VARIATION OF COLLAPSE MECHANISMS OF STEEL CANTILEVER COLUMNS WITH VARIABLE CROSS-SECTION SUBJECTED TO HORIZONTAL CYCLIC LOAD

Abstract

 This paper studies the variation of collapse mechanism of cantilever columns with variable cross-section subjected to horizontal cyclic load. The rigid plastic and elasto-plastic analyses of columns are performed based on the second order theory by using the rigid body – rotational spring models. The rigid plastic approach explains that the collapse mechanisms V and Y every half cycle in columns vary due to the PΔ effects and accumulated residual rotation of springs. The elasto-plastic analysis shows that the instability region exists between mechanisms V and Y. It is compared with the transition region S predicted by the rigid plastic theory. Finally, the instability transition region S of collapse mechanisms is discussed from the point view of seismic design of columns with variable cross-section.