Anchor bolt failure due to concrete breakout

[ars001]

I have a very large lateral load (111k service load) that I'm trying to transfer from my anchor bolts into a 30"x36" reinforced concrete pier. I've tried checking concrete breakout according to the ACI appendix D and don't seem to be getting anywhere near the capacity I need. I'm at crossroads on where to go from here. Is there any design guides untilizing my pier reinforcing? Thanks

 

[UcfSE]

I don't think it's a good idea to transfer that much shear using anchor bolts. What other options have you tried, such as a shear lug or embedded plate?

 

[DaveAtkins]

For large lateral loads, I prefer two embedded plates, one below each side of the base plate. Vertically oriented plates are welded in the field to the edges of the base plate and the top of the embedded plates. With this solution, the base plate is still elevated on a bed of non-shrink grout.

DaveAtkins

 

[shin25]

The shear capacity of the embeds depends lot on their distance from the free end, on the concrete strength, the spacing, etc. The amount of shear that you are trying to transfer seems really high. To make you feel better, you probably can check the numbers from hand calculation with a software (profice) available for free down load from hilti web site.

If it helps.

http://www.us.hilti.com.

 

[ars001]

I started with trying to get anchor bolts to work and I guess that doesn't sound like the best option Where can I find information on design of shear lugs or embed plates as DaveAtkins suggests? I like the embed plate idea but wouldn't have a clue on where to start. I think that is really my only option at this point.

 

[minorchord2000]

You can download one of the AISC design guides from aisc.org. One of the design guides (I do not remember which one)discusses shear lugs to resist shear forces.

 

[ash060]

Can the 30x36 in pier handle the shear load. 111k service is about 150k factored and the pier as a capacity of about 90k without stirrups. Make sure the pier can transfer the load into footing. It will be hard to make the embed to work in the pier does not work

 

[ars001]

Yes, I've check the shear capacity w/ stirrups about 10 times and it works. I've also checked the load transfer from the pier to the footing using the shear-friction design method specified by the ACI. That indeed works too.

 

[DaveAtkins]

If you use an embedded plate with headed welded studs, the PCI Handbook has information on calculating the capacity of a stud group welded to a plate. Plate thickness is based on the stud diameter, and the PCI method takes into account spacing and edge distance.

DaveAtkins

 

[SeanMD]

ACI appendix D doesnt apply since you have reinforcing in the pier breakout will not happen like it would for unreinforced concrete. See AISC design guides 1 and 7. If you use a shear lug make sure you can fit your ties around it at the top of the pier.