Experimental Seismic Behavior of a Full-Scale Four-Story Soft-Story Wood-Frame Building with Retrofits. I: Building Design, Retrofit Methodology, and Numerical Validation

Soft-story wood-frame buildings have been recognized as a disaster preparedness problem for decades. There are tens of thousands of these multifamily three- and four-story structures throughout California and other parts of the United States. The majority were constructed between 1920 and 1970 and are prevalent in regions such as the San Francisco Bay Area in California. The NEES-Soft project was a five-university multiindustry effort that culminated in a series of full-scale soft-story wood-frame building tests to validate retrofit philosophies proposed by (1)Federal Emergency Management Agency's recent soft-story seismic retrofit guideline for wood buildings and (2)a performance-based seismic retrofit (PBSR) approach developed as part of the NEES-Soft project. This paper is the first in a set of companion papers that presents the building design, retrofit objectives and designs, and full-scale shake table test results of a four-story 370-m2 (4,000-ft2) soft-story test building. Four different retrofit designs were developed and tested at full scale, each with specified performance objectives, which were typically not the same. Three of these retrofits were stiffness or strength-based strategies and one applied supplemental damping devices in a pinned preassembled frame. This paper focuses on the building and retrofit design methodologies and specifics and the companion paper presents the experimental results of full-scale shake table tests ranging from 0.2- to 1.8-g spectral acceleration for all four retrofits. (C) 2014 American Society of Civil Engineers.