Check tower drain holes, says Washington safety authority
14 December 2006Following the structural damage that caused a Bellevue, Washington tower crane to be shut down and dismantled, the Washington state Department of Labor and Industries (L&I) is advising the construction industry to ensure that all tower cranes are checked for water and ice damage caused by recent harsh weather.
The preliminary investigation found that the likely cause of the structural cracks was water buildup in the legs of the cranes, coupled with the freezing temperatures. Unusually heavy rainfall in November could have filled the structure with water. The rainfall, followed by a sudden drop in temperature to well below freezing, accompanied by high wind, would have been sufficient to cause the retained water to freeze, causing expansion – and cracking – in the welds of the metal framework. The effect would be similar to water pipes bursting in freezing weather.
L&I is advising that all tower cranes in the state be checked to ensure they have good-sized “weep holes” and that the holes are open and draining properly.
In November, another tower crane in Bellevue, Washington collapsed, killing one.
