The Middletown Press (Middletown, CT)
Q bridge rated just ‘fair’
4 years after opening, cracks to be sealed
NEW HAVEN — The Pearl Harbor Memorial Bridge, which beams with patriotic pride on national holidays and historic dates, received only a fair rating two years after it opened.
After its biennial second inspection, which is underway, the state Department of Transportation will undertake a project to repair cracks that, if not sealed, would threaten the integrity of the bridge that opened to great fanfare in 2015.
The rating, 6 on a scale of 9, was based on the high number of cracks on the surface of the bridge. Most of them are hairline breaks that formed during construction, but many are big enough, as much as onesixteenth of an inch wide, to allow water to seep into the interior of the bridge. There are 100 such cracks highlighted on the northbound span and 115 on the southbound side in the reports.
According to the northbound span report, “there are 91,362 linear feet of cracks. 719 feet of cracks have active leakage and … require attention.” On the southbound side, inspectors found 68,177 linear feet of cracks, with 988 feet needing repair. Together, those numbers translate to more than 30 miles worth of cracks, with less than a third of a mile’s worth needing to be sealed.
“The majority of the cracking occurred during and immediately after the construction,” the report states. “Most of the cracks are shrinkage cracks. Random cracks in the top slab have active leakage.”
None of the cracks, and nothing else in the inspection report,
threaten the safety of the bridge, according to state Department of Transportation officials. But more maintenance will be needed because of its advanced design.
An overall bridge rating is based on the lowest rating of the three main components, in this case the superstructure. A rating of 5 or 6 is defined as fair by the Federal Highway Administration. The deck was rated 7 and the substructure was given an 8, both considered “good.” Other components of the superstructure also were rated 7 or 8, but the concrete girders’ 6 controlled the overall rating.
“It’s governed by the weakest link right now in the inspection,” said Tim Fields, the principal engineer who oversaw the latter stages of the bridge’s design as well as its construction and is now in charge of the DOT’s major structures division.
Once the inspection now underway is complete, the DOT will create a project to seal those cracks that over time would affect the bridge’s integrity, Fields said. “That project will be initiated shortly and hopefully we’ll be out there in two years or less,” he said.
He said most of the cracks are “not unexpected” because of the way the bridge was built. Popularly known as the Q bridge, because it crosses the mouth of the Quinnipiac River, it is the first of its kind in this country, and engineers knew the stresses put on it during construction would cause the concrete to crack.
“Being an extradosed cablestayed bridge, it’s a unique bridge. There’s not another bridge we could borrow lessons learned from,” said DOT Deputy Commissioner Mark Rolfe, who was the district manager for the New Haven area during the bridge’s construction. In order to limit the bridge towers’ height because of nearby Tweed New Haven Airport, the bridge combines a box girder design with a shorterthanusual suspension design.
The northbound bridge opened in 2012. The southbound span opened three years later.
Rolfe said most of the cracks don’t need attention. “Not all cracks are created equal. What matters a lot is the size of the cracks, where they’re located and if they’re growing.”
Once the cracks are sealed, the problem should be solved. and the bridge’s overall rating may actually rise, Rolfe said. “It’s not a today issue. If we left this untreated, it would affect the longterm serviceability of the bridge,” he said.
The first inspection of the two spans that make up the bridge, which carry Interstate 95 northbound and southbound, was conducted from May 31 to midOctober 2017 by engineers with the firm HAKS. The report was issued in February 2018.
Concrete in midair
The cracks were inevitable given the construction method used, Rolfe and Fields said. The bridge is composed of huge hollow concrete girders, on which the concrete deck layer rests. The spans were built out from the towers using what’s known as a form traveler, which pours concrete, then moves to pour a new section. The section of each span reaches out into empty space and “the tips of it are deflecting downward” under the weight of the concrete, Rolfe said. These sections extend “up to 250 feet from each tower until they’re finally joined,” Fields said.
The downward pressure of the concrete cantilevered girders puts stress on the underside of the structure, he said. Then, once the span is complete and partially supported by the cables, the stress shifts to the top of the girders.
“There was very high stress during that cantilever construction and some of those high stresses caused some cracking in the concrete, very minor cracking in the vicinity of the stay cables,” Fields said. “Most of the cracks are very fine shrinkage cracks that don’t go all the way through. This is not necessarily a structural issue” but has to do with the nature of concrete, which is strongest under compression.
There were “very massive concrete pours that were done,” Fields said. “We weren’t really surprised that we now need to seal some cracks. It shouldn’t be viewed as a structural concern. It should be viewed as a maintenance issue that we’re going to be addressing.”
James Falconer, owner of JKF & Associates, an engineering firm in New Haven’s Erector Square, came to the same conclusion when he reviewed the 2,704 pages of the two reports.
“You’re going to need a lot of maintenance in the beginning, which is not what you’re looking for,” said Falconer, who designed the Route 8 bridge in Naugatuck in 1988 and 120 others, though none as large as the Q bridge. He has been a prequalified engineer with the DOT for 30 years.
He said it’s important to seal the cracks “because the ice could get in there and it starts opening. The deterioration goes on and the units get more cracks and it’s not good.”
He said the innovative design of the bridge presented new challenges. “When you are doing a new procedure, you are running the risk of all of a sudden you start getting problems,” he said.
Owner’s manual
“We had anticipated the uniqueness of the structure and developed some principles for our inspectors,” Rolfe said. The guidelines were included in a draft “owner’s manual,” as it’s referred to in the inspection report.
“We needed to learn from the inspection on the bridge where we needed to better define the inspection procedures, where the problem areas [were] where we needed more detail, so we could refine and improve the manual going forward,” he said.
The manual “talks about the severity of different types of cracks,” Rolfe said. “It left a fair amount of discretion to the evaluator as to what rating to assign.” He said the inspectors were conservative in their grades when they rated the girders at the “high end of satisfactory rather than the low end of good.”
As an example that “the rating that was applied to this bridge was very conservative,” Rolfe said, “the foundation system for the bridge is part of the evaluation. … There is no evidence of any settlement whatsoever on this bridge. It should have been rated a 9.” But the lack of settlement — a major issue if it had occurred — was rated at 8.
Since the Q bridge opened, others have been built, including a bridge over the St. Croix River between Oak Park Heights, Minn., and St. Joseph, Wis. While the Q bridge has two sets of towers with cables, the St. Croix bridge has five. The engineers on that project consulted with the Connecticut team during the Q bridge’s construction, Rolfe said.
There is also an extradosed bridge over the Brazos River in Waco, Texas, he said.
Rolfe said “there were multiple levels of review” in designing and building the bridge. The design was by AECOM (formerly URS Corp.) and it was built in a joint venture between Walsh Construction and PCL Civil Constructors. The total cost was more than $550 million. “We commissioned a peer review of that design” by WSP, based in Montreal, he said.
“Are we happy that we have these cracks out there? No, absolutely not. But it’s part of the maintenance of the bridge,” Rolfe said.
“The cracking is essentially superficial and when you have addressed the cracks, then you have addressed the longterm condition,” said Fields.
Below the radar
Rolfe also said senior DOT officials did not get the news of the inspection rating as soon as they should have. “It was below the radar,” he said. “Did it come to my attention right away when it went from a 7 to a 6? It did not.”
He said procedures have been changed to require a higherlevel official sign off on major bridge inspections. “There were other folks here that were keenly aware of it, but they didn’t raise it” to seniorlevel staff. “It would have been nice to have the conversation in draft form,” he said.
Fields said any delay in repairing the cracks is outweighed by having new data from the current inspection. “I think the timing is good to take advantage of the 2019 report,” he said. “We’ll be able to take advantage of the most current bridge inspection data.”