Category Archives: Bridges

Race against clock to fix vital transport artery for Olympics

London faces a race against time to repair a crucial flyover which will carry traffic into the capital for this summer’s Olympics, according to one of Britain’s leading structural engineers.

As we posted last week, the Hammersmith Flyover, which carries 90,000 vehicles a day on the A4, the road between central London and the West, including Heathrow airport, has been closed for two weeks after serious defects were found in the 50-year-old structure. Major traffic congestion is already being caused, which is likely to increase when many schools go back this week.

The cables which squeeze together the separate pre-cast concrete segments of the bridge, known as pre-stressing cables, were found to have corroded because of water damage and to have lost much of their tension – a problem which, if not dealt with, would lead to the flyover collapsing.

Engineers say several other road bridges in the UK are threatened by the corrosion process known as chloride contamination, caused when salty water seeps into concrete when ice melts. Spaghetti junction (Gravelly Hill) near Birmingham was afflicted with chloride contamination and in 2010 underwent repairs costing £2.7m.

In Hammersmith, although the corrosion can be temporarily repaired for the Games, the job is going to be complex and lengthy, according to Dr Chris Burgoyne of the Department of Engineering at Cambridge University, who has been called in by Transport for London to advise on the problem.

Asked whether it would be a race against time to get the flyover reopened in time for the 2012 Games, which begin on 27 July, Dr Burgoyne said: “Yes. It will take a long time to sort it out. You’re definitely talking about months.”

It is now dawning on the organisers of the Games, and in particular the Mayor of London, Boris Johnson, that the state of the bridge is presenting a serious threat to the complex transport plans drawn up to allow athletes and visitors to move around the capital during sport’s greatest spectacle.

On Friday Mr Johnson visited the flyover to inspect the work and was at pains to insist that all would be well. “One thing I can assure Londoners of is a plan is being finalised within the next few days and work is already beginning on strengthening the flyover so it is fully operational well ahead of the 2012 Games,” he said.

But Dr Burgoyne, who is reader in concrete structures at Cambridge, and who agreed with TfL’s consultants’ advice to close the flyover immediately when he learned of the damage on 23 December, explained just how difficult it is going to be to deal with the damaged cables inside the 622m-long structure, which opened in 1962. “These days, in building a pre-stressed concrete structure, you would leave the cables exposed all the way along their length. It means they’re slightly more liable to corrode, but it means you can inspect them easily and replace them,” he said. “But what they did in Hammersmith is they surrounded them with mortar boxes, which effectively stop you seeing what’s going on in the cable. It means you can’t easily replace the cables.

“It’s a big job. A lot of the work would have to be done inside the box sections and access is not easy. I couldn’t stand up… at mid-span it’s only about 4ft high, so working conditions are quite cramped in there. You can’t throw lots of men at one location – there physically isn’t room for them.” He added: “They’ve got to come up with a design, they’ve got to get it checked, and get it approved.”

Transport for London has been working around the clock on the site. The investigation will continue this week before it decides if the flyover is strong enough to reopen even to light traffic.


Serious corrosion fears keep vital road in London closed

Transport for London has been forced to keep the vital A4 Hammersmith flyover closed for further inspections because of serious corrosion of steel supporting cables.

Problems with external concrete sprawling have been known about for several years, but engineers have called for extra time to assess the extent of damage within the 900m bridge structure.

The flyover was closed on 23 December due to concerns about a serious structural defect.

Since engineers and contractors have been working round the clock on a detailed investigation.

They hope to decide shortly on what remedial action needs to be taken and when the flyover can safely be reopened to traffic.

The damage to the aging 1960′s structure has been caused by water ingress, including salt water due to grit laid during the winter months, which has corroded and weakened supporting cables.

Engineers on-site continue to build a full picture of the condition of the complex and aging bridge structure, with much of the work taking place inside the structure.

TfL said that it was exploring all options to reopen the flyover to traffic as soon as possible, but must await the outcome of further work to test the extent of the problems found in the structure.

TfL is also actively working on the design of a solution to strengthen and extend the life of the flyover over the longer-term, by introducing additional cables into the structure.

Leon Daniels, TfL’s Managing Director of Surface Transport, said: “Our team continues to work night and day alongside the world’s leading structural engineers to fully understand the extent of the flyover’s structural problems.

“I have been inside the flyover and seen for myself the unique issues we face,” he explained.

“Safety must be our top priority and we have not taken the decision to close the flyover lightly.

“However, we are working flat-out to determine what measures we must put in place to safely reopen the flyover as soon as possible.”


More Corrosion discovered at the Champlain Bridge

Repairs to the Champlain Bridge will involve a new type of reinforcement to deal with growing problems with corrosion in the bridge’s deck.

In 2012, there will be at least that many weekend closings, maybe more, said Glen Carlin, general manager of the Jacques Cartier and Champlain Bridges Inc.

Carlin was speaking at a media briefing he said is part of a new effort by the federal agency to reassure the public about safety and to be more transparent about the state of the Champlain.

In 2011, $33.3 million (C$) was spent on Champlain repairs, including the repaving of 2.75 kilometres, the replacement of five expansion joints and the reinforcement of several girders and piers.

In 2012, the tab will be $34 million (C$), including 700 metres of repaving and four new expansion joints.

For the first time in 2012, repairs may be done in winter, but they will not affect traffic because they will take place under the bridge, Carlin said.

In the past, reinforcement work involved adding high strength steel cables along the outside edge of the bridge.

Now, work will also involve installing steel cables transversally under the bridge.

“The beams on the bridge are all knit together” with transverse cables, Carlin said. “These cables are starting to get affected by corrosion.” The new cables “will reinstate this transverse posttensioning.”

In 2012, there will be a lot more work on two adjacent federally owned stretches: The Bonaventure Expressway, between the Champlain and the Lachine Canal. The government will spend $11 million, up from $7.2 million.

Highway 15, between the Champlain and Atwater Ave. Ottawa will spend $19 million, almost five times the $4.2 million spent this year. This hike is because of major repairs to Champlain approaches.

A 2010 inspection report obtained by The Gazette last month showed that two overpasses on the Montreal approach to the Champlain are in “mediocre” condition, their concrete crumbling and reinforcement steel corroding. One overpass must be replaced while the other must undergo major repairs.

In addition, the report said a secondary span known as the Nuns’ Island Bridge is deteriorating “very quickly” and requires major repairs.

The Champlain is decaying prematurely because it was not designed to withstand the use of road salt. Because of its unusual design, Ottawa says it would be too expensive and disruptive to traffic to repair it for the long term.

In 2009, Ottawa began a 10-year, $212-million program to repair the Champlain until a new span is built.

This year, another $158 million was added – $27 million for the Champlain, the rest for Highway 15 and the Bonaventure.

The work will extend the life of the structures until 2021. Ottawa says it hopes to have a $3-billion replacement bridge in place by then.

“If the bridge is going to be late by a year or two, we will do what would have to be done to make sure that the existing bridge can be extended by that type of duration,” Carlin said.

“More than that, it’s kind of like planning for something we shouldn’t be planning for. The goal is to get the new bridge in place within the next 10 years.”

A 2010 study warned the Champlain was so dilapidated there was a risk of a partial bridge collapse.

Major repairs have been done since then and the Champlain is monitored closely, Carlin said.

“We are fully confident in its safety. We wanted to show everything that we’re doing to ensure that any risks that are out there on the bridge are being managed,” he said.

“If there’s any doubt regarding safety, we’ll take any measures that are required,” he added, including closing lanes or the entire bridge.

The bridge is crucial for commuters and the transportation of goods. It’s used by about 160,000 vehicles daily, including 14,400 trucks and 400 public-transit buses

Inspection showed Mercier Bridge corrosion trouble in 2006

Five years before Quebec closed part of the Mercier Bridge due to dangerously deteriorating steel plates on the span’s provincial side, an inspection found plates on the federal side were corroding and had to be replaced.

The report said repairing the plates – steel connectors that hold together the bridge’s girders and beams – should be a top priority.

“These gusset plates play a major role in the integrity of the bridge structure,” the report stated. “Therefore, the progress of corrosion at these plates must be monitored, and, if necessary, a capacity assessment should be done to evaluate more accurately the behavior of the material affected by the corrosion.”

The inspections were commissioned by Jacques Cartier and Champlain Bridges Inc., which owns the federal side of the Mercier.

Ottawa reinforced about 50 gussets in 2008, replacing two and repairing the rest. Meanwhile, Quebec, long criticized for neglecting transportation infrastructure, decided not to do work on its gussets.

The Mercier’s federal half was built in the late 1950s, while the provincial part that was closed for gusset repairs went up in the early 1930s.

The 2006 report, by an engineering firm, paints a troubling picture of the Mercier at the time.

For example, it warns the bridge’s side curbs and median were so deteriorated that cars that accidentally plowed into them could be launched into oncoming traffic or off the bridge.

Follow-up federal inspections in 2007, 2008 and 2009 also disclosed in response to the access-to-info request, found that repairs helped improve the overall condition of the bridge’s federal half.

The disclosure that federal officials were advised about gusset deterioration as early as 2006 is another indication Transport Quebec may have missed crucial corrosion on the provincial side.

If the deterioration had been caught earlier, traffic disruptions that affected tens of thousands of commuters during the Mercier closing could have been avoided.

To fix its gusset plates, Transport Quebec closed two of the Mercier’s four lanes on June 14. One of the closed lanes reopened Sept. 6. But, to allow for ongoing gusset work, the bridge still goes down to two lanes overnight and on weekends. All four lanes are to be permanently reopened by December.

This summer, Quebec initially refused to make public the inspection of its side of the Mercier, finally relenting in September under pressure from the public, engineers, politicians and the media.

In September, Transport Minister Pierre Moreau said provincial plates deteriorated “at a faster rate than what was expected” and the damage could not have been caught earlier.

Independent engineers question this version of events, noting corrosion does not speed up.

The 2006 inspection report recommended 37 repairs, nine of which were classified as “A” priority jobs, meaning they were “necessary to maintain the integrity of the system’s structure and of its auxiliary components.”

The first item on the list of top-priority repairs: gusset plates, which, the report said, should be reinforced by 2010.

The report recommended close to $32 million in federal repairs.

The $74-million federal expenditure is part of a $174-million Mercier overhaul that Ottawa and Quebec began in 2008 and that is to be completed by 2014. Quebec has not said how much it has spent on the project so far.

The 2006 federal inspection was the last general inspection of the bridge.



Scotland’s Forth Bridge safety & corrosion tests to be less extensive

A £2.6 million ($4.1 million USD) contract awarded by the Forth Estuary Transport Authority yesterday will see eight sections of the suspension cables tested for corrosion to establish whether and when traffic restrictions may have to be imposed on the crossing.

The organization had originally planned to test twice the number of sections but said the cutbacks had been made after a 56% reduction in its capital budget over three years, which had nearly halved the contract’s value.

Previous tests conducted in 2004 and 2008 established that corrosion had caused a 10% reduction in strength in the cables, eventually leading the Scottish Government to go ahead with a £1.5 billion replacement crossing, due to be completed by 2016, in order to avoid any closure of the route.

Work on the third inspection will begin next spring, with data being available in early 2013.

Barry Colford, chief engineer and bridgemaster, said: “The condition of the main cables is the second-highest risk to the bridge after the condition of the main cable anchorages. We have already begun investigating the anchorages but this inspection of the main cables is also an essential project.

“Although the cost of the work has come down, the nature has not changed significantly and the inspection will still allow the cables’ strength to be evaluated.

But the cuts to the inspection program were criticized by opposition parties yesterday who warned that they could lead to further expenses.


Mercier Bridge inspections reveal alarming decay

Quebec has released long-awaited inspection reports on Montreal’s Mercier Bridge that confirm rapidly accelerating decay in the aging structure forced its closure earlier this summer.

Corrosion noted in a 2011 inspection was so advanced that some bridge parts were perforated and deformed, the reports say.

In particular, the report said, 10 gusset plates that hold beams in an interlocking pattern are severely eroded.

Of 346 bridge parts inspected, 86 were given a “1” rating, meaning that they were deemed “incapable of perfoming required task.”

The 2011 report was dated June 11, and the Transport Ministry banned most traffic from the bridge three days later, citing the need for critical repairs to remedy safety-threatening corrosion and rust.

But Transport Minister Pierre Moreau was quick to point out that long-term repairs to remedy decay were underway when the span was shut down.

“The deterioration was going at a faster rate than what we expected,” but the bridge was in no danger of collapsing, Moreau said at a news conference Monday.

All emergency repairs have been completed, but other work is in progress.

The Mercier Bridge partially reopened Sept. 6, with remaining lanes scheduled to open in December if all repairs are completed.

The summer closure angered South Shore residents, officials and business owners who rely on the Mercier Bridge for daily commutes into the city.

The Transport Ministry has released inspection reports from 2007, 2008, 2009 and 2011 on its website.

The Mercier Bridge comprises two structures, one built in the 1930s and another inbound arm built in the 1960s.


12 Montreal structures considered critical due to corrosion

Montreal Mayor Gerald Tremblay said on Wednesday that 12 bridges, tunnels and overpasses in the city identified by engineers as being in critical condition.

“We have the reports from our engineers that these structures are safe,” Tremblay told reporters at city hall, where technical details on 35 structures were made public.

“From the moment one of our engineers or technicians informs (us) they are not safe, we will close the structure or limit access to it either by (reducing the number of) lanes or limiting the load.

“Just because it is critical doesn’t mean it isn’t safe.”

The mayor also said his administration is raising the annual average amount needed for repairs to $50 million from $30 million because of the advancing age of the 586 structures in the city of Montreal’s network. The request for more funds will be made in a new three-year infrastructure plan to be unveiled Thursday, Tremblay said.

On Wednesday, the city of Montreal made public inspection reports for 35 infrastructures on its territory. Of the 12 listed in “critical” condition, two are closed to the public, and one has undergone major repairs since the information was collected late last year.

The 12 in “critical” condition are:

  • Henri Bourassa Blvd. E./Pie IX Blvd. overpass
  • The former Wellington St. Tunnel under the Lachine Canal
  • Henri Bourassa Blvd. E./Metropolitan Blvd. E overpass
  • Rockland Ave./Bates Rd. overpass
  • Beaudry Tunnel, north side of Notre Dame St. E., near the Port of Montreal (private roadway)
  • Jean Talon St. W. overpass (west of Wilderton Ave.)
  • Jolicoeur St. bridge over Montreal Aqueduct
  • CN Rail bridge crossing l’Acadie Blvd., north of de Louvain St.
  • Park Ave. overpass/Highway 40 and service roads
  • Henri Bourassa Blvd. E./Sherbrooke St. E. overpass
  • Upper Lachine Rd./St. Jacques St. overpass
  • Snow ramp at St. Michel Quarry (no public access)

The reports detail the sites’ deterioration:

  • The Henri Bourassa Blvd. E./Pie IX Blvd. site has support walls that are severely cracked. Exposed reinforcement bars have also been badly corroded.
  • Pillars have a series of cracks in them, with eroded concrete.
  • The Wellington Tunnel, which has been out of service since the roadway was rebuilt as an overpass, suffers severe corrosion on 66 per cent of the structure’s support system.
  • The Henri Bourassa Blvd. E./Metropolitan Blvd. site has corroded beams and severe damage to the structure’s decking, with a risk of falling concrete.
  • The Rockland Ave. overpass’s support structure has lost about 10 per cent of its load-bearing capacity. Concrete is eroding and exposing reinforcement bars to rust and corrosion.
  • The Beaudry Tunnel has severe water damage.
  • Jean Talon St. W. overpass has severe corrosion to its support structure.
  • The Jolicoeur St. Bridge has cracks covering 30 per cent of the supporting walls’ surface.
  • The CN Rail bridge crossing l’Acadie Blvd. has cracks covering 100 per cent of its supporting pillars. About 15 per cent of the supporting walls’ surface is severely damaged.
  • Park Ave. overpass/Highway 40 and service roads: Expansion joints have been paved over. About 40 per cent of the joints’ surface is defective.
  • On the Henri Bourassa Blvd. E./Sherbrooke St. E. overpass, about 80 per cent of the concrete on the eastern wall is severely chipped.
  • At the Upper Lachine Rd./St. Jacques St. overpass, 40 per cent of the support walls’ concrete is severely chipped, exposing reinforcement bars to corrosion.
  • At the snow-dumping ramp at the St. Michel Quarry, 90 per cent of the support wall is covered in cracks, chips and ruptures.

No immediate repairs are planned for the Wellington Tunnel and the Beaudry Tunnel, as both sites are off-limits to the public.

An additional site, the St. Jean Baptiste Blvd. overpass at Highway 40/Metropolitan Blvd. E., was missing waterproofing membrane along its expansion joints, causing moisture to seep in. Concrete was also badly damaged along the joints. Repairs have begun at this site.

In Montreal’s disclosure, the city made public, for each of 35 structures, one-or twopage “inspection summary sheets” on which engineers have rated the deterioration of various elements. For each of the 35, photos of trouble spots were also provided.

Richard Bergeron, of the opposition Projet Montréal party, accused the city of holding back more detailed “engineers’ reports” for its structures.

But city spokesperson Philippe Sabourin denied that. He said the documents made public Wednesday are the complete inspection reports. “We don’t have any other reports,” Sabourin said.

By month’s end, the city is to publish on its website more information about the 520 other structures under its control. For those, Montreal will release the same type of “inspection summary sheets” but will not include photos, Sabourin said.

Tremblay said the city will henceforth provide annual updates on the state of every one of its structures via its website.

This week, Quebec Transport Minister Pierre Moreau pledged to make public inspection reports for all 10,000 structures under his control.

He did not provide a timeline.


Doubts over management of Forth crossing could see bridge expertise lost

Vital specialist bridge engineering skills risk being lost to Scotland due to uncertainty over the future governance of the Forth Road Bridge, the convener of the Forth Estuary Transport Authority (FETA) has said.

The warning comes in advance of a decision by Transport Minister Keith Brown, due in October, on how the proposed new £2 billion Forth crossing is to be managed.

The main options are to manage the new structure along with the existing road bridge in a modified version of the existing governance structure, or to abolish FETA and allow Transport Scotland to manage both bridges.

Fife councillor Tony Martin, FETA’s convener, said: “Staff with unique long-term experience of managing long-span bridges are going to leave us if we can’t tell them what the future is going to be.

“To manage [the bridges] properly it is important that we retain that kind of expertise.”

Senior managers in Transport Scotland, who have a civil service rather than an engineering background, are known to favor a model where the maintenance contracts for the bridges is outsourced to private-sector firms, a system currently applied to Scotland’s trunk road system.

However, as the complex technical and safety requirements of large bridges are distinct from roads, and the current bridge has a reduced safety factor due to corrosion, engineering experts doubt whether Transport Scotland is sufficiently competent or accountable to assume responsibility for the day-to-day management of major long-span bridges.

The agency also has mixed record of negotiating best value for taxpayer with engineering multinationals, and may face criticism over its supervision of the construction contract for, and management of the Government grant to, the Edinburgh tram project.

Martin said: “Although the governance model would have to change, my view is that the bridges should be managed by the people who currently operate a system that employs local people, is flexible and has worked well for 40 years.”

FETA is currently preparing to award a contract to assess the impact of its four-year program of injecting air into its main cable to arrest the rust damage that has threatened to reduce the bridge’s safety factor below the level needed to allow Heavy Goods Vehicles (HGVs) within several years.

If the dehumidification process has been successful, the risk factor will stabilize, but the cables will still require a rolling program of maintenance.

In a separate operation, Northern Irish firm Graham Construction won a £3.5 million contract last month to open up and investigate the bridge’s main cable anchorage, to assess the impact of corrosion in the steel strands that hold the concrete together in the anchorage tunnels.

The excavation is expected to take 12 months and a further 12 months will be required to carry out the inspection and evaluate the findings.

Bridgemaster Barry Colford said: “This is a very important investigation into what are critical components of the suspension bridge… I would stress that there is no external evidence of any problem but it is our responsibility as a bridge authority to inspect every part of the structure in order to ensure there are no hidden issues.”

Transport Scotland successfully delivered the £120m Clackmannanshire Bridge over the Firth of Forth on time and on budget, which was opened by First Minister Alex Salmond in 2008.

However, the civil engineer John Carson, who led the team that built the new Skye Bridge, dismissed the precedent as irrelevant.

“Anyone who knows anything about bridges would know there is no meaningful connection between building a relatively simple short-span concrete bridge to maintaining one of the world’s largest suspension bridges, especially in its degraded form,” he said.

“Barry Colford is a hands-on engineer who has to take responsibility for the safety of the traffic on the bridge on a daily basis.


‘Significant corrosion’ on Stillwater Lift Bridge

STILLWATER, Minn. — Temporary load restrictions begin Thursday for the Stillwater Lift Bridge after the discovery of significant corrosion on some of the bridge’s components.

The Minnesota Department of Transportation (Mn/DOT) says crews discovered the corrosion during a regularly scheduled inspection.

“Although the bridge can safely handle day to day traffic, heavy loads will wear the bridge out more quickly,” said Mn/DOT state bridge engineer Nancy Daubenberger. “Restricting the loads before and during the repairs will help prevent damage to the bridge.”

The temporary posting will reduce the legal load limits as follows:

· Single truck, from 28 tons to 24 tons
· Semi-truck, from 40 tons to 28 tons
· Trailer truck, from 40 tons to 28 tons

Mn/DOT crews are expected to begin work on the bridge later this week. Repairs should be finished in one week to 10 days.

Meantime, supporters of a new bridge say this latest development only strengthens their case for going forward with construction.

“It’s yet another wake-up call that we need a new bridge.  It’s an 80-year-old bridge.  July 1st it celebrated its 80th birthday.  You can keep pouring money into it, but it’s going to keep deteriorating,” said Stillwater Mayor Ken Harycki.

Just this week, Gov. Mark Dayton denied a request by 30 environmental groups to consider a plan for a much smaller bridge on the St. Croix river.

Dayton and bridge supporters have argued the latest plan — calling for a $690 million, four-lane bridge — would cause the least harm and enjoys the widest support.

Dayton has said he wants Congress to approve the project by late September or he’ll consider shifting more than $360 million in federal and state funds to other projects. Congress needs to pass an exemption to the U.S. Wild and Scenic Rivers Act.

The bridge is also scheduled for a repair project in fall 2012.


Plymouth Avenue bridge closed until next year

There’s good news and bad news for traffic users of the Plymouth Avenue Bridge. The good news is that city officials appear to have found the money needed to repair the bridge. The bad news is that it will probably be a year or more before the bridge is open to motor vehicle traffic.

Minneapolis City Engineer and Public Works Director Steven Kotke said most of the money is coming from the State of Minnesota. “We were successful in obtaining two different pots of money. One was kind of an emergency fund that the state had, and then the governor actually put in the state bonding bill $4 million for the Plymouth Bridge, and that gave us a grand total of right around $6 million, which is about what we think we need to fix the bridge.”

He said, however, that the various parts of the repair work need to be done in a certain order and in very close succession, and there’s not enough time to do it all this year. So they won’t be able to start the work until next year.

“The work needs to be sequenced in a continuous manner, so that would not allow us to do the work this fall and then stop for the winter and the start again,” he said. “We intend to get the project all bid out and start first thing in the spring. We’re anticipating it will be about four months worth of work, so that would put us probably near the end of August of 2012 to have the bridge completed and opened back up.

“So the good news is we were able to give everybody the green light to keep moving forward. It would have been nice if we could have started right away, but given the manner of the work that needs to be done, it would prevent that from happening,” he said.

“So we are continuing to finish the final design, and then it has to go through a state review process to make sure everything is right.”

The bridge crosses the Mississippi River and connects Eighth Avenue NE and Plymouth Avenue N. Motorists can cross the river using the Broadway Bridge six blocks to the north.

City engineers closed the Plymouth Avenue Bridge Oct. 22 after finding corrosion in its support system during a routine annual inspection. It was built in the 1980s and was the first of its kind—called post-tension segmental box girder—in Minnesota. City officials brought a consulting firm that specializes in this bridge design, to inspect the bridge and recommend repairs.

They found serious corrosion in at least five of the post-tension tendons in the bridge’s center span. These tendons, Kotke said earlier, are similar to the cables that support suspension bridges, and are designed to keep the bridge’s concrete parts pushing inward when a load is placed on the bridge surface. The concrete, he said, is strongest when it’s in this “compression mode.”

An initial report, issued in late December, recommended four major repairs:

  • Reconfigure the bridge’s drainage system to direct water away from the bridge’s box girders
  • Replace five of the bridge’s corroded support tendons
  • Add more tendons to improve the bridge’s flexing capability
  • Seal the bridge’s wearing surface with a penetrant sealer, or replace the wearing surface.

The bridge is currently open to pedestrians and bicyclists; bicyclists are asked to walk their bikes while on the bridge.