Development of post-tensioned column base connection for self -centering seismic resistant steel frame
Abstract
A post-tensioned (PT) column base connection is introduced for use in a self-centering (i.e., returns to its original position after earthquakes) steel moment resisting frames (SC-MRF). The PT column base connection eliminates inelastic deformation in columns, and enhances self-centering capability of the SC-MRF. The PT column base connection consists of high strength bars that are post-tensioned and buckling restrained steel (BRS) plates. Under cyclic loading, the softening behavior at the connection is achieved by gap opening at the column-beam interface instead of plastic hinging of the column. The PT bars provide restoring force for self-centering behavior while the BRS plates dissipate energy by yielding. To investigate the cyclic behavior of the PT column base connections, a series of the PT column base connection subassemblies were subjected to axial load and cyclic lateral displacements. Test variables included initial post-tension force, initial axial force in column (constant or varying), column size and loading history. Main findings include: (1) the column returns to its original position without residual deformation and (2) the BRS plates dissipate energy by yielding in tension and compression. Design criteria for the PT column base connections were developed along with design equations. Also, analytical models of the PT column base connections were developed. Finally, the seismic behavior of a prototype 6-story, 4-bay SC-MRF with PT column base connections was evaluated by nonlinear dynamic analyses for various ground motions.
Degree
Ph.D.
Advisors
Liu, Purdue University.
Subject Area
Civil engineering
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