A novel slip-critical blind bolt: Experimental studies on shear, tensile and combined tensile–shear resistances

This paper presents the results of a series of experimental tests on a novel Slip-Critical Blind Bolt (SCBB) system recently improved by the second author, which can be used to connect an H-beam to a hollow section column. The connection specimens were subjected to monotonic loading under tension, shear and combined tension and shear in order to study their behavior and strength at the component level. Importantly, the plates separating loads and the slip resistances of the SCBB specimens were checked against the nominal values specified by relevant Chinese codes. The test specimens were found to exhibit stable (constant) bolt pretension for at least half an hour after tightening, at values that could be up to 20% higher than the design pretension specified by the code. The test plates separating loads were on average about 45% higher than the nominal tensile strength of the connection computed using the existing design equation. The ultimate tensile loads of the SCBB assemblies were the ultimate strength of the bolt shanks. The ultimate shear loads associated with the shear fractures of the bolt and sleeve were found to be much higher than the nominal shear strength, typically about three times. Under shear or combined tension and shear, the slip resistance can be estimated conservatively using the existing design equations. A bolt group factor may be needed as the shear resistance of a connection having more than one bolt in series tends to be smaller than the arithmetic sum of the individual resistances.