Load rating of new and existing bridges have been used in state departments of transportation for decades as a method to determine if a bridge is adequate for the expected vehicle traffic on the bridge. Currently, there are several methods available for rating existing bridges; each method is similar to its corresponding design philosophy. The two primary methods used in state departments of transportation are Load Factor Rating (LFR) and Load and Resistance Factor Rating (LRFR). Previously, the reinforced concrete culverts in Tennessee, which is approximately 40% of the bridge inventory, were not load rated. This was because they were not considered critical structures. However, a Federal Highway Administration (FHWA) mandate requires that all existing culverts be load rated. Also, FHWA recommends that LRFR be used on existing culverts in lieu of LFR. The objective of this research was to provide an accurate comparison of LFR to LRFR for reinforced concrete box and slab culverts. It was also necessary to check if the FHWA recommendation is valid or not.
To accomplish the comparison, a database of existing culverts from 1980 to 1990 was assembled. The rating factors for LFR and LRFR were compared via graphical analysis for each member of the culvert for positive flexure, negative flexure, and shear. The graphs plotted the rating factors from LFR on the vertical axis and the rating factors from LRFR on the horizontal axis. The graphs were also separated into box culverts and slab culverts for each of the different levels of load rating performed. From this, it was easy to obtain which method had lower, more severe rating factors. A comparison was also made using the average ratio of LFR to LRFR for all of the results for each load for each member. The controlling live load model for LRFR, live load surcharge, live load distribution factors, and horizontal soil pressure application all affect the rating factors for LFR and LRFR. The results of the study indicate that LRFR is not a viable option for existing reinforced concrete culverts. Furthermore, the recommendation to load rate existing bridges with LRFR is not valid.
|Commitee:||Henderson, Craig, Ramirez Rodriguez, Guillermo|
|School:||Tennessee Technological University|
|School Location:||United States -- Tennessee|
|Source:||MAI 51/04M(E), Masters Abstracts International|
|Keywords:||Bednarcyk, Culvert, Lfd, Lfr, Lrfd, Lrfr|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be