Out-of-plane seismic evaluation and retrofit of turn-of-the-century North American masonry walls

Three masonry walls with their wood backing were extracted from an old thre e-story residential building. These specimens are representative of a type of construction widely used in North America circa 1900, in which a single wythe exterior masonry wall was tied only with nails to the timber structur e, leaving an irregular gap between the masonry and timber walls. rib seism ically retrofit such buildings, special seismic-resistant anchorage of the walls would he required at every floor at a minimum. Questions remained, ho wever, as to the out-of-plane resistance of the remaining walls spanning be tween floors. To partly answer these questions, the three specimens extract ed from the existing building were tested using a shake table, submitting t hem to multiple ground motions of progressively larger intensity until stru ctural failure. These tests have demonstrated that such walls could resist significant out-of-plane inertial accelerations without failure. Performanc e can be increased by different retrofit methods such as providing anchors at midheight to force the wood and masonry wall to move as a unit, and addi ng fiberglass strips epoxied to the masonry wall to increase its out-of-pla ne stiffness and strength.