Methodology for mitigation of seismic hazards in existing unreinforced masonry buildings: Diaphragm testing

An experimental program conducted on horizontal diaphragms subjected to quasi-static, cyclic, in-plane displacement and dynamic, in-plane earthquake shaking is described. The experimental program is one of several tasks in an overall research program, sponsored by the National Science Foundation, whose objective is to develop a methodology for mitigation of seismic hazards in existing unreinforced masonary buildings. Full-scale component tests on horizontal diaphragms subjected to quasi-static, cyclic, in-plane displacement and dynamic, in-plane earthquake shaking were designed and conducted on 14 diaphragm specimens subjected to 139 test sequences that were comprised of intermingled static and dynamic loadings. The quasi-static tests produced deformations in the diaphragms that ranged from elastic excursions to excursions that produced ductilities of 2, 3, 4, and 6; however, only one diaphragm was driven to the ductility of 6. The dynamic earthquake loadings covered the full range of seismicity in the United States from an Effective Peak Acceleration of 0.1 g to 0.4 g.