LAST MONTH'S second international conference on current and future trends in bridge design, construction and maintenance, organised by the structures and building board of the ICE and held in Hong Kong's New World Renaissance Hotel, attracted 130 delegates from 18 countries.
With three of the world's most spectacular bridges already completed and two more at final design stage, and with the £4.1bn West Rail project well advanced, Hong Kong was an ideal location for the event. Inevitably it was the local megastructures that dominated the discussions over the two day event, on 25-26 April.
In his keynote address, Hong Kong Institution of Engineers vice president Dr CK Lau reported on the information already obtained from an array of 900 sensors on the three big bridges: Tsing Ma, Kap Shui Mun and Ting Kau. 'These show that so far the wind and traffic loads actually experienced are much lower than design values, and the deflections much less, ' said Lau, adding that these results indicate the designs were relatively conservative.
Lau concluded by suggesting that the next in this series of conferences should be held in mainland China, - 'to emphasise the need for the proper maintenance of existing structures'. Hong Kong's own programme of bridge maintenance and management, later speakers revealed, was characterised by the relatively new bridge stock compared to the UK.
However, access for maintenance is generally very restricted in the congested urban landscape of Hong Kong and several speakers called for designers of urban bridges to take the provision of access for maintenance and cleaning much more seriously.
Aesthetics were also more important in urban structures, the conference agreed, and some of the best attended papers were those describing the design competition for the record-breaking Stonecutters Bridge and the development of the winning design, in which aesthetics played a major role.
When completed in 2007 the cable stayed structure will be the longest in the world with a main span of 1,018m, and its distinctive single leg towers will reach a record 290m.
Although the prize for the winning design went to a team led by Halcrow and Flint & Neill, detailed design will be carried out by Arup. Arup was already responsible for the design of the viaducts on each side of the crossing, part of the Route 9 project, whose complex planning and programming was also described in a paper on the first day, and the unique 'low noise' viaducts on the West Rail project.
Projects in a dozen or more other countries were also presented to the conference. Delegates were particularly intrigued by the description of the construction of the River Imabeppu bridge in Japan, an unusual hybrid integral structure claimed to offer improved seismic performance together with a 5% reduction in cost and a 25% saving in construction time over conventional concrete alternatives.
The secret is the use of cast-in perforated steel diaphragms - dubbed Perfobond plates - to link the plate girders that form the main beams rigidly to the concrete piers. Balanced cantilever construction was another unusual feature of this project.
Some potentially interesting papers were withdrawn at the last minute. Nevertheless, in his closing remarks, ICE deputy secretary Amar Bhogal hailed the fact that over 60 papers had been presented and that the opportunities for 'networking and making new friends' had been better than ever. He added: 'I believe the future of this series of conferences is now safe, and I will be urging Great George Street to seriously consider mainland China as the venue for the next in the series in 2003.'