Calibration of LRFD Mechanical Design for Movable Bridges

Abstract

This study aims to develop Load and Resistance Factor Design (LRFD) provisions for movable bridges’ mechanical components. It requires the formulation of the limit state functions, determination of the statistical parameters of loads and resistances, development of the reliability analysis method, selection of target reliability indices, and calibration of load and resistance factors. The service and overload limit states for electric and hydraulic motors were considered. Movable bridge owners and operators were surveyed to gather information about the bridge’s condition. The survey results helped to define the limit state functions and the acceptability limits. The target reliability index was established based on movable bridge performance determined by the bridge owner survey. It was concluded that the target reliability index is the same as is used in current practice. Finally, load and resistance factors were calculated and verified so that designed movable bridges’ mechanical components meet minimum safety requirements. The project results will be submitted for consideration as updates to the AASHTO LRFD Movable Highway Bridge Design Specification.