This question has come up a couple of times in the past few days where I live. It snowed ~14" here the other day and a lot of the docks on our lake failed in one way or another. Some just sank under the weight. Some actually failed and the roof collapsed; I suspect from so much weight being so high that the load just toppled the supports like dominoes. A lot of people have been saying the problem will only get worse because as the snow melts during the day and refreezes at night that it will become heavier. Logically this makes no sense. How could the same amount of water weigh more than it did when it was at a different temp? I understand that water expands when its frozen (I did pass the fourth grade). Logically if some of the water melts and runs off during the day the weight will be less because there is less water.
If anyone is looking for a great deal on a slightly damaged Sea Ray call Marine Max, Lake Ozark. All of the marinas are in similar situation and will have tons of damaged boats if anyones looking for a winter project (other than rebuilding a bike of course).
short answer: NO. a pound of lead is the same as a pound of feathers. What you are likely asking? Yes - Ice is heavier per the same volume though. Cool photos!
Well yes and no. It depends on the temperature. Frozen water will change crystalline structure at around -4 C (if I remember correctly, and it is a stretch). But, it gets a little lighter, ice floats indicating a lighter density. However, for most practical applications, the difference is negligible.
With 14 inches uf additional wind exposed cross section, could wind have been a factor as well?
edit: This being Slowtwitch, I just knew if I was wrong someone would call me on it, so I went and did a little checking. I was only half right. Water has a maximum density at +4 C. Ice is less dense than water because it generally crystaliizes in a form that results in four hydrogen bonds as compared to 3.4 on average per water molecule. The resulting ice structure is less dense than water by almost 10%.
Ice still does have many different crystalline structures depending on temperature and pressure. But the bottom line is as the others have said, a pound is a pound.
Often wind is definately a large player. Up in Idaho, a covered storage collapsed because of the wind acting on the built up snow. The engineers correctly accounted for the snow weight, but did not calculate the additionaly force of the wind… duh.
Holy cow! Your answer was exactly the scientific explanation I was hoping for. Then you used the word ‘uf’. It was pretty windy that night but I think that most of the docks that collapsed didn’t have nearly enough support for the load under the ‘open’ end of the dock. Take the middle pic for example, on that dock its got styrafoam under the entire 12’ walkway to the back of the boat, plus styrafoam under the fingers of the dock. The open end of the dock is, well, open. Each of those wells (8 on that dock) are 52’ long and 18’ wide. So the open end isn’t nearly as supported as the closed end and they just toppled over.
Thanks for the answers guys. These silly hillbillies keep saying that when the snow / water refreezes into ice that it will weigh more. Missouri isn’t the crystalmeth capitol for nothing.
For the same volume, say 1 cu ft, ice would weigh more than snow. Right? But if it snowed say 1 ft, then the temp climbs over freezing causing some of the snow to melt and then refreeze, the ice would still weigh the same as the previous snow. Right? Given the same amount of water (I assume its the same amount between the snow and ice on these docks) it should weigh the same. Right?
I would also think that the snow would be heaver on the eaves since that is were the water would run to. Then when it snows more and melts a little there is a dam holding back the water.
Which weighs more…a pound of lead or a pound of gold?
Bit of a trick question, but they do not weigh the same.
Huh?
bigskyti - huh? can you clarify for the non-British?
From Wikipedia: A troy ounce, the only currently used unit of the system, is 480 grains, somewhat heavier than an avoirdupois ounce (437.5 grains).
troy pound is the universal unit of measure for precious metals (gold, silver, etc.) pharmaceuticals and bread…essentially anything considered of great value at a time that everyone was sick with the plague, starving and the Kings held all the gold.
The one shot showing the underside of the roof doesn’t look to have very much support, but it is still standing under all that load. I’d hate to be the insurance adjustor for the owner of the marina.
Are all these slips owned by one person and leased to people, or are they individually owned and the responsibility of the owners?
I’m sure there will be some great deals on “totalled” boats that just need some fiberglass repair on the top decks. Too bad I can’t even afford the bike I want, much less in the market for some of the incredible boats pictured.
I would imagine that the structure is designed to withstand high windloads by flexing slightly, but the additional snow on the roof adds to the structure’s mass, so small movements by the structure put huge dynamic loads on the supports.
Docks are down everywhere, private homes and marinas. The hardest hit (I suspect) is MarineMax, Sea Ray. I don’t know how many slips they had, I’ve never walked the entire complex, but on the side I’m familliar with they must have had 80 or so slips for cruiser type boats (over 40’). They had some smaller slips as well in the 25-35’ range. The docks alone must be worth a small fortune not to mention all of the boats. Most of the boats at MarineMax are leased slips for private boats. I suspect this will be a good time for the damaged owners to upgrade and for people with damamged smaller boats to upgrade to a repaired cruiser.
Whats strange is that this happened in 1979, 1995 and now in 2006. I could understand a few having problems but so many are sunk, flipped or just plain failed under the load. Ours is squatting a few inches lower than normal but it looks like it is level all the way around so I’m happy about that!
It was pretty windy that night but I think that most of the docks that collapsed didn’t have nearly enough support for the load under the ‘open’ end of the dock. Take the middle pic for example, on that dock its got styrafoam under the entire 12’ walkway to the back of the boat, plus styrafoam under the fingers of the dock. The open end of the dock is, well, open. Each of those wells (8 on that dock) are 52’ long and 18’ wide. So the open end isn’t nearly as supported as the closed end and they just toppled over.