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Thermwood

Magnificent Composite Roof Structure Installed in Bahrain

18 August 2006

The new library and conference hall in Bahrain enhances the island nation’s reputation for dramatic architectural presentation.

Artistic expression is especially bold for the conference hall roof, its five huge vault structures demonstrating the versatility of fibre-reinforced polymer (FRP) composites. Installed atop the conference hall, 92 feet (28 metres) above ground level, the vaults represent one of the largest composite roofing structures in the world. Furthermore, the library and conference hall is adjacent to the famous Al Fateh Mosque, whose architectural focal point is the world’s largest composite dome.

Each vault is 164 feet (50 meters) long with a front overhang that is 52.5 feet (16 metres) wide and 30 feet (9.25 metres) high. The half-cone shape of the vault tapers to 26.2-by-19.7 feet (8-by-6 metres) at the rear, manufactured in Firepel K133 flame-retardant polyester from AOC. Engineering for the vaults was accomplished by Composite Designs & Technology of Pune, India, whilst BFG International Ltd. Bahrain manufactured, assembled and installed the roof components following strict ISO 9000 procedures.

“The desired architecture would not have been economically viable in conventional materials,” said Suhas Kolhatkar, Director of Composite Designs & Technology. “Steel and concrete weigh about 40 to 50 percent more than composites and would have imposed tremendous dead weight on the building’s substructure and footing.” For ease of moulding and handling, each vault was divided into six sections of approximately equal weight. Each section was an assembly of moulded panels which were bolted together using rigid, moulded-in flanges.


Moulds were built of reinforced concrete and finished with a cultured marble surface

To eliminate the need transport the large vault sections over a long distance, composite panels were moulded in a manufacturing facility built at the job site. CAD files were transferred to a CNC unit that cut wooden templates for each panel profile. Moulds were then built of reinforced cement concrete and finished with a cultured marble surface. Workers for BFG International Ltd. Bahrain used hand lay-up to mould the composite sections. To achieve high stiffness at a low weight, a honeycomb core was sandwiched between composite laminates of fibreglass chopped strand mat and woven roving in Firepel K133 flame-retardant polyester.


The front fascia with overhang was one of the six sections that were preassembled on the ground

“Firepel K133 polyester resins are specifically designed to be blended with alumina trihydrate to cost-effectively achieve fire retardant properties,” said Bruce Curry, AOC Product Leader for Firepel resins. “Laminates made with Firepel K133 series have passed ASTM E 84 class I flame spread and smoke development, UL 94-HB, UL94-5V and UL 94-V0 test requirements. The resin series also passed tests established by fire standards B 476 for building materials and construction and BS 6853 for passenger trains.”


A front section is crane-lifted for installation atop the conference hall


The five vaults are 92 feet (28 metres) above ground level and taper from 52.5 by 30 feet (16 by 9.25 metres) dimensions in front to 26.2-by-19.7 feet (8-by-6 metres) at the rear

Assembled vault sections were crane-lifted to the top of the Conference Hall and installed in back-to-front sequence. “Each vault was installed within a tolerance level of plus-or-minus three millimetres (0.19 inch), demonstrating the advantage of lightweight composite structures for fast installation,” said Kolhatkar. “The installation of a single vault took three days, including pre-assembly. The entire project, from concept design to final installation, took only 16 months.”






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