Civil Engineering Association

Analysis of Rotational Column with Plastic Hinge

A plastic hinge is a type of energy dampening device allowing plastic rotation
of an otherwise rigid column connection. This device is composed of a weakened portion
of the column prevented from rotating by relatively small steel members. These small
bars are designed to yield and allow rotation before the capacity of the column is reached,
thus acting as mechanical fuses protecting the column from fatigue. After a seismic event
the fuse bars can be easily replaced, restoring the column to its original condition. To
function properly the hinge must become plastic before the column above it yields, but
limiting the deflection at the top of the column is also desirable for the stability of the
overlying structure, necessitating a hinge with some degree of strength. The
experimental setup of this study was constructed in the University at Buffalo’s Structural
Engineering and Earthquake Simulation Laboratory in 2004 and was comprised of a steel
column subjected to lateral displacement at the top with a plastic hinge fixed at the base,
simulating earthquake-induced ground motion on a bridge column. The purpose of this
research was to develop an accurate model of the column-hinge system in the elastic
range of the fuse bars, allowing consideration of the above design criteria for later testing.
Plastic behavior of the fuse bars was not tested. Experimental data was generated using a
quasi-static cyclic loading pattern. The behavior of the system was shown to be in
agreement with the analytical model.