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CROSS Safety Report

Failure of tower crane studs

Report ID: 600 Published: 1 January 2017 Region: CROSS-UK

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Overview

This report describes how non-standard Grade 10.9 studs used to connect a tower crane mast to a steel grillage failed.

Key Learning Outcomes

For construction professionals:

  • Consider introducing a quality management procedure on site for the inspection of safety critical elements being delivered to ensure they are of the required quality

  • It is good practice to ensure all metal anchors and bolts are covered by a Euronorm, European Technical Approval Guidelines (ETAGs) or similar

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There is a crane related issue about the failure of non-standard Grade 10.9, 56mm diameter x 1050mm long studs, used to connect a tower crane mast to a steel grillage. The failure occurred three days after they had been installed and tensioned.

Fortunately, this happened before the crane was erected. Investigations showed that the studs had suffered from delayed hydrogen embrittlement and that the material had been hardened above the specified range for Grade 10.9.

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