British Land to replace a number of bolts on the building after material failure discovered
British Land has said a third steel bolt recently fractured and fell from its 122 Leadenhall Street building, popularly known as the ‘Cheesegrater’.
The developer first reported in November 2014 that two large bolts had failed, prompting it to cordon off areas below the skyscraper and order an investigation into the problem by contractor Laing O’Rourke and structural engineer Arup.
The third fractured bolt fell but “was captured by precautionary tethering put in place last year”, British Land said.
Laing O’Rourke and Arup’s investigation has uncovered a material failure in some bolts and a number will now be replaced as “a precautionary measure”, but no structural problem was identified.
Full British Land statement on Cheesegrater bolt failures
An update on the fractured bolts: In November 2014, we reported that two bolts had fractured at the building. Investigations undertaken by contractor Laing O’Rourke and structural engineers Arup have now been completed. These confirm that the problem is limited to certain bolts. Arup has also confirmed that there is no adverse effect on the structural integrity of the building. A programme to replace a number of bolts will take place as a precautionary measure.
- The investigations included site and laboratory testing of the broken bolts and additional bolts on the building. A third bolt fractured recently and was captured by precautionary tethering put in place last year.
- The tests concluded that the bolts had fractured due to a material failure mechanism called Hydrogen Embrittlement. This is a crack growth mechanism within the bolt material.
- As the problem has been identified and is being rectified no further update is scheduled.