PERFORMANCE OF AN EARTHQUAKE EXCITED ROOF DIAPHRAGM.

The objective of this paper is to study the earthquake performance of the roof diaphragm of the West Valley College gymnasium in Saratoga, California through a complete set of acceleration records obtained during the 24 April 1984 Morgan Hill Earthquake (M equals 6. 1). The roof diaphragm of the 112 ft. multiplied by 144 ft. rectangular, symmetric gymnasium consists of 3/8 in. plywood over tongue-and-groove sheathing attached to steel trusses supported by reinforced concrete columns and walls. Three sensors placed in the direction of each of the axes of the diaphragm facilitate the evaluation of in-plane deformation of the diaphragm. Other sensors placed at ground level measure vertical and horizontal motion of the building floor, and consequently allow the calculation of the relative motion of the diaphragm with respect to the ground level.