An on-line observation system of strong ground motions and immediate response system was constructed at the Disaster Prevention Research Center, Ankara, Turkey. Damage estimation is made for buildings and dwellings and for infrastructures such as roadways, railways, water, gas, electricity and telecommunication systems. Although damage function is inevitable for immediate damage estimation, the damage function of road bridges is not well established. Several bridge parameters were investigated, and damage done to raod bridges in past earthquakes collected to determine the damege function. The damage function and database were used in a test study of damage done to road bridges on the assumption that a part of the North Anatolia fault ruptured.