A programme of works to replace bolts on London’s Cheesegrater has been ordered by the building’s owners after a third one broke off.

Above: The Leadenhall Building... aka the Cheesegrater

Two months after steel bolts began to fail on the brand new  238m-high skyscraper, the owners has received reassurance from engineers that the building is structurally safe but a number of bolts need to be replaced “as a precautionary measure”.

Last November a massive steel bolt fell to the ground from the 47-storey Leadenhall Building in the City of London. A second bolt, connecting the nodes on the megaframe, was also found to be broken. [See our previous report here.]

Co-owners British Land and Oxford Properties ordered a full investigation from their contractor Laing O’Rourke and structural engineer Arup.

British Land confirmed that third bolt has since fractured and was captured by precautionary tethering put in place last year, preventing the bolt from hitting the ground.

These investigations have now been completed, British Land announced today. The investigations included site and laboratory testing of the broken bolts and additional bolts on the building. The tests concluded that the bolts had fractured due to hydrogen embrittlement, a material failure mechanism within the bolt material.

British Land said: “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.”

Breaking bolts is not the first problem related to the steelwork on the building at 122 Leadenhall Street. The specialist contractor that put up the steelwork, Severfield, encountered significant technical challenges on the job, pushing the company into heavy losses in 2013 and costing chief executive Tom Haughey his job.

The Leadenhall Building was designed by architectural practice Rogers Stirk Harbour + Partners. It opened last summer.

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