Research on the Seismic Performance of Belfry Using Vibration Tests and Analysis with a Vibration Exciter

In this study, the seismic performance of a traditional Japanese belfry was clarified through vibration tests and analysis, considering the effects of bell swinging on the frame. An actual two-story belfry was shaken using two exciters, and accelerations were measured with accelerometers installed on the first floor, the top of the bell, and the roof beam. The test cases were conducted in two excitation directions, north-south and east-west, comparing cases where the bell was not fixed and where it was fixed to the capital of the first-floor columns with ropes. From the acceleration time history, the first-mode natural frequency varied by up to 17.0% depending on the presence of horizontal beams (Nuki), while the damping ratio changed by 44.2% depending on whether the bell was fixed. The analysis showed that the first-floor stiffness varied by up to 108.0% due to horizontal beams (Nuki), whereas the effect of bell fixation on stiffness was only 4.80%.