CROSS Safety Report
Suspended granite ceiling collapse
This report is over 2 years old
This report is in relation to the selection of fixings for a suspended ceiling of granite which collapsed in the entrance area of a new office building due to failures of the fixings.
Key Learning Outcomes
For civil and structural design engineers:
Ceilings should be given the same degree of attention as the primary structure during both design and construction to improve safety, reliability and longevity
Selecting the correct fixings for the given environment and anticipated loads is important to ensure they perform as expected
When designing ceilings and other elements for wind pay attention to the possible dynamic effects on fixings
For the construction team:
Quality control and competent supervision on site can help to ensure that ceilings are built in accordance with the design
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This report is in relation to the selection of fixings for a suspended ceiling of granite which collapsed in the entrance area of a new office building due to failures of the fixings. The construction was of 40mm thick granite fixed to a robust sub frame, which in turn was fixed to a composite metal deck. The fixings selected were of an expanded anchor type.
There was no appreciation amongst the designers or installers of the possibility of cyclical or dynamic loading from wind pressures. The European Technical Approval for the bolts stated that the bolt should only be used under static loading. The manufacturers were unable to supply test information to justify the use of these anchors.
Expert Panel Comments
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The key learning point from these two reports (148 and 149) is that there seems to have been no appreciation of the effects of vibration on the fixings. Dynamic action can cause fixings to work loose in substrates and/or nuts to loosen. Whenever there is cyclic action from traffic, wind effects, or machinery then fixings must be chosen that are suitable for both static and dynamic loads. The Standing Committee on Structural Safety (SCOSS) issued an Alert in 2009 – The selection and installation of construction fixings.
There have been a number of CROSS reports about fixing failures which has resulted in the Construction Fixings Association promoting a new BS Code of Practice for the use of anchors in safety critical applications. The drafting is due to commence shortly. In addition, the fixings industry, in conjunction with SCOSS, is drafting a guide to ceiling fixings.
There have been recent press reports of other ceiling collapses, including one from the Middle East about an incident which saw decorative panels fall from the ceiling of a large new mall. There were shoppers present at the time but fortunately nobody was injured. Another ceiling collapse, this time in the UK, resulted in the closure, for an extended period, of a Grade ll listed art gallery.
CROSS has been informed of a number of ceiling failures and they have in common that fact that the loads are uncertain, that the failure of one hanger increases loads on adjacent hangers and that rapid cascade type failure then occurs.
It is also the case that the engineering of such ceilings often seems to be absent and no one takes responsibility. The large number of failures (some accompanied by injury) suggests that the design teams are not identifying ceiling design as an important issue. Fixing details get very little attention by the designer yet they pose significant safety hazards unless spotted by a ‘passing site engineer/design engineer’. We would encourage further examples to illustrate this point. The Introduction provides useful contemporary information on fixings.
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