Leisure/Education
Model showing the leisure
centre's truss arrangement
and the long beams
spanning the main pool
18 NSC
Apr 20
17 a temporary trestle to support the bottom
boom, while it was stabilised with temporary
bracings back to the perimeter column bases.
The higher upstand truss sits at third floor
level and splits the span above the sports hall,
allowing a beam depth which maintains the
clear height requirements of this space.
The upstand truss also forms the
boundary for the central corridor; creating a
physical threshold between the tennis courts
and the circulation at the uppermost level
three.
The truss is 35m-long × 9m-high and
weighs close to 60t. It was assembled on site
on temporary trestles, which were supported
by the lower truss. Once fully assembled,
it was installed to its final position via a
tandem lift using two 500t-capacity mobile
cranes.
The new Britannia Leisure Centre is due
to open in spring 2021. The adjacent existing
facility will then be demolished, making
space for a residential element of the overall
development.
The structure of the City of London Academy Shoreditch Park is a
steel frame of length 100 m with concrete cores for stability at each
end. SCI publication P0701 discusses the issue of expansion joints in
steel-framed buildings in Chapter 7. The options available to the designer
are to either design for the loads resulting from changes in temperature
on a structure, or relieve them. The effects of the temperature change ΔT
(thermal strain = ΔTα; thermal stress = ΔTαE where α = 12 × 10-6 per Kelvin
for T < 100°C) for a theoretical temperature range of -5 to +35°C or say ± 20 K,
are a strain of ± 2.4 × 10-4 or an unfactored stress of 50.4 MPa when the
movement is fully restrained
Examination of Table 7.1 in P070 shows that the maximum recommended
spacing of expansion joints in steel-framed commercial buildings of simple
construction is 100 m. The movement joint in the middle of the 100 m
length of the Academy building therefore requires a movement allowance
of about twice 50 × 10³ × 2.4 × 10-4 mm or 24 mm. If no joint were provided,
the longitudinal members would theoretically experience a stress because
of restraint by the concrete cores from the maximum temperature change
of 50.4 MPa and potentially large forces which depend on the area of the
continuous members.
P070 presents practical examinations of the assumptions outlined above
and considers bolt slip in 2 mm oversize holes and realistic estimates of
temperature ranges compared with the maximum theoretical ones. The
discussion concludes that for simple construction, the restraint of thermal
expansion may not result in problems. The difficulty with making realistic
predictions of forces or movements may well lead the designer to adopt
a safe approach and introduce a joint which will allow the worst-case
movement.
The introduction of a structural movement joint in the middle of a building
must be carried through the envelope design to avoid either leaks or local
cracking or distortion. The details are different for the roof and for the façade.
In the former, an upstand may be formed on each side of the joint (as at a
building parapet) with an insulated channel section, toes down, overlapping
the upstands. In the facades, the cladding system will usually have standard
details of movement joints between panels which can be adopted for the
required movement allowance.
1 Steelwork Design Guide to BS5950 – Volume 4: Essential Data for Designers, SCI
P070, 1991
Movement joints
Movement joints in buildings are introduced to solve
one set of problems and introduce another. Richard
Henderson of the SCI discusses some of the issues.
The eastern elevation of
the leisure centre houses
a triple-height space for
the flume
The lower of the two trusses
helps create the sports hall’s
column-free space
/Trusses
/Construction#Temporary_works
/Construction#Mobile_cranes
/Construction#Mobile_cranes
/Concept_design#Concrete_or_steel_cores
/Concept_design#Structural_options_for_stability
/Braced_frames
/Multi-storey_office_buildings
/Construction
/Building_envelopes
/Facades_and_interfaces
