Vulnerability assessment of reinforced concrete structures for fire and earthquake risk - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 365

change in the concrete strength capacity due to the induced seismic
deformation.
Fire load after an earthquake will be dependent on the amount of com-
bustible materials in the buildings, e.g. furniture and plastic produces, at the
time of the earthquake. A design fi re could be developed based on the
available fi re load and ventilations. However, considering a worst case sce-
nario and for simplicity, a standard fi re was considered in this study for fi re
resistance evaluation of the building. A standard fi re curve is a time-tem-
perature curve, e.g. ASTM E119 (2007), which is used for fi re resistance
tests of structural elements. The results presented in the following section
could not be applied for any building under a fi re following an earthquake.
Types of structural materials, combustible contents in the building, location
of fi re, building geometry and fi re compartmentations are among the many
other major factors that could change the outcomes.
14.4.1 Building structure specifi cations
The six-storey nearly full-scale reinforced concrete building has a total
height of 15 meters, (Kabeyasawa et al. 2005). The building was previously
tested on a shaking table under the 1995 Kobe ground motion at the
E-Defense Miki (or Hyogo), Japan. Details of the structural system, dimen-
sions, and material properties can be found in Kabeyasawa et al. (2005).
Figure 14.2 shows a picture from the building specimen on the shaking
table.
14.4.2 Structural performance of building in fi re with and
without seismic damage
To better understand the effects from the earthquake damage on the fi re
resistance of the structure, the building was numerically analyzed for two
scenarios; (1) for a fi re without any prior earthquake or damage, and (2)
for a fi re following an earthquake with seismic damage. A fi nite element
modeling technique using a structural analysis program called SAFIR
(Franssen, 2007) was employed to model the building specimen. First, analy-
sis was carried out for scenario (1) to assess fi re resistance of the building
before having any seismic damage to the structure. It was assumed that the
fi re started on the fi rst fl oor but was confi ned in the same fl oor and had not
spread to other levels of the building. As a worst case scenario, the analysis
was carried out for an eight hour fi re exposure. A typical fi re in such build-
ings may last less than this time. The eight hour fi re exposure was selected
to induce failure of the building in the fi rst scenario.
In the second scenario, fi re resistance of the building was evaluated after
it was damaged by the earthquake, which was the input seismic excitation