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

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

Oktavianus, Yusak / Goldsworthy, Helen M. / Gad, Emad

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 $F_{u}$ 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 $1.25 d_{b b}$ 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.