Inspirations in Engineering 2013 - page 16

Nomination Category 1: Buildings
Worthing New Pools
This iconic building has been commissioned to replace
an aging 1960s leisure centre and breathe new life into
the architecture of Worthing’s sea front. Wilkinson Eyre
Architects, supported by AECOM, won the architectural
design competition with their design. The sculptural form
echoes the sand and driftwood of the shoreline. The new
leisure centre brings inspirational design into a facility at
the heart of the local community.
The signature element of the structure is the pool hall,
with steps and curves achieved in a complex steel
frame. Clad in copper and glass with a timber soffit, the
pool hall is set alongside the timber-clad concrete frame
of the leisure centre.
Asymmetric Curved Beams
The lines of the pool hall ‘flow’ towards the shore,
supported by two doubly-curved, doubly-asymmetric,
welded box sections. These are 1.3 m deep, span over
50 m and weigh one metric tonne per metre. They carry
axial load, biaxial bending and torsion due to curvature.
Cross-section properties were explored and optimised
using the ‘general cross-section’ module within Scia. In
addition to section checks and stability checks, Scia was
used to calculate the permanent deflection that could be
precambered. Checks were also made on distortional
deformations, using a detailed model of the beam as a
series of plates. High level clerestory glazing sits above
the beams and is framed in steelwork. Movement joints
were introduced in the clerestory rail to ensure that
vierendeel action did not attract excessive axial load to
the rail.
Stability without bracing
The North and South elevations are entirely glazed,
leaving no room for diagonal bracing against the
westerly wind. Lateral stability is achieved with a network
of slender SHS struts concealed within the timber
roof zone. These transmit axial lateral loads to the
adjacent concrete frame. At the steps in roof profile, the
eccentricity is resolved by taking an additional torsional
moment into the fabricated box beams. This achieves
a structure without either diagonal bracing of the heavy
members of a portal frame.
Movements and interfaces
The steel frame supports extensive glazing, a timber
roof, and copper cladding. The lateral stability system
gives a relatively flexible structure. As glazing in
particular is sensitive to movements, the full 3D
steelwork geometry was analysed to predict the
deflections under self-weight, imposed loads and wind
loads. The roof geometry gave rise to interactions
whereby lateral loading created vertical deflection,
and vice versa. It was also critical to provide a sliding
bearing for the timber roof panels, to ensure that thermal
stresses could not build up and cause fixing failure. A
‘movements and tolerances’ report used graphics from
Scia to communicate the movements that follow-on
trades were required to accommodate at interfaces.
Concrete frame - dynamics and non-linear analysis
On the second floor of the leisure centre, long spans
combine with a fitness studio to create a dynamically
sensitive area. Modal analysis was carried out and the
slab designed appropriately to eliminate dynamic effects
from rhythmic activities.
The south elevation of the leisure centre cantilevers over
the beach promenade. To achieve a picture window with
unrestricted views of the sea, columns were omitted
and replaced with a grillage of cantilevering beams. At
the longest span, a 9 m concrete cantilever required
a full non-linear cracked section analysis, with actual
reinforcement modelled. This demonstrated that long-
term deflections will be within acceptable limits.
Collaborative communication
3D analysis and draughting were crucial to
communicating the design to the fabricators. A
combination of Scia Engineer, Autodesk Revit and
Rhinocerous were used by the design team, with both
the steelworker and timber subcontractor developing 3D
models of their packages from design team information.
Worthing New Pools - Worthing, United Kingdom
Software: Scia Engineer
Nomination Category 1: Buildings
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