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Old July 22nd, 2017, 07:57 AM   #12241
VoltAmps
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Quote:
Originally Posted by geogregor View Post
That can't be a reason, bridges in Europe don't have any bigger "dips" than in the US despite being covered by asphalt. In fact I find the difference between the average bridge deck level and the highway level bigger when driving in the US.

Honestly, I could never find definite answer why American engineers stick to policy of concrete decks and European ones to asphalt decks, regardless what is the surface of the highway itself.

It could be, as I mentioned, simply cultural, something like "we have always done it that way". I really don't know.
Riiiight, because you know every bridge in Europe right? I know for a fact these dips exist on bridges in the Netherlands due to areas with soft soil where it has settled

Also I feel like you're trying to imply an asphalt bridge deck is somehow smoother or better than a concrete one which is most definitely not the case
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Old July 22nd, 2017, 10:10 AM   #12242
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Asphalt can be repaired with a simple resurfacing. You can do that overnight with virtually no impact on traffic flow. Replacing a whole bridge deck is a much more complex and expensive task, that's why you see all these repair patches on the satellite image.
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Old July 22nd, 2017, 11:43 AM   #12243
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This is a much more advanced and durable way of building bridge decks.

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Old July 22nd, 2017, 12:10 PM   #12244
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The point is that to smoothen out the pavement, the Europeans only have to resurface the asphalt. In the U.S. the whole bridge structure has to be replaced because the driving surface is also the bridge deck. That is expensive and time-consuming so they rather patch it up as shown in the satellite photo.

The photo you posted shows a bridge construction. Imagine having to shut down a busy bridge for months at the time to replace the deck. Using precast beams is much faster than in-situ concrete pouring.

An asphalt layer over the bridge deck also provides better protection from salt.
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Old July 22nd, 2017, 12:16 PM   #12245
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The picture I posted shows the pouring of a bridge deck. Either way the bridge has to be shut down whether it's re-paving or pouring new concrete. It definitely doesn't take months for either process although asphalt would obviously be a shorter time. It is also less durable and wears out much faster meaning closing down the bridge more often to re-pave so how much time are you really saving? Like I said the picture I posted shows a superior and more durable form of bridge deck.
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Old July 22nd, 2017, 12:18 PM   #12246
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Quote:
Originally Posted by VoltAmps View Post
Riiiight, because you know every bridge in Europe right?
I have driven thousands of miles across all of the lower 48 states, I have also driven thousands of km across different European countries, from the southern tip of Portugal to the far north of Scotland, to eastern Poland.

So, no, I don't know "every single bridge in Europe" nor in America, but I would say I have decent first hand experience with representative sample of bridges across both continents

Quote:
I know for a fact these dips exist on bridges in the Netherlands due to areas with soft soil where it has settled
Excessive or uneven settlement of embankments bordering the bridge structure has nothing to do with the bridge structure, it can occur with any type of bridge. It is irrelevant to the type of the bridge surface.


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Also I feel like you're trying to imply an asphalt bridge deck is somehow smoother or better than a concrete one which is most definitely not the case
I'm not implying anything. I love driving in America and generally have no problems with roads there. In fact I especially enjoy longs, straight empty road in the American hinterland.

But I'm genuinely curious what led to such different standards regarding bridge surfaces in Europe and America. So far nobody provided me with plausible explanation.
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Old July 22nd, 2017, 12:28 PM   #12247
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Asphalt resurfacing can be done overnight, with only 1 or 2 nights of construction needed to replace the driving surface. Asphalt will last for 10 or 15 years without a major overhaul. And if it needs repairs, it can be done in a matter of hours instead of weeks.

Concrete does indeed last longer, but the construction time is also much longer, a typical bridge replacement takes several weeks using concrete beams and several months to even up to a year for in-situ concrete pouring.

Most European countries have phased out concrete on their freeways (as a driving surface). Only a few countries still build new concrete freeways. Traffic is too busy to close down lanes for weeks or months at a time. Reducing congestion by minimizing road work duration is seen as more important than superior durability of concrete.
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Old July 22nd, 2017, 03:15 PM   #12248
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Quote:
Originally Posted by VoltAmps View Post
This is a much more advanced and durable way of building bridge decks.
That same machine is used for bridges that are surfaced with asphalt too. The concrete deck of the bridge deck needs to be smooth regardless if the bridge deck is going to have a concrete wearing surface or not.

Many US bridges do have a concrete (or other granular, such as a pea-coat) overtop of the actual bridge deck. I'm not sure why US engineers have an affinity for this. I agree with Chris, having a asphalt wearing surface (overtop of a waterproofing membrane) protecting the bridge deck seems like it would offer more longevity, (and better ride quality) than what is typical in the US.
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Old July 22nd, 2017, 07:00 PM   #12249
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[USA] United States | Interstate Highways

What do they do in Canada? Asking because I was wondering if the relatively harsh winters in (most of) North America compared to (most of) Europe...relatively harsh summers for that matter...had a role in this. You know, expansion and contraction and all that...(I'm no engineer.)
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Old July 22nd, 2017, 08:14 PM   #12250
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Why do you keep mentioning replacing beams for a bridge? The concrete surface can be replaced without replacing beams
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Old July 22nd, 2017, 10:06 PM   #12251
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Asphalt in Ontario. Even the concrete highways switch to asphalt on bridges.
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Old July 23rd, 2017, 12:58 PM   #12252
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Is this what we're talking about here? I-635 was built by Cintra(Spanish company) Here is my local Dallas observation and the answer from someone that knows:


The answer(from an engineer that designs freeway bridges) is that the surface of a concrete beam formed bridge is paved(he said that's not the right term) or covered with a thicker sandwich of material than the normal roadway, to create a more solid structure, therefore sinking or misalignment comes from the surrounding road rather than the bridge structure. Adding asphalt to this layer requires a more complicated sealant for the asphalt because this type of bridge is far less concerned with drainage than other types which can cause pooling, cracks and potholes(spring and fall thundershowers aren't uncommon). Basically here, its wiser to make the bridge more of a solid structure and have the road align, so they often don't bother adding asphalt to this type of bridge.

He also said you will see the opposite on tube, segmented form(like the tallest high five flyovers) and bridges formed of steel beams in this area. These are more lightweight meaning less of a concrete "surface" is "paved" over them. As we saw with the Coit flyover, this cause sagging between the segments and asphalt and its flexibility have worked better on these roads.

You can see where the asphalt stops where the concrete beam form sections begin. Also notice the lower flyovers on the lower left and upper right are concrete beam formed and completely concrete.

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Old July 24th, 2017, 09:49 PM   #12253
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Quote:
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I don't know how keeping bare concrete on bridges would help with ice and snow. In fact it might make things worse.
Salt used for combating snow and ice is quite corrosive to concrete. If you have layer of asphalt (like in Europe) you can just replace the wearing course every few years quite easily (again common practice in Europe).

If the concrete structure of the bridge have to be replaced or fixed it is much more complicated and expensive.

What's more striking that even on concrete highways in Europe bridges are often paved with asphalt. Completely opposite than in the US where many bridges on concrete and asphalt bridges are just left as concrete.

Does anyone have explanation for such divergent approach on both sides of the Atlantic? Is it just due to historical and cultural reason (like "we have always done it that way")?
I haven't driven on interstates in all states but in the states I have driven, it is very common to see "Bridge Ices Before The Road" sign, basically confirming what you mention.

The practice you mention for Europe is also the standard on Ontario freeways - the MTO standardizes on using Asphalt as the driving surface for bridges.
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Old July 24th, 2017, 10:55 PM   #12254
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Out here in the wet coast rainforest, we have concrete bridge decks. Concrete highways essentially end at the CDN/US border, and north of that are all asphalt, but the bridge surfaces are not.
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Old July 24th, 2017, 11:29 PM   #12255
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I thought the reason bridges may freeze before other roadways is that cold air can get at them from beneath as well as above.
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Old July 24th, 2017, 11:44 PM   #12256
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Yes, I think that is independent of the road surface being asphalt or concrete. Bridge decks cool off faster than the surrounding land.
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Old July 25th, 2017, 01:40 AM   #12257
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I just thought it was interesting that they would have signs for that in the US but not elsewhere, but good to know.
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Old July 25th, 2017, 02:41 AM   #12258
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Quote:
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I just thought it was interesting that they would have signs for that in the US but not elsewhere, but good to know.
They are all over Ontario and rest of Canada, it's just that we have pictograms instead, theoretically could be used other than a bridge, but pretty much... always on a viaduct of some kind:

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Old July 25th, 2017, 04:00 AM   #12259
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^ Those signs aren't nearly as common in Ontario as they are in the US. The US uses bridge freezes before road signs everywhere. I can think of countless bridges in Ontario that aren't signed as such.
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Old July 25th, 2017, 08:14 PM   #12260
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I can say those signs are everywhere in Ohio and Indiana, even on tiny ass back roads. Don't think I've seen a single one in Ontario.
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