ON THE EFFECTS OF CIRCULAR BOLT PATTERNS ON THE ...

CHAPTER 1
1. INTRODUCTION
1.1 General
Among the moment resisting bolted connections, the extended end-plate connections with
approximately 90% compatibility with the available beam sections are the most popular types of the
bolted connections, AISC [1]. Moment resisting bolted connections exhibits a behavior ranging from fully-
restraint (rigid) to partially restraint (semi-rigid) depending on their type and geometric parameters.
Although numerous studies have been conducted on the behavior of these connections, limited attention
has been drawn toward the configuration of the bolt patterns, end-plate deformation, and their effect on
the bolt-force distribution and overall connection performance.
The investigations to evaluate bolt-forces in the connections date back to 1960s with contributions from
Douty and McGuire [2], Kato and McGuire [3], and Nair et al. [4]. These investigations were conducted
on T-Stubs to evaluate the bolt-forces including the effects of the prying force generated near the edge of
the end-plate. Kennedy et al. [5][6] were pioneers in developing a design procedure for determining the
bolt forces in the flush, extended, stiffened, and unstiffened end-plate moment connections. Their design
procedure introduced three stages of flange behavior based on the end-plate thickness condition; thin,
intermediate, and thick. The three main failure modes for end-plate bolted connection are adopted in
Eurocode-3 [7], and AISC Design Guide-16 [8]. Figure 1-1 illustrates the three modes of plate behavior
for each thickness condition.
Mode-1: plastic hinges form at the bolt-line and at the beam web, Figure 1-1(a).
Mode-2: plastic hinges form at the beam web followed by yielding of the bolts Figure 1-1(b); and
Mode-3: yielding of the bolts only while the end-plate remains elastic Figure 1-1(c).
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