“I think it’s rare that you get a challenge of this type, in engineering terms, and fabrication/erection terms. There’s a lot of risk involved, and you’re dealing with a very sophisticated owner. You have to come in and deliver without a glitch. That’s really what’s special about this. It’s a very risky project that they pulled off spectacularly.” – Amanuel Gebremeskel, Steel Awards 2017 Judge
Building 50, known as the assembly building at BMW Rosslyn, is about 60 years old and consisted of a low saw-toothed profile roof supported by numerous columns at close spacings. In 2018, BMW Rosslyn will produce the X3 model instead of the 3-Series and the latest assembly-line technology necessitated that a 4 100m² portion of the current B50 structure be modified. The proposed system, H-EMS (Heavy Electric Monorail System), comprises overhead conveyors fixed to the roof, with height-adjustable hangers that carry the vehicles being assembled. The roof and column structure of the existing assembly building was inadequate for this purpose. The H-EMS system required and a higher and stronger roof structure with fewer columns.
The Rosslyn Plant consists of only one final assembly line, and since the Plant is very compact and congested, the possibility of first erecting a new building adjacent to the existing Building 50 and thereafter demolishing the exiting was not an option. The only option, therefore, was to erect a new roof structure over the existing Building 50 whilst the assembly plant remained operational.
Scope and restrictions
In July 2014 BMW SA set out on the procurement process for the appointment of Professional Services for the design a new roof. At the briefing session, BMW SA confessed that they had no idea on whether it was possible to find a solution to meet the objectives without affecting operations. Should this prove not possible then it would require the entire Rosslyn plant to be shut down for a period of at least six months to allow the old assembly building to be demolished and re-built conventionally? This would have a catastrophic financial impact on the BMW SA and their consumers.
The client’s programme allowed 15 months for roof completion. The short duration of the two shutdown periods within this timeframe eliminated the option of conventional construction.
The following restrictions applied to the design and construction of this roof:
• The shutdown periods available for construction were:
i. December 2015/January 2016 –
ii. December 2016/January 2017 –
• The quantity or quality of vehicles being assembled could not be compromised in any way. The assembly line ran 24/7 during weekdays from Monday 06:00 to Friday 22:00.
• Partially assembled vehicles and assembly line equipment had to be protected when working inside the plant. This requirement was not only as a result of high cost of the vehicles but also due to the fact that some of the assembly equipment are custom made abroad. Damage to some of this equipment could result in the shutdown of the assembly line for weeks or perhaps even months. Weekend construction could not affect the assembly process, and the work area had to be reinstated to BMW’s requirements to allow the 1st shift production to commence uninhibited each Monday mornings.
• The layout of the existing assembly line process could not be altered (even temporarily) to accommodate the construction process.
• Building 50 is not an individual free-standing building. It joins into adjacent buildings on two of its boundaries and is bordered by internal roads on its two remaining boundaries. The shape of the new roof is irregular, with the maximum dimension being 116m long.
• Penetrating through the adjacent buildings to install a tower crane was not possible due to space constraints within the buildings. A tower crane could only be placed on the eastern end of the building. At this position, the required tower crane reach and working loads was extensive. A suitable crane could not be sourced locally and would have to be imported.
• A vehicle assembly plant requires a constant supply of components to workstations along the line. Mobile cranes could be established on internal roads, but only over weekends during pre-determined time slots. The long-term use of mobile cranes was therefore also not feasible.
It took several site visits and deliberations with BMW SA over the restrictions listed above, to establish that the positioning of the tower crane(s) would be critical and that the erection of the steel units could not be done using conventional methods. This, therefore, required an unconventional solution to be adopted.
Nyeleti’s extensive experience with incremental bridge launching was the catalyst to the development of the concept of launching the roof horizontally into its position which evolved into the following steps:
• December 2015/January 2016 shutdown: Excavate and cast reinforced concrete foundations within the plant.
• Construction of an overhead working platform adjacent to the tower crane on the eastern end of the building. The platform had to be constructed slightly lower than the new roof level.
• The roof structure could then be constructed on the platform, one roof bay at a time.
• As a parallel process, columns had to be installed on the foundations, penetrating through the existing roof. This work was performed over weekends, using a self-lifting hydraulic frame to lift and place sections of each column in “Lego-block” fashion.
• With a roof bay completed and the columns in place, the roof section was launched hydraulically – like an incremental bridge launch – and then the process could be repeated.
• Once the entire roof was in its final position, the installation of roof sheeting and vertical cladding could
STEEL AWARDS 2017 WINNERcommence. The interface between the old (lower) and new (higher) roofs needed to be completed along the full perimeter of the new roof before the old roof could be demolished.
• The old roof could then be demolished during the December 2016/January 2017 shutdown and the rubble removed.
• Access could then be handed over to the H-EMS contractor to suspend the new assembly line equipment from the new roof.
This concept formed the basis of Nyeleti’s tender application, and the contract was awarded in October 2014.
Presentation of concept to BMW SA and their reaction
While some representatives at BMW were very appreciative but overwhelmed by the innovative concept that Nyeleti developed, others remained sceptical about the idea until the completion. However, BMW’s senior management (both locally and internationally) were convinced and Nyeleti received approval to continue with detail design and tender documentation.
Due to the stringent requirements of the project, BMW SA was advised to request invited contractors to participate in a pre-qualification process. Only established contractors with a known track record were invited. A site visit was organised before tendering commenced where site constraints and construction concepts were discussed. The contract was awarded to Teichmann Structures in October 2015.
Execution of the project and challenges experienced
The working restrictions of this project had a significant impact on site progress, and some portions of the work took longer than anticipated. The interface between the new and existing building was more complex than expected and required an extensive group effort to resolve.
Teichmann Structures proposed two value engineering options to the design concept which were adopted:
• Instead of assembling the columns in sections from the ground up, the columns – 600*600*16mm steel Square Hollow sections, each 12.8m long – were fabricated as a complete unit and lifted onto the roof structure. Each column was rolled horizontally into position, using a trolley on temporary rails on top of the roof structure. Once in position above the foundations, the column would be tilted 90˚ to a vertical position, and then lowered through an opening in the roof onto its foundation.
• The proposed working platform would have been a temporary structure spanning across one of the internal roads. This was revised to be a permanent (pre-cast concrete) structure located one bay westwards of the original position.
There is a distinct difference in thought process between a client who manufactures several hundred high-quality vehicles per day and a consulting/contracting team who do not have the advantage of a repetitive manufacturing process. Most civil engineering projects would be considered “prototypes” by car-manufacturing engineers and this one was no exception. The construction process was often regarded as “slow and inefficient” by the client, but given the common goal of the project deadline, the differences were not insurmountable.
An “addition and alteration”-project poses significantly more variables than a Greenfields project. Consequently, the contractor submitted numerous variation orders based on unanticipated site conditions.
Feedback on the outcome of the project
The plant was programmed to commence vehicle assembly in the last week of January 2017. The entire team had to work 24 hour shifts over December (during the construction fraternity break!) to meet the handover-deadline to the H-EMS contractor. Practical completion was achieved at the end of December 2016, and the assembly of vehicles started on time. The completion of the interface between the new and existing roofs took longer than anticipated, but the operation of the assembly line was unaffected.
Today BMW has an assembly plant which conforms to their specifications with an assembly process that is ready to start manufacturing the new X3-series in January 2018.
Client/Developer: BMW South Africa (Pty) Ltd
Structural Engineer: Nyeleti Consulting (Pty) Ltd
Main Contractor: Teichmann Structures (Pty) Ltd
Steelwork Supplier & Detailer: Boksan Projects cc
Steel Erectors: Teichmann Structures (Pty) Ltd/ Valoworx 42cc
Surveyor: Pristine Surveys (Pty) Ltd
Cladding Contractor: Roofing Guarantee Company (Pty) Ltd
Temporary Works Engineer: ARQ Consulting Engineers (Pty) Ltd
Hydraulic Equipment: Vanguard Rigging (Pty) Ltd
Corrosion Protection: Dram Industrial Painting Contractors (Pty) Ltd
Nominator: Teichmann Structures (Pty) Ltd
Photographer (photo competition): Teichmann Structures (Pty) Ltd
Photographer (other images): Nyeleti Consulting (Pty) Ltd