Douala Grand Mall is a new mixed used development situated in close vicinity of Doula International Airport. The mall is the first phase of a multi phased development in the area and was commissioned to provide a luxury shopping experience to the public. When completed Douala Grand Mall will be the first of its kind in Cameroon.

The development comprises a 2 level shopping mall with basement parking and is approximately 112.0m x 120.0m on plan. Towards the east of the mall is a single level hypermarket approximately 56.0m x 40.0m on plan. The development was conceptualized by the project architect (Benoy) to be a 2 level steel structure, constructed on a reinforced concrete basement substructure. Raubex Renovo was appointed as the main contractor, with WSP Group Africa appointed as the Civil and Structural Engineers.

The steelwork superstructure comprises duo and mono-pitch portalised frames with a first floor at approximately 5.85m above ground level. Localized 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 (Kingspan), spanning between cold rolled steel purlins (Metsec). The elevations are predominantly cladded with a composite wall panel system (Brucha), with a glass façade facing the food court to the south.

The first floor is a 190mm deep composite slab with a metal deck (Bacacier). The slab/deck is connected to secondary steel beams with shear studs to create a composite construction. In order to reduce the weight of the secondary steel beams WSP introduced cell beams (Macsteel). Due to floor-to-ceiling height restrictions WSP had to revise the conceptual first floor Pratt girders. The girders were replaced by 1.0m deep plate girders as primary beams, spanning between various universal columns (UC) sections on grid. With a restricted ground floor ceiling void WSP had to co-ordinate various services through the plate girders. This resulted in finite element analysis to be carried out, in order to manage local stresses, round the 1.2mx0.5m 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 RC columns on grid or suitable transfer beams.

On ground floor level stability is achieved through transverse and longitudinal vertical ‘X’ bracing and portal braced frames. On the 1st floor level vertical ‘X’ bracing is only provided in the longitudinal direction for stability.

Although the steelwork superstructure is in essence a portalised Pratt truss and column system, WSP found the following technically challenging:

  • Custom made plate girder beams with sizable service openings, requiring finite element design.
  • Large skylight openings in the roof structure.
  • Box girder design with a 16.0m span to support a roof truss coming in at 90 degrees.
  • Connections of the perimeter columns to the retaining wall.
  • Complete perimeter steelwork sub-structure to provide support to the vertical cladding, including parapets.

Douala Grand Mall was conceptualized in the UK and based on an European type of construction, therefore, promoting speed of erection with minimum labor. The project lends it well to this type of construction, with fabrication carried out in South Africa with quick and easy erection on site. Another driving force behind the steelwork superstructure is the poor ground conditions, resulting in low bearing capacities. The steelwork superstructure approach did, however, come with the following challenges:

  • Long lead times due to the importing of all the steelwork.
  • Containers not being released in time by the port authorities.
  • Any steelwork changes on site had to be carried out with local lower grade steel.
  • Local steel comes at a premium price although it is of a lower grade.

Given the above technical and logistical challenges the project team collaborated very well on the project. The steelwork contractor (Cadcon) was involved early on in the project to provide guidance on the procurement of the steel and lead times to get material on site. Macsteel also contributed with the fabrication and design of the cell beams. Issues were also identified early on and everyone on the project team were proactive in order to resolve any issues.

Project motivation editorials are provided by the project nominator. If any technical details, company names or product names are incorrect, please notify the SAISC so that the error can be corrected.

PROJECT OVERVIEW
Physical address of the project
Street Address
Town 
Province
Douala Grand Mall Autoroute de L’aviation Au Lieu dit Bonadiwoto
Google Maps link  
STRUCTURAL STEELWORK
Completion date of steelwork 31/04/2020
Completion date of the full project 15/06/2020
Tonnage and steel profiles used Approx. 1 688
   

CLADDING
Completion date of cladding 15/05/2020
Cladding profile/ type used Brucha (various)
Cladding area coverage Approx. 7 600m2
Cladding tonnage Approx. 133
   

Project team role

Company

Nominator

WSP Group Africa

Client/ Developer

Actis

Architect

Benoy

Architect of Record

PKA Architects

Structural Engineer

WSP Group Africa

Civil Engineer

WSP Group Africa

Quantity Surveyor

 

Project Manager

 

Main Contractor

Raubex

Steelwork Contractor

Cadcon (Pty) Ltd

Steel Erector

Cadcon (Pty) Ltd

Cladding Manufacturer

Brucha

Cladding Supplier

Brucha

Cladding Contractor

Raubex

Corrosion Protection

 

Galvanising

 

Corrosion Protection

 

Paintwork Contractor

 

Photographer, Photo competition

WSP Group Africa

Photographer, Other submitted images

WSP Group Africa

 

If you were a part of this project, and your company details are incorrect or missing – please notify the SAISC so that the error can be corrected.