Technical
24 NSC
Apr 20
core is certainly seen as more expensive in terms of initial cost.
However, a steel composite core has thinner walls (so more
lettable floor area), is lighter, so has the advantage of reduced
foundations, and overcomes the common tolerance and
connection issues at the interface between the concrete core and
the surrounding steelwork. Before dismissing the solution,
designers may like to review the news stories, videos and other
resources relating to the Rainier Square building, Seattle, shown
in Figure 2
The 58-storey Rainier Square building is in the news because
it is stabilised by a steel composite core, consisting of panels
fabricated from two steel plates held apart by bars and
subsequently filled with concrete. The headlines describe this
as ‘radical’, a ‘game-changer’ and having a ‘revolutionary core’.
The building was topped out after only 10 months, 8 months
faster than the program for a conventional core, and
reportedly with a 2% cost reduction (although detail on
precisely which cost, or what has been valued, is not clear).
What is clear is that this solution has generated some interest,
with AISC (the American version of SCI) promoting the concept
as ‘SpeedCore’, the name emphasising a key benefit of the
solution.
UK designers may have a sense of deja vu, since an identical
concept was being used in 2005, when it was known as
‘Corefast’. Back then, the system used ‘Bi-steel’ panels, which
separated the steel plates with a bar friction welded to both
plates simultaneously. Only one manufacturer produced these
panels. Now, panels may be produced by bolting between
plates, or by welding. In both cases, the connecting bar
protrudes through the plate. From 2005 to 2009 there was
limited use of the ‘Corefast’ system, when there were challenges
with a conventional core, or (for example) when it was
advantageous to erect a tower crane on the steel core. Case
studies from the time indicate that the construction period was
significantly shorter than a conventional concrete core.
In addition to the claimed time saving, additional benefits arise
at the interfaces with surrounding floor steelwork. Core units and
steelwork is erected by the same organisation, to the same
tolerance – and brackets, plates and supports may be attached to
the core steelwork to facilitate on-site connections as shown in
Figure 3.
Steel composite cores may not be a panacea for every
structure – but the concept deserves consideration.
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Figure 2 – Rainier Square (Photo: NBB/Sean Airhart)
/Construction#Tolerances
/Steel_construction_products#Flat_products_-_plates
/Construction#Tower_cranes
/Concept_design#Concrete_or_steel_cores
/Construction#Steel_erection