Royal Plaza Hotel, Thailand
Group 24
On Friday 13th August 1993, the Royal Plaza Hotel collapsed suddenly
without any warning. In less than ten seconds, the entire building had
collapsed, trapping 379 people. 137 people died and 227 people were also
seriously injured. There was no obvious reason for failure, as there were
no harsh environmental conditions at the time and no construction work
had been carried out on the building for the last three years.
The Design of the Building:
The initial date of construction for the structure was not available in any of
our resource data, but we do know that the original structure comprised
of three storeys and an underground level. According to construction
permits issued in 1983, the building was used as a massage parlour prior
to becoming a hotel. In 1985, the local building authority granted
permission to convert the three storey building into a hotel. In 1990, a
permit was issued allowing the owners to add additional storeys to the
building. The only testing that was requested by the planning authority,
involved testing the soil to ensure that the original foundations could carry
the extra load with a sufficient safety factor. Tests deemed the
foundations to be strong enough. No testing of the columns has been
recorded.
Uncommon characteristics of failure:
1. The last recorded modification to the building took place three years
prior to the collapse. This is unusual, as most structures fail during
or just after modifications to the building are added.
2. There was no extreme or harsh environmental conditions or
extraordinary large loads applied to the building at the time of
failure. These reasons often factor in the event of a sudden
collapse.
Investigation of the Collapse:
After the collision, several Engineering Bodies launched an investigation.
Detailed studies were carried out on several aspects of the building. This
included
1. Tests on concrete strength
2. Tests on the rebar
3. Soil tests
Tests on the concrete samples taken from the rubble on the site proved
the concrete to be of 10-15 MPa and have reliability of 95%. This
conforms to standards and shows that there was no deficiency in the
quality of the concrete.
Reinforcing steel bars recovered from the site were tested and all
conformed to standards.
Tests carried out showed that the bearing capacity of the soil was
sufficient to support the structure, even with the additional three storeys.
After the excavation took place, the foundation was found to be in good
condition and not the cause of failure.
Cause of Failure:
The collapse was compared to that of a dynamite blast as the building fell
so quick and in a vertical fashion, with little debris to the sides.
Creep deformation:
After eliminating other unlikely causes, the most likely cause of column
failure is due to creep in the ground floor columns, which were under high
stresses. After the addition of three more stories some columns on the
ground level carried dead loads of up to 80% of their strength capacity.
Over the three years micro cracks developed and began to spread in these
overloaded columns. Creep deformation occurred in these columns and
they became shorter than neighbouring columns. This lead to an uneven
distribution of the load causing other columns to be overloaded and be
affected by creep deformation, this redistribution of the load continued
and gradually all of the columns on the ground floor were affected.
Fig 1: Picture showing shear stresses
and shear failure in a short strut
under a compressive load.
Progressive Failure:
When the load in one column exceeded its strength capacity the column
collapsed, as all the columns on the ground floor had been deformed and
weakened and were under loads close to their capacity, the progressive
collapse of all the columns on the ground floor occurred within seconds of
the initial columns collapse.
The addition of three extra floors and their associated loads on the same
set of columns, which had originally designed for three floors, reduced the
safety factor to almost zero. If there had been a higher factor of safety,
one failed column would not cause the building to fail. As the factor of
safety was so low, the other columns on the ground floor were unable to
take the extra load and failed.
Fig 2: Progressive column failure. Diagram shows 1st column failure due to explosive but
mode of failure is analogous to the Royal Plaza Hotel collapse.
Conclusion
Normally in a building a reasonably large safety factor is added to all the
components of the structure. This means that in a properly designed
building if one of the parts of the building is overloaded and fails, the load
will be redistributed and only local failure occurs and not total collapse.
In this particular case economic reasons caused the client, architect and
engineer to cut corners and to sacrifice the safety of the building for a fast
and cheap construction.
Following this disaster stricter guidelines were put in place in Thailand.
Public Universities were ordered to examine the structural stability of 218
buildings, many of which received recommendations for renovation. Also
registration for engineers became much stricter. Guidelines for building
public buildings were also introduced. A third party engineer is required
to crosscheck designs and be held jointly responsible.
Reference:
http://www.thaiengineering.com/column/lesson_disaster/ryplaza_web.asp
http://www.ce.berkeley.edu/~astaneh/1-Publications/Astaneh9ASEC%20%20Blast%20Paper%202003.pdf
J.E. Gordon – “Structures or Why Things Don’t Fall Down”