Seismic Design of Wood Light-Frame Structural Diaphragm Systems

This Guide addresses wood light-frame diaphragms used in buildings of all wood light-frame construction, as well as wood light-frame diaphragms used with other vertical elements of the SFRS, including concrete or masonry walls, steel moment frames, and steel braced frames. “Light-frame” refers to the repetitive, closely spaced wood framing (e.g., joists or rafters) to which the diaphragm sheathing is attached. Of the buildings constructed entirely of wood light-frame construction, many are small buildings, with single-family homes of three or less stories being a majority (Figure 1-2). Medium-size buildings constructed entirely of wood light-frame construction include multi-family residential buildings (Figure 1-3), hotels, schools, and small commercial buildings (Figure 1-4). These buildings are of varying sizes. Buildings of up to three stories have been common for many years. Buildings of up to five or six stories are now being constructed with increasing frequency. A number of commercial and light-industrial buildings constructed entirely of wood light-frame construction often have a large plan area and are primarily of single-story construction.

Buildings constructed using wood light-frame diaphragms with concrete and masonry walls, steel frames, or other
vertical element types, include commercial, institutional, and light-industrial buildings predominantly of one or two stories and “big-box” retail buildings with a large plan area and predominantly of single-story construction. Concrete tilt-up
wall buildings (Figure 1-5) represent a significant portion of wood light-frame diaphragm building inventory in the seismically active western states, while steel deck diaphragms are more prevalent in other regions. Additional seismic performance concerns and seismic design requirements are applicable to wood light-frame diaphragms used with concrete or masonry walls; brief discussions of these additional concerns and requirements are provided in this Guide.