Investigation of ultimate capacity of beam-column joints of precast system

Results of an experimental campaign on precast reinforced concrete columns are described; multi-story columns are considered where, in the construction phase, vertical steel bars are designed to carry the full vertical load in beam-column joints. Under axial force and bending moment, failure of nodes is due to instability of steel bars. An analytical models for prediction of failure load is also proposed, where second-order effects and elasto-plastic behaviour of steel bars are taken into account. Axial force vs. horizontal displacement curves are provided, in good agreement with experimental findings. Experimental results are also compared with numerical results obtained from a non-linear FE model. Starting from the proposed analytical model, some design criteria are illustrated and discussed.