Parametric Influence of Bearing Restraint on Nonlinear Flexural Behavior and Ultimate Capacity of Steel Girder Bridges

摘要

Service lives can be extended for the aging steel girder bridge population, many of which are nominally simply spanning structures, by evaluating structural response and capacity, including system behavior, particularly in the presence of support restraint. Longitudinal shear restraint at steel girder bearings has been observed and documented in numerous studies and bridge tests. The restraint arises from various sources, such as friction restraint at older bearings in good condition, or frozen conditions at bearings with abutment deck joint corrosive deterioration. Longitudinal shear restraint at bearings induces arching action in the superstructure, redistributing and reducing moment demands at midspan. This study analytically investigated composite bridge superstructure system-based flexural behavior, including assessment of load levels to initiate yielding and the sequence of yielding initiations leading to ultimate capacity, considering a range of bearing longitudinal restraint conditions. The computational modeling was validated using two documented ultimate load tests on composite steel girder bridges. Nonlinear load-carrying capacity increased with bearing restraint and was accompanied by decreases in system ductility. Both ultimate load capacity and system ductility were observed to be sensitive to bearing restraint within a narrow range of low support stiffness only, relative to the stiffness required to achieve an effectively pinned response. The yield moment was sensitive to the exact restraint stiffness, but ultimate capacity was relatively insensitive and disproportionately benefitted by even slight support restraint. (C) 2017 American Society of Civil Engineers.