Tensile Behavior of Groups of Anchored Blind Bolts within Concrete-Filled Steel Square Hollow Sections

In this paper, the tensile behavior of groups of Ajax anchored blind bolts used within concrete-filled steel square hollow sections is investigated. Using Ajax anchored blind bolts moment-resisting bolted connections to concrete-filled steel hollow section columns will be possible. Extensive experimental and numerical studies were undertaken. Bolt sizes and section sizes suitable for medium-rise commercial buildings were used. It was concluded that the groups of Ajax anchored blind bolts can reach the ultimate capacity of equivalent groups of standard structural bolts. The location of an Ajax anchored blind bolt relative to the section side walls has a significant influence on its behavior. For bolts located close to the side walls of a section, concrete struts developed and transferred the loads to the corner of the sections. Bolt diameter, concrete grade, and strut angle were found to be the most influential factors in the stiffness of an Ajax anchored blind bolt. A simple theoretical model, based on finite-element (FE) parametric studies, was developed to estimate the tensile behavior of groups of Ajax anchored blind bolts. This was essential for the application of Ajax anchored blind bolts in building construction practice. (C) 2015 American Society of Civil Engineers.