluid due to the wavy rough surface, the frictional resistance of flat plates with painted rough surface of different wave length wave height ratio was measured by tank tests. And, by measuring the surface roughness of painted roughness flat plates with a laser displacement meter, the roughness shape parameter was obtained. By analyzing these tank test results and roughness shape parameters and clarifying the relationship between the roughness parameter and the frictional resistance, the authors proposed a hypothesis about the frictional resistance increasing mechanism by the wavy rough surface, and based on the hypothesis, the frictional drag coefficient estimation formula was derived.]]></description>
      <pubDate>Mon, 20 May 2024 14:02:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/1974266</guid>
    </item>
    <item>
      <title>Tapertube Pile Capacity Prediction: Pile Driving Analyzer versus Static Load Test</title>
      <link>https://trid.trb.org/View/1850794</link>
      <description><![CDATA[John F. Kennedy (JFK) Airport in New York City is experiencing modification and expansion to meet the increased traveling demand. New terminals are being built supported on piles. The soil formation at the site generally consists of sandy fill, followed by a 5-ft thick organic soft layer. Below the organic layer, deep deposits of glacial sand exist with increased density with depth. Tapertube pipe piles are very efficient in this type of soil conditions. The piles achieve capacity through skin friction along the tapered section. The Nordlund method is generally used to estimate static axial capacity of the tapertube pile. This paper discusses the different analytical methods to predict pile axial capacity and presents assumptions using the Nordlund method for tapered piles that were designed for the expansion of the American Airlines Terminal 8 at JFK Airport. The piles consisted of an 8-in. tip diameter and 14-in. butt diameter with a 15 ft long tapered section plus extension. The paper includes the pile driving analyzer (PDA) results, discussing both CASE and CAPWAP methods. A static load test was also performed, and the results are compared with the PDA results. Lessons learned from this project are shared to help the engineering community with future design and construction of similar projects.]]></description>
      <pubDate>Wed, 30 Jun 2021 11:59:45 GMT</pubDate>
      <guid>https://trid.trb.org/View/1850794</guid>
    </item>
    <item>
      <title>On the influence of Reynolds number and ground conditions on the scaling of the aerodynamic drag of trains</title>
      <link>https://trid.trb.org/View/1849169</link>
      <description><![CDATA[The present study examines the possibilities of transferring drag measurement results on reduced-scale train models to the respective full-scale vehicle. A comprehensive experimental and numerical study of the boundary layer and skin friction along trains is performed, focusing on Reynolds number effects. The data are supplemented by an extensive literature study and compared with different approaches from flat plate theory. Good agreement can be found when using the appropriate empiric coefficients and boundary conditions. Simultaneously, the difficulties in determining the skin friction drag of trains due to three-dimensional effects and surface roughness become apparent. The ground simulation analysis, including the effects of ground roughness due to ballast and sleepers, reveals a significant effect of the ground conditions on the vehicle’s aerodynamic drag. Additionally, the effects of elements mounted on the train roof are investigated for different upstream flow conditions. Finally, a scaling method is proposed to transfer drag results from model-scale to full-scale trains based on the findings.]]></description>
      <pubDate>Wed, 26 May 2021 11:20:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/1849169</guid>
    </item>
    <item>
      <title>Evolutionary Computing to Determine the Skin Friction Capacity of Piles Embedded in Clay and Evaluation of the Available Analytical Methods</title>
      <link>https://trid.trb.org/View/1708391</link>
      <description><![CDATA[Deep foundations are very important elements in the routine design of railways and bridges when the loads applied due to these important structures are higher than the bearing capacity of the soil. However, the methods currently available to calculate the bearing capacity of driven piles embedded in clay have been developed based on empirical factors derived from limited tests. Hence, further assessment of these methods and the development of new methods are urgently required. This paper discusses the development of a new robust model to calculate the skin friction capacity of driven piles using the multi-objective evolutionary polynomial regression (MOGA-EPR) analysis. The paper also evaluates the accuracy of the available analytical methods. Real field results of skin friction capacity of driven piles have been used to achieve the objectives of the study. The results showed that the MOGA-EPR predicts the skin friction of driven piles with an excellent accuracy and better than the available analytical methods, with a mean absolute error (MAE), a root mean square error (RMSE), mean (μ), a standard deviation (σ), a coefficient of determination (R2), the variance account for (VAF) and a20-index of 3.4, 4.6, 1.03, 0.24, 0.98, 99, and 0.75, respectively, for the training data, and 4.2, 5.3, 1.12, 0.15, 0.91, 97 and 0.77, respectively, for testing data. In addition, a novel model to predict the skin friction capacity of driven piles has been proposed based on the MOGA-EPR analysis and this model can be used by engineers and researcher with confidence. The evaluation of the analytical methods illustrated that the Lambda method accuracy is better than the Alpha and Beta methods as this method scored a less mean error (MAE = 7.8 and RMSE = 12.5), a less standard deviation (σ = 0.21), a higher coefficient of determination (R2 = 0.91), and higher value for the variance account for (VAF = 89) compared with the other analytical methods. In addition, the Beta method scored lowest compared with the other analytical methods with MAE, RMSE, μ, σ, R2, VAF and a20-index of 17.2, 28.0, 1.07, 1.00, 0.55, 40 and 0.37, respectively. The findings of this study will help to achieve robust calculations of pile capacity and reduce uncertainty associated with the choice of the analytical method used in the design of driven piles in clay.]]></description>
      <pubDate>Mon, 08 Jun 2020 14:42:49 GMT</pubDate>
      <guid>https://trid.trb.org/View/1708391</guid>
    </item>
    <item>
      <title>An experimental investigation into the surface and hydrodynamic characteristics of marine coatings with mimicked hull roughness ranges</title>
      <link>https://trid.trb.org/View/1638822</link>
      <description><![CDATA[Hull roughness is a significant factor in forecasting ship efficiency and is typically measured using R(t)50, the maximum peak-to-trough height taken over 50 mm sample length. There are many potential causes of hull roughness, which can occur at the pre-delivery stage or on ships in service. Little research has focused on how contributors such as modern-day coating roughness and biofouling impact the added drag of in-service ships. This article presents findings from a study of how hull roughness in the presence of different coating types impacts in-service ship performance. The study findings indicate that the importance of hull roughness is undervalued in estimations of drag penalties based on well-applied and relatively smooth coating conditions.]]></description>
      <pubDate>Mon, 23 Mar 2020 12:03:40 GMT</pubDate>
      <guid>https://trid.trb.org/View/1638822</guid>
    </item>
    <item>
      <title>Passive Drag Reduction via Bionic Hull Coatings</title>
      <link>https://trid.trb.org/View/1652537</link>
      <description><![CDATA[The resistance of ships is often dominated by friction between the hull and the water. This study explores possibilities of reducing skin-friction drag in a way inspired by dolphins. These possess a soft skin believed to diminish drag by delaying the transition from laminar to turbulent flow. The underlying mechanism builds on a stabilization of the laminar boundary layer by the compliant surface. To transfer this mechanism to ship hulls, coatings similar to dolphin skin have been designed numerically, made from polymeric materials, and tested in a water tunnel. For the best coating, a drag reduction by almost 3% has been predicted in the boundary layer along the hull model of a small search-and-rescue vessel. The trends of the numerical predictions have been confirmed in the experiments.]]></description>
      <pubDate>Mon, 28 Oct 2019 10:31:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/1652537</guid>
    </item>
    <item>
      <title>Modelling of hull roughness</title>
      <link>https://trid.trb.org/View/1581814</link>
      <description><![CDATA[In this paper the authors present a practical guideline on how to estimate the frictional resistance of ship hulls due to different fouling control coatings. Most of the current methods rely on empirical formulations based on an equivalent sand grain roughness height. These correlations are not universal and cannot be applied to every marine surface. Conversely, the shear stress of a specific coating can be measured in an experimental facility at the same Reynolds roughness number as at full scale. The results can be used to inform the boundary conditions of computational fluid dynamics, where the complex flow around the ship can be computed for any sailing condition. Hence, this methodology allows the estimation of the frictional resistance due to a specific surface in a specific sailing condition. Representative antifouling coating products by AkzoNobel, and wall functions for the open-source code OpenFOAM, are used to illustrate the methodology. Similarities and differences with other methods are discussed.]]></description>
      <pubDate>Fri, 22 Mar 2019 16:15:09 GMT</pubDate>
      <guid>https://trid.trb.org/View/1581814</guid>
    </item>
    <item>
      <title>Development of Axial Load Transfer Curves for PSC Piles in Clayey Soil</title>
      <link>https://trid.trb.org/View/1572491</link>
      <description><![CDATA[This paper presents the analyses of load-transfer behavior (t-z and q-z) of twelve prestressed concrete  (PSC)  instrumented  test  piles  (TPs)  that  were  driven  in  different  locations  of Louisiana. The load transfer method is an efficient and practical tool for the analysis of single driven pile to predict the ultimate load. The TPs were instrumented with vibrating wire strain gauges in order to calculate the skin-friction transfer for different soil layers and end-bearing capacities separately during the static load test (SLT). The SLT was performed on all the TPs after 10 to 14 days of end of driving. Empirical load-transfer models were proposed for both skin-friction and end-bearing capacities previously by different researchers (Fleming 1992, Hirayama 1990, Krasinski 2012, Bohn et al. 2017) after analyzing the instrumented TP results. For  this  study,  skin-friction  transfer  of  each  soil  layer  and  end-bearing  capacities  were measured  and  compared  with  the  previously  developed  existing  models.  The  stiffness parameter for the hyperbolic equation of both skin-friction (Ms) and end-bearing (Mb) was calibrated in order to best match the measurements.]]></description>
      <pubDate>Fri, 01 Mar 2019 15:51:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/1572491</guid>
    </item>
    <item>
      <title>Full-Scale Field Test Study of Skin Friction Development in Sand for ACIP Piles under Compressive and Tensile Loading Conditions for Bridge Support</title>
      <link>https://trid.trb.org/View/1559508</link>
      <description><![CDATA[In this study, the performance of a non-displacement auger cast-in-place (ACIP) piles in sand under compressive and tensile loading was investigated by performing a field load test. In this full-scale load test study, ACIP piles were installed in layered sand, with loose sand [minimum Texas cone penetrometer (TCP) blow count of 7] in the top 4 m with very dense sand (maximum TCP blow count of 95) in the bottom layer 7 m below ground. The load test was performed on a 760 mm (30 in.) diameter fully instrumented ACIP pile with eight 450 mm (18 in.) diameter reaction piles. The test pile utilized a load cell and multiple pile top dial gages to measure applied load and settlement during the load test. Also, vibrating-wire sister bar strain gauges with thermocouples were attached along the length of the test pile and selected reaction piles. The design load for the test pile was 816 kN (92 t) and the test pile was loaded to 2,840 kN (320 t) before unloading. Using the Vipulanandan ACIP pile model, the ultimate capacity was predicted to be 4,545 kN (512 t), more than five times the design capacity. Skin friction-displacement relationships for the test pile in compression and reaction piles in tension were developed with depth representing the loose to very dense sand. The maximum skin friction measured in the very dense sand was 210 kPa (2.2 tsf) in compression and 57.3 kPa (0.6 tsf) in tension. The measured skin friction in the ACIP test pile in compression was more than 50% higher than the TxDOT design standard for drilled shafts in high blow count dense sands.]]></description>
      <pubDate>Thu, 11 Oct 2018 11:01:57 GMT</pubDate>
      <guid>https://trid.trb.org/View/1559508</guid>
    </item>
    <item>
      <title>Numerical Study on Skin Friction and Shock Inception in Various Geometries of Supersonic Nozzle</title>
      <link>https://trid.trb.org/View/1486402</link>
      <description><![CDATA[In the present study, a numerical simulation is conducted to predict the influence of convergent-divergent nozzle geometry and NPR on the skin friction and shockwave location. Various shapes of nozzles are numerically simulated using the Computational Fluid Dynamics code. The shock position is examined to demonstrate the impact of nozzle shape on its location. Skin friction is shown to be smoothly decreasing at the divergent part of the nozzle for all NPRs lower than 2.0. However, an inverse behavioural trend was observed at NPR equal to 2. This could be attributed to the fact that the large disturbance of fluid near the wall is the major factor behind such an oddity. The results also show that the shock position is reliant on the nozzle geometry at certain NPR.]]></description>
      <pubDate>Wed, 29 Nov 2017 14:54:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1486402</guid>
    </item>
    <item>
      <title>Liquefaction-Induced Downdrag on Continuous Flight Auger (CFA) Piles from Full-Scale Tests Using Blast Liquefaction</title>
      <link>https://trid.trb.org/View/1480486</link>
      <description><![CDATA[Deep foundations typically support dead and live loads through a combination of positive skin friction acting along the sides of the pile and end-bearing at the toe of the pile; however, during seismic events, negative skin friction (or downdrag) can potentially develop. Downdrag occurs because of increases in effective stress caused by pore pressure dissipation and settlement by the liquefiable soil layer(s) relative to the pile. This phenomenon creates a dragload that the pile must support in addition to its permanent service pile head load. The depth of the dragload extends to the neutral plane. The neutral plane is the depth where the settlement of the pile equals the liquefaction settlement of the soil and where the axial load in the pile is the greatest. The elevation of the neutral plane is found by trial and error such that the service load plus negative friction should equal the positive friction plus end-bearing resistance. Fellenius reviewed many case histories involving downdrag on piles and concluded that the dragload does not change the ultimate bearing capacity of a pile foundation, but it should be added to the dead load in design. In addition, the designer must also still determine that both the structural capacity of the pile and the tolerable settlement is not exceeded. For seismic events, it has been found that assuming skin friction equals zero in the layer(s) of surrounding soil in which liquefaction occurs will result in little error. The American Association of State Highway and Transportation Officials recommends that the residual strength of the soil in that zone be assumed when estimating negative skin friction in a liquefied layer(s). To evaluate the skin friction of Continuous Flight Auger (CFA) piles, a blast-induced liquefaction test program was conducted at a site in Christchurch, New Zealand.  This TechBrief describes the test program and focuses on the test results of the loaded piles as compared to conventional design practice.]]></description>
      <pubDate>Sun, 27 Aug 2017 18:11:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1480486</guid>
    </item>
    <item>
      <title>Some Observations of the Influence Factors on the Response of Pile Groups</title>
      <link>https://trid.trb.org/View/1453913</link>
      <description><![CDATA[A simplified approach for nonlinear analysis of the load-displacement response of pile groups embedded in multilayered soils is presented in this work. A hyperbolic model is used to capture the relationship between unit skin friction and pile-soil relative displacement developed along the pile-soil interface and the stress-displacement relationship developed at the pile end. Considering interactive effect among piles, the parameters related to the hyperbolic model of an individual pile in a group can be computed. As to the analysis of the response of pile groups, a highly effective iterative computer program is developed using the hyperbolic model of an individual pile in a group. The efficiency and accuracy of the present method is verified using a well-documented field test. Furthermore, a parametric study is conducted to capture the influence of pile spacing and number of piles on the load-settlement response of the pile groups connected to a rigid cap. The pile-group settlement ratio and the pile-group resistance ratio are analyzed to assess the interaction effect among individual piles.]]></description>
      <pubDate>Fri, 28 Apr 2017 10:40:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/1453913</guid>
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