Innovative approaches for predicting RC beam-column connection joint shear resistance

In this paper, an existing analytical approach for estimating joint shear behavior of reinforced concrete (RC) beam-column connections is critically examined and then modified in light of its limitations. The approach considers that joint shear strength is provided by an equivalent diagonal compression strut activated by force transfer to the joint through direct bearing from beam and column compression zones, and via bond between beam or column reinforcement and surrounding concrete. The model had first been developed for estimating joint shear behavior of composite RC column-to-steel beam connections, and then adjusted for application to certain RC beam-column connections (based on limited test results). This paper describes some shortcomings of that approach in light of a much broader experimental database of RC beam-column connection subassembly test data for developing joint shear resistance models. The research then uses probabilistic methods to derive a general relationship between joint shear deformation and the so-called principal strain ratio (including proper consideration of concrete compression softening and reasonable upper limits on joint shear deformation). This updated relationship can be used as a modification in the model for increased accuracy and broader applicability. The resulting modified model compares favorably to other approaches available in the literature for characterizing the joint shear behavior of RC beam-column connections.