Originally Posted by
Chad Fabry
The threaded end is installed in concrete so that the load is not supported by the threads.
Which means, I presume, that the threaded end is recessed down into a concrete footing area on a concrete footing, the adjustments for height made with the treaded screw, then, after final adjustments are made, the recessed down area is filled with concrete?
I would say that it depends on the rating of those screw threads.
I've used 90 ton floor jacks, threaded ones, where each jack, and its threads, are rated to take 90 tons. I believe in a recent thread elsewhere it was guesstimated that a small house might weight 50 to 100 tons, which means one jack, maybe two, to support the entire house (make that three to avoid balancing problems). Of course, I used to use 10 or more of those under one house while doing house leveling on older homes.
To me, the weak link in those threaded adjustable columns would be the columns themselves. If the steel wall is not thick enough, and the column not large enough, a tall column could start to deflect (bend) at its mid-point. A typical compression bow like when one overloads a piece of wood by placing to much weight or load on its top - like a vertical ridge support which is bowed.