While the three previous stands were constructed with an insitu concrete lower tier, the RFU’s tight programme requirements ruled out this option on the South Stand. These restrictions also meant that Bison was asked to manufacture and deliver the major precast concrete components for Twickenham within tight delivery programmes and strict budgetary constraints.
Norman Brown, Director at ABC Structures, said: “Bison’s products met with the architectural and structural engineering requirement for the lower tier structure to seamlessly match the North, East and West stands, which were built of in situ concrete 10-15 years previously, but also satisfied the need for robustness, durability and fire resistance.
“Over 2,200 high-quality precast units manufactured by Bison were incorporated into the construction of the lower tier without any unit being rejected; their efficient delivery arrangements helped ABC Structures to reduce the initial and already demanding 12-week erection period by nearly four weeks.”
The lower tier’s concrete superstructure provides lateral restraint to the insitu concrete frame at the back of the terracing. This supports the steel cantilevered middle and upper tiers as well as the cantilevered steel roof structure.
In cross section, the 450mm wide, 500mm deep precast concrete raker beams for the lower tier span in two directions from the insitu columns at the rear of the terracing. These columns form part of the insitu concrete Vierendeel sway frame.
The ten tonne raker beams are supported at their mid points on circular precast concrete columns. Precast concrete beams span the rear two bays of precast columns supporting the prestressed hollowcore flooring spectator concourses at two levels.
The final section of precast concrete terracing went in the Monday before England played a crucial game against New Zealand.