Dynamic Properties of Light‐Frame Wood Subsystems

Component subsystems in light‐frame wood buildings are tested to provide information useful in analyzing and designing for seismic and dynamic wind effects. Static cyclic tests on shear‐wall panels show that damping ratio increases with panel displacement, whereas static cyclic tests on bending panels show that damping ratio initially increases with panel displacement, but begins to decrease when displacements reach a certain level. Connection subsystems between floors, foundation, and walls—tested on a shaking table under steady‐state vibration (perpendicular or parallel to the foundation length) at prescribed constant panel‐displacement amplitudes—display structural degradation under repeated frequency scans as displacement amplitudes increase. In flexible connection panels (those with walls), dynamic stiffness decreases with increasing displacement amplitude; damping rapidly increases at small displacement amplitudes, then gradually decreases at larger amplitudes. Rigid connection panels (those without walls) are characterized by damping that increases, and stiffness that decreases, at an almost linear rate, as displacement amplitudes grow larger. The testing procedure for connection panels gives consistent, reliable results and should be valuable for modeling degrade in such subsystems.