Behaviour of non-conforming R.C. members under compressive axial load and biaxial bending

Under seismic actions, the structures undergo two simultaneous horizontal compo-nents of the ground motion, which cause a structural response in an oblique direction and biaxial bending in the columns. The current approach to the seismic design of new structures or the assessment of existing ones points out the need of taking into account the contempora-neous presence of the two components of ground motion, in order to make a good prediction of the real structural behaviour, both in terms of strength and deformation capacity. The pa-per analyses the influence of the two components of bending moment on the deformation ca-pacity of reinforced concrete (r.c.) cross-sections and r.c. members (i.e. columns) by using a specific fibre model. The behaviour of the generic member is expressed in terms of ulti-mate/yielding curvature domain for the cross-section and ultimate/yielding rotational capaci-ty domain for the column. The study underlines the influence of the two components of biaxial bending on the deformation capacity of r.c. cross-sections and r.c. members.