As early as 1970, the structural engineering and building safety community recognized that a large number of three- and even some four-story woodframe buildings designed with the first floor used either for parking or commercial space were built with readily identifiable structural system deficiencies, referred to as a “soft story”. The majority of these older multi-story woodframe buildings have large openings and few partition walls at the ground level. This open space condition results in the earthquake resistance of the first story being significantly lower than the upper stories. These buildings, known as soft-story buildings, are prone to collapse during earthquakes. In 2008, the San Francisco Department of Building Inspection and the Applied Technology Council initiated the Community Action Plan for Seismic Safety (CAPSS) project with the main goal of identifying possible action plans for reducing earthquake risks in existing buildings. According to the CAPSS study, 43 to 80 percent of the multi-story woodframe buildings will be deemed unsafe after a magnitude 7.2 earthquake and a quarter of these buildings would be expected to collapse. The NEESsoft project will (1) enable seismic retrofit of soft-story woodframe buildings based on performance, (2) experimentally validate recently proposed concepts in for retrofit of soft-story woodframe buildings, and (3) provide a fundamental understanding of the way woodframe buildings collapse in woodframe buildings through a systematic experimental program in San Diego and Buffalo.
This presentation will explain the design approach which consists of a minimal design for “shelter-in-place” during more common earthquakes (20-75 year return period) and a performance-based seismic retrofit during stronger earthquake (2,500 year return period). Testing at the SEESL lab at SUNY-Buffalo will be highlighted and the upcoming test procedure known as slow hybrid testing explained. Ground motion scaling procedures that are per ASCE 7-10 will be discussed also.
Dr. John W. van de Lindt is a Professor of Structural Engineering at the Colorado State University holds the George T. Abell Professorship. Dr. van de Lindt’s research program has two major thrusts, both related to improving the built environment by making structures and structural systems perform to the level expected by their occupants, government, and the public. He seeks to accomplish this through the development of performance-based engineering and test bed applications of building systems for earthquakes, hurricanes, tsunamis, tornadoes and floods. Professor van de Lindt is currently serving as the project director and PI for a three-year five-university NSF-sponsored project, that has objective of reducing the seismic risk of soft-story woodframe building in North America. Tests at several laboratories around the U.S. (NEES Facilities) are scheduled and the project involves numerous industry and government partners. Professor van de Lindt was also the project director and PI of the four-year five-university NEESWood Project. The final shake table test program took place in June/July 2009 in Miki, Hyogo Prefecture, Japan. The steel moment frame plus light-frame wood building represented the largest building ever tested on an earthquake shake tableundefineddesigned at almost 17,000 sq ft (1,400 sq meters) and 850,000 lbs. The building was designed using Performance-Based Seismic Design (PBSD) techniques developed during the first three years of the NEESWood Project.