EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2011; 40:807–825 Published online 17 November 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eqe.1061 Prediction and validation of sidesway collapse of two scale models of a 4-story steel moment frame D. G. Lignos 1, ∗, †,‡ , H. Krawinkler 1 and A. S. Whittaker 2 1 Department of Civil Engineering, Stanford University, Stanford, CA 94305-4020, U.S.A. 2 Department of Civil, Structural and Environmental Engineering, The State University of New York, University at Buffalo, U.S.A. SUMMARY A research program is summarized in which collapse of a steel frame structure is predicted numerically and the accuracy of prediction is validated experimentally through earthquake simulator tests of two 1:8 scale models of a 4-story code-compliant prototype moment-resisting frame. We demonstrate that (1) sidesway collapse can occur for realistic combinations of structural framing and earthquake ground motion; (2) P -  effects and component deterioration dominate behavior of the frame near collapse; (3) prediction of collapse is feasible using relatively simple analytical models provided that component deterioration is adequately represented in the analytical model; and (4) response of the framing system near collapse is sensitive to the history that every important component of the frames experiences, implying that symmetric cyclic loading histories that are routinely used to test components provide insufficient information for modeling deterioration near collapse. Copyright  2010 John Wiley & Sons, Ltd. Received 16 February 2009; Revised 11 June 2010; Accepted 14 June 2010 KEY WORDS: sidesway collapse; component deterioration; P -  effects; scale model; collapse prediction; deterioration model; loading history 1. INTRODUCTION Difficulties in predicting collapse of building frames with high confidence have been an impediment to the implementation of performance-based earthquake engineering. Although more attention has been focused in the past decade on the limit state of incipient collapse, the triggers for collapse are not well established and robust constitutive models for components through failure are not yet available. This paper seeks to fill some of these gaps in our knowledge, with a focus on steel moment-resisting frames. A significant number of analytical studies on the topic of collapse prediction have been carried out in the past. In most studies it is acknowledged that modeling of deterioration is a critical aspect of collapse prediction. Various analytical models have been developed to capture stiffness and strength deterioration. Foliente [1] summarized the use of the Bouc–Wen model [2, 3] and its derivatives to account for component deterioration [4,5]. Sivaselvan and Reinhorn [6] devel- oped a versatile smooth hysteretic model that includes stiffness and strength degradation and pinching, derived from inelastic material behavior but based on the earlier models by Iwan [7] and Mostaghel [8]. More recently, Ibarra et al. [9] proposed a component deterioration model that ∗ Correspondence to: D. G. Lignos, Department of Civil Engineering, Stanford University, Stanford, CA 94305-4020, U.S.A. † E-mail: dlignos@stanford.edu ‡ Post-Doctoral Fellow. Copyright  2010 John Wiley & Sons, Ltd.