Experiment and analysis of circular hollow section gap K-joints with grade HSB 600 steel

Abstract

Circular hollow steel sections are examples of members that are becoming increasingly popular. The demand of high strength with sufficient ductility for materials is increasing for design of long-span and high-rise structures. HSB 600 steel, High performance Steel for Bridge with minimum tensile yield strength, fy, of 480 N/mm2 for all thickness, was introduced in the Korea Building Code (KBC 2009, 2009). However, current design standards may not be applicable to circular hollow sections with HSB 600 steel since they have been established based on tests of steels with yield stress up to 355 MPa and a ductility ratio up to 0.8. Six full scale circular hollow section gap K-joints were tested and analyzed to investigate the applicability of current design standards. Two series using SHB600 and SS400 steel grades were tested. Three specimens in each series with various gaps between bracing members were evaluated. All chord members were 2,250 mm and brace members were 1,400 mm in length. All chord and brace members were 350mm in diameter and 12 mm in wall thickness. Based on the limited test and analysis results of this circular hollow section gap K-joint, the applicability to current standards, the possible elastic local buckling and gap effects of the different grades of steel are examined.