Seismic strengthening of rocking-critical masonry piers

Systems of discrete wall piers and spandrels created by large openings are particularly weak in resisting in-plane lateral loads. The rocking piers thus stabilized by hold-down vertical forces have excellent strength, stiffness, and ductility in a very stable manner for a safer and better performance under lateral loads. However, the undesirable compressive mode of failure of stabilized rocking piers at larger drifts can be eliminated by the use of yielding energy dissipation device to limit the forces in verticals and thereby the compression force in rocking piers. A displacement-based design procedure can be used to design the energy dissipation devices and other stabilizing elements. A simple mechanics model is developed for the nonlinear load-deformation relationship of the stabilized piers which is accurate enough for design purposes. This performance-based design scheme rationally accounts for the superior ductility and energy dissipation characteristics of strengthened rocking piers.