Behavior and design of demountable and replaceable RC columns with bolted flange connections under eccentric compression

This study developed an innovative bolted flange connection for reinforced concrete (RC) columns, through which the RC columns could be removed and replaced in the event of a change in structural function or seismic damage. The detailed construction of the demountable and replaceable reinforced concrete columns with flange connection (DRCC-FC) is introduced firstly. Then the installation method and replacement requirement of DRCC-FC is presented, and the design formula for flange connection is also given. This study conducted experiments on nine DRCC specimens and one cast-in-place specimen under eccentric compression. The failure modes, loading capacity, deformability as well as strain on rebars and flange plates were investigated. Furthermore, finite element models of DRCCs were established and a parametric analysis was conducted. The effect of flange thickness, flange steel strength and length of connectors on mechanical properties was discussed. Results demonstrated that the failure modes of DRCC specimens were consistent with that of cast-in-place specimen, both of which exhibited yielding of rebars on the tensile side and crushing of concrete on the compressive side. The flange of the specimen with a low thickness appeared plasticity, and the other specimens did not show a significant deformation on the flange plates and bolts, which was favorable for the removal and replacement of the column components. The loading capacity of the DRCC specimens was slightly lower than that of the cast-in-place one, but the deformability was superior. Flange thickness is the main factor affecting the loading capacity and rotational stiffness of the flange connection. Finally, the formula for loading capacity of DRCCs related to flange thickness was presented. Comparison with the finite element and test results indicated that the calculation error of the formula is within 12%.