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CROSS Safety Report

Serious safety failings of high level lattice girder walkways

Report ID: 697 Published: 1 January 2018 Region: CROSS-UK

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Overview

A reporter discusses extremely serious safety failings with the construction of two new high level lattice girder walkways in the fly tower of a theatre.

Key Learning Outcomes

For construction professionals:

  • Quality management and competent supervision on site can help to ensure that the structure is built in accordance with the design

  • Alterations should never be made to the structure without approval by the design engineer

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A reporter discusses extremely serious safety failings with the construction of two new high level lattice girder walkways in the fly tower of a theatre. The two 14m long span identical walkways are 20m above a stage which is occupied during productions. One walkway serves the theatre flying system and is designed to support 14t of counterweight and imposed loading.

The theatre was closed for the works, with a sold out show programmed for the reopening production. The complex construction work was behind programme. On dismantling the walkway erection scaffolding, both walkways sagged. The sub-contractor alleged this was due to design inadequacies. Rechecking of the design confirmed that the design was adequate.

Inspection of the walkways found missing and loose bolts, as well as some web members cut where they had clashed with the scaffolding. The reporter, who was responsible for the structural design, instructed for the cut webs to be replaced and all bolts to be spray painted as they were tightened.

On reinspection, all bolts were found to have been spray painted as instructed, but a significant number of loose bolts were still present. As a final safety check, the reporter had the adequacy of the walkway construction demonstrated by an overnight load test prior to the theatre opening to the public. The root causes are, according to the reporter, severe programme pressure on the fabricator and erection team as well as a lack of appropriate supervision.

As a final safety check, the reporter had the adequacy of the walkway construction demonstrated by an overnight load test prior to the theatre opening to the public

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