Examples of the use of space grids
The following examples illustrate the use of different space grid structures.
Commercial space frame systems can generally be divided into two types 'piece-small' or 'factory pre-fabricated'; practically all are space truss systems. There are many systems available throughout the world and those in the former category usually differ only in the jointing method or shape of members whilst the latter category are distinguished by the form of the modular units. The use of some of the many available systems is described in the following built examples.
At the National Exhibition Centre in Birmingham the Nodus system was used for the roofs of exhibition halls comprising 93 identical 27.9 x 27.9 m space trusses on a 30 m column grid and for the long span roof Hall 7 which is also known as the Birmingham International Arena.
Hall 7 is a column-free area 108 m x 90 m which is divided into 9 bays by box-trusses suspended from a Vierendeel masted structure. The individual bays are infilled with Nodus space grids which were assembled on the ground (complete with all services) before being craned into position.
The largest area of space grid in the world, 53,000 m2, forms the envelope of the Jacob K. Javits, New York Exhibition and Convention Center.
Constructed on a standard grid module of 3.05 m the Javits Center is over 300 m long up to 220 m wide and rises 47 m above floor level. The patented PG system space grid is almost wholly clad in semi-reflective glass. A novel feature of the system is that it is slightly prestressed by tensile rods inside the tubes of the grid. Contrary to normal practice the 27 x 27 m structural bays are dished to the centre where rain water is collected and discharged to the drainage system.
In 1988 the roof of the FFV Aerotech maintenance hangar for Boeing 747 aircraft at Stansted Airport was constructed from the CUBIC Space Frame system.
Here the modules were 4 m deep and the space frame covered a diamond shaped plan, 98 x 170 m on the major axes, without internal supports. The depth of the space frame is about 2 m less than the hybrid plane and space truss structure originally proposed. Although a greater weight of steel was required the lower cost of fabrication meant that it was a cheaper solution overall.
The Sant Jordi Sports Palace is an indoor stadium seating 15,000 which was constructed for the Olympics in Barcelona, in 1992. Designed by architect Arata Isozaki and engineer Mamoru Kawaguchi the space grid roof utilises the structural efficiency of a domed section to reduce the depth of the grid.
The Orona SEO system used for the 128 m x 106 m roof has a depth of only 2.5 m (which is approximately 1/42 of the shorter span) however the section rises 21 m above the perimeter supports. This roof was erected using the patented "Pantadome" system where the space grid was assembled at a relatively low level, with sections omitted and with predetermined hinge lines. Once assembled, the roof was jacked up to its final position during which process the foldable roof changed shape. When the roof reached its final position additional sections of space grid were installed to stabilise the "mechanism". The cladding of the roof consists of black ceramic tiles and zinc sheets laid on an insulated timber deck.
The National Indoor Arena for Sport at Birmingham, completed in 1991, has a triple-layer MERO space truss roof 90 x 128 m which varies in depth from 8 to 10 m.
This arena, is approximately the same size and shape as the Sant Jordi Sports Palace but, for a slightly shorter span, the roof depth is 10 m rather than 2.5 m. This is because the design concept is a flat grid (like a slab) rather than the more structurally efficient dome profile of the roof in Barcelona.
The Mero KK system was used for this roof. Due to the depth of the grid it is triple layer in order to reduce the length of the compression elements in the space truss. Erection of the roof was carried out by assembly of small "spiders", on the arena floor. These were then lifted into position by crane and attached to the previously assembled grid "in the air". The grid is covered with perforated profiled metal decking (fused to purlins supported at grid nodes) acoustic and thermal insulation and a welded Trocal membrane fixed through the insulation to the decking.
The roof structure of the Palafolls Sport Hall, near Barcelona, Spain demonstrates graphically that space grids do not have to be constructed as a flat plane nor to a rectangular plan.
In plan, the roof, designed by Arata Isozaki (architect) and Dr. Julio Martínez-Calzón (engineer) is a half-segment of a 70 m diameter circle. Within this plan the roof is deformed into a three-dimensionally curved surface created from spherical, conical and toroidal segments. Using the ORTZ space truss system the complex geometry of the roof required a relatively dense grid which is only 1.125 m deep. However, this used over 14,000 individual members. The use of CAD-CAM design and manufacturing meant that assembly of the grid went very smoothly despite the complicated geometry.
