In this paper, two new protocols are proposed, developed based on cycle counting and forward ordering of interstory drift time histories for representative mid- and low-rise building structures. The proposed drift protocols involve: (i) ground motion selection and scaling, (ii) representative building selection and modeling, (iii) nonlinear structural dynamic response calculations, and (iv) modified simple range counting to derive amplitude count information. In this work, demand sequencing is considered. This aspect is important, as excursions with the same amplitude occurring at different times will contribute differently to structural damage; therefore, they are sequenced and weighted differently. For this purpose, a damage index concept is used to evaluate each excursion and define instantaneous weight factors. The protocols are applied to a series of in-plane racking tests on window systems. Damage modes and associated drift limits are compared for the proposed protocols as well as several others, namely; a monotonic (static) push, the “Crescendo” (dynamic) loading protocol, and the FEMA 461 (quasistatic) loading protocol.

Storefront window systems have been shown to suffer significant damage during earthquake loading, resulting in the potential for human injuries and significant economic losses. Despite the potential for film-coated windows to minimize seismic-induced damage to window systems, limited study has been undertaken. Furthermore, no thorough study of the effects of loading histories on window system performance has been performed to-date. Finally, previous studies have been limited in terms of their variation of window system geometry. In this work, three variables of interest were studied through in-plane seismic racking experiments of storefront window systems, namely: (i) loading protocol, (ii) window film type and attachment, and (iii) aspect ratio. This paper presents the overall experimental program, the identified damage modes and associated drift limits, and trends associated with variation of the window film and aspect ratio. A companion paper in this issue (Hutchinson et. al. 2011) summarizes studies of the effects of load protocol.