Determining the preload in preloaded bolt assemblies in existing steel structures

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)


Preloaded bolts are used to achieve slip-resistant shear connections. The actual preload force in each bolt has a direct influence on the fatigue and slip resistance of the connection. The strain gauge method is examined for practical assessment of the actual preload because its use is no longer limited by the demands on adhesive curing conditions. The main objective of the paper is to describe how measured strain in the bolt shank and statistical variation of the nominal mechanical and geometrical properties of the bolt are used to determine the actual bolt preload without calibrating every single bolt. The calibration factors established by laboratory and in situ measurements exhibit rather small scatter. The minimum bolt preload required is achieved with a 95 % probability of being exceeded in a bolted connection on a Dutch highway bridge (Middachterbrug).

Original languageEnglish
Pages (from-to)282-286
Number of pages5
JournalSteel Construction
Issue number4
Publication statusPublished - 1 Jan 2017


  • calibration factor
  • in situ measurements
  • preload force
  • slip-resistant connection

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