A new Heliport for Ultimate Heli has been developed next to the N1 highway opposite the Mall of Africa, in Waterfall. The major structural steel aspects of the Waterfall Heliport are the roof structures and gantry crane beams for the two helicopter hangars positioned in Portion 2 and Portion 4 of the heliport.

Portion 2

Roof Structure

The roof structure of the hangar at Portion 2 of the Heliport consists of trusses occurring every 6.65 m or 6.60 m apart and spanning distances ranging from 23.66 m to 28.31 m. The trusses support purlins, roof sheeting and insulation. A portion of the hangar roof in one area is raised to a higher level in order to provide enough clearance for an overhead traveling crane to operate beneath the roof and above the helicopters. This portion of the hangar is used for maintenance of the helicopters.

At the western side of Portion 2, next to the N1 highway, reinforced concrete columns occur at every 6.65 m or 6 m whereas on the eastern side of the hangar, four reinforced concrete columns are separated by distances of 19.8 m,19.95 m and 19.8 m respectively. The large openings between the columns on the eastern side of Portion 2 is to provide enough clearance for the helicopter rotors when these are towed in and out of the hangar. Due to the large opening over these hangar doors, three structural steel girders spanning nearly 20m each have been provided to support the trusses between the columns. These girders also support the heavy Techentrup roller shutter doors which roll up vertically and weigh 1.4 tons each. The vertical deflection of these girders is limited to 10mm to ensure the smooth operation of the roller shutter doors.

The roof structures for the hangars (Portion 2 and Portion 4) were analyzed using the Prokon frame analysis program with loading modelled in 9 different factored combinations. All the structural steel trusses and girders which form part of the roof structures are manufactured using circular hollow sections of varying sizes. The trusses consist of a horizontal bottom chord and a radiused top chord which follows the shape of the curved profile of the roof sheeting. The shape of the roof has been designed by the architects in the shape of an aero foil and the steel structure has been designed accordingly. The depth of the trusses at their deepest point is roughly 2.4 m. Vertical and diagonal chords connect the top and bottom chords spaced at 1.49 m along the length of the truss. The girder trusses comprise of horizontal top and bottom chords with vertical and diagonal chords connecting the two along its length.

Gantry Crane Beams

The gantry crane beams in the Portion 2 hangar under the raised section of the roof are designed to carry an overhead travelling crane with a capacity of 5 tons. This crane is necessary for the removal of heavy helicopter components such as engines and gearboxes. At the eastern side of the building the gantry crane beam spans 19.8 m and on the western side of the building the gantry crane beam is continuous and spans three lengths of 6.6 m each. The eastern gantry crane beam is made up of an 850 mm deep (16 mm thick) web plate and two 500 mm wide (20 mm thick) flange plates, with stiffener plates occurring every 825 mm along its length. The western gantry crane beam is made up of a 254 x 146 x 43 I-beam capped with a PFC200 x 75, with stiffener plates occurring every 510 mm along its length.

Portion 4

Roof Structure

The roof structure of the Portion 4 hangar is similar to that of Portion 2, except that the roof height remains constant along its length, at a similar height to the raised section of Portion 2. Trusses which support purlins, roof sheeting and insulation, occur at each gridline which are roughly 5.6 m apart and span 30 m.

At the western side of the hangar, reinforced concrete columns support each truss on a gridline, while at the eastern side (air side) of the hangar, four reinforced concrete columns are placed roughly 16.7 m apart. Due to these large spans between columns, three structural steel girders spanning nearly 16.7 m each have been provided to support the trusses between the columns.

As with Portion 2, large roller shutter doors which open vertically between each of the columns on the eastern side of the hangar provide enough clearance for the helicopter rotors when they are towed in and out of the hangar. However, since the roof is raised to allow for the operation of the overhead travelling crane beneath, the same girder trusses which support the roof trusses are not able to support the heavy roller shutter doors too. Therefore, an additional steel girder has been provided between each of the columns at a lower level to support the heavy Techentrup roller shutter doors which roll up vertically and weigh 1.3 tons each. The vertical deflection of these girders is limited to 10mm to ensure the smooth operation of the roller shutter doors.

Gantry Crane Beams

Similar to the Portion 2 hangar, Portion 4 was also designed to accommodate an overhead travelling crane with a capacity of 5 tons. The crane in Portion 4 however has been designed to reach the entire floor space and therefore gantry crane beams span across the interior of both the eastern and western perimeters of the hangar and are supported by the reinforced concrete columns. These cranes will in future be used for the removal of heavy helicopter components such as engines and gearboxes.

The gantry crane beam on the western side of the building spans roughly 5.6 m and is continuous along its length. Due to the small span between columns, this beam is made up of a 254 x 146 x 43 I beam capped with a PFC 200 x 75 and stiffener plates occurring every 510 mm along its length. On the eastern side (air side) of the hangar, the gantry crane beams have to span over the hangar door openings of 16.7m, and are made up of a 533 x 210 x 122 I- beam, capped with a PFC 300 x100 and stiffener plates occurring every 1000 mm.

STRUCTURAL STEELWORK
Completion date of steelwork September 2018
Completion date of full project November 2018
Tons of structural steel used 130 Tons
Structural profiles used All Types of Profiles
SA content – if this is an export project All Types
CLADDING
Completion date of cladding November 2018
Cladding profile/ type used Kliptite 700 – 0.58mm thick Z200 C1S roof sheeting and side cladding
Cladding area/ coverage and tonnage Roof – 4454 m2 – 29397 kg