Seismic energy dissipation in bridges with air springs

Seismic loads on bridges may cause large damaging forces in substructure. Isolation and energy dissipating elements or a combination of the two have been used to reduce the transmitted forces caused by seismic loading. The benets of these systems are mainly attributed to the increase of structureʹs natural period of vibration and damping. This paper investigates a new device that works on the same principles. This device is composed of sliding bearings and air springs or airbags. Several bridges are analyzed using the Nishimuraʹs model for air springs; and the sensitivity of seismic response of bridges due to variable spring parameters is investigated and optimum values are obtained. Then, using these parameters for the air spring and solving the equation of motion, the variation of air spring internal parameters with time are investigated. Results show that air springs are very ecient in reducing the eects of seismic forces.