The David L. Lawrence Convention Center in downtown Pittsburgh was built between 2000 and 2003 for the Sports & Exhibition Authority of Pittsburgh and Allegheny County, or SEA. It is a four-level structure, roughly 265-174 m (870- 570 ft) in the plan. An expansion joint along column line X9, roughly 146 m (480 ft) from the west end, splits the center approximately in two. The connections of the expansion joint are exposed to ambient temperatures (WJE 2008).
At about 1:30 p.m. on Monday, February 5, 2007, a tractor-trailer was parked on the second-floor loading dock of the convention center. The trailer had just hitched its bumper to the loading dock. Under the weight, a 6.1 -18 m (20-60 ft) section o the concrete slab and the steel beam supporting it collapsed. There were, fortunately, no injuries. The ambient temperature at the time was about -19 to -14 C (-3 to -7 F). Problems with 18 misaligned portions of the column foundations had halted construction work in November 2001, and the collapse had occurred in the vicinity of the shifted columns. Work was resumed once repairs had been made to some precast concrete beams. The $370 million building opened in 2003. The collapse led to the cancellation of the Pittsburgh International Auto Show (Ritchie and Houser 2007, WJE 2008).
At the time, a reporter for the Pittsburgh Tribune-Review, Mark Houser, called me and sent me a picture of the collapse and asked for comment. From the photo, it was difficult to attempt to figure out what was going on. He noted, however, that the failure had occurred at an expansion joint. Because it had been a cold day, it was possible that the expansion joint detail had played a role. In the newspaper article, I observed,
If you have a bolt holding something on, and it contracts due to cold then you come along and load it up, the combination of the two may be enough to cause a failure where neither one by itself would. An expansion joint will be open the most when it’s coldest. The more an expansion joint opens up, the harder it’s going to be to hold up the gravity load. And at some point, if an expansion joint opens up too much, it may actually slip off (its support) (Ritchie and Houser 2007).
It was, of course, a somewhat wild but educated guess based on limited information. However, the investigation determined that the expansion joint was in fact the culprit.
This partial collapse was, on the whole, a relatively minor and local case. However, it illustrates the principle that many useful failures and near-failure case studies can be found in the newspaper every year. This expansion joint failure occurred near the start of a course on strength of materials that I was teaching, and the newspaper article handouts provided useful material for classroom discussions. A recent connection failure is of more direct interest to students than the case of the Hyatt Regency walkways, which is now approaching three decades old.
The Wiss, Janney, Elstner Associates, Inc., final report can be found on-line at http://www.pgh-sea.com/images/DLLCCCollapseFinalReportFeb%2008.pdf.
