TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
(OP)
WE ARE RELOCATING EXISTING COLUMNS ON A TRANSIT STRUCTURE. THE EXIST. COLUMNS ARE DIRECTLY BELOW THE END OF THE GIRDERS. THE CONTRACT DOCS HAVE US INSTALLING NEW COLUMNS CONNECTED TO THE GIRDER END FOLLOWED BY REMOVAL OF THE OLD COLUMN. THE HEAVIEST COLUMN DEAD LOAD IS AROUND 275K. ONCE THE NEW COLUMN IS ERECTED, ON THE (4) 1 1/4" ANCHOR RODS, I WOULD LIKE TO USE THE LEVELING NUTS TO TRANSFER PART OF THE LOAD TO THE NEW COLUMNS.
QUESTION
1 - DO YOU THINK TRANSFERRING 50% OF THE DEAD LOAD PRIOR TO CUTTING OUT THE OLD COLUMN IS OKAY (AS THE OLD COLUMN IS CUT, THE BALANCE OF THE LOAD IS NATURALLY TRANSFERRED. ALSO THE EXISTING LOADING IS TOUGH TO FIGURE ACCURATELY.
2 - I AM THINKING THAT TURN OF THE NUT APPROACH IS THE ONLY WAY TO FIGURE OUT HOW MUCH LOAD IS TRANSFEERED (TURN OF THE NUT = PITCH DISTANCE => APPLIED STRAIN => STRESS => FORCE IN NEW COLUMN)?
QUESTION
1 - DO YOU THINK TRANSFERRING 50% OF THE DEAD LOAD PRIOR TO CUTTING OUT THE OLD COLUMN IS OKAY (AS THE OLD COLUMN IS CUT, THE BALANCE OF THE LOAD IS NATURALLY TRANSFERRED. ALSO THE EXISTING LOADING IS TOUGH TO FIGURE ACCURATELY.
2 - I AM THINKING THAT TURN OF THE NUT APPROACH IS THE ONLY WAY TO FIGURE OUT HOW MUCH LOAD IS TRANSFEERED (TURN OF THE NUT = PITCH DISTANCE => APPLIED STRAIN => STRESS => FORCE IN NEW COLUMN)?





RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
What is the connection of the existing column to the footings ?
I am guessing something like fully grout supported base plates or something similar.
For my money, supporting anything on leveling nuts temporarily or permanently is looking for trouble. For one thing, many anchor bolt details have features that potentially float unless a large tensile force removes clearance and preloads the assembly.
It also means tightening the upper nuts only clamps the base plate against the leveling nut, not against the grout, or hard shims beneath. The end result is the system sitting on the anchor bolts like a hair brush resting on its bristles with very low lateral stiffness. The anchor bolts also lose the large fatigue resistance inherent with a preloaded, clamped joint.
Rotating machinery, absolutely not.
That opposing nut design is standard practice for Light poles in the parking lot.
I'm sure it sure make truing up the light pole a lot easier, just like the 2 pairs of leveling screws on my builder's level.
RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
If the anchor bolts/rods are in-place already in the concrete pad or slab, and then the welded column and baseplate are lifted into position over the anchor bolts, it seems that only by using the leveling bolts to hold up the assembly is the only practical way to proceed. If so, then it appears you have to "clamp" the upper nuts down against the leveling nuts underneath - which voids any compression being put on the grout. Since the grout always seems to be "pushed" or shoved under the machine foundation or column baseplate later by hand, how do you ever get compression on the assembled baseplate?
Are you then saying that the column cannot be loaded (additional weight and structural steel members) cannot be added to the columns + baseplate until the grout has dried to sufficient strength under the new baseplate?
RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS
RE: TRANSFERRING COLUMN LOAD WITH LEVELING NUTS