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603 Changes in temporary works scheme

Report ID: 603

Published: Newsletter No 46 - April 2017

Report Overview

A multi-storey above-ground structure was designed so that the superstructure rested on a basement liner wall, which in turn was dowelled into the secant piled retaining wall. The temporary works designer placed raking props and whaling beams against the secant wall in the temporary case, which prevented completion of the liner wall.

Report Content

A multi-storey above-ground structure was designed so that the superstructure rested on a basement liner wall, which in turn was dowelled into the secant piled retaining wall. The temporary works designer placed raking props and whaling beams against the secant wall in the temporary case, which prevented completion of the liner wall. A sequence was specified in which all props were removed and the liner wall completed before construction of the superstructure started. Due to changes in construction programme, time pressure and lack of clarity about who was responsible for the overall temporary works strategy, the sequence of construction was changed and the superstructure proceeded without the liner wall being completed. By the time this was spotted, a significant portion of the superstructure was being supported by a partially complete liner wall, with a greatly reduced number of dowels into the secant wall. Work was immediately stopped on this structure until it was deemed safe and delays were incurred as the superstructure could not be continued until the liner wall was completed.

Comments

There have been innumerable failures consequent on change or unauthorised change with unforeseen consequences. Nothing should be changed on site without sanction from the Design Authority and this is a classic case of lack of adequate consideration of the interfaces between Temporary Works and Permanent Works. Was a Temporary Works Coordinator and a Temporary Works Supervisor appointed to help ensure this situation could not occur? The Permanent Works Designers should have provided for at least one safe method of construction, and this should not have been changed without reference back to them. Changes made to designs on site can have severe adverse consequences and again there are similarities with the Edinburgh schools. Procedures must be followed and responsibilities allocated at the start of every project for controlling change.


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