Abstract
A versatile interaction equation expressed in terms of tri-axial force and tri-axial moment components acting at the top of thin-walled circular steel columns is derived to specify their ultimate state under the coupling of the three components of seismic excitations. This interaction equation is intended to be applied not only to the columns of normal T-shaped bridge piers but also to those of the inverted L-shaped piers and the piers of curved-girder bridges where the seismic torsional moment cannot be ignored. The interaction equation is empirically derived by the so-called pushover analysis. The validity and accuracy of the derived interaction equation is confirmed by conducting nonlinear dynamic response analysis on a 2-simple span elevated girder bridge model supported by one inverted L-shaped pier.
