Today marks 50 years since the Ronan Point tragedy claimed four lives following a devastating tower bock collapse.
The disaster led to major investigations that ultimately reshaped the way structures are constructed today. Although five decades have passed, Ronan Point is still used in university lectures as a seminal example of how not to design buildings.
In 1968, a small gas explosion on the 18th floor of the newly-constructed, 22-storey tower block in east London caused a catastrophic collapse of a whole corner of the entire tower. Miraculously only four people were killed.
The causes of the disaster were found to be wide ranging and the consequences had a massive impact on the engineering industry. For the first time, the now fundamental concepts of robustness, and progressive and disproportionate collapse were being thought about.
The tower was built using a prefabricated kit of concrete parts, a new concept developed after the Second World War in response to the need to deliver more homes, faster. Off-site manufactured, precast concrete panels were used as supporting walls for the precast concrete floor slabs above. To “glue” the joints together, the gaps between the elements were supposed to be filled with concrete.
But the new construction technique was swiftly questioned when the small gas explosion was able blow out three load bearing, storey height flank wall panels. This caused the floor panels above to collapse onto the storeys below, causing a progressive collapse of the wall and floor slabs below for the full height of the tower block.
As with many disasters, the investigation found a number of factors which contributed to its collapse, and a number of other issues with the way buildings were designed and built.
One of the most dramatic impacts the accident had, was to change the way buildings were fundamentally designed. Instead of simply building a “house of cards”, the building codes were updated to make sure elements were connected, beams to slabs, slabs to columns, facades to slabs and so on. If one element was removed, loads would be redistributed around the structure saving the rest of the building from collapse – it would not cause a failure, disproportionate to the event.
“The concept of tying and redundancy and alternative load paths, even if serviceability is compromised, the need to try and make sure your structure has some redundancy, is fundamental to the way we now think about things,” says Concrete Centre principal structural engineer Tony Jones.
This concept is now ingrained in design and has become accepted practice.
Another change that had to be made was to the wind code. In the investigation it was found that the code did not adequately address the wind pressures to be considered on such tall structures.
“The wind code was never envisaged was never used for designing a structure like that,” says Jones. “It’s perhaps an example of where the codes didn’t keep up with the pace of the building industry.”
While the investigation into Ronan Point resulted in a number of important changes, one negative impact was felt within the prefabrication industry.
“Pre-fabrication took a step back [because of the impact of Ronan Point] until around five to six years ago when Laing O’Rourke has started to revive it,” says Aecom structure practice lead, UK & I Paul Nuttall. “All that progress that could have happened has fallen to bits. Just think where would it have actually gone in the last 50 years.
“We’re only just coming out of the shackles of the prefabrication aspect of it”
The investigation also brought into focus the way buildings were constructed on site.
It was found that joints were not properly detailed, and that where panels failed to fit together as they should have done, a brute force and ignorance approach was taken to making structural connections.
“What brought them to a head was the poor construction where either they were things which meant to fit and didn’t, the workmen failed to make the right connections appropriately,” says Mott MacDonald head of materials and corrosion technology Paul Lambert. “There were ties which didn’t tie anything and gaps which were filled with cigarette packets.”
Lambert added that the disaster did bring about a greater awareness of quality control and supervision of work on site with the introduction of toolbox talks on site.
“Ultimately the best outcome from every disaster is that people learn from it should, and they did from Ronan Point,” says Lambert.
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