<rss version="2.0" xmlns:atom="https://www.w3.org/2005/Atom">
  <channel>
    <title>Research in Progress (RIP)</title>
    <link>https://rip.trb.org/</link>
    <atom:link href="https://rip.trb.org/Record/RSS?s=PHNlYXJjaD48cGFyYW1zPjxwYXJhbSBuYW1lPSJkYXRlaW4iIHZhbHVlPSJhbGwiIC8+PHBhcmFtIG5hbWU9InN1YmplY3Rsb2dpYyIgdmFsdWU9Im9yIiAvPjxwYXJhbSBuYW1lPSJ0ZXJtc2xvZ2ljIiB2YWx1ZT0ib3IiIC8+PHBhcmFtIG5hbWU9ImxvY2F0aW9uIiB2YWx1ZT0iMTYiIC8+PC9wYXJhbXM+PGZpbHRlcnM+PGZpbHRlciBmaWVsZD0iaW5kZXh0ZXJtcyIgdmFsdWU9IiZxdW90O1NrZXcgYnJpZGdlcyZxdW90OyIgb3JpZ2luYWxfdmFsdWU9IiZxdW90O1NrZXcgYnJpZGdlcyZxdW90OyIgLz48L2ZpbHRlcnM+PHJhbmdlcyAvPjxzb3J0cz48c29ydCBmaWVsZD0icHVibGlzaGVkIiBvcmRlcj0iZGVzYyIgLz48L3NvcnRzPjxwZXJzaXN0cz48cGVyc2lzdCBuYW1lPSJyYW5nZXR5cGUiIHZhbHVlPSJwdWJsaXNoZWRkYXRlIiAvPjwvcGVyc2lzdHM+PC9zZWFyY2g+" rel="self" type="application/rss+xml" />
    <description></description>
    <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>
    <image>
      <title>Research in Progress (RIP)</title>
      <url>https://rip.trb.org/Images/PageHeader-wTitle-RIP.jpg</url>
      <link>https://rip.trb.org/</link>
    </image>
    <item>
      <title>Flexural Resistance of I-Sections for Skewed and/or Curved Steel I-Girder Bridges</title>
      <link>https://rip.trb.org/View/2381721</link>
      <description><![CDATA[Currently, in the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS), the nominal flexural resistance of I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal is conservatively not allowed to exceed first yield at the strength limit state for the following reasons: 

Such bridges typically experience significant differential vertical deflections at the cross-frames resulting in larger cross-frame forces in the elastic range. As interior-pier sections yield and begin to lose stiffness and shed their load, the forces in the adjacent cross-frames will increase. There is currently no established procedure to predict the resulting increase in the forces without performing a refined nonlinear analysis. 
In horizontally curved bridges and severely skewed straight bridges with discontinuous cross-frames, significant lateral flange bending effects can occur. The resulting lateral bending moments and stresses are amplified in the bottom compression flange adjacent to the pier as the flange deflects laterally. There is currently no means to accurately predict these amplification effects as the flange is also yielding.
Skewed supports also result in twisting of the girders, which is not recognized in plastic-design theory. The relative vertical deflections of the girders create eccentricities that are also not recognized in the theory.
Research is needed to address these load and resistance factor design (LRFD) issues to help state departments of transportation (DOTs) achieve more efficient designs and recognize improved accuracy in load ratings for existing bridges. 

OBJECTIVE: The objective of this project is to develop a methodology to determine the nominal flexural resistance beyond first yield at the strength limit state in I-girder bridges that are (1) kinked (chorded) and continuous, (2) horizontally curved, or (3) straight with supports skewed more than 20 degrees from normal. ]]></description>
      <pubDate>Tue, 21 May 2024 17:15:41 GMT</pubDate>
      <guid>https://rip.trb.org/View/2381721</guid>
    </item>
    <item>
      <title>Skew Detection System Replacement on Vertical Lift Bridges (Phase II)</title>
      <link>https://rip.trb.org/View/1907131</link>
      <description><![CDATA[The objective of this work is to prove a new technology system against the existing legacy skew-control technology on the Ellender Ferry Vertical Lift Bridge over the Intracoastal Waterway, located in Calcasieu Parish. The new skew technology shall be as recommended in the results of the Phase 1 study.

The work will include design and installation according to the following tasks: (1) Analyze the existing control system, electrical installation, and structure to determine  how to interface the new technology into the existing; (2) Determine the scope of work required to implement the installation; (3) Perform the installation; (4) Calibrate and test the installation; and (5) Provide support personnel and time for troubleshooting the installation for a period of 6 months.
]]></description>
      <pubDate>Mon, 31 Jan 2022 11:02:41 GMT</pubDate>
      <guid>https://rip.trb.org/View/1907131</guid>
    </item>
    <item>
      <title>Applicability of Approximate Methods of Analysis for Skewed Straight Steel I-Girder Bridges</title>
      <link>https://rip.trb.org/View/1851837</link>
      <description><![CDATA[This project is a continuation of project BE535, Straight Steel I-Girder Bridges with Skew Index Approaching 0.3. That project separated the 26 bridges into five different categories for the purpose of determining an appropriate analysis method. This project would focus primarily on Categories 1, 2, and 3, adding more bridges to that study to confirm that the bridge categories determined based on the 12 bridges previously studied holds true for a larger sample size. Additional bridges will include but are not limited to, bridges with a minimum of 4 girders, and bridges with both contiguous and staggered cross frame arrangements.]]></description>
      <pubDate>Tue, 11 May 2021 14:38:42 GMT</pubDate>
      <guid>https://rip.trb.org/View/1851837</guid>
    </item>
    <item>
      <title>Omni-directional Hysteretic p-y Models for Piles Embedded in Cohesive Soils</title>
      <link>https://rip.trb.org/View/1441862</link>
      <description><![CDATA[The newly developed performance-based seismic design methodologies require accurate estimates of the lateral displacements of a structure, because lateral drift is related directly to the serviceability and safety performance criteria. To achieve a better prediction of engineering demand parameters under various seismic hazard levels or limit states, nonlinear time-history analyses are required. Highway bridges need to maintain functionality after the occurrence of catastrophic earthquake events. The reliability of predictions obtained through nonlinear time-history analyses depends largely on the correct and accurate modeling of the structural features (e.g., curved decks, skewed abutments, uneven column heights, etc.), on the proper selection of the input ground motion records (such that they are representative of the future earthquakes at the specific site of the bridge), and on the accurate consideration of the soil-structure interaction (SSI) effects.]]></description>
      <pubDate>Wed, 04 Jan 2017 10:54:52 GMT</pubDate>
      <guid>https://rip.trb.org/View/1441862</guid>
    </item>
    <item>
      <title>Nonlinear Lateral Performance of Skew Abutments</title>
      <link>https://rip.trb.org/View/1441860</link>
      <description><![CDATA[The lateral force-deflection relationship between an abutment backwall and the retained soil or Concrete Low Strength Material (CLSM) can significantly affect bridge performance. The current inventory of test data that can be directly applied to develop design guidelines is limited to backwalls with zero skew and backfill materials consisting of well compacted clay or silty sand.   Testing and simulation tools are needed for other common conditions such as various non-zero skew angles and amounts of torsional rotation as well as CLSM backfill.]]></description>
      <pubDate>Wed, 04 Jan 2017 10:54:49 GMT</pubDate>
      <guid>https://rip.trb.org/View/1441860</guid>
    </item>
    <item>
      <title>CCTRP 17-01: Development of a Simplified Design Method and Reinforcement Detail for the Acute Corner of Skewed Bridge Decks</title>
      <link>https://rip.trb.org/View/1422701</link>
      <description><![CDATA[In modern transportation projects, skewed bridges are becoming increasingly more common and their degree of skew perceptibly more severe due to more and more restrictive site constraints, especially in urban infrastructure projects. Despite the advantages of skewed bridges, the structural design and construction of the acute corners of skewed concrete slabs present several challenges due to the congested reinforcement details. This may lead to several problems with placing and compacting concrete. At the acute corners of highly skewed bridge decks, the bars perpendicular to the longitudinal axis of the bridge are generally too short to be developed, making them structurally ineffective. In addition, the placement of these bars significantly increases the complexity of construction. Often, as the skew angle increases, large portions of the deck can go unreinforced subjecting them to service issues such as spalling and chipping. The presence of the end diaphragm and an integrated concrete parapet may also have a significant impact on the flexural demand of the deck. In addition, the two-way action of the slab may significantly reduce the flexural demand in acute corners. Hence, an optimal design needs to be developed to account for all these effects to simplify the construction and reduce the costs. This study will use detailed finite element simulation to accurately determine the behavior of skewed slabs. A comprehensive parametric study will be performed to understand the effect(s) of the following parameters on flexural moments and concrete stresses at the acute corner of bridge decks: (1) skew angle, (2) overhang length, (3) girder type, and (4) bridge width and length, (5) end diaphragm, and (6) the presence of an integrated barrier. Concerns about the cost-effectiveness and  adequacy of the current reinforcement detail used for acute corners of skewed decks will be addressed in this study. This research will enable the development of an optimized design method and reinforcement detail to reduce the cost and time of construction, while also increasing the safety of the design. The longevity of the bridge deck will also be improved by preventing cracking of concrete deck that is common in skewed bridges.]]></description>
      <pubDate>Thu, 08 Sep 2016 15:14:28 GMT</pubDate>
      <guid>https://rip.trb.org/View/1422701</guid>
    </item>
    <item>
      <title>Effect of Skew on Shear Loads in Multi-Cell Box Girder Bridges</title>
      <link>https://rip.trb.org/View/1234292</link>
      <description><![CDATA[Multi-cell box girder bridges are the most common type in Caltrans' bridge inventory. Caltrans has adopted the AASHTO LRFD Bridge Design Specifications for the design of these bridges. However, the skew factors for multi-cell box girder bridges are based on a grillage model, which does not capture torsional effects correctly. Further, the AASHTO factors are intended for live load distribution only, and their applicability to permanent loads is unclear. Caltrans has directed the designers to use the more conservative factors in Caltrans' Bridge Design Aids. The skew factors currently in use were developed over 30 years ago, based on simple-span bridges with a limited range of plan geometries. These factors could result in over-design of multi-span bridges. This conservatism coupled with the new truck (HL93 and P15) design loads and improved estimates of prestress losses has led to significant increases in construction costs.]]></description>
      <pubDate>Thu, 03 Jan 2013 15:10:01 GMT</pubDate>
      <guid>https://rip.trb.org/View/1234292</guid>
    </item>
    <item>
      <title>SEISMIC: Evaluation and Improvement of Design Methods and Details for Shear Keys and Stem Walls in Bridge Abutments</title>
      <link>https://rip.trb.org/View/1234200</link>
      <description><![CDATA[Failure of abutment shear keys during an earthquake causes major damage to the abutment stem wall. Isolated shear keys have been proposed and accepted for bridges with skew less than 20 degrees. However, a large number of Caltrans bridges contain skews greater than 20 degrees. Adequate design guidelines need to be developed for bridges where the skew angle exceeds 20 degrees.]]></description>
      <pubDate>Thu, 03 Jan 2013 15:08:25 GMT</pubDate>
      <guid>https://rip.trb.org/View/1234200</guid>
    </item>
  </channel>
</rss>