The behaviour at failure of 266 beam-column joints tested by various authors has
been examined to identify a model for computing the shear strength of internal beam-column
joints under severe seismic actions. This exam has pointed out that during the cyclic loading a
large diagonal cracking comes together with a joint volumetric expansion. Four resisting
contributions to joint expansion have been identified: the concrete one, the beam longitudinal
reinforcement one, the beam constraints contribution against the horizontal joint expansion, and
the stirrup one. The overall shear strength has been taken as the sum of these four contributions,
each dependent on a multiplying factor which has been univocally determined on the
experimental available data. The obtained expression predicts the shear strength in a more
accurate and uniform way than the Eurocode and ACI Code expressions.
