Experimental and Numerical Investigations on Enhancing Ductility of Reinforced Concrete Columns with Substandard Lap Splices Using Hollow Steel Section Collars

Hollow steel section (HSS) collars with significant flexural stiffness in addition to their axial stiffness are proposed to prevent brittle lap splice failures. Experimental program on five full-scale cantilever columns with and without HSS collar strengthening was conducted. The control column without strengthening failed suddenly. HSS collars at 333 mm spacing slightly improved peak capacity, at 200 mm spacing significantly improved peak capacity but showed extensive pinching, and at 100 mm spacing achieved lateral load-deflection response equal to the column without a lap splice. Nonlinear fiber-based modeling using OpenSees predicted the hysteretic response, resulting in close agreement with experimental results.