Design model for hybrid steel-RC walls

Abstract

Hybrid RCS frames consisting of reinforced concrete (RC) column and steel (S) are used frequently in practice for mid to high-rise buildings. RCS frames possess several advantages from structural, economical and construction view points compared to either traditional RC or steel frames. One of the key elements in RCS frames is the composite shear wall consisting of several steel sections encased in reinforced concrete. Regarding the RC walls reinforced by more than one steel profile, namely “Hybrid” wall, although a number of researchers have focused on its various aspects, they are currently not covered by standards because they are neither reinforced concrete structures in the sense of Eurocode 2 or ACI318, nor composite steel-concrete structures in the sense of Eurocode 4 or AISC 2010. This paper is dedicated to present a tentative design model for hybrid walls with several embedded steel profiles subjected to combined axial force, bending and shear. The model is based principally on the design rules of Eurocode 2 and Eurocode 4. Particular attention will be paid to shear (longitudinal and transversal) resistances because preventing shear failure is one of the major concerns when designing a composite structural member. A strut-and-tie model is developed to evaluate the transverse shear resistance taking into account the contribution of the steel profiles. Furthermore, an analytical method is proposed for the prediction of the longitudinal shear stress at the concrete-steel profile interface which allows to design adequate shear connection of the profile to concrete. The proposed design model provides a faire estimation of the part of applied shear which is applied to the embedded steel profiles; this allows to take into account the influence of transverse shear on the combined axial force and bending resistance. When used with design values of bond and friction shear strength of Eurocode 4, the proposed design model gives a faire estimation of the longitudinal shear stress at the concrete-steel profile interface