PROBLEM TO BE SOLVED: To provide a method for determining the degree of damage of a structure by earthquake by utilizing a tremor measurement that can precisely locate a damaged spot and evaluate the degree of the damage of a rigid-frame high bridge including the influence of a ground and a foundation.
SOLUTION: ATop/AMid which is used in the determination of the degree of damage by a database, is approximated by the next equation from respective mode amplitudes AGTop, AGMid, and AGBot at the upper part, the intermediate part, and the lower part of a pillar comprising the influence of the ground and the ground and the foundation. ATop/AMid=(AGTop-AGBot)/(AGMid-AGBot). Besides, the degree of damage of the rigid-frame high bridge is determined by finding the ratio of the natural frequency Fd of only the upper structure after being damaged to the natural frequency F of only the upper structure by the next equation, using the natural frequency F, the natural frequency FG of the whole system comprising the influence of the ground and the foundation, and the natural frequency FGd of the whole system after being damaged. Fd/F=FG×FGd/√(F2×FG2-(FGd)2×(F2-FG2)).