CAPITA SYMONDS STRUCTURES
WILLIAM HARE LTD
BOVIS LEND LEASE
ALLIED LONDON PROPERTIES
The building provides 2,400m2 of high quality grade A office accommodation and 1,380m2 of restaurant and retail space over six floors within a new landmark structure at the entrance to the Spinningfields business and retail development in Manchester city centre.
The building takes the form of two parallelograms on plan, oppositely handed and positioned one above the other, creating at level 2 a roof terrace to the West elevation and a 23m long cantilever to the East. The external cladding and façade diagonal form reflect and complement the structural geometry of the building, drawing attention away from the horizontal plane of the floors.
The design of the building achieved an excellent BREEAM (2005) rating by taking a holistic approach considering all environmental factors. The high proportion of solid insulated panels within the façade benefited the energy demand of the building through a consequent reduction in solar gain.
The office floors have been designed so that they can be fitted out on either an open plan or cellular basis, and the servicing has been provided so that each floor can be sub-divided into two separate tenancies. The floors also have built-in loading allowances for future storage capability and soft spots for tenant plant requirements.
Materials for the building components were selected for their durability and maintenance requirements. In particular the structure was specified for 60 years design life and major components of the envelope 25 years.
The use of steel was the only way such a demanding structure could be delivered economically. The integrated services solution meant that floor zones were minimised, the reduced self weight of the structure meant that the loads to be resolved by the cantilever and the foundations were kept as small as possible, and the high load capacity of steel meant that the cantilever elements could be kept as compact as possible.
The floor construction comprises a 150mm thick concrete slab on composite metal decking on a grid of secondary and primary Fabsec beams.
400mm diameter openings in the 550mm deep beams allowed for integration of the services within the structure zone. The cells were distributed in a regular grid through the irregular beam layout to aid coordination of the service provision. The Fabsec beams were also fire engineered to provide a least cost design considering both the beam weight and intumescent paint thickness.
The 23m cantilever was resolved by making the perimeter steelwork into a 3-storey deep truss, achieving the most economical frame solution possible. The truss philosophy was applied to all four elevations to provide both vertical support to the edge of the floor plate and lateral stability to the upper block. As a result it was possible to omit the concrete cores above second floor level saving money and time.
The structure was engineered to suit the cladding deflection requirements. The linearelastic properties of steel allowed for accurate 3D modeling and prediction of the behavior of the structure, which was then replicated in the on-site deflection measurements achieved by the frame.
The accuracy of construction which was achieved on site is a testament to the high level of skill and workmanship employed by the steelwork contractor in designing and fabricating the complex connections of the structure.
The building plan of two overlaying parallelograms produces a huge cantilever at the front, which provides a clear view of a notable historic building. The diagonal bracings of the 3-storey frame are cleverly aligned with the herring-bone pattern of the curtain walling, concealing the heavy cantilever trusses from the exterior.
A building of obvious quality in many respects.