Inappropriate design 37
reported, whereas the average is below five. By the end of 2010, a substantial amount of snow, in certain regions mounting to about 40 cm, caused
several cases of collapsing roofs. The combination of reduced attention to
snow loading during design and the exceptionally high snow loading in
2010 significantly contributed to the high number of collapses (around 40
in a few weeks time). A major aspect seems to be that designers seldom
considered the so-called ‘ponding effect’ on flat roofs, while this is crucial
information for a correct dimensioning of the emergency water evacuation
system in case the normal water evacuation is blocked, e.g. due to ice formation as was the case here (Parmentier and Van de Sande 2011).
2.3.2 tohoku earthquake and tsunami,
Japan, March 11, 2011
On March 11, a magnitude 9.0 earthquake hit the east coast of Japan, also
hitting the nuclear power plants in Fukushima. Although buildings and
other structures could reasonably well withstand the impact of the earthquake (Japan has a long experience with earthquake resistant structures),
it was rather the quickly following tsunami that caused most of the damage
(and unfortunately thousands of casualties).
According to Clenfield et al. (2011), Japan has suffered 195 tsunamis
since the year 400. Three in the past three decades had waves of more than
10 meters. A 7.6-magnitude quake in 1896 off the east coast of Japan even
created waves as high as 38 meters, while an 8.6-magnitude quake in 1933
led to a surge as high as 29 meters.
The tsunami following the recent Tohoku earthquake in March 2011 also
had wave heights up to 38 meters. Although Japan has invested the equivalent of billions of dollars on anti-tsunami seawalls which line at least 40% of
its almost 35,000 km coastline and stand up to 12 meters high, the tsunami
simply washed over the tops of some seawalls, collapsing some in the process
(Onishi 2011): ‘The height of seawalls varies according to the predictions of
the highest waves in a region. Critics say that no matter how high the seawalls are raised, there will eventually be a higher wave. Indeed, the waves
from Friday’s tsunami far exceeded predictions for Japan’s northern region’.
2.3.3 collapse of the tacoma narrows suspension
bridge, usa, 7 november 1940
All students studying structural behaviour will surely know about the
Tacoma Narrows suspension bridge which collapsed in 1940. During the
design of the Tacoma bridge however, the phenomenon later causing its collapse was simply not known to structural engineers. The bridge pushed the
limits of the state-of-the-art, and, by failing, became a textbook example
for avoiding similar failures in future.
reported, whereas the average is below five. By the end of 2010, a substantial amount of snow, in certain regions mounting to about 40 cm, caused
several cases of collapsing roofs. The combination of reduced attention to
snow loading during design and the exceptionally high snow loading in
2010 significantly contributed to the high number of collapses (around 40
in a few weeks time). A major aspect seems to be that designers seldom
considered the so-called ‘ponding effect’ on flat roofs, while this is crucial
information for a correct dimensioning of the emergency water evacuation
system in case the normal water evacuation is blocked, e.g. due to ice formation as was the case here (Parmentier and Van de Sande 2011).
2.3.2 tohoku earthquake and tsunami,
Japan, March 11, 2011
On March 11, a magnitude 9.0 earthquake hit the east coast of Japan, also
hitting the nuclear power plants in Fukushima. Although buildings and
other structures could reasonably well withstand the impact of the earthquake (Japan has a long experience with earthquake resistant structures),
it was rather the quickly following tsunami that caused most of the damage
(and unfortunately thousands of casualties).
According to Clenfield et al. (2011), Japan has suffered 195 tsunamis
since the year 400. Three in the past three decades had waves of more than
10 meters. A 7.6-magnitude quake in 1896 off the east coast of Japan even
created waves as high as 38 meters, while an 8.6-magnitude quake in 1933
led to a surge as high as 29 meters.
The tsunami following the recent Tohoku earthquake in March 2011 also
had wave heights up to 38 meters. Although Japan has invested the equivalent of billions of dollars on anti-tsunami seawalls which line at least 40% of
its almost 35,000 km coastline and stand up to 12 meters high, the tsunami
simply washed over the tops of some seawalls, collapsing some in the process
(Onishi 2011): ‘The height of seawalls varies according to the predictions of
the highest waves in a region. Critics say that no matter how high the seawalls are raised, there will eventually be a higher wave. Indeed, the waves
from Friday’s tsunami far exceeded predictions for Japan’s northern region’.
2.3.3 collapse of the tacoma narrows suspension
bridge, usa, 7 november 1940
All students studying structural behaviour will surely know about the
Tacoma Narrows suspension bridge which collapsed in 1940. During the
design of the Tacoma bridge however, the phenomenon later causing its collapse was simply not known to structural engineers. The bridge pushed the
limits of the state-of-the-art, and, by failing, became a textbook example
for avoiding similar failures in future.