thoroughfare by up to 3m, and carry
the loads of 21-storeys above, back into
the main frame.
As previously mentioned, Colmore
Row has a couple of high-level steps
(set-backs) in its design. At level 18
this forms a 278m2 private outdoor
terrace for tenants, while two further
steps are located on either side of the
building at floor 21, forming what have
been dubbed the structure’s shoulders.
Above the shoulders, one portion
of the structure rises to the building’s
full height. This contains a kitchen
and back-of-house zone on level 23,
while the remaining uppermost floors
will house the Lantern restaurant that
overlooks the city of Birmingham.
Summing up, Waheed Nazir,
former Corporate Director Economy
at Birmingham City Council, says:
“103 Colmore Row is a massive
vote of confidence in Birmingham.
The commitment to this major new
building will bring high quality office
space to the heart of an expanding
central business district and shows
that Birmingham continues to be a
hugely attractive place to invest and do
103 Colmore Row is scheduled for
practical completion in June 2021.
HISTAR® is produced by ArcelorMittal in S355 and S460. The
advantages of ‘regular’ S460 over lower grades are clear – increased
strength means comparatively smaller sections of lighter weight
and more usable space. For rolled sections in compression, such as columns,
a further advantage of S460 is that the buckling curves in BS EN 1993-1-1
improve by either one or two steps. In the critical minor axis, for rolled
column profiles with a flange up to 100 mm, the specified curve improves
from curve “c” to curve “a”, representing a significant increase in resistance.
If the member is fabricated by welding, Table 6.2 of BS EN 1993-1-1
specifies the same buckling curve for all steel grades. The “mega columns” at
Colmore Row were fabricated from plate with twin webs – the advantage of
S460 in this case is the increased strength.
HISTAR® is manufactured in accordance with a European Technical
Approval (ETA) 10/0156. Importantly, the design strength for HISTAR® S460
does not reduce until the material thickness exceeds 100 mm. Compared
to the design strength from BS EN 10025-4, which specifies a reduced
design strength at thickness steps of 16, 40, 63 and 80 mm, the increase in
resistance can be significant. In HISTAR®, the 90 mm flanges have a design
strength of 460 N/mm², compared to 400 N/mm² for ‘regular’ S460.
ETA 10/0156 also specifies the correction factor βw to be used with
HISTAR® S460 for fillet welds as 0.8, in contrast to the value of 1.0 specified
in Table 4.1 of BS EN 1993-1-8. The use of βw = 0.8 leads to a higher weld
strength and thus smaller weld sizes compared to ‘regular’ S460.
The Carbon Equivalent Value (CEV) is a critical material characteristic when
preparing welding procedure specifications – a higher CEV makes defect-free
welds more difficult. The maximum CEV for HISTAR® S460 up to 63 mm thick
is 0.41, which compares favourably with 0.47 for ‘regular’ S460 of the same
Fabricated box sections offer opportunities to adjust the cross-section to
suit the applied loading and buckling length in both axes. The disadvantages
are the fabrication effort and for closed cross sections, the possible
complexity of the connections. Connections to box sections are often via fin
plates, or beam stubs, or by ‘blind’ fixings with access from one side only.
Mega columns at Colmore Row
David Brown of the SCI considers the use of S460
HISTAR® used for the “mega columns” at Colmore Row
Four mega columns
support the front of
the building and create
a four-storey winter