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ken_sylvania wrote:

Bootstrap wrote:

ken_sylvania wrote: Say you have a flatbed truck where the end of the bed is ten feet behind the rear axle. If you set a 10,000 pound load on the very tail of the bed, you'll see the rear axle weight go up by maybe 12,000 pounds, because some of the weight from the front axle will be transferred to the rear axle. It might be more appropriate to call it the "lever effect."

But I gather the house would have been level at the end of the process, and the cantilever effect would not be relevant?

Well the cantilever effect does shift the weight around on the piles as the house moves. As each of the rollers under the house approaches a crib pile, more weight gets transferred onto that crib pile. So the cantilever effect was certainly relevant. But finally the total amount of weight is the total amount of weight. So if we add up the weights on all the piles and they come to more than the house weighs, we know something is wrong. The only way that could possibly happen would be if we had a beam set up like a see-saw, anchored to the ground at one end, with the load on the opposite side of the support. Even then, we would calculate the tie-down force of the anchor as a negative weight and everything would add up to the total weight of the house.

cmbl wrote:The sum of the reactions of the piles for one specific position of the house will equal the weight of the house.

The sum of the envelope reactions of the piles will be more than the house weighs.

ohio jones wrote:This is true only if the house is stationery.

sta·tion·er·y
ˈstāSHəˌnerē/
noun
US
writing paper, especially with matching envelopes.
writing and other office materials.

cmbl wrote:

ken_sylvania wrote:

Bootstrap wrote:
But I gather the house would have been level at the end of the process, and the cantilever effect would not be relevant?

Well the cantilever effect does shift the weight around on the piles as the house moves. As each of the rollers under the house approaches a crib pile, more weight gets transferred onto that crib pile. So the cantilever effect was certainly relevant. But finally the total amount of weight is the total amount of weight. So if we add up the weights on all the piles and they come to more than the house weighs, we know something is wrong. The only way that could possibly happen would be if we had a beam set up like a see-saw, anchored to the ground at one end, with the load on the opposite side of the support. Even then, we would calculate the tie-down force of the anchor as a negative weight and everything would add up to the total weight of the house.

For each position of the house, if you add up the pile reactions due to that specific position of the house, and get more than the house weighs, something is wrong.

Now look at each pile and take the maximum reaction at that pile caused by any of the positions of the house. That's your envelope reaction at that pile. The leftmost pile's envelope reaction is caused when the house is in the leftmost position. The rightmost pile's envelope reaction is caused when the house is in the rightmost position.

The sum of the reactions of the piles for one specific position of the house will equal the weight of the house.
The sum of the envelope reactions of the piles will be more than the house weighs.

ohio jones wrote:

The sum of the envelope reactions of the piles will be more than the house weighs.

This is true only if the house is stationery.

ken_sylvania wrote:

ohio jones wrote:

The sum of the envelope reactions of the piles will be more than the house weighs.

This is true only if the house is stationery.

House of cards???

ken_sylvania wrote:

ohio jones wrote:

The sum of the envelope reactions of the piles will be more than the house weighs.

This is true only if the house is stationery.

House of cards???

silentreader wrote:

ken_sylvania wrote:

ohio jones wrote:
This is true only if the house is stationery.

House of cards???

He mentioned Hallmark, so it probably is, but not in an envelope, I don't think.