Civil Engineering March 2021 | Vol 29 No 2

Civil Engineering March 2021 23 “We handled this challenge by designing certain structural elements, such as pile caps and retaining walls, to bridge existing services where redirecting services would cause a greater delay in the work compared to innovating new designs around the services,” Van Dullemen elaborates. LATERAL FORCES The line will contain five press machines, one of 2 500 t, one of 1 600 t, and three of 1 000 t. Dies will be manoeuvred using four overhead cranes, consisting of two 60 t capacity slinger cranes, one 63 t gripper crane and one semi-gantry slinger crane of 50 t, with the possibility of adding another 60 t overhead crane in the future. “The higher cranes will run along two aisles, with two along each aisle, which added to the complexity, as the structure must resist combinations of lateral forces from the cranes and wind loads. Due to the large lateral forces and height of the columns required, we designed compound columns with custom I-sections (falling outside available typical sections) to fall within strength and deflection limits,” explains Van Dullemen. WIND LOADING AND VIRBRATIONS Wind loading on the structure is also higher than usual as the building is higher than typical press plants (23.5 m high at the apex). All large reactions of the struc- ture, including the 2.5 m × 1.1 m main crane concrete columns and the perimeter retaining wall, must be supported on a pile and pile cap system due to poor founding soil conditions. Van Dullemen says the press pit, constructed with concrete, will support five press machines, one weighing 895 t, another 610 t, and three weighing 495 t, which will add dynamic loading to the structure during operation. The density and large mass of the con- crete press pit will add to the dampening resistances needed from vibrations and was designed with elements that are deep and stiff enough to minimise deflection for the successful operation of the press machines and equipment. “We had to employ careful consideration while designing the joint details and floor rail connections, which need to be able to accommodate the creep and shrinkage properties which are inherent in all concrete structures,” says Van Dullemen. CAREFUL CONSIDERATION AND COORDINATION “In addition, the very strict construc- tion tolerances of the press pit support concrete and cast-in steel elements required careful coordination between the engineers and contractors. We also had to carefully consider the agreed upon pour sequences to give the highest likelihood of achieving the tolerances requested, with rebar spacing and detailing done ration- ally for easier construction,” says Donnan. The press plant length required ViKO to design an expansion joint to separate the structure in two to mitigate stresses which can be incurred from the temperature dif- ferentials which occur in larger structures. “This required careful coordination between our engineers and Ford to place the cross bracing to resist the large longitudinal crane and wind forces and avoid clashes or obstruction of the flow of traffic within the plant. Anti-vibration construction details were also required to prevent transfer of vibration to the highly vibration-sensitive equipment throughout the structure,” he continues. FINDING SPACE IN THE BODY SHOP The mechanical engineers required as much space as possible inside the 240 m × 145 m body shop (34 800 m 2 ). This meant that the plinths which support the internal columns had to be as small as possible to allow space for the equipment and machinery. “Any wind or lateral forces were de- signed to be resisted by the external col- umns, as only these columns could have large enough plinths to have moment-re- sisting base plates. This also provided the added benefit of not requiring any internal cross-bracing for the structure, freeing up space and avoiding obstructions within the building,” explains Donnan. The roof trusses must withstand high equipment loads, including conveyors for partially complete cars and mezzanines, which required the capacity to support sub-structures connected eccentric to the truss loads. This required the bottom chord of the trusses to resist both axial and potentially large bending forces. Following geotechnical testing and reports, ViKO found that some areas View of the 14 m high compound columns Project Team Client Ford Motor Company Principal agent & lead engineering consultants ViKO Consulting Engineers Main contractor JC van der Linde and Venter Projects Steel subcontractors RSB Contracts & B&T Steel Subconsultants DSP Consulting Engineers CC Piling subcontractors Mega Pile Inland