|
Reliability Analysis and Determination of Load-resistance Factors for Seismic Load Combination of Korean Highway Bridge Design Code Lim Hyun Hong
ABSTRACT Most modern bridge design codes follow load-resistance factor design method based on reliability theory. In reliability-based code, the safety level is expressed as a reliability index which is guaranteed by design nominal strength or required nominal strength by load-resistance coefficient. A method of determining the load-resistance factors that guarantees a uniform and consistent reliability index has been studied, and there has been a concern about what reliability index should be used as the target reliability index. In the case of Korean highway bridge design code(limit state design), research has been actively carried out to propose a load-resistance factor that guarantees uniform reliability for the gravity directional load combination or the wind load combination. A probabilistic model for a corresponding load effect and an appropriate reliability analysis technique has been developed for the dead load effect by the self-weight of the structure or the vehicular live load by the heavy vehicle or the wind load effect by typhoon. On the other hand, there has been no precedent study on an appropriate probabilistic model of the seismic load effect on the bridge structure by the ground motion. In this study, statistical characteristics and a distribution type are determined by applying Monte-Carlo simulation and Kolmogorov-Smirnov test respectively for an equivalent static seismic load effect model for dynamic seismic load effect on bridge structures . In addition, this study defines the limit state for the seismic load combination of Korean highway bridge design code (limit state design method) by introducing RRD (Ratio of Return period to Design life) concept, which is the ratio of the repetition period to the design life cycle, and discusses determining the target reliability index. Finally, the load-resistance factors are determined and proposed through the strength-based optimization technique. At this time, the optimization process proceeds independently of other load combinations considering the failure mode of the limit state function and discusses its validity. Key Word Reliability-based design method, Load-resistance factor, Korean highway bridge design code(limit state design), Seismic load combination, Seismic load effect probabilistic model, Target reliability index
|