Seismic FRP Bond Strengthening of the Critical Splice Region in Wide Reinforced Concrete Columns

摘要

This paper presents preliminary results of a broader ongoing experimental study on the seismic bond strengthening of the critical reinforcement splice region in wide reinforced concrete (RC) columns or bridge piers confined with Carbon Fiber Reinforced Polymer (FRP) laminates and having bending about their minor axis. Large lateral drifts induced by strong earthquakes may result in splitting bond failure of the spliced bars, or rapid bond degradation at the splice location, leading to possible structural failure of the columns or piers. Previous research has verified the effectiveness of external confinement using FRP composites for improving bond performance of the spliced reinforcement of columns or piers having circular cross section, or rectangular cross section subjected to cyclic loading about their major axis. The preliminary experimental program reported in this paper consists of testing two full-scale wide column specimens under extreme substandard splice detailing associated with relatively short splice length, small concrete covers, small transverse spacing between the spliced bars, and complete absence of internal steel ties within the splice region. The test results showed that, despite extreme substandard splice detailing, the use of external FRP confinement improved the bond strength of the spliced bars, delayed the bond stiffness degradation under cyclic loading, and increased the energy dissipation capacity of the wide columns. However, the corresponding improvements were not as effective as anticipated. Consequently, before a final conclusion is drawn, more tests will be carried out on similar specimens but using instead more realistic and practical splice details as well as internal transverse steel ties for satisfying the minimum detailing requirements of the ACI 318-11 for gravity load designed axial members.