Failure Mode Assessment of Flexure- and Shear-Sensitive RC Members

Under seismic load, Reinforced Concrete (RC) members may exhibit a flexure-controlled ductile (F) failure; otherwise, they may exhibit a shear-controlled brittle (S) failure or a combined flexural-shear (FS) failure. The identification of the failure mode determines RC members’ expected (and modelled) strength and deformation capacity. Approaches for the classification of the expected failure modes are proposed in the literature and, in some cases, adopted in codes. However, the use of a “discrete” pre-modelling classification (F/FS/S) does not allow the definition of a unique, failure mode-independent, “modelling structure” valid for whichever structural member. A preliminary study for the evaluation, based on experimental data, of a non-discrete failure mode classification, by means of a “membership function”, is presented. The proposed membership function can be used to preliminary define a unique set of predictive equation for the assessment of the deformation capacity of RC members up to the complete loss of strength resistance.