Jib Crane Foundation Cracks
Jib Crane Foundation Cracks
(OP)
I am trying to find out where to look to determine if the grout used at the foundation of a pillar type jib crane is satisfactory or not. The crane rated 2 ton with a 36" x 36" base plate sitting on a 2-1/2" thick, 39" x 39" grout slab. Cracks are visible along the thickness of the grout slab at its outer edges, however the cement below the grout is in very good condition. I don't have much of a background when it comes to foundations.





RE: Jib Crane Foundation Cracks
Loadwise: What axial, shear, and moment reaction is at the base?
RE: Jib Crane Foundation Cracks
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It is unknown when or how the cracks formed, the crane has been at the location for a hand full of years. The exact grout specifications are unknown, but grout typically used in this type of application is high strength, non-shrink grout. I don't believe the grout contains pea gravel. The mast was set plumb with leveling nuts and then grout was flowed into place, the base plate is 1-1/2" thick and inset into the 3" thick grout (not 2-1/2" as mentioned before).
The axial load along the pillar is approximately 2830# (crane utilizes a 1 ton hoist). The moment reaction is approximately 628 in-kips about the center of the 36" wide base plate.
RE: Jib Crane Foundation Cracks
You may want to perform a closer look at the condition of the baseplate and verify if the thickness is acceptable and there are no major stress concentrators. Looks like it needs the rust to be sand blasted off and the plate coated. You may want to consider anodoc protection to reduce the rate of corrosion. You make also want to look at the bolts closer. Also look at ways to reduce water intrusion betwqeen the baseplate and grout.
In general it doesn't sound like you are having a servicieability problem other than corrosion, correct?
RE: Jib Crane Foundation Cracks
I would remove the grout which is above the bottom of the plate, along with any other cracked grout. Then the base plate can be prepared and recoated, and the grout reinstated, but only up to the bottom of the plate.
RE: Jib Crane Foundation Cracks
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RE: Jib Crane Foundation Cracks
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RE: Jib Crane Foundation Cracks
RE: Jib Crane Foundation Cracks