Strength Degradation Model for Low-Rise Reinforced Concrete Walls Derived from Dynamic and Quasi-Static Tests Julian Carrillo, a) M.EERI, and Sergio M. Alcocer, b) M.EERI Results from a previous experimental program demonstrated that loading rate, strength mechanisms associated with the failure mode, low-cycle fatigue, and cumulative values of displacement, and dissipated energy strongly affect the degradation properties of reinforced concrete (RC) walls for low-rise housing. Thus, data obtained from quasi-static (QS) cyclic tests should not immediately be assumed to represent a conservative lower bound on a specimen’s capacity. Aimed at numerically correlating results measured during dynamic and QS-cyclic testing, this paper proposes a strength degradation model. The model is readily applicable to seismic design or assessment of performance of existing and new structures. A seismic demand model is also proposed for correlating the intensity and duration of a given earthquake-induced movement to parameters that define the degradation model. Correlations are deemed useful for interpreting the results of QS-cyclic tests and for calibrating hysteretic and behavioral analytical models obtained from QS testing. [DOI: 10.1193/011713EQS008M] INTRODUCTION The seismic performance of structural systems and components is commonly assessed through experiments using quasi-static (QS) and shake-table testing. In QS testing, the strain rate and low-cycle fatigue effects still generate uncertainties about the reliability of this method. In shake-table testing, drawbacks are basically related to the cost of testing, equip- ment limitations, specimen size, and the associated scale effects, as well as the difficulty of controlling movements during testing. Despite extensive experimental research effort in the last three decades, some important issues about the influence of testing methods on structural performance continue to be the subject of discussion and disagreement among researchers. For instance, there is concern that QS testing, which forms the basis of current design values, is not representative of the actual demand imposed by a seismic event, and thus, can lead to nonconservative designs (Gatto and Uang 2003). To identify and assess the main parameters affecting the strength degradation observed during shake-table and QS-cyclic testing of reinforced concrete (RC) walls for low-rise hous- ing, an experimental and analytical research program was carried out. The first phase of this program (Carrillo and Alcocer 2013a) was aimed at identifying the causes of observed Earthquake Spectra, Volume 31, No. 1, pages 197–214, February 2015; © 2015, Earthquake Engineering Research Institute a) Research Professor, Departamento de Ingeniería Civil, Universidad Militar Nueva Granada, UMNG, Colombia, Carrera 11 No. 101-80, Bogotá, Colombia b) Research Professor, Instituto de Ingeniería, Universidad Nacional Autónoma de México, UNAM, Ciudad Universitaria, CP 04510, Mexico City, Mexico 197