Erratum for “Calibration of Live-Load Factor in LRFD Bridge Design Specifications Based on State-Specific Traffic Environments” by Oh-Sung Kwon, Eungsoo Kim, and Sarah Orton

This erratum provides corrections to the results published in the paper by the authors. In the paper, it is assumed that the maximum live loads in 75 years of bridge lifespan follows a Gumbel type I distribution. The parameters for the distribution were estimated based on the 100 days of simulation results of live load using weigh-in-motion (WIM) data collected in Missouri. During the batch processing of the data to calculate the reliability indices of the selected bridges, Gumbel type I distribution for minimum values was mistakenly used rather than that for maximum values. Because the effect of live load was underestimated by using minimum value distribution, the reliability index reported in Fig. 6 in the original paper was overestimated. The reliability indices are recalculated after correcting the issue. Figs. 6 and 7 in the original paper should be replaced with the new figures provided here.

As observed in Figs. 6 and 7, the reliability index is somewhat lower than the target reliability index of 3.5. The relatively low reliability index is primarily the result of the adoption of the Gumbel type I distribution, which was used to evaluate 75-year maximum live load effect. In the original study for the development of the LRFD specification (Nowak 1999), the tail portion of the cumulative distribution was subjectively extrapolated on normal probability paper. This method tends to result in a lower maximum response than the Gumbel type I distribution, as discussed in the report published by Kwon et al. (2011; Section 4.4.5). Because the reliability index highly depends on the adopted projection method, rather than calibrating the live load factor to achieve a reliability index of 3.5, the live load factor is calibrated to achieve the reliability index of bridges when the average daily truck traffic (ADTT) is 5,000, which is used for the latest study on load factor calibration (Kulicki et al. 2007). It is expected that the bridges designed with the live load calibration factor will have a uniform reliability index regardless of ADTT. The revised live load calibration factor is presented in Table 2. Table 2 in the original paper should be replaced with the new table provided here. More detailed information can be found in the revised report by the authors (Kwon et al. 2011).