In Seismic Zone 4, there are many older, existing buildings that do not meet the lateral strength, drift control, and ductile detailing requirements of the 1991 Uniform Building Code. A preliminary study using hypothetical buildings indicates the additional strength, stiffness, and energy dissipation can be provided by a non-invasive retrofit scheme involving the replacement of the existing cladding with structural (steel) panels and energy dissipating cladding-to-frame connections. To examine this retrofit scheme in detail, two older, existing buildings will be studied. A preliminary design will be done first, which includes: (1) design decisions regarding the relative structural contributions of the existing frames and the cladding system to the retrofit building system; and (2) for the cladding system, design of practical cladding-to-frame connections and their attachments, and development of a design procedure for the cladding panels. The feasibility of this seismic retrofit scheme will be assessed analytically by subjecting the retrofit perimeter frames to a set of ground motions with ranges of peak ground accelerations, predominant frequencies, and durations. The research will advance the state-of-the-art in passive control of structures in two ways: (1) by identifying conditions under which the structural characteristics of cladding and cladding-to-frame connections can be effective and efficient, and (2) by providing a foundation for the development of rational guidelines for the designs of energy dissipating cladding systems for either existing weak buildings or newly designed buildings.
