Repair and reconstruction of civil structures - Assessment and Refurbishment of Steel Structures - page 181

There was also a local fire on the first floor. The middle column V1 and the middle
longitudinal stiffener between bonds 0 and 1 were damaged. The middle column was
slightly bent (the maximum deviation over the full height from the floor was 20.0 mm)
and in its lower region there was buckling of the column wall. The nature of this buckling
and size of the deviation are shown in Figure 5.61.
In order to determine the effect of the fire on the properties of the steel work, a
stretching test and a notch toughness test were carried out. Specimen material was taken
from the lower chord of the middle longitudinal stiffener between bonds V2 and V3 on
the first floor and from the lower table of the middle stiffener 0-1 on the ground floor. In
the streching test, the yield value, ultimate strength, elongation, and contraction were
measured.
The results of the test were as follows:
• The structure was made of 37(S235) steel
• The yield values and ultimate strength showed a wide spread but were within normal
limits. Only the ultimate strength of specimen No.1 was lower than that assumed for
S235 steel
• The elongation and contraction measures were relatively high for all specimens,
providing evidence of that the material properties of the steel used were sound.
• The notch toughness of test bodies 1, 2a and 2b was relatively low, reaching only 40 to
50 per cent of the notch toughness of test bodies 3a, b and c.
Figure 5.60 Deformation of the beams
at the top of the window frames
between bonds V1 and V2 in the south
bay