Rotational Stiffness of Exposed Column Base Connections: Experiments and Analytical Models
Publication: Journal of Structural Engineering
Volume 138, Issue 5
Abstract
The rotational flexibility of column base connections is often ignored in structural simulation of moment frames in which the bases are assumed to be either fixed or pinned. Although structural response is sensitive to base flexibility, methods to properly characterize base flexibility are not readily available. Motivated by these issues, a new approach to characterize the rotational flexibility of exposed column base connections is presented in this paper. The method leverages existing design procedures for base connection design, such that the rotational stiffness may be calculated with modest effort once the design has been completed. The method is validated through comparison with nine experiments, which interrogate a range of parameters including base-plate size and thickness, level of axial load, anchor-rod strength, and concrete strength. The comparison between the test and the predicted values indicates that, on average, the method predicts the stiffness with accuracy, such that the average test-to-predicted ratio is 0.89. The method is particularly accurate for conditions in which the moment-to-axial-load ratio is large, whereas it overestimates the stiffness of connections with high axial load, relative to the applied moment. A detailed analysis of the results is presented, accompanied by a discussion of the limitations of the proposed approach.
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Acknowledgments
The authors are grateful to the American Institute of Steel Construction, which funded the experiments that served as the validation test bed for this study. The authors also thank Ivan Gomez of AIR-Worldwide and Gregory Deierlein of Stanford University for their support and close collaboration in the planning and conduct of the experiments. The staff at the NEES Berkeley site also receives our gratitude. The findings presented in this paper reflect the views of the authors and not those of any funding agency.
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Published In
Journal of Structural Engineering
Volume 138 • Issue 5 • May 2012
Pages: 549 - 560
Copyright
© 2012. American Society of Civil Engineers.
History
Received: Apr 8, 2011
Accepted: Aug 15, 2011
Published online: Aug 17, 2011
Published in print: May 1, 2012
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