Bolted connections represent a large percentage of the built structures in today's construction practice. A previous REU project focused on the evaluation of resistance factors for high strength bolts in tension and shear. A question that is still open deals with the deformation capacity, both in elastic and inelastic range, of high strength fasteners in tension, as a function of the length of the threaded portion that is included between the connected parts, the so-called grip. On one hand, the more threads are included within the grip, the more likely is that a surface imperfection will initiate fracture of the bolt prematurely. On the other hand, if very few threads are included in the grip, the state of stress at fracture will be forced to find a different path from the classical 45 degree failure surface. This implies both increased apparent strength and decreased ductility, since the fracture surface will resemble more that of a brittle material. This study will investigate 100 lots of high strength fasteners, of grades A325, A490, F1152, and F2280 and will establish a relationship between strength and ductility and the number of threads in the grip. It is anticipated that 500 fasteners will be tested with varying grip conditions, measuring both strength and elongation at failure.

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