Cast-in and post-installed rebar anchorage systems in RC column foundation joints: Experimental investigations

This paper discusses an experimental program aimed at comparing different reinforcing bar (rebar) anchorage systems in reinforced concrete (RC) column-to-foundation joints (CFJ). A total of 13 tests on full scale CFJ are presented. Within the test matrix, cast-in straight (CIS), cast-in with bent-in hook (CIH) and post-installed rebar (PI) systems are employed for anchorage of the column main rebar in the foundation concrete. The specimens were designed to trigger different failure modes (and their combinations) specific to the rebar anchorage zones. This paper provides the details of the test program, specimens, test procedure and the results. Behavioral perspectives for different rebar anchorage systems (CIH, CIS and PI) are discussed based on the test observations. A discussion of the test results within the framework of expectations outlaid in design of the test specimens is also presented. The study highlights that high bond strength offered by PI system used in the present investigation resulted in flexural yielding of column at lower anchorage length in comparison to the CIS reinforcement. It is also shown that concrete breakout failure typically considered in fastening technology is also applicable in case of cast-in anchorages with bent in hooks, although it manifests in a slightly different manner. The test data presented in this paper offers the necessary benchmark data required for system specific assessment and design approach for the rebar anchorage zones in CFJ. A proposal for system specific assessment and design approach and its comparison with the available assessment and design approaches in the light of experiments presented in this paper and also those available from the literature will be presented in another paper.