Civil Engineering March 2021 | Vol 29 No 2

Civil Engineering March 2021 47 Douala Grand Mall Douala Grand Mall is a new mixed used development situated in the vicinity of Douala International Airport in Cameroon, commissioned to provide a luxury shopping experience to the public. The development comprises a two-level shopping mall with basement parking along with a single level hypermarket. The steelwork superstructure comprises duo and mono-pitch portalised frames. Localised raised steelwork platforms, with suitable grating to support various plant, are situated above the roof line. The roof consists of a composite roof panel system spanning between cold rolled steel purlins. The elevations are predominantly cladded with a composite wall panel system, with a glass façade facing the food court to the south. Structural framing The first floor is a 190 mm deep composite slab with a metal deck which is connected to secondary steel beams with shear studs to create a composite construction. Cell beams were introduced to reduce the weight of the secondary steel beams. Due to floor-to-ceiling height restric- tions, the conceptual first floor Pratt girders had to be replaced by 1 m deep plate girders as primary beams, spanning between various universal column sections. Various services had to be co-ordinated through the plate girders, requiring finite element analysis to manage local stresses around the 1.2 m × 0.5 m service openings in some of the plate girders. The perimeter ground floor steel columns are supported on a reinforced concrete retaining wall, enclosing the basement parking. The internal ground floor steel columns are in turn supported on reinforced concrete columns or suitable transfer beams. Challenges and benefits Douala Grand Mall was conceptualised in the UK and based on European con- struction methods that promote speed of erection with minimum labour. The steel fabrication was carried out in South Africa and transported to Cameroon for quick and easy erection on site. However, the long lead times due to the importing of all the steelwork posed a challenge, along with the fact that any steelwork changes on site had to be car- ried out with lower grade local steel which comes at a premium price. The technical and logistical challenges required significant collaboration from all parties. The project team also had to be highly proactive to identify and resolve issues early on.  WINNER IN THE EXPORT CATEGORY KEY PLAYERS Client/Developer Actis Architect Benoy Structural engineer WSP Group Africa Main contractor Raubex Steelwork contractor/ erector Cadcon Cladding manufacturer & supplier Brucha