Lecture 13

Question 1

30. What were the reasons that the 22-storey tower block of flats, known as Ronan Point, was constructed of the Larsen-Nielsen precast concrete system of large panels in 1967/68, and which of today’s basic requirements in structural design (refer to Slides 4-8 to 4-14) did the tower’s design and execution not have to satisfy

Answer 1

• There was a sudden increase in housing demand due to the increasing population so the use of precast concrete to make singular apartments and stack them on top of each.
• Pre-cast concrete was a cheap and easy to build.
• The pre-cast concrete tower blocks were imported from Europe, where only some were modified with the UK regulations.
• The blocks were never intended to be more than 6 blocks high.
• The blocks lack redundancy as one element failed the whole tower collapsed. There was no regulations that the blocks needed to have structural redundancy and progressive collapse.
• In the design the walls supported the floors above and the floors supported the walls above

Question 2

31. What error did the engineers and architects on the Ronan Point project make before the first panel to the tower was erected?

Answer 2

• The engineers tampered with the design as the tower was never meant to be built for more than 6 floors.
• This is down to human error.
• Walls and floors were all made from pre cast concrete then lowered into place
• There was no steel frame.
• The stability came from the dead weight carried down the crosswalls.

Question 3

32. What features of the panel system in the execution of the Ronan Point Tower led us to refer to it as a house of cards, and what would you understand if a professional engineer used this term when in a conversation about the L’Ambiance Plaza apartment building that collapsed in 1978 like a “house of cards”

Answer 3

• Collapsed like a house of cards as it was a progressive collapse. When one member failed and collapsed it caused the other member to also collapse. This is due to no redundancy.
• In the other disaster the concrete slabs all fell on top of each other causing the one below to collapse.

Question 4

33. The house of cards collapse of the South-East corner to Ronan Point was cause by a series of domestic gas explosions. Following the incident, what average pressure (in kN/m2) did the inquiry team determine could have caused the blow out of an outer wall panel in Miss Ivy Hodge’s lounge, and the disproportionate collapse? How does this pressure from the explosions compare to the actual pressure in the kitchen, as determined by the forensic engineering investigation

Answer 4

• The average pressure of the explosion was between 21-63
• However the wall would have blown out at a average pressure of 21 which is a third of the actual explosion
• The joints had no resistance to the expolsion.

Question 5

34. What might have been the consequence of the same series of gas explosions at the third storey on the South-East corner of Ronan Point, and why

Answer 5

• The disaster might have been prevented by the extra frictional force from thr dead weight.

Question 6

35. Even if the gas explosions on 16 May 1968 had not started to expose the deficiencies in the Ronan Point Tower, give three more of the inquiry’s findings that could have been a root cause to a “house of cards” collapse? With what basic requirement in structural design are these findings to be associated

Answer 6

• The design was for a wind speed of 63mph but the tower was 60 m above ground and could reach 105mph wind speeds. The suction of the wind could have caused a similar effect.
• Impact of heat of a fire could have done the same thing
• The quality of construction was questionable with also poor workmanship.
• These are poor ductility and edundancy

Question 7

36. Following the inquiry lead by Sir Arthur Pugsley the government agreed a dual standard with all new system-built flats having to resist explosions of 34 kN/m2, but existing ones having to be strengthened to withstand a loading of only 17 kN/m2. As this latter pressure loading is below that in the Ronan Point disaster what other measure was taken, with other 1960s multi-storey blocks of flats, to prevent a similar failure from happening again? What might a present owner of one of these flats do that could compromise this other essential safety measure, first enforced in the early 1970s

Answer 7

• The south-east side was rebuilt and the rest of the structure was reinforced with blast angles, tied the walls and floors together.
• The mains gas was removed