Title:
Flexural Behavior of Reinforced Concrete Columns Strengthened with Wire Rope and T-Plate Units
Author(s):
Jae-Il Sim and Keun-Hyeok Yang
Publication:
Structural Journal
Volume:
106
Issue:
5
Appears on pages(s):
697-705
Keywords:
columns; confinement; ductility; flexural capacity; strengthening; wire rope.
DOI:
10.14359/51663110
Date:
9/1/2009
Abstract:
This study presents the flexural behavior of reinforced concrete columns strengthened with unbonded wire rope and T-shaped steel plate units. Seven strengthened columns and an unstrengthened column were tested to failure under constant axial load and cyclic lateral loads to explore the significance and limitations of the strengthening procedure developed for resistance against earthquakes. The main variables investigated were the volume ratio of wire rope, axial load level, and the presence of mortar cover for strengthening steel elements. In addition, the theoretical monotonic lateral loaddisplacement curve for strengthened columns is simply derived using the combination of section laminae method and the idealized curvature-displacement relationship. The flexural capacity of columns strengthened without mortar cover was slightly higher than that of the unstrengthened column. On the other hand, the flexural capacity of strengthened columns with a 60 mm (2.36 in.) thick mortar cover was at least 2.5 times higher than that of the comparable strengthened columns without mortar cover. The developed strengthening procedure was particularly effective in enhancing the ductility of the columns, showing that the displacement ductility ratios and work damage indicators in the strengthened columns were much higher than in the unstrengthened column. The monotonic lateral load-displacement relationship of the column specimens predicted from the proposed numerical analysis is in good agreement with backbone curves obtained from measured cyclic lateral load-displacement relationships. ACI 318-05 underestimates the flexural capacity of the strengthened columns, however, as the confinement effect is not considered in the equivalent stress block of concrete specified in ACI 318-05.