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Fears over Bangkok bridge design


THE DESIGN and manufacturing quality of a specialised bridge enclosure system being installed on Bangkok's new cable stayed Rama VIII bridge, has been questioned by the system's inventor.

FaberMaunsell, which holds patents for the high-tech structural protection system in the Europe and the US, but not Thailand, fears that key design and fabrication considerations could have been overlooked by the local Thai consultant hired to copy the design.

'This is probably the largest application of this system to date and we are the only people to have used it, ' said FaberMaunsell business development director Peter Head.

The design and build contract for the Rama VIII bridge was awarded in 1998 to a joint venture of China State Construction, PPD Construction of Thailand and BBR Systems of Switzerland.

UK consultant Scott Wilson has provided site inspection and geotechnical design (NCEI November 2000).

FaberMaunsell concerns began after being quizzed over its patented system by Canadian consultant Buckland & Taylor, which designed the cable stayed structure. Despite regular commissions for the system in the UK, the firm was not retained to carry out detailed design for the complex plastic reinforced enclosure in Bangkok.

Instead a direct, unauthorised copy of the system was commissioned by the client and designed by a local consultant to protect the 475m long steel plate girder and reinforced concrete deck bridge, which is now nearing completion.

In use, a series of glass-fibre reinforced plastic panels form a modular system, suspended beneath the deck to shield structural components from the elements. The safe design and installation of this is a specialised skill and FaberMaunsell said that it feared the local firm employed to design the system will lack the expertise to use it safely.

'The configuration of the glass reinforcement and choice of resin type is absolutely critical, ' said Head However, UK consultant Mott MacDonald, which acts as engineer to client Bangkok Metropolitan Administration and designed of the initial scheme concept, dismissed Head's fears, saying it was satisfied with the enclosure design.

'Our role is to both make sure that all designs are satisfactory and to ensure that nothing supplied would infringe copyright laws, ' said project director Chris Davis. 'We treat all submissions in the same way, and they all have been through the full audit process.'

The final 8m segment of the 300m main span deck was lowered into place late last year.

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