ACOUSTIC EMISSION TECHNIQUE FOR EVALUATION OF DAMAGE TO LAMINATED RUBBER BEARING

Abstract

 Many bridge bearings suffered severe earthquake loads during the 2011 Great East Japan earthquake; however, no suitable technique exists to evaluate damage to laminated rubber bearings. This paper describes the Acoustic Emission (AE) technique for laminated rubber bearings both for damage assessment after earthquakes and health monitoring of old bridges.
 First, laboratory tests were conducted using the damaged laminated bearing specimens after the pre-loaded tests. Characteristic AE behavior was observed in the severely damaged specimens during the cyclic loading compression tests. These specimens had many small voids in the rubber, which were found from the microscope observation of the specimens being cut after the loading tests. Then, on-site AE monitoring was carried out at two sites. Many AE hits and large AE energy were observed from the deteriorated rubber bearings; however, few AE activities were observed from the new bearings.
 These two tests indicated the effectiveness of AE monitoring for early warning and damage assessment of laminated rubber bearings.