Flexure-shear interaction phenomena in seismic assessment of reinforced concrete frames.

Seismic assessment of reinforced concrete (RC) buildings under seismic loading requires the ability to model the effective non-linear response and to identify the relevant failure modes of the structure. Due to the lack of application of capacity design principles, existing RC structures can exhibit premature shear failures with a reduction of available strength and ductility. In particular, several researches have shown that the shear strength decrease with the increase of flexural damage after the development of plastic hinges and, in some cases, this can cause a premature and unexpected shear failure in the plastic branch with a consequent reduction of ductility. The scope of this paper is to study the flexural-shear interaction phenomena in order to understand their influence on the behaviour of the structures and to show how these phenomena can be implemented in a finite-element analysis. The analysis have been conducted with Opensees that has specific commands able to model the flexural-shear interaction phenomena. In the present research a specific model was developed, implementing some state-of-the-art simplified models aiming at capturing the complex interaction between shear and flexural damage mechanisms have been proposed and implemented in regulatory building codes and guidelines. Based on this model, a series of validation analysis have been performed, in order to verify the reliability of the formulation.