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Mabey trials bridge off-site
17:00 24 Mar 2004
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Mabey Support Systems has completed an off-site trial of an
overbridge that will handle Euston Road traffic while excavation
takes place beneath the bridge for a new ticket hall at London's
King's Cross Underground station.
"Off-site trials are usually very rare, but the client Infraco Sub-Surface requested one due to the nature of the job," said Chris Carter, Mabey's commercial director. "The bridge will be on site for 40 weeks from July/August, but has got to behave like a permanent bridge."
The trial took place in Flint, North Wales, and took four weeks to set up and check. But Mabey will have just four nights and three days to erect the bridge in London. "We only have four hours each night to erect the Quickbridge. We have to do it when the trains aren't running because the crane will straddle the Tube line.
"So we have had to develop a very specific lifting programme," said Carter. "During the day, the pair of four-men crews will only be able to do finishing work on the deck, nothing that involves lifting." Carter says the operation should be relatively simple as it is "basically just lifting and putting each piece of the bridge in place".
The Quickbridge, which will cater for two lanes of traffic, is supported by steel portal frames delivered complete with parapets, kerbs and anti-skid surfacing. All the braking and traction forces are transferred through the decks to the fixed abutment. The bearings are close tolerance to cater for the client's design approach and the portal frames will be fed through the carriageway to a pedestrian tunnel beneath where the foundations will be located. The holes will be formed with a piling rig leaving sleeves for the portal legs.
"If there are any problems they will be logistical, namely physically moving this much equipment in a short timeframe during a road closure and at night.
"But this is why the off-site trial is a great idea. We don't want any surprises on the night; the cost of any disruption would be phenomenal," said Carter.
The value of Mabey's contract is £370,000, while the overall cost of the new ticket hall, being constructed by a Taylor Woodrow/ Costain jv, is £70m.
"Off-site trials are usually very rare, but the client Infraco Sub-Surface requested one due to the nature of the job," said Chris Carter, Mabey's commercial director. "The bridge will be on site for 40 weeks from July/August, but has got to behave like a permanent bridge."
The trial took place in Flint, North Wales, and took four weeks to set up and check. But Mabey will have just four nights and three days to erect the bridge in London. "We only have four hours each night to erect the Quickbridge. We have to do it when the trains aren't running because the crane will straddle the Tube line.
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"So we have had to develop a very specific lifting programme," said Carter. "During the day, the pair of four-men crews will only be able to do finishing work on the deck, nothing that involves lifting." Carter says the operation should be relatively simple as it is "basically just lifting and putting each piece of the bridge in place".
The Quickbridge, which will cater for two lanes of traffic, is supported by steel portal frames delivered complete with parapets, kerbs and anti-skid surfacing. All the braking and traction forces are transferred through the decks to the fixed abutment. The bearings are close tolerance to cater for the client's design approach and the portal frames will be fed through the carriageway to a pedestrian tunnel beneath where the foundations will be located. The holes will be formed with a piling rig leaving sleeves for the portal legs.
"If there are any problems they will be logistical, namely physically moving this much equipment in a short timeframe during a road closure and at night.
"But this is why the off-site trial is a great idea. We don't want any surprises on the night; the cost of any disruption would be phenomenal," said Carter.
The value of Mabey's contract is £370,000, while the overall cost of the new ticket hall, being constructed by a Taylor Woodrow/ Costain jv, is £70m.
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