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Title: Causes of pretension loss in high-strength bolts
Authors: Riveros, Guillermo A.
Mahmoud, Hussam.
Rodriguez Lopez, Santiago.
Keywords: Hydraulic gates
Bolts and nuts--Fatigue
Bolted joints--Fatigue
Axial loads
Tensile architecture
Shear (Mechanics)
Failure analysis (Engineering)
Publisher: United States. Army. Corps of Engineers.
Engineer Research and Development Center (U.S.)
Information Technology Laboratory (U.S.)
Series/Report no.: ERDC/ITL ; TR-16-2
Abstract: Abstract: High-strength bolts are used extensively in structures and are regarded as a reliable option for connections subjected to cyclic fatigue loads in comparison to welded and riveted connections. Previous studies have highlighted that the fatigue of bolts in tension is not a concern if the bolts are properly pre-tensioned. However, these studies have not considered the potential loss of pre-tension. Nevertheless, a recent application of properly pre-tensioned bolts in miter gates that were subjected to multi-axial fatigue, producing tension and shear stress reversals, shows extensive fatigue cracking that was manifested through complete bolt failure. Sufficient observations and reports exist suggesting the possibility of fully pre-tensioned bolts coming loose due to shear stress reversals where the maximum transverse design load is below that of what would cause the connection to slip. The problem of transverse vibrational loosening of bolts and the issue of bolt fatigue has been extensively researched. Only recently have these subjects been considered together although no studies of this interaction have been conducted on high-strength bolts. Certain mechanisms mark the onset of bolt loosening and fatigue when bolts are subjected to cyclic shear or shear combined with tension. The actual mechanisms and limits at which this occurs are to be explored in this report. Future experimental and numerical studies will be conducted by the authors to verify these mechanisms for high-strength bolts and provide design and installation recommendations.
Appears in Collections:Technical Report

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