Wrongly Designed Base Caused Tower Crane's Collapse, L&I Concludes

Washington state's Department of Labor and Industries announced Friday the findings of its investigation into the Nov. 16, 2006, collapse of a construction crane in Bellevue that heavily damaged an adjacent condominium building, killing a lawyer who lived there. A flawed engineering design that resulted in a base that was designed to withstand only about 25 percent of the pressure the 210-foot crane actually required was the cause, L&I determined.

"The inadequate design of the tower-crane base clearly led to the collapse of the structure," said Steve Cant, assistant director for L&I's Division of Occupational Safety and Health. "The problem was compounded by the failure of the general contractor to maintain and inspect the crane base in accordance with the manufacturer’s specifications." The crane's collapse prompted the Washington Legislature to pass new laws this year creating programs to certify construction cranes and their operators. L&I will administer the programs. "We're pleased that Governor Chris Gregoire and the Legislature enacted changes in the oversight of construction cranes because this kind of tragedy, in which workers and innocent bystanders could be at risk, should not happen again," Cant said.

L&I said the Bellevue crane's base design "was unusual in that a typical standard construction-crane base would be a poured concrete pad in which crane anchors would be embedded. The base structure designed for this crane consisted of a configuration of steel I-beams welded and bolted together as an H-frame and attached through a set of collars to four concrete pillars. Non-standard bases are necessary in some situations, and they can be engineered to ensure structural integrity and safety. However, in this case the base system design was not strong enough to support all the possible critical load combinations. It needed to be at least four times stronger to operate safely." Magnusson Klemencic Associates, the engineering firm that designed the base, was cited for failing to ensure the design specifications met the specific recommendations of the crane manufacturer and issued a proposed penalty of $5,600. Lease Crutcher Lewis, the general contractor for the project being built, was cited for failing to conduct periodic inspections to determine the crane's deflection limits were not exceeded and issued a proposed penalty of $5,600; the firm also was filed $3,600 and cited for attaching to the crane advertising banners that exceeded the size recommended by the manufacturer. Oversized signage could have affected the control and operation of the crane, L&I said. The agency said its investigation included four other companies, but no violations by them were found and they were not cited.

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