ABSTRACT
Based on current rating methods, about one in nine of the 607,380 US bridges are considered to be structurally deficient. However, not all these bridges are at risk of collapse as current code-specified analytical methods are generally conservative and may underestimate the true safety levels of existing bridges. For these reasons, there has been considerable interest in developing methods that combine field measured data with analytical models to obtain more accurate assessments of existing bridges.
This paper presents a Response-Based Load and Resistance Factor Rating (RB-LRFR) method that utilizes strain data to evaluate the safety of existing bridge members. Appropriate live load factors are calibrated to reflect the uncertainties associated with estimating the parameters and random variables needed to rate a bridge component using field data. The implementation of the proposed methodology is illustrated using a composite steel girder bridge as an example.
