Steel anchor bolt embedment in concrete problem 2

[PostFrameSE]

I have a steel beam column that I'm needing to anchor into a concrete pier. Using Appendix D via the "Simpson Anchor Designer for ACI 318" program I'm not getting anything to work. I have a moment of 198ft-k and shear forces of 16.5k. My breakout strength is the controlling factor. I have nearly 90 kips of tensile force on my anchors in an overturning moment situation so I'm using (3) 1-3/8" anchors per side. Due to space restrictions, I can't make my steel base plate or concrete base any bigger. What options do I have for my six anchor-in-base-plate scenario? Surely there has to be something I could do....and I'm just not thinking of it. Any thoughts would be appreciated.

 

[kslee1000]

If you are on the border line, have you think and try a shear key to take out the shear currently acting on the anchor?

 

[DaveAtkins]

If you can develop the anchor bolts into the pier, by embedding them deeply, and develop the reinforcing in the pier so that it can resist the applied moment, the connection will be OK (no matter what the Simpson Anchor Designer says).

DaveAtkins

 

[Lion06]

I'm assuming that your issue is tension and not shear. Here is a paper that discusses how to lap headed anchors with pier reinforcement to get away from the App. D calculations.

 

[Lion06]

I wouldn't necessarily trust the Simpson program anyway. I compared it to my spreadsheet for several examples which were worked by hand and in PCA Notes, and it had real problems once you started introducing eccentricities and moments.

 

[kslee1000]

Yes, I think EIT is correct. Missed the controlling factor. I was thinking anchor instead.

 

[SKIAK]

I was told by some Simpson reps (and its pretty odvious if you think about it) that the anchor designer software they put out isn't really indended to design cast in place anchor bolts but provide a comparison to their products. I would consider the spreadsheet route. They said they were working on updating it (I haven't used it in a while) to be more useful to the designer with cast in anchors, but didn't give mention of when. I agree with StructuralEIT, avoid Appendix D if you can.

 

[KBVT]

StructuralEIT - Did you develop your spreadsheet based on worked examples such as PCA notes or did you construct it directly out of Appendix D. I have been tasked to put together the same type of design tool at my company and was curious as to what your methodology was. Appreciate any help.

 

[kslee1000]

Did you try HILTI?

 

[PostFrameSE]

Thank you all for your replies. I would much rather sink the anchors deeper or somehow work out the development length issue than to worry about Appendix D. If that's how other people are designing, I will too.

The issue is tension, and you guys and that paper have been helpful.

I did notice today when I opened up the Simpson program that there was an update available, and it WAS more friendly to designing with anchor bolts, but it couldn't solve my problem. I'll revert to a spreadsheet or hand calcs.

Thanks again.

 

[Lion06]

I constructed it directly out of App. D. It is extremely thorough, and accounts for every possible situation I could think of. It took a lot of time to put together all of the logic statements. I have one input/output page where all of the geometry and other parameters are input. I have a separate sheet for tension, shear, bolt group analysis, and interaction. Each sheet references the appropriate input from the input/output sheet. The logic statements can get rather intense when the anchors get close to the edge and that controls the embedments to use for design, or when the breakout is affected by three edges and the embedment for design is something other than the actual embedment. The most intense logic statements come when the shear load is parallel to the edge and all of the ca values get thrown on their head. I have it set up so the spreadsheet recognizes which way to flip the geometry so that you don't have to constantly change it in your input. I also have a bolt group analysis to account for eccentricities. It took me quite a while to put it together - probably about 40-50 hours. I also put together a 30 page presentation on App. D in general and my spreadsheet specifically. I included several worked examples to demonstrate the accuracy. The worked examples were from PCA Notes, and one that I just made up, but the spreadsheet was developed right out of App. D.

 

[StructuralEngGuy]

I might suggest a program called Quick Anchor. It was developed by SK Ghosh and is pretty easy to use. It has input information for eccentricities, but I have not had the time to test its accuracy for those types of complex situations. It's fairly inexpensive too at under $100 which far outweighs the cost of developing a spreadsheet under company time. It gives you a pretty thorough output as well so you can do a sanity check and make sure things make sense.

 

[Lion06]

I just found an error in Hilti's Profis yesterday. I emailed them about it. I'll let you know when I hear that it's been corrected.

 

[bootlegend]

StructuralEIT,

Maybe you could just post some screenshots. I have been contemplating creating a worksheet for a while now. Does your program do irregular conrete geometries? (Round piers, etc?)
Also, did you include the calculation of developments, etc if the Appendix D checks fail?

 

[Lion06]

It will only do rectangular concrete geometries. Ca distances can be different in all directions (i.e. the anchors need not be centered on the concrete), but it does have to be rectangular. A round pier can be approximated pretty closely with a square.

It doesn't do development calcs for rebar, it's strictly for App. D. I've gone through some of the development calcs already, and that's pretty easy, straightforward, and quick. It would also add another dimension of complexity to the sheet.

 

[KBVT]

One issue with the Hilti Profis software is that it does not calculate the effective embedment of headed studs correctly. It does not incorporate the thickness of the embedded plate, which ends up shorting you on your breakout calculations. The issue seems to arise for stud lengths less than 5".