Lift installed
#31
09-18-2013, 12:23 PM
Nick
If it matters to anyone please see the following;
I agree with you, the compressive strength for residential concrete is on the order of 2000psi to 2500psi. However the soil bearing capacity, below the concrete is much lower. As a result there is bending in the thin slab as the col weight is distributed to the soil. ie the problem does not stop at the top of the slab.
If the lift column loads are constrained to being vertical there probably isn't much of an issue and I haven't heard of any failures, not that I look for them either.
The situation where problems might occur is if the soil below the slab settled away from the underside of the slab. The other problem that might occur is that many of these columns are not concentrically loaded by design. This puts a bending moment on the column which is transmitted to the concrete slab. You don't here of these type of failures either.
As you pointed out the real problem is that if your car is up on the lift and there is an earthquake. Then the columns are laterally loaded (at the top) and the bending moment in the slab becomes very high. I don't think any 4" to 6" slab on grade could sustain this condition regardless of reinforcing.
An earthquake may not be the only way lateral loads are applied to the columns as they may get bumped from other vehicles.
The discussion of slab on grade reinforcing, col base plate design, and anchor bolt capacities has been left out of the discussion for reasons of simplicity.
D
If it matters to anyone please see the following;
I agree with you, the compressive strength for residential concrete is on the order of 2000psi to 2500psi. However the soil bearing capacity, below the concrete is much lower. As a result there is bending in the thin slab as the col weight is distributed to the soil. ie the problem does not stop at the top of the slab.
If the lift column loads are constrained to being vertical there probably isn't much of an issue and I haven't heard of any failures, not that I look for them either.
The situation where problems might occur is if the soil below the slab settled away from the underside of the slab. The other problem that might occur is that many of these columns are not concentrically loaded by design. This puts a bending moment on the column which is transmitted to the concrete slab. You don't here of these type of failures either.
As you pointed out the real problem is that if your car is up on the lift and there is an earthquake. Then the columns are laterally loaded (at the top) and the bending moment in the slab becomes very high. I don't think any 4" to 6" slab on grade could sustain this condition regardless of reinforcing.
An earthquake may not be the only way lateral loads are applied to the columns as they may get bumped from other vehicles.
The discussion of slab on grade reinforcing, col base plate design, and anchor bolt capacities has been left out of the discussion for reasons of simplicity.
D
The loads from the weight of a car are two small. Considering most concrete has a compressive strength of 2500psi, spreading 4000-7000 pounds over apprximately 144 sq inches is nothing. Footings required for vertical lateral loads are generally much much higher than that.
#32
09-18-2013, 09:46 PM
Great lift! I have the same one (also with a 220 motor). I recommend getting a jacking tray to compliment your RJ-45 so that you can get the entire car off the ramps, as needed. Also, as others have stated, BendPak has been around a very long time (30+ years or so) and has a great reputation for taking care of customers. Do a search on the net and you'll find that they are very consistent at addressing customer issues.
Also, with regards to your leak, I'd probably just replace the fluid in your motor with hydraulic fluid, since it's thicker than automatic transmission fluid (which was most likely what was put in by your installer since it's easier to find locally). You can empty out all of your existing fluid, or even partially empty it, and then add hydraulic fluid. It's okay if you have both in there. You won't damage anything.
Also, with regards to your leak, I'd probably just replace the fluid in your motor with hydraulic fluid, since it's thicker than automatic transmission fluid (which was most likely what was put in by your installer since it's easier to find locally). You can empty out all of your existing fluid, or even partially empty it, and then add hydraulic fluid. It's okay if you have both in there. You won't damage anything.
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