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Tests on the Installation Characteristics of High Strength Fasteners in Lap Splice Joints

Wehr, Michael C.

1995

The proper performance of slip-critical bolted joints requires adequate fastener tensions. The Research Council on Structural Connections of the Engineering Foundation requires minimum fastener tensions for these slip-critical connections. Past research done in the field and laboratory indicates variations in final fastener tension. Different methods of tightening fasteners and different conditions of the joined materials result in various final fastener tensions.

This thesis describes the research of various methods of tightening fasteners by conducting experiments on joints with instrumented fasteners. Electronic strain gauges provide information that translates into real time fastener tension. The turn-of-nut and calibrated wrench installation methods provide the main delineation between tests. Both of these methods of installation rely upon a “snug tight” condition before application of a final tightening pass. Tests conducted provide information on the adequacy of different “snug tight” conditions. Also, variations in connected material thickness and out-of-flatness affects final fastener tensions. Twenty-nine tests evaluate the results of using different combinations of tightening and material conditions.

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