Strengthening of reinforced concrete corbels using pre-tensioned anchor rods.

Abstract

Reinforced concrete (RC) corbels are defined as short cantilever members with span-to-depth ratio (a-d) less than one. They are typically used as supports for precast beams or indoor cranes. Strengthening those corbels might be needed due to aging, deterioration, or a change of the load demand on the structure. Several options are available for strengthening RC corbels including: RC jacketing, wrapping FRP sheets, steel plates, or adding pre-tensioned or passive anchor rods. This study aims at investigating the behavior of reinforced concrete (RC) corbels strengthened using pre-tensioned anchor rods. A total of ten as-built and strengthened corbels specimens were tested under monotonic loading up to failure. The test parameters included: (1) span to depth ratio of the corbel (a-d), (2) concrete compressive strength (f’c), (3) number of pre-tensioned rods, (4) and location of pre-tensioned rods. The results showed that strengthened corbels had significant strength improvement with a delay in crack formation and propagation. The increase in corbel’s strength was dependent on the aforementioned parameters. It was higher for corbels with higher concrete strength and lower span-to-depth ratio a-d. The results of the experimental tests conducted in this study in addition to ones available in the literature are compared against existing strength prediction models. The change in the failure mode with the increase in the pre-tensioning force is analyzed and correlated with the predicted governing mode. After comparing and analyzing the experimental results, modified strength prediction models are suggested for strengthening RC corbels with pre-tensioned anchor rods.