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base plate with anchor rods

base plate with anchor rods

base plate with anchor rods

(OP)
Base plate with anchor rods : they have to be always pre-tensioned as per AISC steel design guide 1 or they can be "snug tightened" ? In such a case "snug tight" means and foresees a minimum torque (i.e. according to size and steel quality of the anchors) or simply the operation of the most powerful fitter ?

RE: base plate with anchor rods

Unless you are using special bolts in tension(see the code) the answer would be :are you expecting load reversals such as due to wind or earthquake? If yes, pretension. If not, snug tighten. Anchor pretensioning is an expensive procedure to my knowledge. In my area(seismic zone even) only wind turbine poles and tower type buildings (tall and slender) have their anchors pretensioned.

RE: base plate with anchor rods

Refer to Page 14-12 "Anchor Rod Nut Installation" in AISC Manual (15th edition). Gives examples of when pretensioning is recommended. You shouldn't specify a pretensioned threaded rod because the bond to concrete will prevent the pretension from being achieved.

RE: base plate with anchor rods

AISC bolt specifications do not apply to anchor rods, so you shouldn't use the terms pretension or snug tight. Pretension forces can be great than concrete strength, and snug tight is half a turn past the plies making contact.

Don't specify a tightness or torque, and you'll get something in between.

RE: base plate with anchor rods

slickdeals... you need a 'spacer' to allow the bolt to have a length that can be 'stretched' to develop the tension... likely lessens with slippage within the concrete it is anchored in... had an incident in Ottawa where I was using rock bolts to secure a high uplift force in a stairwell under seismic loading... I did not spec a pre-tension load... didn't think I needed it. It was just an anchor embedded in concrete.

The plan examiner insisted it be sleeved, so, I put 5' of polyurethane foam tube on it and it was accepted... He had no idea of what he was doing, and, I didn't want to argue with the dude.

Dik

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