Group Behavior of Double-Headed Anchored Blind Bolts within Concrete-Filled Circular Hollow Sections under Cyclic Loading

Abstract

Seven full-scale curved T-stubs connected to concrete-filled circular hollow sections (CFCHSs) using groups of double-headed anchored blind bolts (DHABBs) have been cyclically tested in this paper considering different configurations of the DHABBs and the addition of a through bolt (TB) and shear blind bolts (SBs). The cyclic testing consisted of axial forces being applied to the T-stub stem and transmitted to the column through the bolted T-stub flange connection. The relative contributions of the embedded heads, TB, SBs, and heads bearing on the tube wall to the total applied force obtained from finite-element analysis (FEA) for each specimen considered in the experiments have been summarized. Furthermore, a parametric study has been performed using FEA software to make an assessment of which parameters are the most influential in achieving a higher secant stiffness at 0.6 Fu provided that the bolts are fully pretensioned, sufficient concrete strength is provided, and the embedded heads have sufficient embedment depths. The results show that the thickness of the T-stub flange is the parameter that is most influential in increasing the secant stiffness of the connection, and it is recommended that a flange thickness of 1.25dbb be used. The second most important parameters are the addition of a TB and SBs because these are effective in preventing premature stiffness degradation resulting from concrete cracking.