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Newsletter No 24 - October 2011

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Report Overview

This Newsletter is the first to be published on the new Structural-Safety web site (www.structural-safety.org) which combines the activities of SCOSS and CROSS. For those who were receiving publications from either group there is no need to re-register, and those who wish to register for the first time will find a link on the home page of the new web site. The need for continued vigilance has been illustrated in recent weeks with the dramatic and deadly collapses of two major temporary stage roofs: one in Indiana USA, and one in Belgium, with a total of eleven fatalities and many injuries, and several other recent collapses of similar structures. The subject is being considered by SCOSS and their views will be published in due course. There has also been the collapse, with two deaths, of a cantilever stadium roof being erected in Holland, the death of a man in London from falling masonry, and the collapse of a large canopy under construction at a UK school with several injuries. Reports in this issue of the Newsletter start with the comprehensive description of design error provided by a major firm of consulting engineers. This is much appreciated as it has been provided with the full backing of the company concerned. CROSS is a platform for sharing information without revealing names or identifiable details and the more widely CROSS is trusted the more effective it will become. Other reports deal with construction issues including tower crane bases, the care needed when using certain epoxy grouts where there are high ambient temperatures, another retaining wall failure, and more concerns about lack of control and supervision on sites. DRD Roads Services in Northern Ireland have become the latest Government Department to join CROSS as a backer and this follows the arrangements already in place with the Highways Agency in England. Their Safety Management Procedures now include a section on the confidential reporting scheme and any issues that would help with lessons to be learned will be passed on through senior management. The Department is responsible for: • regional strategic planning and development policy; • transport strategy and sustainable transport policy; • provision and maintenance of all public roads; • public transport policy and performance; • certain policy and support work for air and sea ports; and • policy on water and sewerage services and management of the Department’s shareholder interest in Northern Ireland Water. 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

227 Checking at a price

In relation to the checking of calculations on behalf of local authorities for building regulation submissions (CROSS Newsletter No 20 report 210) a reporter is concerned about checking engineers who are paid very low hourly rates.

228 Hoarding blown onto child (news)

A two-year-old child escaped with minor injuries injury after a 2.4 m high, 17m wide, shop hoarding collapsed on him as it was blown over. The main contractor and the hoarding sub-contractor pleaded guilty to breaching the Construction (Design and Management) regulations 2007.

240 Failed two storey retaining wall

A developer built a small estate adjacent to an existing property (shown on the left of the photograph) with a retaining wall between the two. The reporter checked the proposal on behalf of the owner and told the developer that it was not safe and would be dangerous.

241 Lack of control on site when underpinning

The concern is in relation to the sequencing of construction and the lack of control on site from competent persons. The reporter says that a Victorian building with four storeys and a basement was being converted to a small hotel. As part of this work the basement level was being lowered by approximately 1m.

244 Failure of epoxy fixings due to high temperature

Two mobile phone towers were erected on the roofs of two nearby buildings using drilled epoxy anchors into the roof slabs. During a storm of moderate intensity, both towers collapsed; the failure mechanism being the pull out of the anchors from the drilled holes.

245 Generic designs for steel beams in domestic buildings

The reporter has been approached by an architectural services company to produce generic steel beam designs. He says that load assessment could be done by the company, and then a (possibly) unqualified person refers to the “generic design” for a specified span to check that the assessed load is less than the apparently allowable load given by the programme. This, according to the reporter, is not a safe practice and CROSS should be alerting local authorities to be vigilant.

257 Foundation base plates for tower cranes

On two different contracts it was observed that the foundation base plates for tower cranes have suffered from low compaction of the concrete on which they rest.

262 Asymmetric bridge design and construction – a near miss

During the construction stage of an arch footbridge, says a reporter, a design error was identified that had been indirectly revealed by an associated error in construction. It is reported that effective correction of these errors was expensive but resolved the potential performance safety issues.