Wednesday, March 4, 2009

March 3rd, 2009

Jeddah, Saudi Arabia
A tower crane collapsed in Jeddah yesterday for unknown reasons. The jib of the crane stretched accross a street and struck two cars. Two were taken to the hospital and there were no reports of death.
The article (linked below) notes that the crane was anchored at the 4th floor (tie in or base anchored on a elevated base?) and was only three years old. They suggest that it was old or overloaded but I would suggest that there are many other potential causes. Towers touching floors cause fulcrum points. Was a collar installed properly? Where is was "tied in" was it properly engineered for the loads intended? Tower cranes have limits installed and are intregal to the crane. On most PLC (primary logic controlled) cranes found on virtually all 3 year old cranes it would be difficult to overload them. Design criteria for cranes mandates that they be designed to handle loads of 150%. To overload a modern tower crane, you'd have to have a shock load, load the crane with another piece of equipment while the load is suspended, intentionally bypass the limits, or have a limit failure. I've been on a crane that was overloaded around 115 to 120% of capacity due to computer fault and poor judgement. It's an ugly event and any experience would tell you to get that load off of the crane. I don't buy the overload and would suggest that design or other failure occured.
Since most of the articles were in Arabic, does anyone else have anything to add? And a number of you had this story in hand yesterday. I noticed my statcounter picked up a surge of hits. I looked for a crane accident yesterday and was unable to find one. I'm using Google alerts. Does anyone have a suggstion for your better options.

Edit: Good pictures found Here

انهيار رافعة برجية

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