Title: Lateral Load Response of Strengthened and Repaired Reinforced Concrete Columns
Author(s): B. John Bett, Richard E. Klingner, and James O. Jirsa
Publication: Structural Journal
Appears on pages(s): 499-508
Keywords: columns (supports); damage; earthquake resistant structures; flexural strength; frames; lateral pressure; reinforced concrete; repairs; shear properties; short columns; shotcrete; strengthening.
The effectiveness of three different repair and/or strengthening techniques in enhancing the lateral load response of identical reinforced concrete short columns was studied. Based on an 18 in. square prototype, three column test specimens were constructed to two-thirds scale, using identical geometry and reinforcement. The test specimens representing existing columns had a 12 in. square cross section reinforced with eight No. 6 longitudinal bars, 6-mm ties spaced at 8 in., and a l-in. cover. Spacing of the transverse reinforcement, while greater than current design requirements, was intended to represent typical practice of column design in seismic regions of the U.S. in the 1950s and early 1960s. One of the specimens was tested, repaired by jacketing, and then retested. The remaining two specimens were strengthened by jacketing prior to testing. A single lateral displacement history and constant axial load were used for all tests. Both the strengthened and the repaired columns performed better than the original column. Columns strengthened by jacketing, both with and without supplementary crossties, were much stiffer and stronger laterally than the original, unstrengthened column. The column re-paired by jacketing was also much stiffer and stronger laterally than ti original column and performed almost as well as the strengthened columns.