CROSS Safety Report
Collapse of infill wall panel
This report is over 2 years old
A blockwork infill wall panel approximately 4m wide and 9m high between two building collapsed in high winds.
Key Learning Outcomes
For construction professionals:
Quality assurance and competent supervision on site can help to ensure that the structures including infill wall panels are built in accordance with the design
Effective communication of essential design information and details in an accessible form to tradespeople working on site can also ensure the works are in accordance with the design intent
For civil and structural design engineers:
Adequate design details and specifications should be provided for bespoke wall panels to ensure there is no ambiguity as to what detail should be applied to the construction
The type of wall tie, method of fixing, spacing and tie frequency should be carefully considered and clearly conveyed on the construction drawings
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A blockwork infill wall panel approximately 4m wide and 9m high between two buildings, A and B, collapsed in high winds. An investigation was carried out by the reporter's firm in conjunction with other parties and the main findings were:
Frame cramps (wall ties) remained fixed in place on the A side of the failed panel, whereas they were torn from the steel on the B side
The wall panel was subject to significant wind load, predominantly from the rear, funnelling down a service corridor, but potentially also from suction on the other side
Side A frame cramps (wall ties) had failed, and the wall slipped off them, possibly due to fatigue and buffeting, although most likely due to lack of ties. Ties were installed at 450mm centres rather than 225mm.
Embedment of ties was 45mm rather than the specified 50mm minimum
Shot fired ties used, where tec / self-tapping screw fixings are recommended by manufacturer (although the use of shot fired ties is industry norm)
There was no bed /joint reinforcement
Lack of specific architectural detail
Recommended action to be taken in future, says the reporter, are:
Where there is a bespoke wall always ensure that there is a design detail / specification, so that there can be no ambiguity as to what detail should be applied to the construction. Do not rely on standard details which may be sufficient for more normal sized walls.
Consider the type of wall tie, the method of fixing, the spacing and frequency. Clearly defined details should be incorporated into the project inspection and test plan, with sign off at key stages.
As a general comment - practitioners should always ensure that inspection regimes are thorough, robust and documented
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