Ronan Point Collapse
Group 1: John Mulhaire
Robert Patterson
David Hatch
Robert Morgan
Introduction
On the morning of 16th of May 1968 an explosion caused the collapse of one
corner of a 23 storey block of apartments in Clever Road, Newham in east London killing
4.
Ronan Point was named after Harry Ronan (a former Chairman of the Housing
Committee of the London Borough of Newham). It was modern architecture's Titanic,
and spelled the end of the high-rise as a viable solution to the post world war 2 housing
crisis. This new style of housing could facilitate large numbers of people, save land and
labour, and be constructed quickly.
The tower was built by Taylor Woodrow Anglian using a technique known as
Large Panel System building or LPS. Building started in 1966, and construction was
completed on 11 March 1968. It cost approximately £500,000 and had a life expectancy
of 60 years.
Construction
The Ronan Point Apartment Tower was constructed using the Larsen-Nielsen system.
This system was developed in Denmark in 1948. The Larsen-Nielson system was
“…composed of factory-built, precast concrete components designed to minimize on-site
construction work.
The use of prefabricated concrete members - large panel systems
Here, a set of concrete parts are made at a factory and are transported to the site.
Walls, floors and stairways were all precasted, where they are then lifted into
place with a crane and then joined together. This joining process requires
precision and skill, and it is thought that the failure to join the panels correctly led
to the Ronan Point collapse. The structure of Ronan Point and other LPS
buildings of the time relied on gravity holding everything together.
Each floor was supported by the load bearing walls directly beneath it. Gravity load
transfer occurred only through these load-bearing walls. This wall and floor system fitted
together in slots. These joints were then bolted together and filled with dry pack mortar
to secure the connection
Collapse
The southeast corner of the Ronan Point Tower collapsed on May 16, 1968 at
approximately 5:45 a.m. The collapse was initiated by a gas-stove leak on the eighteenth
floor in apartment ninety. The force of the explosion knocked out the opposite corner
walls of the apartment. These walls were the sole support for the walls directly above.
This created a chain reaction in which floor nineteen collapsed, then floor twenty and so
on, propagating upward. The four floors fell onto level eighteen, which initiated a second
phase of progressive collapse. This sudden impact loading on floor eighteen caused it to
give way, smashing floor seventeen and progressing until it reached the ground
Cause of failure
Due to massive pressure from the public a panel was formed by the government to
investigate the collapse. The report which was published later that year showed the the
collapse was initiated by the gas explosion. A sub standard brass nut was used to connect
the hose to the stove. The nut had a thinner flange than the standard nut.
The building research station and college of London proceeded to perform extensive
battery tests to show how much force internally Ronan point could withstand. The results
showed that the walls could have been displaced by a pressure of 19.3kPa. however it
was estimated that the kitchen and living room walls were displaced at a pressure of only
1.7kPa while the exterior wall was moved at a gas pressure of 21kPa
Ultimately, the collapse of Ronan Point was due to its lack of structural redundancy. It
had no fail-safe mechanisms, and no alternative load paths for the upper floors should a
lower level give way. Without any type of structural frame, the upper floors had no
support, and fell onto floor seventeen. The panels forming floor seventeen could not
support the sudden loading caused by the upper five floors that fell on it. They then gave
way, and the process continued until it reached the bottom level.
The southeast corner of Ronan Point was rebuilt as a separate section of apartments and
then joined to the existing building by means of walkways. Ronan Point was reinforced
with blast angles as part of the reconstruction. Gas was also banned from Ronan Point
Technical aspects
The inquiry revealed that strong winds and/or the effects of a fire could also have caused
a progressive collapse. The building was designed to withstand wind velocities of 63mph.
However a wind of 105mph could be expected at 200 feet above the ground every
60years, within the life expectancy of the building. The building code used for the design
of Ronan Point and its sister buildings was issued in 1952.This set of codes were not kept
up to date. In 1963 a new study was produced showing higher than stated winds were
likely to occur. According to the study,
“the suction effect of the pressures applied by such winds in particular the opening of the
joints as the tower block bent in the wind, would have similar effect to the explosion.”
Fire also would have had a similar effect on Ronan Point. The study stated, “it is
estimated that fire could so expand and ‘arch’ the floor slab and bend the wall panel, as to
displace or rotate an H-2 joint to a dangerous degree.” (Wearne, 2000). Upon architect
Sam Webb’s recommendation, a fire test was conducted sixteen years after the collapse
of the southeast corner, which verified this theory. Webb had followed the issues
concerning Ronan Point since its partial collapse. He predicted that after approximately
fifteen years of service, Ronan Point would develop serious structural problems,
especially with the joints In a conversation with some tenants of Ronan Point he stated,
“there would be gaps between walls and floors through which smoke would pass; that
you’d be able to hear people and their television on different floors.”
Professional Aspects
The findings of such magnitude of poor workmanship performed in the construction of
Ronan Point led to the demolition of the remaining Larsen – Nielson system built towers.
At the time these buildings were erected, the building codes did not adequately address
them. Large concrete panel construction was the height of innovation at this time, and
little was known about how it would perform. The building regulations in effect at the
time contained a ‘catch all’ clause known as the ‘functional requirement on structure’.
This clause contained no mention of redundancy or progressive collapse (Bignell
1977).
The collapse of the southeast of Ronan Point initiated changes to the regulation codes.
Building codes now take in account for the possibility of progressive collapse and of
forces from an internal explosion. The codes also require minimum amounts of ductility
and redundancy.
The concept of quality control in the construction process was recognized after the
dismantling of Ronan Point. Although the design flaw was the primary downfall of
Ronan Point, poor construction quality could have led to future problems with the
building’s structural integrity. It is imperative that quality control is enforced in the
construction process to ensure public safety. “As with all other construction materials,
the best designs in pre-cast and pre-stressed concrete can be ineffective unless the work
done in the field is of high quality. If the design is marginal, construction deficiencies
can compound the errors increasing the potential for serious problems. (Feld and Carper,
1997).
Educational Aspects
There are a few lessons that can be learned from this collapse. Firstly it is an example of
what can happen when an alternative load path is not provided. We can learn from this
the importance of building codes and the importance of monitoring construction quality.
References
www.lalamy.demon.co.uk/ronanpnt.htm
en.wikipedia.org/wiki/Ronan_Point
www.open2.net/modernity/3_13.htm
shippai.jst.go.jp/en/Detail?fn=2&id=CA100063