Experimental study on mechanical properties of locally composite steel and steel fiber reinforced concrete beams

Abstract

Addressing the construction challenges of steel reinforced concrete structures, steel fibers are employed as replacements for longitudinal rebars and stirrups. Additionally, considering the tensile and compressive properties of steel fiber reinforced concrete, the locally composite steel and steel fiber reinforced concrete (LCSSFRC) structures are proposed. Four-point bending tests were carried out on 18 LCSSFRC beams. Different steel fiber volume fractions (ρsf), specimen lengths (l), concrete cover thicknesses for upper and lower parts of steel compression flanges (Css and Csv), and specifications of shaped steel (Is) were studied. Considering the crack development, bearing capacity, ductility, and final damage pattern, the failure modes of 18 specimens were divided into interface failure, bending-torsion failure, and bending failure. Two types of load deflection curve models were established based on the relationship between failure modes and load deflection curves. Furthermore, the sudden load drop was closely related to the development of bonding cracks. Due to the “bridging effect”, specimens showed increasing trends in bearing capacity and ductility with the increase of ρsf. And it is worth noting that there existed a coupling effect of Csv and l on both the bearing capacity and ductility. Increasing ρsf, Csv, and Is was effective for inhibiting the stiffness degradation.