Building with earth - Gernot MINKE (1)

15.3
Earthquakes are caused by the movements
Therefore, one of the main structural tasks
of tectonic plates or by volcanic activity. The
when designing earthquake-resistant build-
world’s most earthquake-prone regions are
ings is to insure that walls do not fall out.
shown in 15.3. In Asia, earthquakes with
intensities of 8 on the Richter scale have
been recorded; in the Andes, ones measur-
Structural measures
ing up to 8.7. Annually, nearly a hundred
earthquakes are recorded with intensities
When designing for earthquake-prone
above 6, and twenty with intensities above
zones, it should be considered that the seis-
7 on the Richter scale. Several thousand
mic forces acting on a building are propor-
people are affected by earthquakes every
tional to its mass, and that deflection
year.
Buildings are mainly struck by the horizontal
increases significantly with height. When
designing two-storeyed buildings, therefore,
15.6
acceleration created by the movement of
it is advisable that the ground floor be built
the earth. The vertical accelerations created
solid, while the upper floor is kept light,
by seismic activity are less then 50% of the
preferably with a flexible framed structure.
horizontal ones.
Heavy roofs with slabs, slates and tiles
Since loam buildings are rarely higher than
should be avoided in principle.
two storeys, this section mainly discusses
Walls usually fall outwards because they lack
the earthquake resistance problems of these
a closed ring beam, sufficient bending and
kinds of buildings.
In one- or two-storeyed buildings, the prin-
shear strength, and because door and window
openings weaken the wall structure.
bad good ideal
ciple danger during earthquakes is that
Under seismic influences, forces are concen-
walls will fall out and roofs will come down.
trated into the corners of these openings,
creating cracks. In order to reduce the danger
of collapse, the following points should
be kept in mind:
1. Houses should not be located on inclined
sites (15.4).
2. The building’s resonant frequency should
dangerous
safe
15.5
not match the frequency of the earth movement
during earthquakes. This means that
heavy houses with solid construction should
15.2
not rest on hard rock bases, but instead on
136
Earthquake-resistant building