Inappropriate design 33
unfortunate example of progressive collapse. In a more robust bridge design
(Ionită et al. 2009), the consequences of a badly conceived detail would
have been less dramatic.
2.2.2 sinking of the sleipner a offshore
platform, norway, 1991
One of the most impressive failures of a man-made structure was the sinking of the Sleipner A offshore platform in Norway in 1991 (Collins et al.
2000). The Sleipner A platform was a concrete base structure consisting of
24 cells and 4 shafts, 110 meters high. On August 23, 1991, as the platform
was gradually positioned deeper into the water of a fjord near Stavanger
in order to mount the platform deck on top of the 4 shafts, a sudden leak
occurred in one of the cells. The entire platform sank to the sea bottom,
causing a seismic event of magnitude 3.0 on the Richter scale, and only
leaving a pile of concrete rubble in the deep fjord. The economic losses were
enormous, going into hundreds of millions of American dollars.
At the request of the Norwegian structural engineering firm responsible
for the design of the Sleipner A platform, Professors Collins and Vecchio
of the University of Toronto, Canada, thoroughly studied the reasons for
the dramatic loss of the platform (Collins et al. 2000). They came to the
following conclusion: “While the exterior walls of the cells were circular,
with a radius of 12 meters, the interior walls, which separated the cells,
were straight. At the interior section points of these interior walls, a small
t riangular void called a tricell was formed. There were a total of 32 such
tricells. Because these tricells had openings at the top, they filled with
water once the top of the cells were submerged. Therefore, the walls of
Figure 2.4 View of failed hinge of tensile pendulum pillar (with corroded prestressing
wires).
unfortunate example of progressive collapse. In a more robust bridge design
(Ionită et al. 2009), the consequences of a badly conceived detail would
have been less dramatic.
2.2.2 sinking of the sleipner a offshore
platform, norway, 1991
One of the most impressive failures of a man-made structure was the sinking of the Sleipner A offshore platform in Norway in 1991 (Collins et al.
2000). The Sleipner A platform was a concrete base structure consisting of
24 cells and 4 shafts, 110 meters high. On August 23, 1991, as the platform
was gradually positioned deeper into the water of a fjord near Stavanger
in order to mount the platform deck on top of the 4 shafts, a sudden leak
occurred in one of the cells. The entire platform sank to the sea bottom,
causing a seismic event of magnitude 3.0 on the Richter scale, and only
leaving a pile of concrete rubble in the deep fjord. The economic losses were
enormous, going into hundreds of millions of American dollars.
At the request of the Norwegian structural engineering firm responsible
for the design of the Sleipner A platform, Professors Collins and Vecchio
of the University of Toronto, Canada, thoroughly studied the reasons for
the dramatic loss of the platform (Collins et al. 2000). They came to the
following conclusion: “While the exterior walls of the cells were circular,
with a radius of 12 meters, the interior walls, which separated the cells,
were straight. At the interior section points of these interior walls, a small
t riangular void called a tricell was formed. There were a total of 32 such
tricells. Because these tricells had openings at the top, they filled with
water once the top of the cells were submerged. Therefore, the walls of
Figure 2.4 View of failed hinge of tensile pendulum pillar (with corroded prestressing
wires).