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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
Short steel and concrete columns under high temperatures
umn 1 in the series C63-60 (C63-60-1) as an example. Although
the yield strength diminished for the column subjected to the oven
before the static test, the behavior of the column was modified rela-
tive to the column that remained at room temperature, increasing
its ultimate strength. The actual yield strength also ceases to be
well defined for the heated column. This finding was repeated in all
of the tests. A potential cause for this result could be a modifica-
tion in the microstructure of the steel, which caused the composite
column to behave differently.
Figures 7 – 9 and 10 – 12 present the temperature increase
on the surface of the steel tube, at the steel-concrete inter-
face and in the concrete core for the 30- and 60-minute tests,
respectively.
Figure 9 shows the behavior of the temperature in the concrete
core and suggests that the temperature was lower in the tubes with
larger diameters and thicknesses.
Figures 10 – 12 show the graphs for the 60-minute exposure
time for the elevation of temperature on the surface of the steel
Figure 5 – Yield Strength: columns at room temperature X columns after exposure to high temperatures
Table 3 – Maximum temperatures and yield strengths
F – Yield strength for the columns at room temperature
u
q
F Yield strength for the columns after cooling
u.
–
GROUP
Composite TRRF Oven
Temp.
Steel
Temp.
Concrete
Temp.
F
u
q
F
u,
F
u
q
F
u,
Column
(min)
(°C)
(°C)
(°C)
(kN)
(kN)
C 6-30
1
30
890
800
290
900
850
0.944
2
30
890
500
150
900
950
1.056
S 6-30
1
30
880
570
150
900
900
1
C 6-60
1
60
1,200
1,140
690
900
500
0.556
2
60
940
630
370
900
860
0.956
S 6-60
1
60
940
670
440
900
970
1.078
C 8-30
1
30
750
700
170
1,200
1,000
0.833
2
30
880
500
150
1,200
S 8-30
1
30
880
450
170
1,200
1,200
1
C 8-60
1
60
860
810
660
1,200
1,040
0.867
2
60
940
630
380
1,200
1,200
1
S 8-60
1
60
900
640
470
1,200
1,200
1
C 63-30
1
30
750
550
125
1,400
1,400
1
2
30
890
450
100
1,400
1,400
1
S 63-30
1
30
890
450
100
1,400
1,400
1
C 63-60
1
60
945
650
250
1,400
1,400
1
2
60
940
590
230
1,400
1,400
1
S 63-60
1
60 950
700
330
1,400
1,400
1