A worker responsible for inspecting bolt-nut connections at the David L. Lawrence Convention Center in Pittsburgh didn't check connections that may have contributed to a Feb. 12 collapse of a steel truss that killed one worker and injured two others, investigators at a coroner's inquest about the accident learned.

Begun in early June and continued on June 25, the inquest will resume July 22. After its conclusion, presiding lawyer Michael George and Allegheny County Coroner Cyril Wecht will decide whether to recommend filing charges.

Earlier testimony dealt with the use of smaller nuts to secure the truss instead of larger, heat-treated ones (ENR 6/17 p. 12). During the second session, officials learned that contrary to previous testimony, larger nuts had been at the site. Clark Shaffer, an oiler on a crane, said he'd seen 2-in.-deep nuts and 1-in.-deep nuts in opposite corners of a tool shed.

Patrick McKelvey of Solar Testing Laboratories, a Cleveland-based firm hired by the owner, the Sports & Exhibition Authority, to inspect aspects of the $332-million project, said he didn't think he was supposed to check the anchor bolts or raker strut connections until after the "pullback" and tightening of roof cables that tie the structure together.

Upon questioning by Allegheny County First Assistant District Attorney Edward Borkowski, witnesses said they believed that ironworkers installing the thirteenth truss line were fit to work.

Then testimony zeroed in on responsibilities of Solar Testing Laboratories. Borkowski asked McKelvey for the party responsible for "looking at the connections" prior to Solar's inspection. McKelvey answered that it was the general contractor. The project has no general contractor but Turner-P.J. Dick-ATS is the local joint venture construction manager.

George also asked McKelvey how he knew he was not supposed to inspect the strut until after the cable pullback. "Word-of-mouth, as well as through my company," McKelvey said.

McKelvey and his supervisor, Solar operations manager William Gross, both said it wasn't their responsibility to make sure the proper nuts were used on the steel rods. McKelvey also said he wasn't aware the strut required the 2-in. nuts. "If I would have looked at line 13 and saw the wrong nuts up there, I wouldn't have known the difference," he said.

McKelvey said he checked between 30 and 50% of bolt-nut connections for tightness. "Did anyone tell you that the raker strut or the anchor bolt connection were not critical connections?" George asked. "No, not specifically," McKelvey said, adding, "I'm not an engineer. I walk around with a torque wrench. That's my job. The guys I work with are all professionals. I was under the impression that everyone knew what they were doing."

Williams Form Engineering Co. Vice President Mark W. Williams said the nuts used on the truss weren't designed for that purpose. The Grand Rapids, Mich., firm provided bolts and nuts used for the convention center. It provided about 200 threaded steel rods, or bolts, that were 1 in. in diameter and 18 in. long.

When asked for his conclusion on the collapse's cause, Williams said, "Jam nuts were used instead of the full-strength nuts. I was amazed that it stayed up as long as it did."