Saving Bridges From Earthquakes

Researchers at the University of Buffalo and the Multidisciplinary Center for Earthquake Engineering Research (MCEER) have discovered a new method to minimize the impact of earthquakes on bridges. The testing performed by UB's Structural Engineering and Earthquake Simulation Laboratory (SEESL) on a bridge model could soon be implemented for real bridges.

The plan is not to provide stronger ground attachments for the bridge, but to make them more resistant to earthquakes by attaching them with footings that enable them to jump a few feet in the air when an earthquake occurs.

Doing this has a number of benefits:

a) By jumping up in the air when the earthquake occurs, the bridges avoid the complete transmission of the earthquake vibrations to the bridge.

b) The bridges jump only a few inches off the ground for durations of less than a second. So its influence on the bridge is minimal.

c) The process of expanding, retrofitting and replacing the bridge parts much less expensive that it is with fixed footings.

Instead of try to make the bridge stronger, this method uses an unconventional type of thinking to minimize the impact of the earthquake on the bridge.

Since the bridge lifts only a few inches of the air, it comes back to its original position without any problem. Also, the time for which the bridge jumps depends on the dimensions with which the bridge is built. So this factor is very much controllable.

Devices called hysteretic or viscous dampers are attached to the base of the tower. This device absorbs some of the vibrations produced by the earthquake and also controls the amount of uplift the bridge experiences.