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

Figure 1-2 Typical Extended End-Plate Connection With Circular Bolt Pattern Configuration
Uneven distribution of the bolt-forces in the connection bolts causes high stress concentration on the
bolts closer to the beam flange which results in an early yielding of these bolts. The pinching
phenomenon is due to the reduction in pre-tensioning force in the connection because of the yielding of
the bolts or fracture in the end-plate. The elongation of the bolts significantly reduces the pre-tensioning
force in bolts which leads to strength reduction of the connection in the subsequent loading cycle during
cyclic loading. In addition, pinching may occur if early yielding of the end-plate takes place before the
bolts are fully loaded. The end-plate thickness vs. bolt diameter ratio is an indicator of connection
performance which will be addressed and discussed in this research.
Based on experimental and numerical investigations, the proposed circular bolt pattern configuration
in the steel bolted connections results in a more uniform distribution of the forces in the bolts. This
prevents early yielding of the bolts in the connection during loading which consequently reduces the
pinching effect.
The objectives of this research are divided into the following primary goals:
1- To reduce and redistribute bolt-forces in the moment resisting bolted connection by changing the
bolt pattern configuration. Due to unique deformation characteristics of the end-plate in the
connections with a circular bolt pattern, the far bolt can engage and experience load in an earlier
stage of loading when it is compared with the connections with a square bolt pattern. This
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