Behavior of Flared-Column Bents Under Seismic Loading


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Title: Behavior of Flared-Column Bents Under Seismic Loading

Author(s): H. M. Nada, D. H. Sanders, M. Saiidi, and S. El-Azazy

Publication: Special Publication

Volume: 209


Appears on pages(s): 133-150

Keywords: bent; bridges; circular columns; flared; seismic; shake table

Date: 9/26/2002

Past Earthquakes have shown that flared columns are susceptible to pre- mature shear failures. In the 1999 Northridge Earthquake, Shear failures have been caused by a plastic hinge formation occurred at the base of the flare and a subsequent increase in the level of column shear demand above design levels. This paper presents an experimental and analytical study that is examining new details for flared columns and joints. The primary feature is a gap at the top of the column and the amount of transverse flare reinforcement. Two two-column bents were tested on the shake table to examine dynamic effects as well as column and beam interaction. The test specimens had different amounts of confining reinforcement in the flare. The detail proved an overall ductility that is above the minimum limit recommended by the current specifications. Test also showed that gap started to close at ductility level that is below the recommended limit.