Strength of compression lap-spliced GFRP bars in concrete columns with different splice lengths

Recent years have seen valuable research work on using glass-fiber-reinforced-polymer (GFRP) bars in reinforced-concrete (RC) members under compression. Nonetheless, lap splicing of GFRP bars under compression has not yet been explored with due consideration of its components. To address this knowledge gap, this paper comparatively demonstrates the results of an experimental investigation pertaining to the effect of splice length on the compression lap splicing of GFRP bars in concrete columns. The experiment comprised 11 large-scale circular columns measuring 300 mm in diameter and 1600 mm in height: seven specimens reinforced with GFRP bars, three specimens with steel bars for comparison purposes, and one specimen without reinforcement (plain concrete). All columns were tested under a monotonically increasing concentric load. The test variables included the reinforcement type (GFRP versus steel) and splice length. The results were compared in terms of the stress-strain curves, ultimate loading, displacement capacity, and splice strength. The test results indicate that the required compression splice length for GFRP bars is less than that required for steel. As the strength of a compression splice consists of end-bearing and bond components, the contribution of each part was scrutinized in detail using measured strain values. The required splice length for GFRP bars was considerably based on the end-bearing component. Based on the experimental results, a length of 8db can reliably be considered as the required splice length for No. 5 GFRP bars in compression.