Title: Cyclic Load Tests of Reinforced Concrete Columns with High-Strength Bundled Bars

Author(s): Jong-Jin Lim, Hong-Gun Park, and Tae-Sung Eom

Publication: Structural Journal

Volume: 114

Issue: 1

Appears on pages(s): 197-207

Keywords: anchorage; bond; bundled bars; columns; cyclic tests; reinforced concrete; seismic design

DOI: 10.14359/51689254

Date: 1/1/2017

Abstract:
For economical column design and the seismic retrofit of existing columns, bundles of two or more bars can be placed at the corners of the column section for longitudinal reinforcement. Because such bundled bars can cause premature bond failure, potential adverse effects on the column strength and ductility need to be investigated. In the present study, cyclic lateral loading tests were performed for the columns with high-strength bundled bars (fy = 578 and 588 MPa [83.8 and 85.3 ksi]) and continuous hoops. On the basis of the test results, the effects of the bundled bars on the strength, ductility, and failure mode of the columns were analyzed. The test results showed that the flexural strength of the columns was decreased by premature bond failure in the plastic hinge region. Further, the shear resistance of the transverse hoops significantly affected the failure mode and ductility of the columns. On the basis of such test results, the details of high-strength bundled bars for seismic design were recommended.