Wind

We had a windy weekend. On Saturday morning I went down to the harbour front (Moll de la Fusta) and found some trees and street signs blown down and the whole place littered with debris of old palm branches blown off the trees,

But of course the big thing was the tragedy in Sant Boi de Llobregat, where four children were killed when a sports hall collapsed. They were practising baseball – Sant Boi is major centre for baseball in Catalonia – when their monitors decided that the wind was too strong and that they should go inside for shelter. A local weather station recorded a wind speed of 122.2 kph at the time of the disaster. The sports hall was run by the local council, all its papers were in order and it had been inspected by an architect in 2002.

What happened was this. It was a rectangular brick building with a ridged roof. The roof was exactly at right angles to the wind. This led to a drag effect, which is exactly what makes aeroplane wings take off. That would have been OK, but when the door was opened for the children and monitors to enter, the wind was channelled into a tunnel, which meant that it hit the inside of the hall at four times its original velocity – in other words it went at about 500 kph into a hall where the roof was already under strain from the wind. The whole thing gave way, but of course the roof didn’t come off cleanly. It brought the rest of the hall down.

There is a Catalan university (UPC) that tests structures for extreme wind effects, but only in very unusual buildings. Routine testing of all buildings is just not possible.