ACI Structural Journal, V. 110, No. 3, May-June 2013. MS No. S-2011-220 received July 12, 2011, and reviewed under Institute publication policies. Copyright © 2013, American Concrete Institute. All rights reserved, including the making of copies unless permission is obtained from the copyright proprietors. Pertinent discussion including author’s closure, if any, will be published in the March-April 2014 ACI Structural Journal if the discussion is received by November 1, 2013. Experimental Evaluation of Disproportionate Collapse Resistance in Reinforced Concrete Frames