Determination of the Load-Resistance Factors

for Reliability-Based Codes by Optimization

Changhoon Bae

ABSTRACT

   In current years, the limit state design is the general trend for bridge design specifications which suggests load-resistance factors for structural members of a bridge with dominant ultimate limit states to equally satisfy the target reliability index. To verify that existing load-resistance factors equally satisfy the target reliability index, the reliability assessment is executed for AASHTO LRFD and KHBDC-LSD by calculating the required strength which can be generated from load-resistance factors. Prior to the reliability assessment, the normalization is introduced in this study, which nominal loads and nominal resistance are expressed as the ratio to the total nominal load. The generalized reliability assessment is possible by applying the normalization without the length and the cross sectional details of a bridge related to absolute values of nominal loads. According to the reliability assessment results, both specifications do not guarantee equally the target reliability level. To resolve this problem, it is necessary to establish calibration formulation which can generate load-resistance factors to satisfy evenly the target reliability index. By applying this calibration process, revised load-resistance factors are proposed for both specifications.