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broken. Therefore, joint elements which connect different elements are introduced and behaviors are
examined.
Case A
In Case A, joint elements are not considered. Only contact forces are taken into account and joints
cannot resist tension forces.
CaseB
In Case B, joint elements are considered. So, not only contact forces but also tension forces are taken
into account. During the 1995 Hyogo-ken Nanbu earthquake, many old wooden houses were collapsed
because the first floor was smashed by the strong seismic motion. In many cases, second floor
remained without being broken. We can presume that the joints of the first floor were too weak to
sustain the strong shock of the earthauake. Therefore, we assumed that the joint strength of the first
fl
Table 4.1 Contact parameters
o. _.._ n no
Fig.4.1 Two-story structure model
A*
K n (N/m)
K^N/m)
C fl (N-sec/m)
K n (Nlm)
Human body
0.277
7.949xl0 4
3.974xl0 4
2.095xl0 3
0.0
Structured/kg)
0.677
3.944xl0 4
3,944xl0 4
1.256xl0 3
1.256xl0 3
Case C
In Case C, joint elements are considered. If all joints were strong enough to sustain the earthquake,
houses could avoid collapse and many people could survive. Therefore, we assumed that the joints of
the first floor are as strong as those of the second floor.
Modeling of the human body
The human body is modeled as a circle element. The radius r and the density p have been evaluated
as 0.26m and 1.706xl0 2 (£g/m 3 ), respectively, using physical examination results. The mass and
inertia moments are calculated according to these values. Four human elements are put on each floor,
and the impact accelerations experienced by these people are computed. The human elements on the
first floor are numbered as 1, 2, 3, and 4 from the left, and those on the second floor are numbered as
5,6, 7, and 8 from the left.
Spring constant and Damping
Coefficient
Spring constant and damping coefficient (K H ,K^C a ,C^
of wooden houses are assumed to be