Vulnerability assessment of reinforced concrete structures for fire and earthquake risk - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 372

Onset of cooling - column A

Onset of cooling - column B

0.004
0.002
0.000
-0.002
-0.004
-0.006
-0.008

Time (hours)

0 5 10 15 20 25 30

Column A

Failure

Column B

Loading after cooling

14.8 Time history of the axial deformation ratio response for Column
A and Column B (test data).

14.5 Residual seismic resistance of fi re-damaged

building columns

This case study explores the second scenario in which residual seismic load
capacity of fi re-damaged structural elements is investigated. For the purpose
of this case study, two reinforced concrete columns, Column A and Column
B, made with siliceous aggregate, previously tested at the National Research
Council Canada (Lie et al. , 1986), were selected. The clear height of both
column specimens was 3760 mm. Column A was exposed to a standard fi re
ASTM E-119 for one hour and Column B was exposed to the same fi re for
two hours. A constant axial load was applied during the test. After terminat-
ing the fi re, the two columns were kept intact until they reached ambient
temperature. Then, they were then loaded until they reached their axial load
failure. Figure 14.8 shows axial deformation response of the two columns
during the fi re test, the cooling phase, and the fi nal loading.
A numerical analysis was carried out using VecTor3 (2008), a nonlinear
fi nite element analysis program for three-dimensional reinforced concrete
solid structures subjected to quasi-static load conditions developed at the
University of Toronto. The analysis was fi rst done for these two column
specimens for the purpose of model validation under the axial load. Then,
the same numerical analysis was carried out using the software to estimate
the residual seismic capacity of the two columns.

14.5.1 Axial load response analysis (verifi cation)

Maximum temperatures reached at various depths, in the cross-section of
the two columns, during the heating and cooling period were obtained and
averaged from the test results (Lie and Woollerton 1988) as illustrated in
Fig. 14.9. Then, the numerical simulation was carried out to evaluate the