The modules must adhere to BAA’s Design Standards. We had to conform to guidelines with regards to aesthetics and adopting commonality across projects. Performance criteria were set with regards to acoustics, fire rating, U-values, thermal performance and deflection. We were expected to adopt Manufacturing and Glazing tolerances in lieu of normal construction tolerances. The modules had to be of a size that could be transported on the back of a lorry and lifted into place with the minimum of effort.
BAA demanded a Target cost of £16,500 per linear metre for the corridor modules when Traditional methods of construction were costing £25,000 per linear metre. They wanted 85% manufactured off-site with only 15% construction airside. The supporting structures also varied from flat to sloping, with a maximum 4 degrees pitch.
There were a number of challenging issues with the structural design for the corridor modules. We needed to manufacture these using ‘one-piece flow assembly’ similar to that adopted within the car manufacturing industry, to help speed up construction and meet tight deadlines. We also need to have separate elements that could then be joined together i.e. the roof, walls and floor to allow the assembly process to work. One of the most interesting parts was opting to use the aluminium glazing mullion structurally. So rather than having a steel structure
that the mullion fixed back to, we chose to increase the aluminium extrusion of the mullion and to provide enough stiffness for this to act structurally. We had issues with the different material properties of aluminium and steel and tested the as-built structure to prove the calculations. We also had to deal with bi-metallic corrosion. We worked closely with Bryden Wood Associates and MACE to work collaboratively and exceed BAA’s criteria.