Work Ongoing for Pittsburgh Bridge Replacement

WEDNESDAY, AUGUST 3, 2022


Last week, two of the first beams for the Fern Hollow Bridge replacement project were delivered in Pittsburgh, with hopes that the project will be completed by the end of the year. The original bridge collapsed at the beginning of the year and, thanks to emergency declarations and federal funding, will be replaced years before it would have been able to otherwise.

According to the Pennsylvania Department of Transportation, the construction of the new bridge will be one of the fastest rebuilds the region has ever seen, and it will also use the largest pre-stretched concrete beams the department has ever worked with.

Construction Schedule, Next Steps

At a news conference on July 25, PennDOT District 11 Executive Cheryl Moon-Sirianni said meeting the year-end goal hinges on construction continuing to go smoothly.

“We are dealing with the same supply-chain issues as everybody else,” said Moon-Sirianni. “But we are super excited that the project is moving this fast.”

Moon-Sirianni added that the department is having a “little difficulty” procuring a bridge barrier, nothing “obviously we’re not opening a 90-foot high bridge without a barrier.”

At the event, four large columns are visible from the ridge near the bridge site. According to reports, after the news conference, a 150-foot-long concrete beam was hoisted between a column and the west side of Fern Hollow, then slowly lowered and put into place. Each beam weights 108 tons.

“Today brings us one day closer to reconnecting one of the most important things in our city, infrastructure,” Pittsburgh Mayor Ed Gainey said.

It was also announced that two local artists from Pittsburgh, John Peña and Carin Mincemoyer, will complete aesthetic projects for the bridge.

“We’ve hired two artists through the office of public art. One artist is charged with doing some aesthetics to the top of the bridge, and then the other artist is charged with what can be done on the columns,” explained Moon-Sirianni.

Additionally, a crosswalk with signals midway between the end of the bridge has been added to design plans to provide safe passage for walkers and bikers using the mixed-use path in one side of the bridge. These are expected to be placed after the bridge reopens due to an order backlog of about a year. The bridge will also likely open with temporary lighting until steel poles arrive for the same reason.

The remaining concrete I-beams, coming to a total of 21, will be delivered to the site two per day through Aug. 5. There will be no deliveries on weekends. The beams were built at Pennstress in Blair County.

As of Monday, half of the support beams were in place, and with the rest expected to be completed by Aug. 16. Then, crews will get ready to pour concrete. Moon-Sirianni said the cooperation of the city, the contractor and the permitting agencies has been invaluable to keep this project moving so quickly.

What Happened

On Jan. 28 around 6:40 a.m., the Allegheny County Police Department was notified about a partial bridge collapse over Frick Park. Emergency crews arrived at Forbes Avenue Bridge, also referred to as the Fern Hollow Bridge, around Forbes and Braddock avenues.

An articulated Port Authority bus and four passenger vehicles were on the bridge at the time of the collapse, along with a fifth passenger vehicle that drove off the east bridge abutment following the collapse. First responder crews rappelled 100 to 150 feet to reach victims, while others formed a “human chain” to rescue people from the bus.

Initial reports from witnesses described a loud noise and hissing sound, along with a strong smell of natural gas in the area. Responders later confirmed that the collapse caused a gas line to break, prompting an evacuation of homes in the surrounding area. Authorities were eventually able to off the gas line, but a few hours later service was restored and families were permitted to return to homes, according to Pittsburgh Fire Department Chief Darryl Jones.

President Biden was briefed on the collapse and spoke with state and local officials prior to his arrival in the city. Biden visited the bridge site around 1:30 p.m. that day ahead of his previously scheduled trip to Carnegie Mellon University’s Mill 19 research and development center to talk about infrastructure, the economy and supply chain issues.

Later in the afternoon, 13 members of the National Transportation Safety Board investigation team arrived at the site of the collapse. In their short time there, investigators were reportedly already able to study some of the bridge elements. On Jan. 29, the NTSB announced it had launched an investigation into the collapse, planning to look at the full history of the bridge, including design, construction and maintenance.

NTSB Chair Jennifer Homendy told reporters at a briefing in Pittsburgh on Jan. 29 that the investigation would be “lengthy.” Currently, the final board report on the cause of the collapse will not be issued for 12 to 18 months, but the NTSB hopes it will take less time.

Pennsylvania Gov. Tom Wolf signed a proclamation of disaster emergency for the county following the collapse, authorizing state agencies to use all available resources and personnel, as necessary, to manage this emergency situation. According to the release, time-consuming bidding and contract procedures, as well as other formalities normally prescribed by law, are also waived through the proclamation.

A similar declaration was signed by Gainey on Jan. 30. The declaration will increase the availability of federal funds, facilitate closer coordination between PennDOT and Department of Mobility and Infrastructure (DOMI) and speed up cleanup and reconstruction of the Fern Hollow Bridge.

Crews from Allegheny Crane Rental lifted the Port Authority bus from the site on Jan. 31. Utilizing a 400-ton crane, the company’s largest piece of equipment and built on site at the collapse, the bus was lifted by straps underneath it.

The 447-foot, rigid steel frame bridge with three spans was built in 1970 and owned by the city. According to reports, the posted weight limit of the bridge is 26 tons and sees an average of more than 14,000 vehicles a day.

Forbes Avenue is a four-lane, non-divided roadway with two travel lanes in both directions. Sidewalks flanked the travel lanes on both sides, and at the time of the collapse, some snow had accumulated on the roadway and bridge surfaces. The bridge goes across Frick Park, one of the city’s largest parks, over the Hot Dog Dam Dog Park and a public walking trail.

Gainey told reporters the bridge was last inspected in September 2021, with the report from Pennsylvania Department of Transportation stating that the bridge received an overall “poor” rating and has been consistently found to be in this condition in since 2011. The deck condition and superstructure condition received poor scores, while the substructure condition gained a “satisfactory” rating.

Preliminary NTSB Investigation

In its preliminary report, the NTSB reports that the bridge was an uncoated, weathering steel, three-span, continuous rigid “K” frame structure with two welded steel girders, welded steel floor beams and rolled steel stringers. The ends of the structure rested on reinforced concrete caps on stone masonry abutments, with each girder additionally supported by two inclined, welded and uncoated weathering steel frame legs on concrete thrust blocks.

According to the release, certain areas of the welded steel girders were identified as being fracture critical, but no primary fractures were found in those areas. Initial assessment indicates the collapse began at the west end of the bridge.

As more debris are removed and areas are more accessible, further examination is expected to be performed. The NTSB also plans to conduct forensic examination of several of the bridge’s components, as well as evaluate the design of the bridge, its condition at the time of the collapse, its maintenance and rehabilitation history and its inspection and load rating history.

Footage recovered from the seven cameras on the Port Authority bus will be analyzed for further information by a group of specialists. These cameras include one forward-facing camera, one right side aft facing camera and five interior cameras.

The initial assessment of these cameras is reportedly consistent with the initial assessment of the bridge components.

“The recovery of evidence, including extraction and documentation, is expected to be a lengthy process,” the NTSB wrote. “All aspects of the collapse remain under investigation while the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar events.”

In May, the NTSB provided an update on the recovery of structural components and tests currently being conducted to evaluated materials used when constructing the bridge, as well as a review of new footage recovered from a transit bus camera system.

Investigators reviewed video footage from the time of the collapse from two of the cameras on a Port Authority transit bus. The cameras, one forward-facing and one rear-facing the curbside, were determined to have “investigative value” with frames depicting events of interest.

The first frame, from the forward-facing camera, reportedly shows the bridge deck separating at the east expansion joint. The second frame, from the curbside camera, reportedly shows that, at nearly the same time, the west end of the bridge had already fallen off the west abutment.

“Thus far, the investigation has not found any evidence of widespread deficiencies with rigid K-frame superstructure types,” wrote the NTSB. “All aspects of the collapse remain under investigation while the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar events.”

Additionally, while the preliminary report listed ten vehicle occupants as being injured during the bridge collapse, further investigation has confirmed a total of nine occupants in six vehicles, including the Port Authority transit bus. Of the injuries, two vehicle occupants sustained serious injuries, two injuries were minor, four were uninjured and the injury status of one is unknown.

That same month, a newly released inspection document revealed that the Fern Hollow Bridge had “major decay” prior to its collapse, including exposed rebar, corrosion, holes in the steel cross-beams and spalling in the bridge deck.

The Pittsburgh Post-Gazette obtained a partially redacted copy of the October 2021 inspection report from the Pennsylvania Department of Transportation in response to a Right to Know request. In the 106-page document, a section under immediate improvements needing prompt action listed “none.”

The 26-ton weight limit from 2014 was also kept after the inspection, with the report citing that “because the condition of the main load carrying members has not changed significantly, the 2014 Load Rating Analysis is still valid.” However, sections regarding the data that led to that original weight limit were reportedly redacted by PennDOT.

In the report, eight short-term, Priority 2-level improvements were included, with the most expensive being “repair spalled and delaminated concrete underside” for $160,000. Seven Priority 3 recommendations were also noted, including “upgrade bridge rail to current PennDOT standards” for almost $178,800.

“The remaining cross bracings are in poor condition. The cross-bracing exhibit uneven weathering, laminar rust, severe corrosion and holes in webs at bracing connections,” stated the 2021 inspection report. “The cross bracing is deteriorating due to malfunctioning drainage systems in addition to deterioration, contamination and seepage through the deck concrete (previously noted).”

Additionally, the steel legs reportedly showed significant deterioration, being in “poor condition,” some stiffeners exhibiting 100% section loss and “laminar rust and holes in the web.” Up to 50% section loss was seen on the bolts on the inside of a girder splice plate connecting the west end of the bridge to the central portion.

Inspectors also found spalling on the underside of the concrete bridge deck, with water seeping from the top of the deck through to the steel below. This, inspectors believed, was caused by chlorides from winter salt.

Replacement Design Plans

In March, PennDOT announced design and construction plans to replace the bridge, in collaboration with City of Pittsburgh officials and the Federal Highway Administration. PennDOT reports that it has selected HDR Inc. and Swank Construction Company to design and construct the new bridge. The Design Build partnership plans to take environmental complexities into account regarding its location with Frick Park.

According to the release, the team determined after evaluating several options that a three-span continuous composite prestressed concrete I-beam with integral abutments would be the best structure type. Material availability, cost, design concerns and delivery time, along with supply chain concerns, were factored into the decision.

The new structure will reportedly remain along the same roadway alignment and width, but plans to include four 10-foot-wide travel lanes, two-foot-wide shoulders on both sides, a five-foot-wide sidewalk and a 10-foot 5-inch-wide shared use path on the southern side of the bridge.

Aesthetic treatments planned include treatments to the concrete pier columns and bridge barriers, painting of the beams, a stream restoration plan, ornamental bridge lighting and a site restoration plan with tree plantings to restore damaged areas. PennDOT is consulting with Pittsburgh Parks Conservancy and the Pittsburgh History and Landmarks Foundation and seeking public input on these elements.

Emergency declarations issued following the collapse reportedly allowed the city and PennDOT to manage construction and design for the project immediately, while also using emergency procurement procedures through the FHWA to being work within seven days of the collapse. These emergency procedures have allowed the replacement to occur two to three years earlier than would have been possible using typical design and construction methods.

The Pittsburgh Post-Gazette reported that construction began earlier this month for the $25.3 million replacement bridge with the pouring of concrete for the first caissons to support two sets of columns that look like double capital Ts. The previous bridge had steel supports at each end. PennDOT and contractor HDR said that they hope most of the construction can be completed this year, with a final completion date being determined by how quickly the concrete beams are available.

   

Tagged categories: Accidents; Bridges; Bridges; concrete; Department of Transportation (DOT); Government contracts; Health and safety; Infrastructure; Infrastructure; NA; North America; Ongoing projects; Program/Project Management

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