Steel Column Base Plate Anchorage Design Example | Using AISC 15th Edition| Civil PE Exam Review
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- Опубликовано: 10 мар 2021
- I reveal one of my BIGGEST Civil PE Exam TIP for those who stick around!
Kestava Engineering gets into the design of a steel column base plate anchorage. We show how to determine the tensile uplift acting on an anchor due to eccentric column loads with a design example that walks us through the AISC 15th edition steel manual. This design example is very likely to show up in some form of the civil / structural professional engineering exam. This is a great steel column design example for design professionals as well!
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When you do summation at C, shouldn’t the first part be (320k)*(7.5”-d2)......? Since that’s the distance from point c to eccentric load?
that's what i was thinking aswell
Yeah small mistake on his part im sure. Doing it this way yields 16K so the answer should still be the same
You guys always showing me up! great work! you are correct Edgar, mistake on my part. You just got pinned to the top of the comments my friend. Cheers
Yeah I caught that. I went through the math and saw that he did his solution correctly though in spite of the flub on the screen.
Really good video as all of other videos. Any update on when other videos be back?
I am a senior mechanical engineering student working on a capstone design project. I am part of a structural team designing a factory and was assigned columns and column foundations. Very helpful video in my learning process.
Dude that was quick thanks 😊
always got your back Winter.
nice video, thanks! can the eccentricity from M/P fall outside of the base plate?
I'm pretty sure this is incorrect but I might be wrong here. The two things that throw me off are 1) why would you assume the resultant force of the compression is in the center of the compression flange? A majority of the beam will be in compression so it's guaranteed to be closer towards the web and 2) the summation of moments are incorrect. You still made the eccentric force equal to Pu x eccentricity which would only be the correct summation if it was taken about the center of the W section. Moving the summation point to the cl of the compression flange would change this calculated moment pretty dramatically.
I believe your tension resultant would be higher if you accounted for these two things. Let me know what you think!
@datdude8103 - it's my understanding that any eccentric load positioned outside the column flange would try to rotate the column about said flange. Consider a spread footing where e is much greater than L/6. At a certain increased eccentricity the entire footing could be in uplift. Also see the illustration at the beginning of the video. Thanks for the example Rich.
So much wordy!! You may be a good teacher for primary school!
my hope is to keep working on my explanation skills and make each new video more clear than the last. hopefully I was able to help you out in this one!
Great video. Very helpful! One question I had while you finished up solving was should we worry about a prying action in this problem? Maybe it is very simplified for exam purposes but with the eccentricity of the bolts and the column flange. A prying action would be present. Just a thought? Awesome channel! Keep up the great work!
Yes, absolutely! most likely I would check to see if the base plate is sufficiently stiff so that prying action does not need to be considered. there is an equation for this check in the AISC section about prying.
Hey Kesteva. If the eccentricity calculated was to be within the web, like 6" from center. ex(320 axial, 160 Moment) where e = ((160/320) x 12) = 6" . would the force couple distance be the same as your video example (T & C having the same points) C @ middle of right flange & T @ middle of bolt resisting pullout? or would the "C" be located 6" rt of center?(putting it within the web region) .
Thanx bro for sharing ur knowledge
no problem my dude, more videos coming attcha soon!
You got the answer correct but the equation needed be about c for both e and sum of d1 and d2.
Is there any force due to the anchor bolt at right hand side? I cannot imagine a free body diagram of the problem.
Great example, could you give example of stiffened base plate on the concrete support?
Yeah that's a great idea! thanks Lachin
I love your video. Always clear and easy to understand.
In which case C is not equal to T?
Hey Matthew, well the compression would actually be resisted against the compression block of some shape in the concrete footing. so it depends a little bit
Great video. Any examples on the baseplate design?
Gotta get a wind design example going but then I WILL crush a baseplate design example. Wyatt. You ready for a crazy year with Team Kestava?! yaya
Nice video.
Btw for table 7-1 shear, if thread condition was not mention in problem do we assume condition X?
The PE would provide that information, BUT if you have a problem that doesn't specify then you want to be conservative and assume threads are included in the shear plane and assume the lesser bolt shear capacity. really good question Joji
Great explanation. Thank you!
Hey Kestava. How do you approach this problem if there is eccentricity in the column and one of the bolts falls inside the flange?
you wouldnt design the base plate with only bolts inside of the WF if that were the case. the tension loads that would result from the eccentric loads would be extremely high. typically you only detail pinned column bases, with no eccentric loads, with anchors inside the flanges.
need a nice break line on the top horizontal line of that A-A section view amigo.
Good call!
can you explain the proof behind the eccentricity equation e=M/P that determines the actual location of the line of action of the axial force?
the e=M/P comes from balancing the forces on the footing. I should do a quick video on this!
It’s crazy how engineers get a “feeling for things” I knew it was an inch before I saw the answer
so true
so nice bro
Thank you so much 😀
Hey thanks for the effort and for share your knowledge, great content ( better than my classes ) jajajaj, hey question what is the method to design that base plates with stiffeners, there is a method? or the only chance to design these stiffeners in columns base plates is with FEM?
Hey Cesar - there is ALWAYS a way to calculate something by hand. I agree baseplate stiffeners is a little challenging to do by hand but there are some simplified conservative calculations we run to design simple stiffeners. would you like an example sometime?
@@Kestava_Engineering That will be great, is not easy to find hand calculations, most of the documents speaks about FEM simulations. Thank you so much
The location of the compression (C) does not always align with the column flange. It depends on the concrete bearing strength under the base plate. The base plate size and thickness also need to be checked in order to transfer the moment to the concrete below. You can assume the location of compression (C) but it needs to be verified later.
In reality, however, a steel column with base plate and anchor bolts is considered a "pinned" connection and cannot resist large moment. The steel column needs to be embedded in a concrete grade beam with welded rebar on the column to transfer the moment to concrete grade beam. The concrete pad footing below is designed to resist the vertical load only.
agree
Could you please clarify Why do we not take the applied moment of 200 ft-k into account???
we do! we take the moment into account when determining our eccentricity and finding our resultant reaction and location.
@@Kestava_Engineering our eccentricity=>no moment? Thsi means that there is no moment from P like -320*7.5, as it is balanced with M=200 (but even this not real as right part of base plate come in to contact with concrite and reaction force appered). Yes you found point where M balanced with P (if it perfect rotation joint) but it doesnt mean that you can remove M in the sum equation and keep the P. So take assumtion where rotation point is like you said about H beam flange welding point, then do sum for all load as P, M, T, and C(if it can akts) to get T.
Develop a program on the lug welded to the bottom of the base plate.
I feel pretty dumb but I when I solve for 'T' (found @ 11:26), I end up with 155.9 kips. what am I missing?
Robby - im so sorry for the confusion! (a few other team emembers caught my error in the comments below). i should have written -320k * (7.5"-d2)
you did a mistake sir, in 16:24 we have d1=(d+1.5)/2 not as you mentionned
I doubt if that boy ever saw a real anchor bolt and real concrete.
DANG BURN! I will admit I could always use more field experience, but thankfully I have been able to successfully identify anchor bolts and sometimes... I can identify concrete.
@@Kestava_Engineering key word in your answer is verb WILL.)))
@@Kestava_Engineering Your calculations are very primitive(((
Read the room... We're all supportive here, and he did a great job showing how to solve this problem for the PE exam. I hope you've found something nice to say to someone in the past year since you left this comment :)