Strength and ductility of R.C. columns strengthened with steel angles and battens

In this paper the behaviour of R.C. members externally strengthened with steel angles and battens subjected to axial force and bending moment is analysed. A fibre model was utilised to predict the moment–curvature diagrams of the strengthened members on the basis of stress–strain curves of the constituent materials (confined concrete, steel bars and angles) recently derived by the author. The stress–strain curves utilised for compressed concrete were able to take into account the confinement effects induced by longitudinal (bars and steel angles) and transverse (stirrups and battens) steel reinforcements. Constitutive laws in compression for confined concrete and steel bars and angles were utilised for a preliminary calibration of the compressive response of axially loaded columns strengthened with steel cages. Therefore axial force and bending moment diagrams and moment curvature diagrams were derived and verified against experimental data available in the literature. Finally, a parametric analysis showing the influence of the main parameters governing the problems (angle and strip geometry and mechanical properties of constituent material) was carried out, mainly referring to moment axial force domains, moment curvature diagrams. The analysis showed the effectiveness of this reinforcing technique in improving both the strength and the ductility of R.C. columns.

► Flexural behaviour of strengthened columns with steel angels and strips. ► Extensive comparison with available experimental data referred to member under compression and flexure. ► Numerical comparison with existing codes in terms of moment axial force domains. ► Parametric analyses in term of available ductility and moment–curvature diagrams.