Research on the Brittle Fracture of Steel Profiles in Steel-Concrete-Composite Construction Systems

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The steel profile encased reinforced concrete construction method (named SRC in Japan) has been believed to be one of the most ductile and consequently one of the most effective construction against earthquake excitation. However, in some cases, at the beam to column joints in such construction the plastic deformation capacity becomes very lower because of the existences of scallops at the beam end for welding especially under alternately repeated cyclic bending In order to make clear the existing ductility of beam to column joints in steel concrete composite construction, especially in steel profile encased reinforced concrete construction, the low cycle fatigue fracture tests under alternately repeated cyclic bending are carried out by the loading system shown in Fig. 1 with various constant deflection amplitudes on various types of joints, i. e. column to beam joints (C-Butt), beam to column joints (B-Butt) and beam to column joints with scallops (B-Butt-Sc) illustrated in Fig. 2. The low cycle fatigue fracture limits of such various types of beam to column joints in steel profile encased reinforced concrete construction are summerized and illustrated in Fig. 3 in comparison with some other joints such as reinforced concrete (RC), steel (S-B-Butt-Sc) and composite (Comp-B-Butt-Sc) construction. This figure shows very clearly the lack of ductility by the existence of scallops in joints for welding. The brittle fracture modes in encased steel elements are illustrated in Fig. 4.