Tag Archives: London

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spokesman said: “TfL must realise that we cannot simply accept patch-jobs to prolong the life of this monstrous outdated and crumbling structure.”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

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

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.”

SOURCE: http://www.constructionenquirer.com/2012/01/03/serious-corrosion-keeps-a4-flyover-closed

British engineers help to save WWII Dornier Do-17 German bomber from its last battle – Corrosion

Researchers from Imperial College London are working with the Royal Air Force Museum to clean the Dornier Do-17, known as The Flying Pencil (Fliegender Bleistift), and prevent further corrosion once it is removed from the water.

In 2010, shifting sands uncovered the aircraft, which lies off the Kent coast and was previously protected by layers of sediment, exposing it to the corrosive effects of seawater and threatening to destroy the aircraft entirely.

Dr Mary Ryan from Imperial’s Department of Materials, who is working on the project, said: ‘This is the last remaining intact Flying Pencil of its kind in the entire world, so the significance of this project to our history cannot be underestimated.”

‘We have been analyzing fragments already brought to the surface and it is absolutely fascinating to see how this bomber, which crash landed more than 70 years ago, has been so well preserved by the layers of sand.’

One of the challenges for the Imperial team is devising a method for cleaning and removing the corroded layers from the Flying Pencil’s aluminium fuselage, which contains large amounts of the corrosive agent chloride from the seawater.

The researchers are currently testing a solution based on citric acid, which is found in high concentrations in citrus fruit, to remove the surface layers of corrosion and sea deposits such as crustaceans from small pieces of wreckage already retrieved.

The aim is to develop a solution that is powerful enough to clean the bomber, but not so powerful that it damages any remaining paint and markings on the aircraft, which are of historical significance. Any remaining chloride on the metal surface could lead to further attacks of corrosion when the plane is on display.

The Imperial team will also help to work out the best environmental conditions for displaying the bomber in the museum. For example, too much humidity in the air could lead to condensation on the metal, which would activate further corrosion.

Once the research is complete, a team from the museum, working with specialist underwater archaeologists and recovery experts, will use a lifting cradle to support the weight of the fragile aircraft as it is brought to the surface, currently planned for spring 2012.

The Flying Pencil was brought down by the RAF on 26 August 1940, during the height of the Battle of Britain while en route to attack airfields in Essex with a large German formation.

It crashed into the shallows off Goodwin Sands killing two of the crew members, who were later recovered and buried in a military cemetery. The other two crewmen were taken prisoner.

Ian Thirsk, head of collections from the Royal Air Force Museum, said: ‘At the moment, we are attempting to trace the relatives of the crew members who survived this fateful mission, in order to help engage visitors to the museum about the human story behind this episode of the war.

‘As the last surviving example of the Dornier Do-17, this aircraft is truly unique. We think this old bomber has one last scrap left in her — the battle against corrosion.’

Once the aircraft is lifted from the seabed, it will then be transferred to the museum’s conservation facility at Cosford, and then placed on display in the planned Battle of Britain Beacon Wing at the museum’s London site.

SOURCE: http://www.theengineer.co.uk/sectors/aerospace/british-engineers-aid-attempt-to-save-german-bomber/1010776.article