New Seismic Design Provisions for One-Story Structures with Flexible Diaphragms and Rigid Vertical Elements

It has long been recognized that the seismic response of one-story tilt-up concrete wall buildings (and similar buildings with flexible diaphragms and rigid vertical elements) is controlled by the flexible diaphragm much more than the rigid vertical elements. Widely used seismic design provisions have not recognized or incorporated this behavior, however. Now, new seismic design provisions recently developed for ASCE 7-22 explicitly recognize this response behavior, drawing from extensive numerical studies published in the guideline document Seismic Design of Rigid Wall-Flexible Diaphragm Buildings: An Alternate Procedure (FEMA P-1026) and supplemental studies of bare steel deck diaphragms. In fact, the new design provisions go a step further to introduce a zone of reduced shear demand that improves seismic performance by allowing distributed yielding away from the diaphragm perimeter. This webinar will first present the concepts behind the new seismic design provisions, and the numerical studies addressed in FEMA P-1026 and supplemental bare steel deck diaphragm studies. A design example will then be presented, along with design and detailing tips and recommendations for practicing engineers.