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32 votes
Accepted

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

If I model this as a simply supported beam having load at mid span [...] I suspect that this is where your analysis went awry. First off, you should always model bridges with distributed loads, not a ...
Wasabi's user avatar
  • 13.1k
22 votes
Accepted

Why would a bearing plate that further concentrates load onto small surface be used?

Because bridges and other structures are not static objects. They must be allowed to flex under varying loads and also accommodate changes in length from thermal expansion. The hinge pin allows ...
Dave Tweed's user avatar
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18 votes
Accepted

Why was a coil chosen over a straight for this overbridge?

source google maps The distance between the intersection and the rail is 100m, The road would need to rise about 10m to clear the track. This would mean a average grade of 10%. However you also need ...
ratchet freak's user avatar
10 votes

Why would a bearing plate that further concentrates load onto small surface be used?

The reason is pretty simple. Steel is significantly stronger than concrete. Nowadays we have high-performance concretes with $f_c > 100~\text{MPa}$ (and ultra-high-performance, which is ...
Wasabi's user avatar
  • 13.1k
8 votes

How does the parabolic curve help in the integrity of a suspension bridge?

The next time you see some kids playing jump rope, go out and ask them to hold the rope perfectly straight. If two kids hold the two ends of the rope with it dangling until it is almost on the ground,...
user1683793's user avatar
  • 1,030
7 votes

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Since this bridge is crossing over a waterway, besides aesthetics, the arch-shaped bridge provides several advantages: Less restrictive over the height of marine traffic due to more headroom in the ...
r13's user avatar
  • 8,227
6 votes
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How and WHY does the tension in an arch dam or bridge change as the degree of curvature and radius of curvature change?

The presence of tension in an arch is not really dependent on the curvature but on how well the arch matches a catenary shape. Robert Hooke famously stated: As hangs a flexible cable so, inverted, ...
atom44's user avatar
  • 2,641
6 votes

Why would a column expand before accepting load through a narrow thunk?

The column top holds some narrow thunk and that thunk holds the driveway floor. I think we have some nomenclature that needs to be cleared up here. What I believe you're calling a "thunk" is ...
grfrazee's user avatar
  • 3,587
5 votes

How can large bridges be made resistant to earthquakes?

Actually very long bridges (and super-tall buildings) often have less issues with earthquakes than their smaller brethren. This is due to them generally being much more flexible and therefore having ...
Mr. P's user avatar
  • 318
5 votes

Why are expansion joints on prestressed concrete box girder bridges sometimes not located directly above the bridge piers?

Because the extension of the longer span past the column into a cantilever allows it to enjoy the benefit of the cantilever part's positive moment effect on the reduction of the midspan negative ...
kamran's user avatar
  • 22.5k
4 votes
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What is the preferred composition for modern concrete bridges?

In structural situations, portland cement concrete is what is used. The properties of asphalt change with temperature and it never really "sets". It is a viscous liquid that cannot support long-term ...
hazzey's user avatar
  • 10.7k
4 votes
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What is the deepest bridge pier in the world?

It's not a bridge, but if you wish to consider the depth of marine structures generally, a good example is the Troll A platform in the North Sea. From Wikipedia: "The Troll A platform has an overall ...
AsymLabs's user avatar
  • 652
4 votes
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Bridge terminology - railing-like parapet

I do a lot of bridge inspections in Ontario, Canada following OSIM (Ontario Structural Inspection Manual). Based on your photo, I would hazard to guess this is an older style barrier system. I would ...
Forward Ed's user avatar
  • 1,221
3 votes
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Camber Diagram for Steel Girders but not for Concrete Girders

CPCI girders are prestressed precast concrete girders, right? (Every region seems to have their own acronym for these things so it's not the name I'm familiar with but the mechanics should be the same....
ingenørd's user avatar
  • 1,288
3 votes
Accepted

From the viewpoint of a civil engineer, what was the purpose of this bridge?

The location makes sense from a civil engineering perspective. The bridge has to span the river channel without being washed away during flooding events. A narrow, steep canyon works well for this ...
PJNoes's user avatar
  • 218
3 votes

When should anti-bursting reinforcement be used?

BS5400 has been superseded and withdrawn, so you probably shouldn't be using it. That said, when I last used it, I did provide bursting reinforcement for bearing plinths. In general, just because ...
AndyT's user avatar
  • 3,143
3 votes

Is there a specific name for diagonally braced truss members like those on the Queensboro Bridge?

There are a variety of names for these, but they all have a similar theme: Laced strut/tie Lattice or Batten bracing Lattice truss Lattice Girder I'm sure you get the idea. These were popular in ...
atom44's user avatar
  • 2,641
3 votes
Accepted

Did this artist take some licence with the Royal Albert Bridge - or has its appearance changed?

Probably artistic interpretation. #i see the differences you are alluding to but they don't look like things you could reasonably alter in a structure. The artist's rendering looks like an ...
Chris Johns's user avatar
  • 15.2k
3 votes

Light frame at tunnels and bridges

Such measures do exist, but they don't always prevent careless drivers from ignoring the measures and crashing into low bridges. One bridge that I know of has been hit at least 100 times and has been ...
Fred's user avatar
  • 9,687
3 votes

Why do these piers have a height miss-match?

It could be the tops are at just the same level, only with deeper beams to cover larger spans at the right hand side, except the last beam upfront is not installed yet. The missing beam and the angle ...
kamran's user avatar
  • 22.5k
3 votes

How does the parabolic curve help in the integrity of a suspension bridge?

A suspension bridge cable is the most effective use of material. Because it uses high tensile cables in a position where they are the most effective material: tension. The parabolic shape is the ...
kamran's user avatar
  • 22.5k
3 votes

Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Spreading the upward reaction load from the support pillars is one reason, the function of an arch translating vertical load to horizontal thrust is another. But there are already good answers saying ...
ItWasLikeThatWhenIGotHere's user avatar
3 votes

What are these objects attached to the cables of this bridge?

From a website of a manufacturer of a similarly shaped item, this may be a variation on a Stockbridge Damper: Note that the shapes of these types of devices vary from application to application and ...
fred_dot_u's user avatar
  • 7,227
3 votes

How long would it take for the Brooklyn Bridge to collapse if the four main cables were cut where they connect to the ground?

If the Brooklyn Bridge was a familiar suspended-deck suspension bridge, it would probably collapse in less than a minute if all the main cables at one end failed simultaneously. The Brooklyn Bridge is,...
David Bailey's user avatar
2 votes

Most efficient way to build a toothpick bridge

You didn't specify cost of glue. If the glue is of no cost (other than end to end joints as you mentioned) then my inclination is to think outside the box here. You could shred the toothpicks into ...
CBRF23's user avatar
  • 363
2 votes

Detailing Fixed Cotton Duck Bridge Bearings

Remember than large structures have to move or they will fracture. Think of the wear equation and the coefficient of friction in the two options. PTFE is an amazing polymer, goretex. Even if it is a ...
ShuddaBeenCodin's user avatar
2 votes

Why would a column expand before accepting load through a narrow thunk?

I find such a column hard to justify. As mentioned by @grfrazee and @ChrisJohns, what you are calling a "thunk" is usually called a bearing plate, and these are responsible for transmitting the force ...
Wasabi's user avatar
  • 13.1k
2 votes
Accepted

What kind of simplified structural system would a Leonardo bridge use?

We will solve for n members with these assumptions. members are L ft long by 2H, (H=L/20) thick and assuming the notch depth at H on the center to accommodate next member linkage. Loads are ...
kamran's user avatar
  • 22.5k
2 votes

Why was a coil chosen over a straight for this overbridge?

In 1909, the same thing was done twice on the Canadian Pacific Railway rail line through Kicking Horse Pass in the Rocky Mountains: Two circular tunnels (dashed white lines) were dug into the ...
Ray Butterworth's user avatar
2 votes

What is the deepest bridge pier in the world?

The Tasman bridge in Hobart, Tasmania has a pile 265ft below mean water level. This on the western side, I understand, so is not connected to the highest span. http://www.parliament.tas.gov.au/...
greenman240755's user avatar

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