Will my garage floor hold a motorhome ?help

Holy ****! Most of your comments are valid, but way too much worry. I have been pouring concrete for cows and machinery for forty years, sometimes in less than optimal conditions. Sometimes it might crack or break or even frost heave. I’m pretty sure that it will never swallow the motor home whole for a hundred years or so. Me thinks there are bigger things to worry about;)

joshuajim wrote:

Pangaea Ron wrote:
I'm baffled to understand how tire pressure would impact allowable loads to the concrete slab and compacted sub-grade below. So a 200 psi tire would transfer twice as much weight to the slab? It possibly
could, but the motorhome weight does not change nor do the dead loads to the slab which was the OP's question. The denser air of course would weight more, and the tire profile and footprint might change.

If 200#, then the contact patch would be 1/2. The OP question was ONLY if a 4000PSI slab would support his motor home.

To continue, the weight transferred would be the same, but the pressure applied would be higher; it would be more concentrated.

For actual tires, the relationship between contact area and tire pressure is anything but directly linear because they have considerable structure of their own and don't really behave like balloons. The stiffness of the sidewalls contributes a good part of the weight carrying ability (exactly how much depends on many variables, such as the sidewall height/aspect ratio).

joshuajim wrote:

westend wrote:
Guys, it's not that simple, at least in the building engineering world. There are forces of compression, tension, restraint, strength, loads (both live and dead), and others I've lost in my memory.

The OP states a compaction of up to 40" of fill and a further layer of gravels, also compacted. He is far above any typical placement of slabs for the use involved. Letting these base layers sit and compact/firm up over a span of time also add to the integrity of his installation. About the only thing that would aid in the strength of the slab is installation of steel rod. He has used wire, which is adequate for this use.

I completely agree with your first paragraph, but I have issue with your second. Letting material "set" over time will result in the material settling, but never compacting. If that was the case, then every piece of native soil would be at optimum compaction due to millions or billions of years of "setting". No, native soils is at 65 to 80% of optimum no matter how long it sets.

In the practical sense, in the type of area where I live, soil subsidence (falling) and expansion occurs with the seasons. Also, we have no idea if the owner parked anything inside this area prior to placing concrete. That would also aid in compaction. As would foot travel. Regardless, the weight of 40" of gravel will tend to compact by itself from just the weight.

I've done a fair amount of concrete placement and driveway/patio paving brick construction to know how things work with different sub-soils and gravels/sand. In my area, letting fill sit through a Winter improves compaction and results in less subsidence with the final product.

Pangaea Ron wrote:
I'm baffled to understand how tire pressure would impact allowable loads to the concrete slab and compacted sub-grade below. So a 200 psi tire would transfer twice as much weight to the slab? It possibly
could, but the motorhome weight does not change nor do the dead loads to the slab which was the OP's question. The denser air of course would weight more, and the tire profile and footprint might change.

If 200#, then the contact patch would be 1/2. The OP question was ONLY if a 4000PSI slab would support his motor home.

I'm baffled to understand how tire pressure would impact allowable loads to the concrete slab and compacted sub-grade below. So a 200 psi tire would transfer twice as much weight to the slab? It possibly
could, but the motorhome weight does not change nor do the dead loads to the slab which was the OP's question. The denser air of course would weight more, and the tire profile and footprint might change.

Delete - double post

westend wrote:
Guys, it's not that simple, at least in the building engineering world. There are forces of compression, tension, restraint, strength, loads (both live and dead), and others I've lost in my memory.

The OP states a compaction of up to 40" of fill and a further layer of gravels, also compacted. He is far above any typical placement of slabs for the use involved. Letting these base layers sit and compact/firm up over a span of time also add to the integrity of his installation. About the only thing that would aid in the strength of the slab is installation of steel rod. He has used wire, which is adequate for this use.

I completely agree with your first paragraph, but I have issue with your second. Letting material "set" over time will result in the material settling, but never compacting. If that was the case, then every piece of native soil would be at optimum compaction due to millions or billions of years of "setting". No, native soils is at 65 to 80% of optimum no matter how long it sets.

Guys, it's not that simple, at least in the building engineering world. There are forces of compression, tension, restraint, strength, loads (both live and dead), and others I've lost in my memory.

The OP states a compaction of up to 40" of fill and a further layer of gravels, also compacted. He is far above any typical placement of slabs for the use involved. Letting these base layers sit and compact/firm up over a span of time also add to the integrity of his installation. About the only thing that would aid in the strength of the slab is installation of steel rod. He has used wire, which is adequate for this use.

joshuajim wrote:

myredracer wrote:

joshuajim wrote:

myredracer wrote:

Cummins12V98 wrote:

joshuajim wrote:
The concrete is 4000 PSI, your tires exert approx 100 PSI. Do the math.

HUH???

Double huh. Sorry, but that's a mega-OMG...

Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.

No Huh about it.

So you can spread a layer of 4000 psi concrete on your lawn and you'd be okay? The native soil, fill material, compaction, reinforcing and correct placement procedure of concrete aren't factors? How does tire pressure relate to live load and concrete strength?

And FWIW, F=ma... :)

IF you had read the OP's post which states "Ok my pole barn has a 4” slab, 4000 psi concrete with fiber and wire mesh,,,it compacted bankrun gravel and crusher under it..." you would realize that your reply is non-responsive.

To put it in the simplest terms possible. if the RV weighs 30.000# and has 6 tires on the ground that equates to 5,000# per tire +/-. The 100# air pressure (assumed) in the tire pushes on all interior surfaces of the tire including the tread area. That would result in a contact patch of approximately 50 square inches. The tread which is hopefully connected to the interior of the tire resists the 100# load exerted on every square inch of contact patch with an EQUAL 100# per square inch resistance per Newtons Third Law.

50 square inches of 4,000# concrete has an ultimate load of 200,000#.

F=ma? Lets hope his floor is not accelerating.

QED

Are you a structural engineer?

myredracer wrote:

joshuajim wrote:

myredracer wrote:

Cummins12V98 wrote:

joshuajim wrote:
The concrete is 4000 PSI, your tires exert approx 100 PSI. Do the math.

HUH???

Double huh. Sorry, but that's a mega-OMG...

Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.

No Huh about it.

So you can spread a layer of 4000 psi concrete on your lawn and you'd be okay? The native soil, fill material, compaction, reinforcing and correct placement procedure of concrete aren't factors? How does tire pressure relate to live load and concrete strength?

And FWIW, F=ma... :)

IF you had read the OP's post which states "Ok my pole barn has a 4” slab, 4000 psi concrete with fiber and wire mesh,,,it compacted bankrun gravel and crusher under it..." you would realize that your reply is non-responsive.

To put it in the simplest terms possible. if the RV weighs 30.000# and has 6 tires on the ground that equates to 5,000# per tire +/-. The 100# air pressure (assumed) in the tire pushes on all interior surfaces of the tire including the tread area. That would result in a contact patch of approximately 50 square inches. The tread which is hopefully connected to the interior of the tire resists the 100# load exerted on every square inch of contact patch with an EQUAL 100# per square inch resistance per Newtons Third Law.

50 square inches of 4,000# concrete has an ultimate load of 200,000#.

F=ma? Lets hope his floor is not accelerating.

QED