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CROSS Safety Report

Steelwork connection design

Report ID: 25 Published: 1 March 2006 Region: CROSS-UK

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Overview

A reporter was asked to design connections for a multi-storey building for which the frame had been designed by another engineer. The result was a near collapse situation.

Key Learning Outcomes

For construction professionals:

  • Consider appointing a competent temporary works coordinator (TWC) on site who should be able to ensure all temporary works are carefully considered and planned

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

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This reporter specialises in structural steel only and is a consulting engineer for fabricators. They were asked to design connections for a multi-storey building in a UK city. The structure consisted of steel columns supporting steel beams that supported concrete floors. Lateral stability of the frame was to be provided by concrete cores and walls around the lift shaft and stairs.

The main consultant provided loads for the beam end to column connections which were all shear only loads. The reporter designed for these forces only using ‘green book’ end plates and fin plates to carry shear (with nominal tie forces).

Some months later the reporter discovered that the steel frame had been erected but not the concrete cores due to a change in plan, concrete was being poured onto the floors, and the main contractor had draped tarpaulins over the sides of the building to shield workers from the wind.

They said; ‘It is a miracle that the structure did not collapse. I can only put it down to the fact that the wind was light at the time’. They advised their client, the steelwork fabricator, to add temporary steel bracing immediately but this process took the best part of a week during which the frame was vulnerable.

‘It is a miracle that the structure did not collapse. I can only put it down to the fact that the wind was light at the time’

It appeared to the reporter that the main consultant had a contract with the main contractor which stated that temporary stability was not the consultant’s responsibility. Responsibility was passed by contract to the steel fabricator yet the fabricator did not appreciate the requirements for temporary stability and the possible consequences.

Expert Panel Comments

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Some years ago a building in Scotland collapsed under similar circumstances and there were fatalities. Had there been a collapse in this case there would have been civil, criminal and moral issues and it is probable that all parties concerned could have become involved.

The main designer should have made clear what was required to give both horizontal and vertical stability to the structure. At tender stage there should have been a method statement taking account of stability and construction sequences.

Sub-contractors and their designers should all have been engaged in thinking about temporary stability, and it may be a common feature on sites that there are breakdowns in communication which could lead to such situations.

Clarity of thought, acknowledgement of responsibility for the consequences, and competence in execution are all essential. CROSS welcomes other examples of divided responsibilities to see if there is a trend here.

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