Approach for developing calibrated service limit states for the AASHTO LRFD bridge design specifications

The current service limit states of the AASHTO LRFD Bridge Design Specifications are intended to ensure a serviceable bridge for the specified 75-year design life. These limit states are based upon the traditional serviceability provisions of the AASHTO Standard Specifications for Highway Bridges. They are formulated to achieve component proportions similar to those of the Standard Specifications. However, these service limit states were not calibrated using reliability theory to truly achieve a determined life with a specific level of certainty as the tools and data necessary to accomplish this calibration were not available to the LRFD code writers. This paper describes the approach used to develop calibrated service limit state for use in AASHTO LRFD.