Abstract

AASHTO’s Manual for Bridge Evaluation (MBE) provides guidance for analytically evaluating bridge capacity based on available design information and the results of field inspections. This analysis results in a rating factor (RF), which quantifies a bridge’s safe load carrying capacity. RF accuracy, however, depends on the availability of information about structural details and material properties. As such, load rating bridges without design plans is difficult as field inspections alone often cannot provide enough information to perform detailed analysis. In many instances this means that a bridge would possess a substandard rating factor (RF < 1.0) simply due to the conservative assumptions required to perform traditional analysis. The most effective method for safely modifying such conservative theoretical rating factors is through load testing. Load testing measures actual bridge behavior and, for most bridges in good health, finds an increase in load rating is justified. This project utilized load testing to load rate 14 bridges in Kentucky that lack structural plans. Researchers first determined theoretical ratings using MBE-prescribed methods. For information typically taken from design plans, but which could not be measured directly, data-backed methods for making conservative assumptions were developed. For most bridges included in the study, theoretical rating factors alone suggested load postings were necessary. Load testing was then carried out utilizing tandem rear-axle dump trucks with measured axle weights. Multiple single-lane load cases were selected to maximize the effects being rated. Strain data were collected in real time using a wireless reusable strain gage system. Using these data, researchers computed a field test adjustment factor using MBE methods which directly modified the calculated theoretical RFs. Ultimately, load testing provided sufficient evidence to safely recommend that load postings were not necessary for any bridges in this study.

Report Date

2-2025

Report Number

KTC-25-14

Digital Object Identifier

https://doi.org/10.13023/ktc.rr.2025.14

Download

Share

COinS