Monday, September 7, 2009

Liverpool crane collapse: tower and foundations scrutinised

Investigations into the causes of the crane collapse in Liverpool in early July are focusing on the tower structure and foundations.

In response to CJ's questions, Bowmer & Kirkland (B&K), which is the main contractor on the site where the accident occurred, said the Health and Safety Executive (HSE) has impounded the collapsed Wolff 500 crane and will undertake chemical, metallurgical and structural tests over the coming months.

With work restarted on the Kings Mill Dock site, the HSE has ordered that the crane's foundation is left undisturbed and is planning to excavate and investigate the structure once details of the process have been finalised.

B&K also confirmed that the collapsed Wolff 500 was the second crane to be mounted on the suspect foundations, replacing a much smaller unit, a Wolff 100 which had been initially erected (January to April 2009) using a tower reducing section.


tower and foundations scrutinised


This means the replacement crane had a maximum load movement many times that of the original unit. However, B&K said the process had been planned, adding: "Investigations to date have confirmed that the tower crane base was designed and built around the use of a Wolff 500B luffing crane and the loadings, base and tower supplied for the Wolff 500B crane."

The maximum bending moment on the tower and highest strain on the foundations would be when the bigger crane (with the heavier counterweight) has its jib luffed up either unladen or with a light load on the hook. It was while in a similar position that a freak gust of wind lead to the fatal crane collapse in Liverpool in 2007.

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