 sj |
||
|
||
BS: Forth Road Bridge spans 50 years?
|
|
|
|||||||
|
BS: Forth Road Bridge spans 50 years? |
Share Thread
|
||||||
|
Subject: BS: Forth Road Bridge spans 40 years? From: Rog Peek Date: 15 Dec 07 - 04:09 PM I was watching part of a program on BBC2 tonight where it was explained that the wires in the cables supporting the Forth Road Bridge were snapping due to rust weakening them. This in spite of measures having been taken to prevent the ingress of water. It seems that it has already lost 10% of its wires, and that if this continues the Bridge will have to be closed in 2014. This prompted me to find out when the bridge was built. The answer, 1964. This means that if the worst happens, then this bridge will have lasted just 50 years. Now, this further prompted me to find out when the Brooklyn Bridge was built. Answer, 1883. This means that this suspension bridge continues to carry motor vehicles after 124 years of service, and will continue to do so it seems for a number of years more. This, in spite of the fact that during construction, due to a financial swindle in one of the companies supplying the wires for the cables, a quantity of wires used in the cables were substandard. Now, experience has taught me that while change can be for the better, all too often it isn't. It would appear that this may be the case when it comes to the construction methods as applied to suspension bridge design. Rog |
|
Subject: RE: BS: Forth Road Bridge spans 40 years? From: Newport Boy Date: 15 Dec 07 - 05:42 PM The problem is related more to the size of the bridge than just the construction method. Brooklyn Bridge is less than half the span of Forth. The methods used for the cable construction were remarkably similar. The problem on Forth (and also Severn) was first investigated following discovery of corrosion in US suspension bridges of similar size and age. The 10% loss in wires (which I think is a slight simplification) sounds dramatic, but bear in mind that the main cables have a huge safety factor. For the Brooklyn Bridge it's variously quoted as 4 or 5 times, and the UK bridges won't be that different. Phil |
|
Subject: RE: BS: Forth Road Bridge spans 40 years? From: Rog Peek Date: 15 Dec 07 - 06:02 PM I don't understand what you mean by 10% in loss of wires is a simplification. Do you mean it is an estimate? I understand the rest of what you are saying, but it seems to me that a 50 year life span for a 19 million pound bridge doesn't seem very much. Rog |
|
Subject: RE: BS: Forth Road Bridge spans 40 years? From: Steve Shaw Date: 15 Dec 07 - 08:51 PM I'm sure two or three cans of WD40 would do the trick. |
|
Subject: RE: BS: Forth Road Bridge spans 40 years? From: wysiwyg Date: 15 Dec 07 - 11:15 PM And duct tape. I lost a dishwasher rack this way, with water getting into the wire under the plastic coating and rusting it all to crap. ~S~ |
|
Subject: RE: BS: Forth Road Bridge spans 40 years? From: Sorcha Date: 15 Dec 07 - 11:20 PM I'm not sure I quite understand either. Does salt or fresh water matter? I'm thinking Golden Gate and several others but I don't know the ages of all of them. Humber, Verrazzano Narrows (fairly new?), Flaming Gorge (Colorado, US), isn't there a bridge in Sydney, Aus? |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Joe Offer Date: 16 Dec 07 - 12:44 AM I think some photos are in order. It certainly is a magnificent bridge, but not as memorable as the Firth of Forth Bridge. How far apart are the two bridges? This page makes them look like they're almost side-by-side. Do they keep the same cables on bridges for a century or more? I thought there would be some sort of replacement program. This page (click) is a study of an extensive test of the Golden Gate Bridge cables in 1967 and 1973, which found very little deterioration. Apparently, the cables were later sealed in plastic to further prevent corrosion. This page (click) is a more general discussion of bridge maintenance. Wikipedia has fascinating articles on cable-stayed bridges and suspension bridges (who knew there was a difference?). Years ago, I saw a museum exhibit on the Golden Gate Bridge, and I was surprised to see how the cables were made. The wires aren't twisted at all - it's just a big, highly compressed bundle of straight wires, covered with a red lead paste, and wrapped very tightly with another wire that is then sealed with paint and plastic. It looks like a solid pipe, and you can't imagine it has any flexibility at all. I love to walk famous bridges - and the Golden Gate is one of my favorite bridge walks. I guess that one and the Brooklyn Bridge are the longest bridges I've walked. -Joe- Oh, and I have to add a link to this page of photos of the Firth of Forth Bridge. Can I walk either bridge? |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Newport Boy Date: 16 Dec 07 - 05:52 AM Wow! I go to bed for 8 hours, and the questions pile up. First - I'm not an authority and I'm not a designer. I was a civil engineer and I've worked on the construction of bridges, but not suspension or cable-stayed bridges. I've been retired since 1993. I live near Bristol and worked for 8 years for Freeman Fox & Partners, designers of the Forth, Severn and Humber road bridges. One of my occasional jobs was to act as guide to visitors to the Severn Bridge, so I've been down inside the anchorages and up to the top of the towers. (Also, if you promise not to tell, I once walked over the cable spinning platform during construction - I was stuck on the wrong side of the river when the ferry had stopped, and security wasn't very tight in 1965). I also visited the Humber Bridge during construction of the towers and went to the top of the north tower. [Further episodes of my life history in other threads!!] Rog - The 10% is a sample. I don't know the details, but on both Forth and Severn the cables have been exposed and examined at a small number of places. A break in a single wire may theoretically mean that wire is useless over the whole length, but bear in mind that that length is well over a mile on Severn. The hanger cables are clamped on the main cable, and although a wire may be broken at one point, it may still be carrying load some distance away. Sorcha - Yes, exposure is one of main problems. These 3 bridges are all on tidal estuaries and exposed to salt spray. Severn is also particularly exposed to the southwest gales. There are large suspension bridges with similar cable construction all over the world. There's a good list here Bridge spans although I think it needs an update. Joe - Some good photos of Forth. The road and rail bridges are fairly close - a few hundred yards at the north end. I think the Severn bridge is more elegant than Forth, which still has a steel truss - Severn is an aerodynamic box deck. Some photos here Severn Bridge . These also show some details of the cable construction. Your reference on bridge maintenance includes details of cable replacement on a Venezuelan bridge. This is a cable-stayed bridge, where individual cables provide support at various point on the deck. One cable can be removed without the bridge collapsing. Suspension bridges are entirely reliant on the main cables - you could cut the deck into pieces (as long as each piece had 2 hangers) and still walk across - I wouldn't recommend driving. I was involved in replacing the cables on Newport Transporter Bridge - pictures here Transporter bridge . A few years after these photographs were taken, inspection revealed that the cables holding up the cantilever (right of the tower in the main picture) was almost corroded away. The bridge was immediately closed, and eventually all the cables were replaced. The bridge was originally opened in 1906, and is one of only half a dozen still operating worldwide. And, Joe, you can walk over the Forth and Severn road bridges - I've walked and cycled both. If you stand still in the centre of Severn, the movement as heavy traffic passes is quite amazing. You will realize how flexible suspension bridges can be. You can't walk the rail bridge. If you can get over, and you need a guide, give me a call. Phil |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: maeve Date: 16 Dec 07 - 06:25 AM Thanks for the cogent explanation, Newport Boy. So I've one more question. How would repairs to a suspension bridge such as the Severn or the Forth be approached? maeve |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: goatfell Date: 16 Dec 07 - 06:33 AM there's the kircandine bridge that crosses the Forth as well, so there are really Three Bridges that cross the Forth. Tom And I wathced the programme last night as well. Snap |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Newport Boy Date: 16 Dec 07 - 07:05 AM Doesn't a woman know how to ask the difficult questions! Well, Maeve, replacement of a main suspension cable on a bridge the size of these would not be easy. Forth has over 11,000 wires in each cable, and the cables were constructed by carrying these wires (probably in small groups) from one anchorage over the two towers to the other anchorage and back again. This cable spinning took quite a while, with no need to consider traffic below. A feasibility study has been carried out on replacement or upgrading, and I understand that it is considered possible, but with years of disruption to traffic. Publication of the report is expected early in 2008. There is also a generalised study here , but I don't want to buy it!! I think the plan for Forth is to construct a new crossing (bridge or tunnel) before cable replacement is necessary. Load restrictions are likely to be necessary if cable deterioration continues. Phil |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Rog Peek Date: 16 Dec 07 - 08:15 AM Thank you Newport Boy, you've made this thread very informative and interesting. Rog |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: maeve Date: 16 Dec 07 - 08:36 AM Well heck, Newport Boy, the asking was easy!(Smiles modestly) Thanks for taking a stab at the answer! maeve |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Ernest Date: 16 Dec 07 - 10:49 AM A bit off topic: Some information/photos about the Forth Bridge are in this book edited by the Canadian Center of Architecture which has a collection of photos by Evelyn George Carey documenting the building of said bridge: http://www.amazon.de/Forth-Bridge-Tangent-Bridge-Cinema-Metrique/dp/3037780487 Best wishes Ernest |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: catspaw49 Date: 16 Dec 07 - 01:24 PM Joe, I am completely ashamed of you. Where is the dignity of your roots? There you are, a lad from the Great Lakes States with a purported love for walking bridges and yet you seem to have turned your back on one of the greatest, the longest 2 tower between anchorages in the western hemisphere, the elegant Mackinac Straits Bridge. Note that they have an annual bridge walk! But have you done it? An American from the Great Lakes on THIS thread and you don't even mention Mighty Mac. You're pathetic. You've gone completely over to the California Zombie people haven't you? Or just go hang with your Brit buds here and walk some "Forth" rate bridge and see if I care...........You're obviously beyond hope. I'm ashamed to even know you................ Spaw |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: GUEST,The black belt caterpillar wrestler Date: 17 Dec 07 - 07:53 AM Am I right in remembering that the Brunel designed Clifton Suspension Bridge (using chains not wires) has main chains that came from an earlier bridge across the Thames? |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: gnomad Date: 17 Dec 07 - 08:30 AM Humber Bridge had a mention further up. You can walk or cycle this one (free) or pay the toll to drive. The downhill side on a bike is quite a flight. We regularly get quite strong winds on this coast, if you drive over during a high crosswind the lurch to one side and back as you pass through the shelter of the bridge piers can be exciting. I see that the designed life for it was 120 years, but recent TV reports suggested that this may need to be adjusted, same problem as on the Forth. I think it will outlast me, though (dons old crone kit) I remember it when the north anchorage was just a huge hole in the ground waiting to be filled with concrete. |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: GUEST,Keinstein Date: 18 Dec 07 - 05:08 AM Brunel designed the Clifton bridge, but the company building it (it is still a private toll bridge) ran out of money and it was not completed in his lifetime. After his death, a committee of engineers completed it as a memorial to him, using the chains from his Hungerford suspension bridge, which was at the time being replaced by a new bridge to carry railway traffic. The Forth railway bridge is certainly impressive. It was deliberately massively over- engineered, as confidence in civil engineering was low following the collapse of Thomas Bouch's original Tay Bridge. Which is an excuse once more to quote the magificent poem by William Topaz McGonagall concerning that sad event: Hhhrrmph (clears throat, left thumb in lapel, head slightly back, right arm extended and slightly raised): The Tay Bridge Disaster Beautiful Railway Bridge of the Silv'ry Tay! Alas! I am very sorry to say That ninety lives have been taken away On the last Sabbath day of 1879, Which will be remember'd for a very long time. 'Twas about seven o'clock at night, And the wind it blew with all its might, And the rain came pouring down, And the dark clouds seem'd to frown, And the Demon of the air seem'd to say- "I'll blow down the Bridge of Tay." When the train left Edinburgh The passengers' hearts were light and felt no sorrow, But Boreas blew a terrific gale, Which made their hearts for to quail, And many of the passengers with fear did say- "I hope God will send us safe across the Bridge of Tay." But when the train came near to Wormit Bay, Boreas he did loud and angry bray, And shook the central girders of the Bridge of Tay On the last Sabbath day of 1879, Which will be remember'd for a very long time. So the train sped on with all its might, And Bonnie Dundee soon hove in sight, And the passengers' hearts felt light, Thinking they would enjoy themselves on the New Year, With their friends at home they lov'd most dear, And wish them all a happy New Year. So the train mov'd slowly along the Bridge of Tay, Until it was about midway, Then the central girders with a crash gave way, And down went the train and passengers into the Tay! The Storm Fiend did loudly bray, Because ninety lives had been taken away, On the last Sabbath day of 1879, Which will be remember'd for a very long time. As soon as the catastrophe came to be known The alarm from mouth to mouth was blown, And the cry rang out all o'er the town, Good Heavens! the Tay Bridge is blown down, And a passenger train from Edinburgh, Which fill'd all the peoples hearts with sorrow, And made them for to turn pale, Because none of the passengers were sav'd to tell the tale How the disaster happen'd on the last Sabbath day of 1879, Which will be remember'd for a very long time. It must have been an awful sight, To witness in the dusky moonlight, While the Storm Fiend did laugh, and angry did bray, Along the Railway Bridge of the Silv'ry Tay, Oh! ill-fated Bridge of the Silv'ry Tay, I must now conclude my lay By telling the world fearlessly without the least dismay, That your central girders would not have given way, At least many sensible men do say, Had they been supported on each side with buttresses, At least many sensible men confesses, For the stronger we our houses do build, The less chance we have of being killed. |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Folkiedave Date: 18 Dec 07 - 05:43 AM Graeme Miles wrote a song about it. I can unfortunately remember bits - sing by Mike and Norma Waterson as a duet. "Oh where is the young lad, the young engineer? Not seen him in these parts for many a year, Well if you mean Johnny, you'll find him up north, At work on the new bridge that spans o'er the Forth". Finishes with my favourite line "As the men from the south and the men from the north, Will meet and complete the bridge over the Forth". If anyone knows of anyone who has recorded it I would be really grateful. |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: markpde Date: 28 Dec 07 - 12:19 PM I work as a driving instructor. In 1964, 4 million vehicles crossed the 'new' bridge. In 2004, the figure was 24 million. Try telling that to parents who think their children have 'too many driving lessons'. I'm also old enough to remember (vaguely) crossing the Forth on the ferries. I was only a child then, but it was pleasant; exciting; an adventure. Why is everybody in such a rush? Progress is not always for the better. Hopelessly naive comment, I know, but sometimes thoughts like that are therapeutic. Slow down, world!!! |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Murray MacLeod Date: 28 Dec 07 - 07:22 PM Spaw appears to be extremely jealous of the magnificent erections to be found on this side of the Atlantic imo |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Wainwright99 Date: 28 Dec 07 - 11:46 PM Er, Sorcha ... yes, there is a bridge in Sydney Australia - in fact there are a few... in fact quite a few. Most of our Oz cities and towns have several bridges.... You are no doubt thinking of the Sydney Harbour Bridge, built in the late 1930s and still very much in use and safe - in fact they are going to widen it sometime down the track. |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Sandra in Sydney Date: 29 Dec 07 - 06:47 AM Sydney's 7 Bridges Walk |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: Newport Boy Date: 29 Dec 07 - 07:19 AM Worth a note that the Sydney Harbour Bridge was designed by Ralph Freeman (1880-1950). His son, also Ralph (1911-1998) was responsible for the design of the Humber Bridge, and teams under his direction designed the Forth and Severn bridges and both the bridges over the Bosporus. The firm also designed the Auckland Harbour Bridge. Phil |
|
Subject: RE: BS: Forth Road Bridge spans 50 years? From: danensis Date: 29 Dec 07 - 11:03 AM My late father-in-law Robert Edward (Colin) Campbell was involved with the design and manufacture of the ropes used in many suspension bridges around the world. Indeed he invented many of the processes for drawing these ropes, but got little credit for it. It seems strange that there should be a quote about the Tay Bridge disaster in the same thread, as his great uncle was killed in that disaster - indeed his grandfather married the younger sister of the victim, after her father died of a broken heart. John |
