rlcam

Here I go again/Photobucket

46 posts in this topic

Please be patient guys I am from Alabama,you know the home of Forrest Gump.

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The last one is a pic of the hwy 31 bridge upriver in the morning..Hope this works...Robert

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We told you it would not be hard !!!!!!!!!!!!!!!!!!!

Very nice Pics Ricam.

Just had to add this - Here is a real bridge they are going to blow it up again on New Years Eve. pete:

SydneyHarbourBr.jpg

SydneyHarbourBr2.jpg

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Not as impressive as the Bridges above, but I am proud of it.

My brother and I built this last year, he's the artist, I'm the engineer. What a team!

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Bruce, yes it does but there is a rock in the way and where's the water????.Nice work Dave . Pete

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Actually, just beyond the trees, to the left, about 150 yds, is a very nice lake. Never fished it though, too far from home. I thought about taking by tackle with me when we were doing the installation, but that would not have gone down well with my brother, left to do the work!

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If there was a lake that close, my brother and I would never be able to get any kind of work done. With the exception, of course, of the work done with rod and reel in hand.

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rlcam,

That's a cool bridge. I think you said "drawbridge" in your first post. Does it open, and how?

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Mark - this looks like a bridge down the coast at Batemans Bay N.S.W, not as big or as beautiful as the H 31 bridge but here is a brief description on how they work. pete

Truss Bridges

A beam, or girder, bridge is limited in span by the strength of its girders. This limitation is overcome by assembling a system of supporting members in triangles above the horizontal span girders to form trusses. Leonardo da Vinci sketched truss bridges, and the Italian architect Andrea Palladio probably built several. Two truss bridges were built in Switzerland about 1760. Truss-bridge construction, however, did not develop on a large scale until after 1840. In the United States the use of wooden trusses with iron tie-rods led to a combination cast- and wrought-iron construction about 1850 and, later, to steel trusses.

Opening Bridges

Where provision must be made for the passage of shipping under the bridge and where it is impracticable to build the bridge high enough for complete clearance, a movable span is constructed.

The oldest type is the 'bascule' bridge, on the principle of the drawbridge. The Clyde River bridge is of a less common type - the 'vertical lift'. A girder is lifted by counter-weighted cables suspended from the two towers.

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Mark, the bridge I operate is a lift span.The span between the two towers is what lifts up when a barge or big house boat needs through.We have to coordinate with the train traffic so we can keep both moving.It all runs electrically unless we have a power outage and then we have to use a diesel motor(located on the bridge) to raise it. The hwy.31 bridge used to be a lift bridge also until they replaced it several years ago,its just upriver from me.I sit in a small tower office on the south bank at the end of the bridge.I have to sit here most days watching people fish(sometimes I might bring a rod or two with me,if you know what I mean).

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Thanks Pete. I've always been facinated by the different bridges I've seen over the years. Both the designs, and the engineering behind them.

The idea of trusses, and how load is transfered, is something I use, but not every day, in wood framing.

I'm always amazed at the engineering of opening bridges on rivers, whether they are draw bridges, or pivot bridges. The point load on the pivots or hinges is enourmous, and the cable/pulley systems, along with the winches that do the lifting, are just facinating.

Someone posted pictures of a water wheel lock system that was built in Europe, to get boats down from one level to another. It is so cleverly balance that the muscle to move it is minimal. But the loads are enourmous. Clever people, for sure.

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The Falkirk wheel. Yes, I posted it, an awesome piece of modern engineering. But you have to respect the guys that built the old masters a hundred, even two hundred years ago. Their work looked good too.

This is where I fished every night after work when I was in Sweden. Alvsborg bridge, Goteborg.

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Just look at that geometry!

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rlcam,

Does the section lift in one piece, or does it open in the middle?

Vodkaman,

I am really impressed by the old structures that people made hundreds of years ago. They had figured out the engineering without the math and formulas, from trial and error and experience.

I did some work on a windmill that some rich guy in Malibu had imported from Denmark. The whole thing was made out of wood. Amazing.

He had converted it into a guest house, complete with a tin bathtub that was actually in the shape of a person, with a small end for the head, and a larger section for the body. I guess, when you had to carry the water up four floors, it made sense to keep the shape as efficient as possible.

Kind of like lure building.

Spike-A-Pike,

What is a semidry?

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I saw a doco a while back about the guy (forgot his name) who built the Brooklyn Br in N.Y, I think it was the first pre-stressed cable bridge ?? very interesting story of engineering firsts - very smart people. pete

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You would think that with todays mathematical and engineering knowledge, computer stress analysis and simulations, that designing bridges would be childs play.

Not so. Just a few years ago, a new bridge over the Thames, in London, had to be closed very shortly after the ceremonial opening. The bridge had a very slight sway. This caused the people to walk in step with the movement, also it is a natural instinct for humans to walk in step with each other. It just happened to be that the frequency of this step pace matched the resonent frequency of the bridge and the sway was dangerously magnified. How embarrassing for the designers!!!!

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I enjoy the History Channel and several similar channels with major engineering accomplishments. As bridges go, the two I think of are the Golden State Bridge and the Mackinaw Bridge. There’s one other, the Tacoma Narrows bridge (aka: Galloping Gertie). It collapsed in 1940 shortly after it open.

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Of the above, the Tacoma is my favourite, purely as the collapse was all about vortices, my favourite subject! Come to think of it, I haven't mentioned vortices for quite a while. Nice to get the first one of the year out of the way.

Vortex vortex VORTEX!!!

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I would like to see you at the Air Mobility Command annual confrence on Low Level Wind Sheer. I know the Royal Air Force used to send line officers to the event. We used to have a running joke bout going to the Low Level Wind Sheer test range... You would know it better as the golf course.

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V.M - I have had that happen on some of those pedestian motorway crossing's near here, especially the one near the local Aussie Rules Club, I always thought it was the beer/wine.pete

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