2007-12-23 13:43:47 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
All bridges are exposed to air on all sides so it allows cooling from all surfaces. Many bridges are also exposed to wind that tends to deposit more moisture on bridges. Another factor is that many bridge decks are made of concrete because it is more durable then asphalt. Concrete is light in color and therefore does not absorb as much heat from sun light as dark asphalt.
2007-12-23 13:50:31 · answer #1 · answered by meestaben 3 · 1⤊ 2⤋
This Site Might Help You.
RE:
Why Exactly do Bridges Ice Before Roads?
2015-08-18 18:26:41 · answer #2 · answered by Ernest 1 · 0⤊ 0⤋
They do not always.
When they do, it is because the ground is warm, and the air is cold. The bridges are insulated from the warm ground, and cooled by airflow on four of six sides.
In some instances, the road will ice, and bridges will not. This occurred on I-80 between Rock Springs and Rawlins WY about a year ago. The situation then was that the ground was cold, the air was warm and humid, with high cross winds (>40 mph). The airflow was sufficient to warm the bridges, but the ground was very cold, so the moisture out of the air deposited on the roadway. Traffic was not going fast enough to generate enough heat to prevent the moisture from freezing. It was very very slick.
2007-12-23 14:02:13 · answer #3 · answered by Nigel M 6 · 0⤊ 1⤋
They have exposed structures underneath that are perfectly shaped to serve as cooling fins. When cold airs hits those exposed beams it does a great chilling job and the bridge surface gets colder than a road surface that just touches the earth underneath.
2007-12-23 14:19:20 · answer #4 · answered by Rich Z 7 · 1⤊ 0⤋
Lower thermal mass, basically you have air cooling the bottom and sides of a bridge road bed in addition to the road surface itself. The road only has the road surface cooling it and as such cools slower.
2007-12-23 13:52:01 · answer #5 · answered by Kevin C 1 · 1⤊ 1⤋
They are suspended above ground so they lose the isolating effect of the ground. Cold air above and below, means freezes before other road surfaces!
2007-12-23 13:50:01 · answer #6 · answered by Anonymous · 2⤊ 0⤋
The heat from below the surface of the earth keeps the earth warm, oh, and also the earth absorbs heat from the sun and so this keeps the earth warm. But bridges don't have that, so they freeze quicker.
2007-12-23 13:51:36 · answer #7 · answered by Anonymous · 1⤊ 1⤋
Bridges freeze faster because they do not hold the earths ground temperature
2007-12-23 13:50:48 · answer #8 · answered by Anonymous · 0⤊ 1⤋
the higher up you are the cooler the temp. Also, roads are on the ground, insulated underneath by the dirt and gravel, they're closer to the earth's core.
2007-12-23 13:52:44 · answer #9 · answered by Queen of the World 5 · 0⤊ 3⤋
i think because air is able to also cool them from underneath as well as from above. twice the cooling
2007-12-23 13:46:38 · answer #10 · answered by , 1 · 2⤊ 1⤋