Category Archives: Concrete

Cost of Corrosion Increase – Forth Road Bridge

Significant inaccuracies in the as-built drawings for the Forth Road Bridge’s cable anchorages are to dramatically increase the cost of corrosion investigations, the “New Civil Engineer” publication learned this week.

Examination of the bridge’s southern anchorages – which hold the huge suspension cables in place – is taking much longer than anticipated because they are deeper and steeper than the on the original as-built drawings.

The Forth Estuary Transport Authority (Feta) is investigating the condition of the 48 year old anchorages after a resident engineer’s report raised concerns about the possibility of corrosion in the post tensioned strands within them.

In a capital update report to the bridge authority, Forth Road Bridge chief engineer and bridgemaster Barry Colford says the cost of the inspection is likely to be “significantly higher than the original estimate” of £3.5M.

“It’s a very resource driven contract,” Colford told NCE. “As the rockhead level was higher and there more was concrete [than anticipated] the contractor has had to spend more money.”

 

The anchorages are four concrete filled tunnels – 80m deep on the south side, 57m deep on the north side – and up to 14m in diameter.

The anchorages each transfer a load of 14,000t from the main suspensions cables into the bedrock.

Each anchorage consists of 114 ducts with four post-tensioned, galvanised, 32mm diameter high tensile steel strands made up of 19 wires in each.

With the original access chamber to the bottom of all four anchorages filled in, the only way to assess the condition of the strands is to dig down and open them up, said Colford.

Contractor Graham began the anchorage investigation on the southern bank in August 2011 under a New Engineering Contract (NEC) 3 Option C target cost contract with a target cost of £3.5M.

But after investigations began, engineers discovered that the ducts were 400mm deeper and were at an angle of 33˚, not 30˚ as recorded on the as-built drawings.

“It’s a significant change to what we expected and it is very disappointing the as-built drawings of a major structure were not correct,” added Colford.

Graham will begin exposing up to nine stands on each of the southern anchorages by the end of the year. Consultant Fairhurst will assess the strength of the anchorages by the end of 2013.

Colford is in discussions with Graham about the size of the compensation event – the cost of work unforeseen at tender stage – and £220,000 has already been agreed.

The extra funds for the anchorage investigation are contributing to an overall deficit of £3.5M in Feta’s capital budget for 2012/13.

Its capital funding was cut by 58% by Transport Scotland last year.

Colford said budget shortfall would be met by using some of Feta’s £5.8M reserve, as well as delaying or cancelling “non-committed” schemes on the bridge.

He was also seeking additional funds from Transport Scotland.

SOURCE: http://www.nce.co.uk/news/structures/forth-anchor-corrosion-probe-costs-pushed-up/8635624.article?blocktitle=Exclusive-news-from-NCE-magazine&contentID=204

Corrosion likely culprit in roof collapse

The partial collapse of a shopping mall roof last weekend was likely the result of a combination of factors the most likely cause was corrosion of the reinforced concrete, said Mark Green, a Queen’s University engineering professor.

On Saturday afternoon a section of the roof at the Algo Centre Mall (Kingston, Ontario) collapsed.

A section of roof about 12 metres by 24 metres fell.

The roof supported a parking lot and at least two vehicles fell into the mall when the roof came down. Because the roof served as a parking lot, corrosion could have been an even greater issue because of the salt used to clear the surface of ice during winter.

Green said it was also possible that the design of the building may have included an aspect that made it more susceptible to collapse.

Twenty-two people were injured in the collapse.

Police also said at least 30 were missing.

In 2010, mall owners Eastwood Malls Inc. spent about $1 million to repair leaks in the roof that had been ongoing for several years.

But hints of a catastrophic collapse may have been easily overlooked, Green said.

“The warning signs may not have been that obvious,” he said.

In April 2010, a section of the parking garage at Confederation Place hotel in Kingston collapsed, damaging about 20 vehicles and closing the hotel for several days for repairs.

In 2006 a bridge in Laval collapsed, killing five people. That bridge had been inspected shortly before it fell, Green said

That bridge collapse prompted inspections of other bridges in Quebec and Green said he expects buildings similar in age and design to the Algo Centre to undergo additional inspections in the coming weeks.

On Monday a small piece of concrete fell off the Gardiner Expressway hitting a car below.

SOURCE: http://www.thewhig.com/2012/06/25/corrosion-likely-culprit-in-roof-collapse-expert

24-Inch Water Pipe Burst Closes Dallas Street

A water main break in Dallas released enough water to stop traffic and close one street for at least a day.

The 24-inch water pipeline burst on Beckley Avenue, under the Commerce Street Bridge.

“The possibilities of the failure could be corrosion, electrolysis that occurs there, it could be ground shift,” explained Randy Payton, with Dallas Water Utilities.

According to Payton, each year Dallas spends about $100 million on pipe replacement.

“Dallas has an aggressive approach in replacing its pipelines annually,” he said.

It’s expected to take a full day, up to 20 hours, to repair or replace the pipe.

There are some 5,000 miles of pipeline running through the city of Dallas.

Payton said it’s unusual for larger pipes to break and that the 24-inch pipe on Beckley is, “…a reliable pipe. Generally, like I said, it only fails once or twice a year — throughout the system.”

The large size of the burst pipe will require more manpower to repair/replace it.

SOURCE: http://dfw.cbslocal.com/2012/06/06/24-inch-water-pipe-burst-closes-dallas-street/

Road cave-in caused by corrosion in slab

MUMBAI: The Andheri (E) road cave-in on Tuesday was caused by corrosion of steel in a slab, it has been revealed prima facie.

Consultant D S Joshi, who made the submission to the BMC, told TOI that material from the site had been sent for laboratory tests to ascertain the reasons for the corrosion. “I would be able to give the exact reasons once the report is available. It would take about a week,” he added.

Meanwhile, the BMC on Wednesday decided to conduct an audit of all concrete slabs over nullahs across the city.

The 30-ft road in Gundavali village has two lanes on either side of a 20-ft-wide nullah. The road was built by laying slabs atop portions of the nullah in 1985.

N V Merani, chairman of the Standing Technical Advisory Committee (STAC), said the nullah’s water could have eroded the earth below the slabs. “The other possible reasons could be lack of maintainance or poor quality,” he said, adding that laboratory results could only shed light on the extent of loss of strength due to corrosion and not the reasons behind the same.

“This can be found out only through close inspection of the corroded section by an experienced engineer,” he said.

Two weeks ago, the STAC had raised the issue of old civic bridges with the BMC. There are 253 bridges in the city; of these, 102 are over waterways, 17 are flyovers, 41 road overbridges, 93 foot over-bridges and subways.

“We did a study of 34 old bridges three years ago. By now, they should have been repaired or reconstructed. But nothing has moved,” said Merani.

The STAC had recommended that a separate chief engineer be appointed to exclusively monitor bridges and concrete roads. The BMC has created a post not filled it up. “The MMRDA is constructing flyovers and roads and handing them over to the BMC. The corporation needs to appoint a person to that post. We have even suggested that if they cannot promote an engineer, they can get someone on deputation. But decisions in the BMC are ad-hoc,” he said.

SOURCE: http://articles.timesofindia.indiatimes.com/2012-05-24/mumbai/31839803_1_bmc-slabs-bridges

Hammersmith tunnel ‘solution to crumbling flyover’

A west London council has said building a tunnel is the long-term solution to replace a “crumbling” flyover.

The Hammersmith Flyover has been under repair works since December and is scheduled to reopen fully on 30 May.

Hammersmith and Fulham Council said: “We must continue to push for an alternative solution, and that is a tunnel.”

Transport for London (TfL) said the flyover “would be able to survive for several further decades”.

A council spokesman said: “TfL must realise that we cannot simply accept patch-jobs to prolong the life of this monstrous outdated and crumbling structure.”

TfL Surface Transport spokesman Garrett Emmerson said: “Our engineers, contractors and traffic control operators continue to work flat out to deliver a permanent fix to the Hammersmith Flyover well ahead of the 2012 Games.

“The structure would be able to survive for several further decades.

“However the Mayor has also asked us to consider long term options for the area and that work will consider a range of possible solutions to the area’s future needs.”

The strengthening works, which began in January, have seen about 200m (650ft) of the central reservation along the flyover removed, a new structural slab and concrete barriers installed, as well as tailored anchorages for the new cables installed within the structure.

TfL has been carrying out two weeks of overnight closures to flyover since 15 May to carry out the final parts of this work.

It said it would return to the structure in 2013 for more strengthening work which will be carried out, where possible, with no weight or lane restrictions and minimal closures to the flyover.

SOURCE: http://www.bbc.co.uk/news/uk-england-london-18095448

Corrosion Work on George Washington Bridge will take 10 years

Peter Zipf sounds more cardiologist than civil engineer when he talks about subjecting the George Washington Bridge to the equivalent of the classic battery of tests for heart disease and finding the first signs of plaque.

“It really is a little like giving somebody an EKG and checking their cholesterol levels,” said Zipf, the Port Authority’s chief engineer. “There are certain things you know you have to watch for, to catch them before they go too far.”

And chief among those certain things, as a bridge ages, is the corrosion that can sap the strength of its steel.

“Moisture is the big culprit,’” continued Zipf. “You have to constantly monitor the amount of corrosion and the rate of deterioration, and then determine when to intervene.”

The GWB’s test results have spurred the Port to intervene now and undertake the biggest rehabilitation in the 81-year history of the world’s busiest bridge. When the work is completed in 2022 – yes, 10 years from now – the Port will have spent $1.5 billion, a piffle in comparison to the $6-billion-to-$8-billion that it would cost to build the GWB today.

The centerpiece of this your-tolls-at-work program will be the first-ever replacement of the GWB’s suspender ropes, all 592 of them. The ropes, vertical bundles of woven steel wire that attach to the four main cables and support the deck, will be replaced a couple or three at a time to keep the 600,000-ton bridge on an even keel.

To assist, the Port, fittingly, has hired Ammann & Whitney, the consulting engineering firm founded by Othmar Ammann, the man who designed and built the GWB and five other suspension bridges in the city.

The Port will also rehabilitate the upper level’s deck (work already in progress), remove the lower level’s original, and failing, lead paint, rebuild the 177th and 178th Street ramps as well as the multiple ramps to the GWB bus station and repair the Center and Lemoine Avenue bridges.

“The bridge can withstand this extreme work because it’s very robust in terms of strength – remember it was built to handle rail,” explained Zipf. “So that extra strength becomes a safety factor that gives the bridge the tolerance for rehabilitation.”
(Careful readers will recall the Thruway Authority will spend more to build the new Tappan Zee Bridge strong enough to support rail – or serious rehabilitation in the next century, if rail is never added.)

Does any or all of this mean the bridge-and-tunnel crowd is doomed to construction delays at the GWB for 10 years?
“In all of our work, through design, staging of construction and so on, we strive to minimize the impact on traffic,” pledged Zipf. “We’ll only close a lane during off-hours or at night, so if you cross the bridge at rush hour, you aren’t going to be aware that anything’s going on.”

…For 10 years.

http://www.recordonline.com/apps/pbcs.dll/article?AID=/20120409/BIZ/120409746/-1/NEWS

EPA: US needs $300B in sewer, water work

A federal study shows municipalities nationwide need more than $300 billion worth of essential upgrades to long overlooked water and sewer systems over the next 20 years.

The need is acute in Northeastern states with older systems like New York, which needs $29.7 billion worth of improvements, U.S. Sen. Charles Schumer said Wednesday. But he said that price is a “just a drop in the bucket” compared to the higher cost of continuing to upgrade parts of sewer and water systems when emergencies strike. He is pushing a bill that would counter planned funding cuts in the federal transportation bill now being negotiated in Washington.

“EPA found that the nation’s 53,000 community water systems and 21,400 not-for-profit, non-community water systems will need to invest an estimated $334.8 billion between 2007 and 2027,” stated the federal Drinking Water Infrastructure Needs Survey and Assessment, which is updated every four years.

The National Association of Counties’ 2008 report estimated the need for water and sewer upgrades at $300 billion to $450 billion nationwide and the federal stimulus project provided just a fraction of that as the recession reduced local governments’ revenues.

“This is a very serious concern,” said Carolyn Berndt of the National League of Cities. “Many communities have a long-term plan to replace all their underground water infrastructure, but even if they do a couple percentages of pipes a year, it’s still going to take over 100 years for some of them to replace it all.”

She said local governments have been paying more than 95 percent of the cost of water and sewer upgrades since the 1990s as federal aid has declined. Schumer said federal aid covered 75 percent of local costs in the 1980s and 1970s.

“It’s a huge undertaking,” Berndt said. “Some of these pipes are 100 years old. That’s why they continue to see water main breaks.”

The group supports Schumer’s effort, which comes as Congress works to cut spending.

SOURCE: http://online.wsj.com/article/AP219f0f0323df453694748991f44b896d.html

Corrosion threat on Ohio bridge deck discovered

Grout packed into bundles of steel cables that compress the Veterans’ Glass City Skyway’s concrete deck sections together may contain elevated levels of salts that would cause those cables to corrode prematurely, the grout’s manufacturer has warned the Ohio Department of Transportation.

The I-280 bridge over the Maumee River, which opened five years ago, is one of several dozen projects across the United States that used grout made at a Marion, Ohio, plant owned by Sika Corp. U.S. in which excessive chloride compounds, traced to cement the plant bought from an unnamed supplier, have been discovered.

Also potentially affected is the Perry Street bridge in Napoleon, which carries State Rt. 108 over the Maumee and was replaced in 2005, the U.S. 33 bridge over the Ohio River between Pomeroy, Ohio, and Mason, W.Va., and as many as eight other smaller bridges in Ohio. Mike Gramza, the planning and engineering administrator at the transportation department’s district office in Bowling Green, said about 30 projects were affected overall.

Mr. Gramza and a Sika spokesman both said last week they are not yet sure that the particular batches of grout used in the Toledo or Napoleon project contained the elevated chlorides. A company alert identified all grout produced in Marion during an unspecified time that ended in March, 2010, when production there stopped.

In the worst case, they said, chloride presence would not create an imminent — or even short-term — safety hazard on the $273 million bridge built between 2002 and 2007.

But there is the possibility, they said, that as the bridge ages, chloride in the grout could cause the cables — known formally as “post-tensioning tendons” — to corrode and fail sooner than they otherwise would.

Samples will be taken within a few months from the Skyway, Mr. Gramza said, for testing “to see if there is a problem or not.” “It’s not an immediate issue,” he said, “But it could impact the life of the structure.”

More than 3 million pounds of grout from five sources was used on the I-280 bridge to seal ducts through which the post-tensioning strands pass. Those cables, which are distinct from the stay cables that support the bridge deck vertically, compress the bridge’s precast concrete segments against each other and also maintain transverse tension to reinforce the structure.

Grout is a mixture of water, cement, and sand that hardens once mixed. Its purpose in post-tensioning tendons is to protect the steel cables from moisture, road salt, and anything else that would cause them to rust.

Mr. Gramza said the transportation department’s specifications for project materials included an 0.08 percent limit on chlorides in the grout, a normal industry standard. But the suspect grout from Marion, he said, had chloride concentrations as high as 0.5 percent.

Chlorides — the most common of which is sodium chloride, otherwise known as table salt — accelerate the corrosive action of water and oxygen on metals such as steel.

So as long as the grout keeps air or water from reaching the post-tensioning tendons, chlorides’ presence in the grout causes no damage.

But over time, it is likely that tiny cracks will develop in the grout. Any air or water that seeps into it through the post-tensioning tendons’ outer ductwork might eventually reach the cables themselves, delivering the grout’s chlorides — plus any salt already in the water from ice control on the bridge — to the cables and initiating the corrosive chemical reaction that creates rust.

Mr. Gramza said that although grout delivered to the project was tested for strength, it was not tested for chemical composition. The transportation department learned of the problem in “late October or early November,” when it was notified by Sika, he said.

Diana Pisciotta, the Sika Corp. spokesman, agreed that grout is not routinely tested for chloride concentration.

She would not elaborate on how the problem came to Sika’s attention, disclose the source of the cement used at the Marion plant, nor comment on any theories Sika may have about how that cement came to be high in chlorides. But she said the company had been forthright in notifying the grout’s users once it identified where material made in Marion had gone before production halted in 2010.

“We at Sika are not happy that this has happened. We have tried to be proactive in reaching out to people. This really is a situation where you want to be aware,” Ms. Pisciotta said. An advisory describing the matter on a Sika company Web site, dated Dec. 6, said the company had, “over the past several months,” been “working aggressively to address reports” of excessive chlorides in SikaGrout 300 PT product made in Marion.

“There is a concern that, depending on the level of elevated chlorides in the grout in installed locations, the risk of corrosion in the tendon strands could increase,” the advisory said. “While this issue could affect the long-term service life of certain infrastructure projects [roads, bridges, etc.] where the impacted grout was used, Sika is unaware of any damage to structures to date arising from this elevated chloride issue.”

In November, 2010, Sika began “an enhanced quality-control testing regime” that includes chloride analysis for SikaGrout 300 PT made at other plants.

With one exception, listed by the company, all of the Marion-produced grout had lot numbers ending with the letter “M” on bags of the material.

Mr. Gramza said detailed records were kept showing the sources of grout used on various areas of the I-280 bridge, so sampling will be limited to areas where Sika’s Marion-made grout was used. Samples will be tested at a transportation department laboratory, a Sika lab, and a third-party location, he said.

“If there is a problem, we will have to investigate it, and evaluate the potential impact on traffic,” he said. The transportation department will consider Sika liable for the cost of any corrective measures, Mr. Gramza said.

Asked Sika’s position on its liability exposure, Ms. Pisciotta responded: “Our intention is to collaborate with them [ODOT] as they review this issue. We will continue the conversation with them as to what the appropriate next steps are.”

The grout problem is at least the fourth significant materials problem with the Skyway.

In 2004, about 184 cubic yards of concrete was removed from the bridge’s central pylon after sample testing determined a particular batch was weaker than required. Later in the project, officials discovered cracks in the plastic coatings on the bridge’s stay cables and ordered them replaced at the supplier’s expense.

And in 2008, a year after the bridge opened to traffic, inspectors discovered that epoxy glue holding the stay cables’ stainless-steel sheaths together was not holding up and the sheaths were slipping. The sheaths were welded together to remedy that problem.

The bridge also has had sporadic problems with ice forming on its pylon and stays during winter storms, then falling off in sheets onto the roadway when the weather warms, but so far this winter, such ice has not been an issue.

SOURCE: http://www.toledoblade.com/local/2012/02/06/Corrosion-threat-on-Skyway-bridge-deck-discovered.html

Radiation, rust seen in tsunami-hit Japan reactor

The first look inside one of Japan’s tsunami-hit nuclear reactors showed radiation, steam and rusty metal surfaces scarred by 10 months’ exposure to high temperatures and humidity.

The steam-blurred photos taken by remote control Thursday found none of the reactor’s melted fuel but confirmed stable reactor temperature and showed no major damage or ruptures caused by the earthquake last March, said Junichi Matsumoto, spokesman for the plant operator, Tokyo Electric Power Co.

TEPCO workers inserted the endoscope — an industrial version of the kind of endoscope doctors use —through a hole in the beaker-shaped containment vessel at the Fukushima Dai-ichi plant’s No. 2 reactor, hoping the first look inside since the crisis would help them better assess reactor conditions and make repairs.

Results of the 70-minute operation were mixed.

Some parts that were photographed were not identifable, and experts are still trying to identify what the photos show, Matsumoto said. Radiation was apparent as it interferred with the electronic device and was visible as static on the images.

The photos also showed inner wall of the container heavily deteriorated after 10 months of exposure to high temperature and humidity, he said.

‘Given the harsh environment that we had to operate, we did quite well. It’s a first step,’ Matsumoto said. ‘But we could not spot any signs of fuel, unfortunately.’

He said it would take more time and a better technology to get to the melted fuel, most of which has fallen straight down into the area that the endoscope could not reach. TEPCO hopes to use the endoscope to look inside the two other reactors that had meltdowns but that also would require customization of the equipment and further reduction of radiation levels.

Better assessment will help workers know how best to plug holes and cracks in the containment vessel — a protective chamber outside the core — to contain radiation leaks and gradually work toward dismantling the reactors.

Three of six reactors at the Fukushima plant melted down after the March 11 earthquake and tsunami knocked out the plant’s cooling systems and set off the world’s worst nuclear accident since Chernobyl.

TEPCO and nuclear officials have said that melted fuel probably fell to the bottom of the core in each unit, most likely breaching the bottom of the core and falling into the primary containment vessel, some dropping to its concrete floor.

Experts have said those are simulation results and that exact location and condition of the fuel could not be known until they have a first-hand observation inside.

The probe Thursday successfully recorded the temperature inside the containment vessel at 44.7 Celsius (112 F), confirming it stayed below the boiling point and qualifying a ‘cold shutdown state,’ the stable condition that the government had declared in December despite skepticism from experts.

The probe failed to find the water surface, which indicate the water sits at lower-than-expected levels inside the primary containment vessel and questions the accuracy of the current water monitors, Matsumoto said.

The government has said that it would take 40 years until the Fukushima plant is fully decommissioned.

SOURCE: http://www.khaleejtimes.com/displayarticle.asp?xfile=data/international/2012/January/international_January715.xml&section=international&col=

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.

SOURCE: http://www.independent.co.uk/life-style/motoring/motoring-news/race-against-clock-to-fix-vital-transport-artery-for-olympics-6286998.html