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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>Passive Force Behavior for Skewed Bridge Abutments During Combined Lateral and Rotational Loading</title>
      <link>https://rip.trb.org/View/2427634</link>
      <description><![CDATA[As part of pooled fund study TPF-5(264), led by the Utah Department of Transportation (UDOT) and supported by the Federal Highway Administration (FHWA) and a few other state departments of transportation (DOTs), large-scale passive force-deflection tests were performed on a simulated bridge abutment to investigate the effect of skew angle on passive force behavior. Tests were conducted at abutment skew angles of 0°, 15°, 30°, and 45° with a backwall that was 11 ft wide and 5.5 ft tall. Backfills included sand and sandy gravel compacted to 95% of the modified Proctor maximum dry unit weight. Test results indicate that the passive force decreases significantly as the abutment skew angle increases to 45° relative to non-skewed walls. The results also indicate that the reduced passive force for a skewed abutment, Pp(skew), can be predicted using a simple reduction factor, Rskew, multiplied by the passive force for a non-skewed abutment with the same roadway width. The skew reduction factor was relatively consistent for all soil types, wingwall styles, and backfill width-to-height ratios investigated. The Phase II part of the previous study included testing of additional backfill materials and an inclined loading (push-and-rotate) condition for a 30° skew angle. No significant effect on the passive force skew reduction factor was observed in the inclined loading testing that involved relatively small rotation. Based on the previous study results, the skew reduction factor has already been implemented in the California Department of Transportation (Caltrans) Seismic Design Criteria, along with geotechnical guidelines for Oregon DOT and UDOT. However, as designers have started applying this approach, several questions have arisen. For example, in most of the field abutment tests, the simulated bridge abutment was forced to move longitudinally into the backfill soil.  In contrast, during earthquake loadings, the abutment has been observed to rotate. Although this rotation angle is quite small, it can lead to a significant difference in longitudinal displacement from the edges of the abutment from rotation. This would be expected to lead to a triangular distribution of pressure on the backwall of the abutment. Designers want to know (1) if the skew reduction factors remain the same when rotation is involved, and (2) if it is necessary to distribute the passive force non-uniformly along the backwall of the abutment.

The objective of this new study is to assist with the calibration of numerical  models by conducting a series of large-scale skewed abutment, passive force-displacement tests with enough abutment offset from rotation to evaluate the skew reduction factor and backwall pressure distribution. The maximum rotation and displacement would be larger than in the previous testing. As availability allows, the tests would be conducted at the same Salt Lake Airport test site used in the previous study.
]]></description>
      <pubDate>Thu, 12 Sep 2024 17:01:49 GMT</pubDate>
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      <title>SPR-4619: Back-calculated Dynamic Modulus Master Curve from the Time Histories of Falling Weight Deflectometer Surface Deflections</title>
      <link>https://rip.trb.org/View/1879925</link>
      <description><![CDATA[The analysis of deflection data collected by the falling weight deflectometer (FWD) provides a quick and reliable way of characterizing the properties of the asphalt layers as well as assessing the load-carrying capacity of existing pavement structures. This research will provide the back-calculation methodology of the |E*| master curve for the asphalt pavement layer using the time histories of FWD surface deflections and layered viscoelastic forward algorithms in an iterative dynamic back-calculation procedure.]]></description>
      <pubDate>Thu, 23 Sep 2021 15:18:02 GMT</pubDate>
      <guid>https://rip.trb.org/View/1879925</guid>
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      <title>Continued Monitoring of LA710 Phase I Rehabilitation</title>
      <link>https://rip.trb.org/View/1234326</link>
      <description><![CDATA[A recent example of a pavement design using structures, materials and construction specifications developed as part of the research performed by the University of California (UC) Contract Team for the Department is Phase I of long-life rehabilitation of LA-710 in Long Beach. A mechanistic-empirical design approach was used for this project as part of an earlier PPRC project. The Partnered Pavement Research Center (PPRC) will complete the monitoring and documentation of the first 5 years of performance of the innovative designs used on this project. This includes testing for deflection, ride quality and tire/pavement noise. It is anticipated that the final pavement performance evaluation will take place in Fall 2008 with a final report submitted soon after to Caltrans as a permanent record for the project. This report will include the mix and pavement design results, construction information, and a summary and evaluation of the periodic performance measurements as well as tests performed on cores and slabs taken from the as-constructed pavement. These results will be used by the Department as the basis for further implementation of the mechanistic-empirical design method used on this project, and provide valuable calibration data for the design procedure which will result in improved future designs. These results also provide validation for the innovative construction technique used on this project (55 hour weekend closures).]]></description>
      <pubDate>Thu, 03 Jan 2013 15:10:32 GMT</pubDate>
      <guid>https://rip.trb.org/View/1234326</guid>
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