MoDOT Research Report Announcements: November 2024

Tuesday, November 12, 2024

Load and Resistance Factor Rating Methodology Recommendations for Missouri Bridges

Traditionally, MoDOT performed bridge load ratings using the Load Factor Rating (LFR) methodology. With the adoption of Load and Resistance Factor Design based Load and Resistance Factor Rating (LRFR) methodology, MoDOT is migrating to LRFR for rating bridges. The primary goal of this study is to develop and recommend load posting policies using the LRFR methodology consistent with the current LFR policy. The goal was accomplished using MoDOT-provided information on approximately one hundred reinforced concrete, prestressed concrete, and steel bridges each, and about thirty concrete culverts throughout the state and in different commercial zones. The research conducted to compare the two rating methodologies has shown that the LFR and LRFR methodologies of rating differ in (a) bridges rated in LFR govern in interior girders while with the LRFR method, most bridges will govern in the exterior girders; (b) LRFR ratings are lower than the LFR ratings; (c) the number of posted bridges increased for LRFR over those required to be posted by LFR. This points to a necessary change associated with the LRFR posting threshold to meet the current practice used by MoDOT. Recommendations based on the study of the various objectives applicable to each of the bridge/culvert types have been provided in this report.

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Report number: cmr 24-021
Published: November 2024

Project number: TR202122

Authors: Thiagarajan Ganesh, John Finke, John Myers, Bao Tran, Ronald Cheruiyot, and Nirav Khanal

Performing organization: Missouri Center for Transportation Innovation

Wednesday, November 6, 2024

Developing Implementation Strategies for Risk Based Inspection (RBI)

This project's goal was to improve asset management through Risk-Based Inspection (RBI) practices. The research was intended to amplify the results of prior research that produced the Proposed Guidelines for Reliability-Based Inspection Practices. Under the new provisions of the National Bridge Inspection Standards (NBIS), bridge owners that implement a risk-based inspection (RBI) analysis can determine risk-based inspection intervals of up to 72 months for certain bridges. This research focused on developing implementation strategies to aid bridge owners in implementing these new NBIS rules. Reliability Assessment (RAP) meetings were held in six states during the research. Risk models were developed and applied to 60 sample bridges. These data were analyzed by comparing results with target values developed during the research. A data-driven methodology for analyzing the risk models based on bridge inventory data was developed. This methodology provides a means of calibrating and verifying the risk models. The method was found to be effective at analyzing the models and communicating their effectiveness. It was also found that there was consistency in the risk models developed by different RAP and these risk models were consistent with the target ranges developed through the research.