Unified Code Calibration for Short- to Medium-span and Long-span Bridges with New Vehicular Live Load Model

Abstract

There are two bridge design codes in Korea adopting reliability-based load-and-resistance factor design for short- to medium-span and long-span bridges, respectively. Unified code calibration is required for the bridge design codes since their load-resistance factors were developed separately. Moreover, there is lack of consistency of theoretical backgrounds for a design vehicular live load and the statistical model of a vehicular live load effect. Therefore, the new statistical model of a vehicular live load effect and the corresponding design lane load are proposed based on the same data and the unified code calibration is conducted for the Ultimate Limit State I and V applying the current and new statistical models of the vehicular live load effect. The calibration is performed by adopting the optimization scheme for uniformly satisfying a target level of reliability. Load factors of the Ultimate Limit State I are defined depending on load compositions so the suggested load-resistance factors are applicable to design not only short- to medium-span but also long-span bridges. Furthermore, calibrations of the Ultimate Limit State V are conducted for short- to medium-span and long-span bridges, respectively. Reliability indices evaluated by proposed load-resistance factors more uniformly satisfy the target reliability index than those calculated by load-resistance factors in the current bridge design codes.