ABSTRACT
To develop the simplified diagnosis system for steel bridges, the author tried to apply the survey method using small FWD system as making system of impulse force. The most important point is a limit of flexural rigidity of bridge decks to apply this method because the index of evaluation is a displacement of bridge decks and the applied impulse force given by small FWD system was quite small. Then it is tried to change the index to the acceleration, and the author confirmed that the vibration of bridge decks of high rigidity can be measured with the acceleration. It is also confirmed that the vibration of whole superstructure of road bridge was also measured with the acceleration given by FWD system. It is noted that the used bridge in the study mentioned above is very sound one.
