AS PART of the UK contribution to the High Winds in Urban Area project under the United Nations International Decade for Natural Disaster Reduction programme, investigators recently made a visit to the target cities.
The project is based in the department of civil engineering at the University of Portsmouth under Professor Brian Lee and Dr John Wills. Also associated as a consultant is Professor Tom Wyatt of Imperial College.
The focus is to attempt to make an assessment of the damage potential when a severe typhoon makes a direct land fall on a city centre in the coastal region around the South China Sea. Hong Kong, Shanghai and Manila are indentified as representative target locations. The damage scenario specifically focuses on the likelihood that wind-borne debris will be the direct cause of failure, and breakage, to fully or partially glazed curtain wall buildings. This is excaberated by the changes in architectural fashion.
In the mid-1960s there were no fully glazed buildings in any of the target cities, but there are now many hundreds of such buildings in all the cities around the Pacific Rim. Sooner or later one of these new city centres will face the full force of a typhoon. Anything which is not tied
down, and many things that are, is capable of becoming flying debris. The project is faced with answering to a number of questions.
How is the momentum and energy of the debris related to its damage potential? How is the size, shape and density of the debris related to its flight characteristics? At what speed does debris fly, can it gain height or bounce off the ground? How do poorly fixed objects beak free and subsequently fly, and to what extent is flying debris in a typhoon made up of the broken bits of upstream buildings? And finally, how is the total of damage at such time related to the magnitude of the wind speed and to the structure of the typhoon itself?
Assistance has been received from the Hong Kong Observatory, the Shanghai Meteorological Bureau and the Philippines meteorological service PAGASA. During the course of their visit to Hong Kong the team visited the Ting Kau cable stayed bridge between Tsing Yi island and the mainland at Tsuen Wan to the north of Kowloon.
The project will report its findings in the autumn.