NEWS BRIEFS
“Wrong Screws” Cited in Collapse
J. Michael Ruane Judicial Center in Salem, MA
An OSHA-aided investigation determined that a heavy exterior wall panel that fell from a Massachusetts courthouse under construction “failed because a contractor used the wrong type of screws, the Salem News reports.
A worker was seriously injured on the ground when the 500 lb. limestone panel fell four stories in July 2010.
After months of investigation, the state Division of Capital Asset Management determined that the zinc-coated screws used by contractor Lighthouse Masonry Inc. on the $106 million state courthouse project “were not the type specified in the design of the fastener system.”
“Use of the wrong screws was the ‘direct cause’ of the limestone panel falling,” the Salem News reports.
OSHA utilized national forensic engineering firm Simpson Gumpertz & Heger to conduct the investigation. SGH determined that the contractor should have used polymer-coated screws instead of zinc-coated self-drilling fasteners, which reportedly failed due to hydrogen embrittlement.
Cracks were also found in other fasteners when the 154 limestone panels were removed following the accident.
SGH also found that “the adhesive anchor from the stone that fell was installed in an improperly cleaned hole,” though the anchor was determined to have failed after the stone panel struck the ground.
Lighthouse Masonry, which was cited for safety violations, is currently reinstalling the limestone panels under “extraordinarily strict on-site inspection,” DCAM said.
At the time of the accident, local reporter Tom Dalton said called the collapse “eerily reminiscent of the Big Dig, when a Jamaica Plain woman was crushed to death in a 2006 ceiling collapse inside a tunnel.”
Even with the right screws, designers face an uphill battle convincing the public of the structure’s safety and durability.
“Sounds like a bad design even with the right screws,” a reader commented on the Salem News website. “How well are the polymer coated screws going to hold up 50 years from now? The whole idea of drilling holes and screwing into epoxy just doesn’t seem safe.” ©2011 GlobalFastenerNews.com
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