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Newsletter No 46 - April 2017

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Report Overview

Two Alerts have been issued by SCOSS recently: Structural stability/integrity of steel frame buildings in their temporary and permanent condition, and Inquiry into the construction of Edinburgh Schools. Both highlight problems with the quality of construction and the lack of supervision on site. Six of the seven reports in this issue relate to quality issues and it has been a common theme in CROSS reports. The trend is disturbing and it is only by chance, good luck and timing, that there were not multiple casualties. If there had been large scale fatalities, then public outcries and government intervention would have meant that instead of these events being near misses they would have become weapons with which to attack the construction industry. A much better attitude to safety must be cultivated by clients, designers, constructors and supervisors to protect themselves and the public. The urgent need to restore Resident Engineers and Clerks of Works to sites must be recognised. These and other critical recommendations are given in Report of the Independent Inquiry into the Construction of Edinburgh Schools which makes for sobering, but essential, reading for all involved in the safety of buildings. The success of the CROSS programme depends on receiving reports, and individuals and firms are encouraged to participate by sending concerns in confidence to Structural-Safety.

Overview of Reports in this Newsletter

602 Padstones out of position leads to collapse

This report concerns the partial collapse of a terrace of four storey houses during construction. The roof was timber and steelwork. The superstructure precast concrete floors were supported on front and rear façade walls and internal steel beams.

603 Changes in temporary works scheme

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.

607 Settlement of driven piles

A railway platform was constructed on piled foundations and it was noticed that one pair of piles and their associated cross head settled soon afterwards.

615 Inadequate bolted connections supporting stairs

When precast concrete stairs are installed, the landings are normally supported using either proprietary telescopic connectors (AKA ‘invisible connections’), or by means of an RSA bolted to the wall. When an RSA is used, the wall is drilled to fix the bolts, whether they be expanding fixings or chemical fixings, and frequently the drilling may hit reinforcement.

619 Unrestrained stone cladding

A leisure complex completed in the early 2000s has a steel frame with infill panels of block covered with thin stone cladding and a person was injured when a large piece of cladding fell. Local investigation revealed that there were insufficient vertical or horizontal dowels to restrain the cladding.

626 Partial failure of PC tank unit on installation

The use of precast concrete units to construct water retaining structures is becoming more common but their safe installation is not as straightforward as may be suggested.

641 Square HSS expansion due to freezing

A reporter has come across problems in British Columbia (temp range -30oC to +40oC)of cracking due to the ingress of water and freezing. One was a painted 2" (50mm) Square HSS on a sloped Pedestrian Railing, and the other is an Epoxy Paint coated 1" (25mm) Square HSS on a Stair Handrail also on a slope. In neither case were drain holes provided yet both hollow sections split as a result of frost action.

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