Big Dig's Tunnel Ceiling Failure
The National Transportation Safety Board (NTSB) has determined that the probable cause of last year's fatal ceiling collapse in the I-90 connector tunnel of Boston's Big Dig was the use of an epoxy anchor adhesive with poor creep resistance.
The NTSB said, in its report released on July 10, 2007, there is a general lack of understanding and knowledge in the construction community about creep in adhesive anchoring systems.
In its report, NTSB asks ASCE to:
"Use the circumstances of the July 10, 2006 accident in Boston, Massachusetts to emphasize to your members through your publications, Web site, and conferences, as appropriate, the need to assess the creep characteristics of adhesive anchors before those anchors are used in sustained tensile-load applications"
NTSB Findings
The NTSB met in a public session on July 10 to discuss and consider the accident report related to last year's ceiling failure. Such public sessions are held regularly to review special investigation reports, safety studies, and other Board products. At this session, the Board released a synopsis of its findings and gave a series of presentations detailing the events in Boston and the NTSB conclusions. The full NTSB hearing proceedings are available for viewing online. A final full report is expected to be released within several weeks.
Standards
Issues related to adhesive anchoring systems and concrete are referenced in the American Concrete Institute's (ACI) Edition of the Building Code, 318 Standards, which are under revision. The draft revisions are currently available for public comment. Comments are due by August 15.
Technical Papers
Strength of Epoxy-Grouted Anchor Bolts in Concrete