Let’s Design a 60 Ft. Suspension Bridge
fingersandtoes
| Posted in General Discussion on
That’s what two local handymen did for a client down the road who wanted a path to the other side of his 20 ft deep ravine. I went and looked at it today as the new owner is a bit worried – and rightfully so.
It is made up of six railway tracks, some angle iron, a half inch cable and a PT wood deck. Everything but the wood is severely corroded even though the bridge is only two years old. Sorry no pictures – I’ll try and get some before the thing collapses.
Oh, and last weekend the owner used it to stage group wedding photos!
EDIT: PICTURES KINDLY ADDED BY JOHN7G IN POST 39.
Edited 10/16/2009 2:02 pm ET by fingersandtoes
Replies
You could start here
http://entrylevelliving.files.wordpress.com/2008/03/silbermann-henri-brooklyn-bridge-4800186.jpg
and work your way to the Golden Gate
I thought sure this was McDesign
(no help, sorry)
maybe tell him this pic is the mock up
Lord no, I don't want to have anything to do with it. There isn't a thing about it I trust. I just can't believe they blithely decided to have a go at something that size with no experience.
An intriguing concept, though somewhat frightening. Got pics?
i'm curious,what do you suppose it would cost to privately build a engineered bridge to span 60' over a 20' ravine? i'm guessing on the north side of 150k for a walking bridge.
how come its rotting away? is it the treated wood with steel causing it?
might be cheaper to form it and pour it full of cement!
the older i get ,
the more people tick me off
I've seen ranchers build bridges that long using pre-deflected "I" beams, and welding a mesh deck and rails directly on the beams. They usually truck in the beams half as long as needed and splice'em on site. Then they snake each beam over and weld or bolt it to the headwalls on either end, then attach the deck and rails. Your bridge is only as good as the headwalls/footings at either end anyway, so you better put some wing-walls there to stop erosion. These bridges are good enough to drive a tractor or truck over the creek.
yeah, i know of one that's built out of old tractor-trailers. i can't
recall if it's two or three welded together end to end.it spans a
very deep draw.
Be kind of a beech if the draw flooded, wouldn't it? ;-)
Wing walls? Funny guy!
There are two concrete blobs at each end of about 3 yards material each into which the railway tracks have been poured upside down. The tracks are bolted together with straps which have loosened on one side so there is an 1 1/2" gap between them. Then were originally supposed to be straight, but the builders never managed to get them that far up so the bridge sags about three feet in the middle. On the bottom of the tracks are welded pieces of angle iron of various lengths pointing down from which a cable is attached. The corroded cable (nothing is galvanized or painted and this is on the ocean front) is attached through holes in the railway tracks where they enter the concrete blobs by somehow tying big knots in it. Above all this is a rickety structure of Pt decking and rails.
The present owner gets no sympathy from me. He bought the property for 1.6 million without a building inspection and never even looked at the bridge, which he knew had been built by two ex-navy guys supplementing their pensions as handymen. Now he wants to "put some posts under it" which will only make things worse.
we definitely need pics now.
The more you keep talking the more FUBAR it sounds
>>had been built by two ex-navy guys supplementing their pensions as handymen.<<
Swabbies woulda painted it.
Sounds like a jar-head-fubar to me... ;-)
"Sounds like a jar-head-fubar to me... ;-)"
Definitely navy. The one who appears to be the brains of the gang must have been a higher up - not an officer, but something that inspires fear or respect because they generally defer to him. Unfortunately his wife has run off with someone she met on the Internet, an all too frequent occurrence around here, and he is now stuffed to the gills with prescription mood alterers, making it difficult to get much insight into what they were thinking when they set out on this adventure.
Wing walls? Funny guy!
Headwall erosion has probably condemned more bridges than any other condition.
It's probably the least-considered aspect in bridge design--except by professional bridge engineers.
And, the simple matter of fact of it is that there is no such thing as an inexpensive bridge. The only thing more expensive than a good bridge is a collapsed one (one of the bons mot I remember from my CE classes). I know of some engineers who will hold (if pressed, and off the record, and after sufficient adult libation) that it's almost better to let hacks build these things to only "scare the willies out of all users" as that tends to limit the risk. Which helps keep vehicles off structures barely able to support pedestrians.
And a "pedestrian only" bridge is actually "worse" in design. City built one over a creek bed in a park, running from 150 flood year contour to 150 flood contour. Engineer was grilled over the specs for this monster afterwards. Said worthy used two 300# persons per square foot of deck and assumed they were jumping up and down to start the desing load. City fathers goggled a bit, until the engineer produced photos of bridge inaugurations, anniversaries and the like, when they'd be covered in people, often dancing or the like. That bridge is blocked off right now--flood condition took the approach to one headwall away.Occupational hazard of my occupation not being around (sorry Bubba)
My BIL owns property in Connecticut that has a stream on the property (used to be the site of a gristmill, long since gone.He owns land on both sides of the stream, and initially wanted to build his new house on the far side from the road. So, he started asking various businesses for proposals and bids.The lowest number he got was "a $30,000 retainer, to begin the engineering work toward designing a bridge". And it seemed to be a forgone conclusion that the engineering work would be at least twice the retainer.
And that would have been for a design. No bridge included.
I won't be laughing at the lies when I'm gone,
And I can't question how or when or why when I'm gone;
I can't live proud enough to die when I'm gone,
So I guess I'll have to do it while I'm here. (Phil Ochs)
This past year we sold 7 60' flat cars for bridge use in the Sacramento area of Calif. look up on eBay or check out the local C.P. and ask if they are selling any used flat cars. far cheaper than building from scratch.
Probably 20 years ago or more, I was a church youth group leader, and we took the kids to a service project working on houses in the appalacia section of Ohio.
One of our jobs was to re-roof a cabin-kinda thing that an older woman was living in.
The road was on one side, and the cabin was on the other side of a stream. There was a footbridge only, and no way to ford the stream with a truck. So, all of the tools, ladders, and materials had to be hand carried across this single-file bridge.
Which was supported mainly by a pair of old railroad rails -- and like yours, the "handrails" were nothing more than some steel cable.
And if your waling pace matched the "harmonic" of the bridge, this thing would bounce more than three feet below and above its steady-state position.
Which was kinda scary if you had a roll of 90 pound roofing on your shoulder.
Scary -- but that bridge had been there for more than thirty years.
I won't be laughing at the lies when I'm gone,
And I can't question how or when or why when I'm gone;
I can't live proud enough to die when I'm gone,
So I guess I'll have to do it while I'm here. (Phil Ochs)
Railroad track is far from a structural material. I've seen it used in place of I beams, but it's really quite weak, and not as rigid as one might think. The weight alone is fearsome - enough to make it bow even before a live load is applied.
Greg
RR track is very "structural" if you're not spanning more than 12" ;-)
If one was to build a truss out of that material it would be very strong, but not practical & the weight would kill most mobile cranes.
FS&T
as a volunteer for my church camp i have designed (with the help of a structural enineer) and built a bridge (30,000 lb capacity) and ropes challenge course ( 30 ft above grade) suspended from cables. the forces invloved in these types of structures are significant and not always intuitive. An engineered design is always going to be more than you would like to pay but worth every penny. A failure of this structure resulting in a 20 ft fall is real bad.
i would suggest you look on line for prefabricated bridges the type used in parks. Just google prefab bridges. These companies will provide a engineered solution for a premanufactuered structure that will come with a warrantee. A 60 foot span is well with in their capablities.
Gotta tell you a Boy Scout rope bridge tale. While on Okinawa, my Boy Scout troop built a three rope bridge across a Benjo (Read that as Sewer) ditch for a pioneering project. Unfortunately, we had no trees on either end to anchor the load carrying rope to, so used a series of three stakes driven well into the ground as support anchors. We used all the appropriate rope sizes & constructed it one Sat AM. It was raining and after the third pair of boys entered it to cross, the supports on one end slooooooooooowly pulled out of the rain sodden ground & dropped two boys slowly into the rather trashy water about 10 ft below.Hope the bridge we are reading about never does that.DonDon Reinhard
The Glass Masterworks
"If it scratches, I etch it!"
This could be an interesting project! Let's start 'imagine- eering' (Sorry, Mickey!)
First, let's recognize what makes a suspension bridge different from every other type of bridge. Well, as I see it, the deck itself doesn't really hold anything up. Rather, the weight is transferred to the cables as tension ... which in turn press straight down on the towers at either end.
So ... the cable anchors need to 'pull' just as hard in the opposite direction. This means they need to be big, heavy, and anchored deep. I'd say the anchors at either end are the real keys to the design.
The "towers" don't need to be anything fancy. All they need to do is hold the cables up, let the cables (at least theoretically) slide back and forth, and ne able to support the bridge load, only this time as simple compression. I suspect that ordinary 8x8 pressure treated poles would be strong enough. And, at 20ft. long, they're plenty tall enough, even allowing for the bottom 4 ft. to be set in the ground.
The hardest part of the cable design is attaching the smaller cables that go straight down to the deck, I suspect, for your light loads, you'd be better off using chain instead of cable; then you can hand the verticals from links as you go along.
The vertical chains in turn support cross-ties, which are what bear the weight of the decking and traffic. Now ... for the decking ...
As i think this through, I realize that, to a certain extent, the decking needs to be free to float around, rather than be rigidly fixed in place. There's no denying that this bridge will move in response to changes in loads. That's really not much of a surprise; I suspect every kind of bridge moves more than we realize.
We do need the decking to be somewhat stiff, and able to at least carry it's own weight across the gorge. This will make the construction a lot easier; you'll be able to work from deck level, rather than from atop the cables.
So ... I'd use TJI's to make a big box beam to serve as the deck. Off the cuff ... I'd use 9-1/2 TJI's, 16" centers, so there would be four across a 4ft. wide deck. Cover top and bottom with plywood to make the 'box.'
The devil is in the details, and the details you have to wrestle with are the length of the vertical chains, and the arc of the top cable. As the bridge is assembled, the cable will curve down more, which means that the length of the verticals will become shorter. You'll have to constantly adjust, or the bridge will have a pronounced curve -up or down- depending upon the load. Ideally, you will have a slight upward arch to the deck when the bridge is empty.
Once the all the boxes are installed and connected together, you can tie them together with another layer of plywood, and add the decking atop that.
Now, mind you, this is just armchair dreaming .... I've never done anything even remotely like this .... but that's how it seems it should work!
First, let's recognize what makes a suspension bridge different from every other type of bridge
Even better, this is not a "suspension bridge" at all.
Go back and read the second description (I think). This is a jack-strut structure; the cables are underneath and sprung off the rails from below.
Pictures would probably be good, is not also worse at the same time.Occupational hazard of my occupation not being around (sorry Bubba)
I built a 55' bridge over a 16' deep ravine, but it was split into three spans with trestles supporting.
Owner was an archy. They accepted my design without any lawsuits later! <G>
I was one of my favorite projects! We set rope rigging in big fir trees at both ends and rigged up a block and tackle to slide on the ropes so we could lower the 20' treated 4x12's into place.
A thread like this without photos is an outrage! I am so disappointed in you....
Profuse apologies over the lack of photos. I will try and get back tomorrow and satisfy your appetites. I am really enjoying the discussion.
Thanks. We can't fully gloat without pics.
Full specs, ready to build:
Might be a little bigger than necessary, but at least it'll reach the other side....
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
well, as is happens, there is expertise here at breaktime associated with suspension bridges -
here's a thread from zak, about building one -
View Image"there's enough for everyone"
Profuse apologies over the lack of photos. I will try and get back tomorrow and satisfy your appetites.
Another day has come and gone. Why are you keeping us in suspense, Mr. Roebling? http://www.nps.gov/upde/historyculture/roeblingbridge.htm
just give us the coordinates and we'll look at in Google streetview
;-)
I've ridden my bicycle across Roebling's bridge. It's really quite an interesting piece of history.
View Image
The upper Delaware river is part of my extended stomping grounds. Beautiful area.
The history of the canal system that brought anthracite coal from NE PA to NYC and other places is quite remarkable. The Roebling bridge, being part of the original canal, makes it even more so.
I've ridden across the bridge on two wheels as well, often. The road up the Lackawaxen creek from there is very scenic. Zane Grey's summer home is right there too, tended now by the NPS. It's definitely worth a visit.
Ok. I went and took several photos and have spent the best part of the evening trying to attach them with no success. Rather than spend more time, I suggest to expedite things anyone who would be kind enough to volunteer, I will Email them the photos and they can post them.
I"m game. Send them on.
There are several provincially-built suspension foot bridges here in New Brunswick, typically they have a steel tower at each end, made of two pieces of steel piling.
Here is a link to some info, might give you some ideas:
http://suspension.nblighthouses.com/
This one in New Portland, Maine might be good for a few ideas. It was built in 1864-1866 and is said to retain many of it's original components. They did something right.
View Image
"There can be no doubt that Socialism is inseparably interwoven with totalitarianism and the abject worship of the state…Socialism is in its essence an attack not only on British enterprise, but upon the right of ordinary men and women to breathe freely without having a harsh, clammy, clumsy tyrannical hand clasped across their mouth and nostrils" -Winston Churchill
Here's a pedestrian bridge between Brunswick and Topsham ME, across the Androscoggin River. It replaced one built by Roebling in 1892, washed away in the 1936 flood.
View Image
LOL .......... my little brother's apt. building is in the pic. Good to see the bridge rehabbed- it was in pretty rough shape when I saw it last. Next trip back I hope to get to see the new (to me) Penobscot Narrows Bridge along with a visit to the observatory in the tower.
"There can be no doubt that Socialism is inseparably interwoven with totalitarianism and the abject worship of the state…Socialism is in its essence an attack not only on British enterprise, but upon the right of ordinary men and women to breathe freely without having a harsh, clammy, clumsy tyrannical hand clasped across their mouth and nostrils" -Winston Churchill
The bridge had a major rehab a few years ago. It still has an amusing (or terrifying) bounce to it.
I haven't been on the Narrows bridge yet either. I'll go up in the tower, but DW will wait below:-)
Redoing the railway here along Highway 59 1 mile away as a part of the NAFTA I-69 coordor.
Replacing the wooden bridges with concrete / steel.
The contractor gave me a 30' section in great shape, heavy multi-beam set up and railroad ties angle iron bolted to and over the beams. I could have had more sections. Our dirt / sod hauling contractor sent his 18 wheeler and hauled the short distance for free He keeps cows on my property at no lease charge and we help each other often.
One unintentional discovery: beams down pushed with the dozer perpendicular across the ground destory unwanted plants and provides rough fairly level grade.
The plan: drill three bell bottom piers on each side of the creek, reinforce and fill with concrete, set 6" steel reinforce bearing slab on top of the pier tops and fasten the bridge to the slab. Country boy enginneering. Material cost $600.00.
If I needed 60' - two 30' spans and a designed center support simialr to the railroads design.
Location is on my property and casual, set up to facilitate land clearing and so on for development . It should support golfcart / bulldozer / tractor / backhoe / truck and trailer / cows and horses / foot traffic......maybe not all at the same time during a woop de doo parade : - )
and the pictures from Mr FingersAndToes:
View Image
View Image
View Image
View Image
were these old navy guys thinking they were in the Bridge On The River Kwai while they were building this? I can hear them whistling the Comet song now.
The reality in the photos is scarier than the word picture originally made.
Wood in the thing looks more sound than the steel--and, that ain't much at all.
Would take 3-4x the structure there juts to demolish it properly. And it need demolishing, since it's probably impractical to find enough darwin award candidates to pogo stick on the thing.Occupational hazard of my occupation not being around (sorry Bubba)
I'm not sure what their intent was with the steel. The cables could've done a decent enough job without the excess weight of the rails.
But he just said the cable had knots in them. I'm not sure how steel cable does with that kind of bending as strength goes, but in climbing ropes, knots usually reduce the strength considerably depending on the knot.
John, thanks again for posting the pictures.
All questions about corrosion aside, I wonder once they had decided on this approach why they didn't make the supports longer? The cable is at most a couple of feet below the rails. More depth would have made a lot of difference.
I'm not sure more depth would've made that much of a difference with the way the RR track sags and the splices failing. More tension on the cable would've allowed less of the sag.
I'm not sure how steel cable does with that kind of bending as strength goes, but in climbing ropes, knots usually reduce the strength considerably depending on the knot.
Old RoT I grew up with for plow-steel wire rope was it needed 5x the radius of natural-fiber line. So, if a person had (nominal) 3/4" manila over a 3" sheave, that person would would need a 15" sheave for 3/4" wire.
The "gotcha" being that you could probably replace 3/4" manila with 3/16"-1/8" wire, which would let you use a 3" sheave.
While spurs and kinks in wire rope after "knotting" might add grip when set in concrete, it's no where near what a porfessional bridge engineer would call "anchored" as a guess (but the 1-2 yard "puddle" at the heads isn't really much more than a bodge, anyway). Occupational hazard of my occupation not being around (sorry Bubba)
>While spurs and kinks in wire rope ...<
none of that is making for a sunny day for the wire rope as I see it. More than likely the weakest poiint in this process after the RR tracks is the knots in the wire ropes. bad scene all around.
And how to dismantle the OP bridge? Cutting the wire ropes would probably casue some significant wetlands disturbance.
And how to dismantle the OP bridge?
Scaffold up on both sides from below. Two loops of detcord at 10'-0" OC from middle to ends. Rig for center-out detonation. Take down scaffolding. Installation and removal of scaffolding will have made ad hoc "road" access possible. Blow object into ten foot chunks and drag then up for disposal (this sould be done the night after DNR serves for wetlands habitat destruction; which makes the subsequent mess a "clean up" which is an improvement, not a down-mark).
Alternately, a body would rig four temporary gin poles to support two catenary sweeps, from which enough support could be strung to properly support the thing while it is being demolished into smaller parts. For correct OSHA (and CalOSHA IIRC) compliance, you'd need a span wire 6' above the work area capable of supporting the entire crew from fall-arresting harnesses.
Also, you'd need a survey of all trees in the "work area" with a plan for providing tree protection, and a storm-water pollution containment plan, a protected wildlife survey, and a boatload of silt fencing.
Bubba answer might be to borry a tussle of shoppin carts, stuff same wid big-ole trash cans, y'know, the big grey rubb'rmade ones. Have a hose in the cans, so you kin fillem with water after theu rolls to the middle and all. Iffin one t'ain't 'nuff, you kin roll 'nuther, an nuther down until it is. Make a mess when she breaks, sho''nuff; but she'd be done and down. Jack hamer out the far ends and tow out with a tractor.
But, I may be biased.Occupational hazard of my occupation not being around (sorry Bubba)
And how to dismantle the OP bridge?
diamond charges on the cables...
V'd block charges on the girders and joint plates...
shaped platter charges on the ankors...
intermitten counter diamond charges to cut up the RR rails into manageable pieces...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Or let nature take its course - which I suspect will be what happens.
where's the adrenaline rush in that???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
As a bridge engineer I'll point a couple of things based on those four photos;It's not a suspension bridge but a cable truss (among other names). Because of the sag it might be acting as a stress-ribbon bridge under enough weight. That type of bridge can be unstable if not designed properly.It should be closed immediately and demolished.The stringers of the PT deck are probably carrying a lot of compression since the railway ties aren't (though they should be). Care must be taken during demolition not to just remove the deck without propping the bridge up first.The bridge has no shear strength, particularly with the type of connection used between the railway ties. A traditional truss bridge uses diagonals for this purpose. A deeper top beam (top chord) with proper connections would also have worked here. The top chord's prime job is to be in compression, which it's doesn't seem to be doing here.The bridge can't be fixed in it's current form.Putting a wedding party on that thing could have ended tragically.Dave
DB Cooper! Just the man we've been waiting for!
Honestly, I admire you for having the self restaint to limit your critique to professional terms.
Now that you've fulfilled that responsibility, how about explaining other ways of safely constructing a footbridge across such a span. This topic has certainly aroused a few of my dormant brain cells, others here too I suspect. So, enlighten us please.
There are many ways to span that distance. Other than budget, one of the biggest variables is the soil conditions, particularly the stability of those banks. If it was a commercial application like a golf course they'd probably put in a premanufactured steel truss bridge with a timber deck. If it's private then it might depend on whether there's a reclaimed structure or materials that can be used, like the flat-bed bridges someone mentioned earlier.The type of bridge attempted here was a reasonable choice. It was just horribly executed. As I mentioned earlier a deeper beam at the top instead of those cobbled together railway ties could have worked. It's also clearly a damp environment and any steel should be protected - particularly those cables.I'll leave the rest to the local structural engineer who should be hired to design a replacement. We're not that expensive considering what could be at stake.Dave
It might be worth the owner's time to cast about locally (more or less) for any temporary bridges that have been used in road construction. I've seen several around here that have been used, taken down, and then "stored" for years. It's a cr@p shoot, of course, to find one that's the right length & configuration, and it wouldn't be cheap (even if "surplus") but it would be a lot of bridge for the money if you found the right one.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
The area is mostly clearcut logging and is festooned with bridges of the most dubious safety- mainly constructed of logs and dirt. They build temporary structures out of anything that happens to be around. I don't think you would want to use one again.
Surespan out of Duncan probably has something kicking around.
That's a thought.
I'm not sure it is really necessary to replace the bridge. It leads to a little deck in the middle of no where. When I saw it I couldn't understand what had lead anyone to build a bridge there in the first place. A lot of work for little return.
how often have you come across people that have "need" and "want" thourghly confused???
"got to have" is a powerfull force...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
To and From zip line stations.Problem solved!
we have a problem???
here???
no way!!!
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
but then we'll have to put in a cable car to get to the lead tower...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Here's a 60-foot footbridge, pre-fab it sez: http://www.nynjtc.org/hike/popolopen-gorgepopolopen-torne-loopThe bridge it replaced was two 12"x60' logs with planks nailed across them. It held up for many years.Here's another footbridge farther down the creek, but this one's about 500 feet: http://www.dormanlongtechnology.com/English/projects/Popolopen.htm. Cost about 5 mil, IIRC.This looks like fun: http://en.wikipedia.org/wiki/File:Puente_colgante_peatonal_construido_artesanalmente.jpg
Edited 10/18/2009 6:39 am ET by NietzschesMustache
Just a thought here: Go to the local Guard unit and ask about a "Baily Style Bridge", The Combat Engineers "love" to put these things in. I'm thinking you might get a "surplus" one, and have the Guard unit put it in as a "training exercise" sort of thing. Heck, those engineers would also love to "take down" the old bridge as a training exercise to boot. All you'd have to do would be to provide the baily, and a few cases of beer. And we "Guardsmen" love our beer!
" Although I have the right to remain stupid, I try not to abuse that right"
I couldn't agree more .... there's nothing wrong with that old bridge that a little C-4 wouldn't fix!
The local coast guard is an auxiliary unit made up of volunteers, mainly (like here on BT) of a certain age. When a call comes in some get so excited they have to leave them on the dock with another member to look after them. Now that I think about it they are the same type of guys who built the bridge!
Edit: Oops - You meant some other type of guard. I don't think we have them here in Canada.
Edited 10/18/2009 12:43 pm ET by fingersandtoes
I love the hand rails on that last one! (I'd crawl across, if I crossed it at all.)
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Thanks for posting those links. Good examples of how it's done in different parts of the world.
Have you visited Bear Mountain State Park? I've been to the great old lodge but never hiked there.
Edited 10/18/2009 11:14 am by Hudson Valley Carpenter
I live nearby. I like to take visitors hiking along Popolopen.
OK. I used to commute through there on Rt. 6, sometimes to work at West Point and other times down the Palisades Parkway to Rockland County.
Anyway, I'm glad to have the URL to that website. Thanks again.
On my trips to Maine crossing on the NY State Thruway I've always been facinated by the Erie Canal . Are there worthwhile sights to visit, rides to be taken, and possibly a central website or two of info? Always in a rush to get from one point to the other but DW and I thought maybe one of these years we'd stop and poke around.
"There can be no doubt that Socialism is inseparably interwoven with totalitarianism and the abject worship of the state…Socialism is in its essence an attack not only on British enterprise, but upon the right of ordinary men and women to breathe freely without having a harsh, clammy, clumsy tyrannical hand clasped across their mouth and nostrils" -Winston Churchill
I understand there's a bike trail along the canal that's real nice. Never seen it, but read about it.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
The Erie Canal is farther upstate than I usually get, Syracuse and Rochester for example. I just tried a search using "Erie Canal visitors information" and got a bunch of interesting hits.
BTW, if you're interested in cycling there are many "rails to trails" rides along abandoned rail lines which have been converted for that purpose. There's a national web site for rails to trails too.
As you might imagine that kind of riding is very pleasant and safe. I recommend it as a way to get out of the car and see the countryside in a pristine environment.
With all the waterfront around here there are lots of local companies that make aluminum ramps for docks. If I were to get involved that is what I'd recommend. Having a structure that only exerts vertical loads on the two ends would make everything much simpler.
I share HudsonValleyCarpenter's curiosity. Any insight would be welcome.
I do have one one quibble with your post, which you would not have known having no local knowledge: Most weddings here end tragically anyway.
Assuming you really do design bridges, have the appropriate credentials and education, and have some relevant experience - and I have no reason to doubt your word - your input here is most welcome.
Indeed, we've had a few bridge threads lately! I can guess, but that's all I'm doing ... and I hope my posts have been clear on that point!
So ... first off: HOW would you demolish this thing?; and,
WHAT would you design to replace it?
It's may not be that difficult to demolish. It just needs to be shored, say off the banks, before removing the deck since the deck looks like it might be participating in holding the bridge up. I couldn't say anything for certain from four photos.Dave
Dave, I'm glad you said that it's "not a suspension bridge" I was thinking along those lines.
I am not, nor claim to be a bridge engineer, but have worked on seismic upgrades on quite a few.
I have helped design a few small spans on job sites to carry heavy loads to get equipment & material from point A to B.
I'm known as Mr overkill when it comes to that, as I would never want one of my structures falling & injuring someone.
Just off the top of my head would a camelback truss style work on a lower budget that the pic would lend one to believe?
help me out here, i've looked and looked but i see no railway ties on that bridge, but i do see some train rail. no wooden ties. what am i missing?
"what am i missing?"
YOU didn't miss anything.
Sorry, quite right. Not sure how I got ties in my head. They're rails.
Looking at the pictures ... that's not badly corroded at all! Rails are made of a simple steel that shows rust very dramatically. The salts in the wood made the rust even more dramatic than usual.
Actually, it's not a bad attempt. One of the earlier posters hit on the weak sopt: rails are not the best structural shape, and are very heavy for the strength you get. Had they used proper I-Beams of the same overall size, the bridge would likely have only half the 'sag' that you see. Ditto for square tubing.
If you can tighten the cables, you might be able to get rid of the sag. Those cables are what are holding it all up.
If the cables are frayed, or the anchors insecure in any way, the bridge is beyond repair, and needs a complete rebuild.
Edited 10/16/2009 2:03 pm ET by renosteinke
I should reiterate: I am having nothing to do with fixing this thing. My interest is purely in it's entertainment value.
I'm not sure the cables can be tightened easily. They are knotted at each end which would seem to pose a problem. Also their present tension has caused the angle irons welded to the rails to twist outward so the force they resist is no longer vertical. The thing sways alarmingly when even a single person crosses it.
Incidentally, up here Jarheads are called Pongos and Swabbies are Plugs.
Wow.
What that bridge needs is a laser guided bomb.
Call Homeland Security; with an entire Wedding Party onboard it could be considered a weapon of mass destruction.
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
""Call Homeland Security; with an entire Wedding Party onboard it could be considered a weapon of MASS destruction."" only if it is Catholic wedding... ;-)
Life is Good
You wouldn't need a laser guided bomb, you could probably drop that thing in a few minutes with a sawzall.
A sawzall requires proximity to that evil thing. Did you ever read the short story "The Mangler" by Stephan King? I get the same feeling about that bridge.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.