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CROSS Safety Report

Responsibility for change

Report ID: 50 Published: 1 February 2007 Region: CROSS-UK

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Overview

The inadequate substitution of lintels led to them buckling, and the surrounding masonry cracking.

Key Learning Outcomes

For construction professionals:

  • Any proposed change in specification to construction elements should be reviewed and approved by the design engineer

For civil and structural design engineers:

  • Share your knowledge of the behaviour of products, components, and materials

  • Routinely raise the risks associated with substitutions to contractors and the wider project team

Full Report

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During the construction of two three storey blocks of flats with masonry walls and precast concrete floors, the contractor requested that they be allowed to substitute an alternative make of steel lintels for those specified by the structural engineer. This was agreed and a change order was issued.

The replacement lintels were selected by the contractor’s supplier, using equivalent loading capacity from the manufacturers’ tables. The contractor did not request the engineer to recalculate loads and confirm the specification. Because of eccentric loading and the lack of triangulation above the lintels the substitutes began to buckle, and masonry cracked.

The buildings, which were structurally complete at the time, had to be evacuated and propped. There was a ten week delay to the project whilst a design solution was found and implemented. The inadequate lintels were cut out and new steel members were inserted. Analysis of the situation concluded that because of the number of parties involved, both contractors and consultants, there was no clear line of responsibility for reacting to and controlling the change.

Expert Panel Comments

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A very large number of failures are as a result of change during the late stages of design or construction. The initiator of change needs to be very aware of the risks involved and of the difficulty in identifying accountability for structural robustness in a typical project with many parties.

It frequently happens that the initiator is unaware of the potential consequences of his proposals. If the design is to be changed, then, unless the contractor is a designer i.e. they are employed on a Design and Build form of contract, or JCT with a design element, he has no mandate to design anything; it must be done by the original designer.

This lack of clarity is a matter of great concern to CROSS. It is recommended that designers engaged in a Design and Build contract keep their clients alerted to these risks. An extreme example recently was of a changed component that failed under load and a death resulted.

This lack of clarity is a matter of great concern to CROSS. It is recommended that designers engaged in a Design and Build contract keep their clients alerted to these risks

The lesson is never to make unauthorised changes and always refer the need for a change back to the designer who must be the one to determine whether this is appropriate. A contributory cause of the 1974 Flixborough explosion was plant modification that occurred without a full assessment of the potential consequences.

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