Behavior of novel CFST circular column-to-foundation connections under cyclic loading

Despite several advantages of Concrete Filled Steel Tube (CFST) columns, these are still not very popular in construction due to the non-availability of well-established, efficient, and ductile connections of these columns with the reinforced concrete (RC) foundations. The present study proposes two novel CFST column-to-foundation connections that are efficient and have adequate ductility to withstand inelastic deformation cycles under moderate to extreme seismic loading. The first proposed connection was developed by shape modification of the cavity used in the first-stage concrete of the RC foundation, whereas the second proposed connection was developed with a concept of mechanical interlocking. The connections were tested under cyclic lateral loading for simulating the seismic excitations. Two more connections representing controls were also tested. The first was a conventional CFST column-to-foundation connection, and another was a regular RC column-to-foundation connection. The test results establish the better performance of the proposed connections. Finite element (FE) models were developed to predict the behavior of experimentally investigated RC and CFST column-to-foundation connections. The prediction was in good agreement with the experimental results.