Abstract
The natural rubber bearings of Tobu viaduct and Rifu viaduct ruptured due to the 2011 off the Pacific coast of Tohoku Earthquake.
In order to investigate into reasons for the rupture, we performed material testing using some specimen obtained from the ruptured bearings. We also made the performance testing using the existing natural rubber bearings which appeared to be undamaged under visual examination located near the ruptured natural rubber bearinga and the new bearings which were reproduced by rubber compsition at the time of construction.
As a result, it turned out that the allowable design force of the existing natural rubber bearings was above the standard values,but that the ultimate shear defomation perfomance of them was lower than that of the the newly made bearings.
