Field distribution factors and dynamic load allowance for simply supported double-tee girder bridges

Brian Kidd, Sandip Rimal, Junwon Seo, Mostafa Tazarv, Nadim Wehbe

Research output: Contribution to journalArticlepeer-review


This paper discusses the field testing of two single-span double-tee girder (DTG) bridges in South Dakota to determine live load distribution factors (LLDFs) and the dynamic load allowance (IM). One bridge had seven girders and another had eight girders. The longitudinal girder-to-girder joints of both bridges were deteriorated in a way that water could penetrate and the joint steel members were corroded. A truck traveled across each of the two bridges at five transverse paths. The paths were tested twice with a crawl speed load test and twice with a dynamic load. The LLDFs and IM were determined using strain data measured during the field tests. These results were compared with those determined according to the AASHTO Standard and the AASHTO LRFD specifications. Nearly all the measured LLDFs were below the AASHTO LRFD design LLDFs, with the exception of two instances: 1) An exterior DTG on the seven-girder bridge and 2) An interior DTG on the eight-girder bridge. The LLDFs specified in the AASHTO Standard were conservative compared with the measured LLDFs. It was also found that both AASHTO LRFD and AASHTO Standard specifications were conservative when estimating IM, compared to the field test results for both bridges.

Original languageEnglish
Pages (from-to)69-79
Number of pages11
JournalStructural Engineering and Mechanics
Issue number1
StatePublished - Apr 10 2022

Bibliographical note

Funding Information:
The work presented in this paper conducted with support from South Dakota Department of Transportation (SDDOT) and the Mountain-Plains Consortium (MPC), a University Transportation Center (UTC) funded by the U.S. Department of Transportation (USDOT). Additional help for this study was provided by the South Dakota State University (SDSU). The contents of this paper reflect the views of the authors, who are responsible for the facts and accuracy of the information presented. The truck, truck drivers, traffic safety equipment, and the heavy equipment were all provided by the SDDOT. The authors would like to thank Bob Longbons of the SDDOT research office for his support and efforts, and Zach Gutzmer of SDSU for his help during the course of this project. The research team is grateful to all those who participated in the field tests.

Publisher Copyright:
Copyright © 2022 Techno-Press, Ltd.


  • Double-tee girder bridges
  • Dynamic load allowance
  • Field testing
  • Live load distribution factor
  • Longitudinal joint damage

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Mechanics of Materials
  • Mechanical Engineering


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