Concrete pouring cited in accident

By Jessica Bloch, BDN Staff
Posted Oct. 30, 2009, at 9:09 p.m.

ORONO, Maine — Construction on a Percent for Art project at the University of Maine’s Dean Paul Cloke Plaza halted Wednesday afternoon when an arch form being filled with concrete failed, felling a second arch being used in the project.

No one was hurt in the accident, which occurred about 5 p.m., said Dana Humphrey, dean of UM’s College of Engineering, who happened to be watching the work as the accident happened.

He estimated Friday that 12 people were working at the site and others were watching, but no one was close to any of the concrete that came out when the arches partially collapsed on each other.

The arches being used at the Cloke Plaza site were designed by UM’s Advanced Structures and Composites Center and similar in theory to those used for its bridge construction projects, including a bridge that went up last fall in Pittsfield, but not the same, according to Humphrey.

Humphrey said it is believed the bridge technology was not at fault, but that the accident appeared to be caused by a mechanism used to pump concrete into the arch, which is made out of a composite material.

The design of the plaza includes two composite bridge arches that overlap each other at a point over the plaza. On Wednesday, Humphrey said, the first arch was filled without incident. The second arch was filled, but at one point the concrete pumper applied pressure to the filled arch, and the cement mix burst through the side.

“That then caused the arch being filled to partly collapse,” Humphrey said. “It shifted a little bit, and that partly collapsed the other arch. There was no issue with the engineering used to design the arch. The construction technology that was being used just didn’t work for this circumstance.”

The incident startled those on the work site, Humphrey added.

The arches, which had a span of 98 feet, were being held in place at the time by temporary scaffolding. The destroyed arches were removed Thursday and Friday.

Cloke Plaza is bordered by Crosby Lab, East Annex, Neville Hall, and the new engineering and science wing at Barrows Hall.

Humphrey said the incident has set back construction, which was supposed to have been completed in December. Other elements destined for the plaza, including landscaping and a bell from the tower of the former Wingate Hall, which was damaged in a 1943 fire, will be installed as planned.

New arches for the plaza likely will not be installed until next summer as the project’s engineers re-evaluate how the arches will be filled and wait for better construction weather.

“The engineering for these [arches] was fine and it was sound, but we certainly had some good lessons learned about what kind of technique we’ll use to fill the arches in the future,” Humphrey said. “[The arches] will still be a wonderful part of the plaza. The overall concept is one we were very excited about, and we’re still very excited about it.”

The total budget for the project is about $169,000 and is funded by Maine’s Percent for Art law, which reserves 1 percent of construction funds for all state-funded projects to provide artwork for the public areas. The program is run by the Maine Arts Commission.

Advanced Structures and Composites Center Director Habib Dagher said he was told the center’s portion of the project budget was about $20,000. Dagher said he was not closely involved in the project.

Both Dagher and Larry Parent, the center’s senior R&D program manager, said the center’s bridge technology was not at fault, and the arches used at Cloke Plaza were not the same as those used in bridges.

“The method [for pouring the concrete into the arches] is still evolving, and the bridges we’ve built both used different methods,” Parent said. “Something unexpected happened in the filling process [Wednesday], and we don’t know what that is.”

The center’s bridge technology underwent eight years of testing before it was deployed in Pittsfield. There have been no complaints about that bridge in the year it has been in place, Dagher said.

Humphrey said Buster Simpson, the artist who designed the plaza project, was at the site when the accident happened.

http://bangordailynews.com/2009/10/30/news/bangor/concrete-pouring-cited-in-accident/ printed on August 2, 2014