Seismic performance of concrete-filled SHS column-to-beam connections with slip-critical blind bolts

Abstract

This paper investigates the use of slip-critical blind bolts to connect I-beams to concrete-filled steel square hollow section (SHS) columns. The strength and stiffness of the resulting joints are determined experimentally for the purpose of classifying them according to the Eurocode. Their suitability for use in special moment frames is also assessed through cyclic bending tests. Three types of beam sections are tested, being a compact welded section, a reduced beam (flange) section, and a reduced beam section with concrete slab at the top. All tested joints are full strength according to the Eurocode, allowing the connected beams to reach their respective plastic moment capacities. In addition, they are rigid for braced and unbraced frames, except for the reduced beam section specimen, which are semi-rigid only for unbraced frames according to the Eurocode. However, all specimens have sufficient ductility to be used in special moment frames, with no pinching effect in their hysteretic moment-rotation curves. Their initial rotational stiffness is dominated by the stiffness of the column flange in bending, which can be conservatively estimated using the formulation presented in this paper.