The Captive- and Short-Column Effects

Captive-column and short-column conditions are a significant source of serious earthquake damage. These conditions originate in the architectural design of the building. For this reason, this paper first presents the architectural reasons why these conditions occur and explains in nontechnical language their detrimental effect on building response. The effects are presented from a multidisciplinary perspective—engineering, architecture, and construction—because their solution can only be achieved by an integrated approach to building design that recognizes the interaction of these three disciplines. The accidental modification to the original structural configuration leading to a captive column by restricting its freedom to deform laterally due to the presence of nonstructural elements that partially confine it is presented. The case of short columns subjected to earthquake effects is also discussed. Examples of damage due to these effects in numerous earthquakes are presented, and the architectural decisions leading to captive and short columns are reviewed. The structural explanation of the behavior is discussed. Experimental research related to short and captive columns is presented. Recommendations to handle this type of problem are given.