Design procedures for hinge restrainers and hinge seat width for multiple - frame bridges

During an earthquake adjacent bridge frames can vibrate out-of-phase, exceeding the range of support provided by the hinge seat, leading to collapse. The collapse of bridges in recent earthquakes due to hinge unseating emphasized the importance of providing an adequate number of hinge restrainers to limit the relative displacement between hinges. Current restrainers design procedures are not adequate because they do not account for controlling factors in the response of multiple-frame bridges. A multiple-step design procedure based on a linearized numerical model, is developed. The procedure accounts for the phasing between frames with a modal analysis. Parameter studies show that the procedure works well in limiting the relative hinge displacement for a wide range of parameters. The required number of restrainers decreases as the frame period ratio and the frame target ductility increase. A simplified single-step restrainer design procedure for hinge restrainers is also developed. Comparisons with current restrainer design procedures show that the new multiple-step and single- step procedures are more accurate than current procedures for designing hinge restrainers. Pounding of frames and engaging of restrainers produce forces and displacements significanty different than what is typically assumed in design. <