Dynamic tests were conducted on four buildings of the old McKinley School in Santa Clara County, California. The buildings, single-story timber structures, were vibrated by means of an eccentric-mass type vibration generator to determine their resonant frequencies, associated mode shapes, and damping factors. The test results from two of the buildings are used to illustrate the dynamic behavior of such structures.
Typically, the buildings had three basic modes of vibration that have been designated transverse, longitudinal, and flexure of the roof diaphragm. The resonant frequencies of transverse and longitudinal modes ranged from 7 to 10 cps, and the damping factors varied from 3 to 4 per cent. The resonant frequencies of the flexure modes of the roof diaphragms ranged from 6 to 10 cps and the damping factors from 1 to 3 per cent.