38. Vibration Experiments with an Actual Mooden Building Conducted with a view to Confirming the Aseismic Properties of the Brace-struts(Sudikai) and the Principal Column(Daikoku-basira)

The results of our mathematical investigation and model experiments made previously with respect to the aseismic properties of brace-struts and the principal column were confirmed by means of vibration experiments of an actual single-storied wooden building. Vibrational forces were inparted to the building by means of a vibrator formed of a revolving bicycle rim with an added eccentric mass. The vibrator was placed on a beam in the central p. art of the building, driven initially with hand with the greatest possible speed, and then remain in a freely rotating state. Since the rotating speed of the vibrator tended to diminish, the frequency of the forced vibration changed from time to time. There were five conditions in the construction of the brace-structs in these experiments. When, for example, two struts, both 12cm wide and 4cm thick, were fixed crosswise to the building, the resonance amplitude and the resonance period were reduced to 40 percent and 80 percent respectively of those of the original structure. The vibration experiments of the actual wooden building also showed that the brace-struts fitted to a structure are effective both in reducing the resonance amplitude and in increasing the resonance frequency. The solid viscosity coefficient of the wooden building in the present case, both from the forced and free vibrations, was shown to be almost 4・10^8 C.G.S. units