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CROSS Safety Report

Inadequate steel beam splice

Report ID: 343 Published: 1 October 2013 Region: CROSS-UK

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Overview

A reporter raises concerns of an inadequate steel beam splice they came across on site.

Key Learning Outcomes

For civil and structural design engineers:

  • Highlight to contractors the importance of receiving subcontractor designs and drawings well in advance of fabrication and installation and the safety issues that may arise if they are not received

  • If possible, attend site and inspect the installation of safety critical elements and connections

  • If you are unable to attend site, ask the contractor for site photos of the installation of critical structural elements

For the construction team:

  • Proper planning and allowing adequate time can ensure all subcontractor designs are checked and approved prior to construction on site

  • Alterations such as the addition of splice connection should not be made without approval from the design engineer

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As part of a project a reporter provided the design for a steel beam. The client sourced this from a fabricator, and it came with a mid-span splice. When the building control officer asked for a calculation substantiating the splice the reporter’s client, the fabricator, apparently stated that the splice was a full structural connection.

The reporter found that the capacity of the splice was around 20 kNm which was only about a third of the design moment required. By this time the beam had been installed and partially loaded but fortunately no collapse had occurred. Remedial works were then carried out.

Expert Panel Comments

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In many steel structures connections are the weak link. The words ‘full structural connection’ are meaningless and betray that whoever designed/detailed the splice did not understand what they were doing. A mid-span splice, which is unusual, was apparently introduced without the knowledge of the designer, and if this had been discovered prior to installation would doubtless have been questioned.

Perhaps the conditions of engagement of the designer did not include site inspections. Connections are generally designed by the steelwork contractor and the majority of them have competent engineers capable of designing connection details to support the applied actions. Also BCSA and SCI have published a number of guides on the design of simple, moment and composite connections both to BS 5950 and more recently the Eurocodes.

These design guides include procedures for designing beam-to-beam splices. Once again provided the client employs a reputable steelwork contractor this shouldn’t occur. In principle the architect (if there is one), as lead designer, should advise the client on the requirements for an engineer to be responsible for overall stability and on the engagement of competent contractors.

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