slab thickness for anchor bolts
slab thickness for anchor bolts
(OP)
I am looking for information on how thick of a concrete slab I need for 3/8" or 1/2" anchor bolts used to keep a machine from walking while in operation.
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slab thickness for anchor bolts
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RE: slab thickness for anchor bolts
The weight of the machine and the allowable soil bearing pressure will determine the size of the pad, the thickness will have to be determined based on these requirements such that it can distribute the weight of the machine to the soil.
RE: slab thickness for anchor bolts
Mark
RE: slab thickness for anchor bolts
apetr26542 is correct in asking the weight of the machine. If it is moving there is work/force being exerted. If the machine is 10K and moving 10 cm that's not so much. If it is 10 T and moving 10 cm, that is a much bigger problem. In other words, the force exerted on the concrete by the anchor bolts is only part of the stress seen by the pad.
Griffy
RE: slab thickness for anchor bolts
The bolts must be designed to resist both the shear force generated by the lateral forces and uplift (if any). Embedment is recommended to be at least 8 times the bolt diameter. You must have enough concrete cover underside of the bottom of bolt to ensure bolt performance.
Design doesn't end there. If this is a floor mounted equipment, you have to check whether slab alone can resist all forces or whether you need to provide a thickened pad large enough such that you don't get a soil settlement and/or slab failure.
All depends on the size and weight of the equipment as well as applied lateral force.
RE: slab thickness for anchor bolts
So based on whyun's post, 8 times bolt diameter (i.e., 1.2")would require the anchor to penetrate 4 inches. Would that make sense?
Mark
RE: slab thickness for anchor bolts
RE: slab thickness for anchor bolts
Mark
RE: slab thickness for anchor bolts
Either way, for cast in place anchor bolts the code specifies 3" cover on the bottom for exposure to earth without putting a strict minimum on depth as a function of embed thickness. I would suggest you make the embed no more than 2/3 to maybe 3/4 of the depth unless you follow recommendations by a specific manufacturer for a particular bolt you choose such as the post-installed type, or if you have a particularly deep slab(>12"). I should say that usually by the time you size your foundation/slab for all design loads and provide your 3" of clear cover it is usually thick enough to accept your anchors without a big problem.
RE: slab thickness for anchor bolts
I agree with UcfSE about use of post-installed anchors as it is extremely difficult to set the cast-in-place anchors precisely to match the bolt holes of the equipment.
RE: slab thickness for anchor bolts
RE: slab thickness for anchor bolts
Visit www.icc-es.org to search for research reports on various products. For example, if you do the search, you may find ER-4627 which is for Hilti Kwik Bolt II (expansion anchor into concrete). Report provides shear and tensile capacities for various diameters and embedments.
RE: slab thickness for anchor bolts
I think you misunderstood my comment or I wasn't clear in stating it. What I suggested to DrejzaVu was to talk to the machine manufacturer, they surly know the loads imposed by the manchine and the reactions to the bolts and they have (in my mind) an obligation to provide it to their customers. Once you have that information the sizing of the bolts and anchorage requirements can be determined.
Hilti, Fastenal and other bolt manufacturers know from their own testing and publish in their catalogs their various fastener capacities. Since they are in the business and are reputable, I take them at their word.