Tensile Behavior of Groups of Double-Headed Anchored Blind Bolts within Concrete-Filled Square Hollow Sections under Cyclic Loading

Abstract

In this paper, the cyclic behavior of groups of double-headed anchored blind bolts (DHABBs), which are anchored within concrete-filled square hollow sections (CFSHSs), is investigated. The DHABB used in this study consists of a conventional headed anchored blind bolt (HABB) with one additional head, between the existing end head in the embedded region and head next to the tube wall. A series of full-scale experiments were conducted on the pull-out behavior of groups of DHABBs under cyclic loading. The specimens consisted of groups of two DHABBs, four DHABBs, and four DHABBs with one through bolt (TB). The effects of load distribution between individual bolts and of internal concrete cones overlapping from individual blind bolts are also investigated. The failure mode and sequence, cracking pattern, and the strain distribution for each test are explained in detail. A comprehensive three-dimensional (3D) finite element model was developed and the results were shown to compare well with the experimental results. The finite element (FE) model was then used in parametric studies to ascertain the influence of various parameters on the behavior of blind bolted connections. The effect of tube thickness, flange and web thickness of T-stub, sizes and configurations of DHABBs, and TB and the concrete compressive strength were investigated. Among them, the flange thickness of the T-stub was found to be the parameter that has the largest effect on the tensile behavior of blind bolted connections.