Designing RC Columns in Autodesk Robot Structural Analysis

[@nivinahmedhassanghaboun1391]

Great job, I really find your tutorials very helpful and interesting. I want to ask, if you can provide a video related to the design of Box culvert and pipe culvert using Robot structural analysis. Thank you again for your efforts.

[@CivilEngineeringEssentials]

Hi there, Sure thing, but I need to finish the warehouse design series first. Stay tuned for more content, CEE

[@stephanc7192]

Great video

[@CivilEngineeringEssentials]

thnx a lot, you are most welcome PS: Sorry for the late reply. I had a ton of things to finish and now I am gradually getting back

[@johanlike6699]

can I ask why would we reduce the moment of inertia in the first place? is it some kind of security coefficient?

[@ZohanWaseem-v9j]

Great one

[@CivilEngineeringEssentials]

thnx a lot. Stay tuned for more content.

[@M.RashidAdi.1995]

Thank you very much

[@CivilEngineeringEssentials]

You are most welcome Also, sorry for my late reply, I had tons of stuff to do so I was unable to reply in a timely manner,.

[@richardbelec3816]

In steel columns, is the a video explaining in details the process of designing base plates with anchors with concrete columns with or without stirrups? Does Robot details graphic loads distribution in those situations?

[@CivilEngineeringEssentials]

I still have no detailed video about it, but I might add it to my ToDo list. Stay tuned for more content.

[@anasbentounsi1272]

I have a question about the buckling model: Suppose the column (25X25) with a masonry wall and is subjected to wind loads in the Y direction of its local axis, resulting in a moment MZ on the column. Should we turn off the Y direction and let the Z direction be on, because MZ is much greater than MY? Is that correct? I hope you understand me, if there any way to send you a picture of my robot model

[@CivilEngineeringEssentials]

I do not agree in turning of any direction in the buckling check. I understand that your point is: There is no My, so buckling around y is not an issue. However, buckling can happen even if no moments are present around y. It can happen solely due to the Axial Forces. Now, if you are an ACI318 user, then you would think: Why do I care about buckling y? there is no moment to be "amplified". (For non ACI users: Moment amplification is a method of including buckling effects by increasing the moment using a factor). Now here is the plot-twist: the ACI318 code specifies a minimum moment you have to apply. So in that case, if you were to "hand-calculate" your column, and your column is slender around Y, then you would have to apply M2min on Y and even perform moment amplification. I hope my words made sense. Also, sorry for the late reply, we are at the end of the academic year, so a lot of paper work. Regards, CEE

[@anasbentounsi1272]

@@CivilEngineeringEssentials Thank you so much CEE, very good explanation

[@mwangibenson5199]

was the column braced or unbraced? How does robot handle these two situations?

[@CivilEngineeringEssentials]

Hi there I do not remember my inputs back then to be honest but: Autodesk robot always calculates the effective length factor k and as per ACI code calculates the klu/r factor and compares it to decide wether it us long or short. If you refer about if the atructure itself is braces or not, this is an input that can be provided by the user

[@mwangibenson5199]

@@CivilEngineeringEssentials okay 👍

[@borisdjokaboris6424]

Can you do a video on this including the FIRE PROVISIONS . ITS IS REALLY A THING, because increasing the size of the column and cover doesn't change anything to the ERROR DISPLAYED after running the calculation.

[@CivilEngineeringEssentials]

I will keep that in mind, there are some fire options you can select, but I did not do a dedicated video about it. Stya tuned ^_^

[@BorisDJOKOKOUONGA]

@@CivilEngineeringEssentials Boris DJOKO KOUONGA @CivilEngineeringEssentials Yeah thanks, sir it's really a thing, fire provision for column effective length of 4m or >3m don't pass in robot. Even with a cover of 40mm

[@niisarpei3676]

Great content Sir. However I realized you applied a stiffness modification factors to your frame according to ACI recommendation. That is for beam 0.35 to Iyy and for columns 0.7 to Ixx ( instead of Iyy and Izz) Please clarify. Thanks

[@CivilEngineeringEssentials]

I agree, there was a slight video editting mistake I did. if you check the input section a split second before I apply, you will see that the modification factor for all stiffnesses (Ix Iy and Iz) was modified. The input process of those modifications was -however- cut during editting. To clarify: ACI code requires you to modify the bending stiffness of the beams and columns with corresponding factors. Technically speaking, members can bend around yy and zz. So those two Inertias should be modified, which I did (but was shown for a split second only). Further proof to this is when looking at the K factor calculation of the column. The Inertias are reduced. I still agree with your concern about Ixx. ACI code says nothing about it. It is the torsional stiffness of the beam. Now first off, Ixx will not affect anything in our calculations. There is nothing causing torsion on the beam. Still, my logic behind reducing it is based on the theoretical part. You see, for a perfect cylinder, Ixx = Iyy + Izz for rectangles, it is different. Still, I thought that: if Iyy is reduced and Izz is reduced, it stands to reason to reduce Ixx. and that is the logic behind reducing all inertias by the same amount. Still, you are right. it is only visible a split second before hitting the apply button. My video editting was not on point at that position. Hope that clarifies the issue. I will add this clarification to the description. All the best, CEE

[@niisarpei3676]

@@CivilEngineeringEssentials you are right sir. in a full building model with vertical and horizontal loads applied, stiffness values in all directions is reduced according to code requirements. I realized in the column design, the columns has a reduced stiffness values but was confused abit in inputting during column section definition and the video editing. Thank you for the clarification. I really understand it now.

[@CivilEngineeringEssentials]

@@niisarpei3676 Most welcome. I am glad you liked it.

[@tukangsipilofficial1362]

alhamdulillah thank civil engineering essentials

[@CivilEngineeringEssentials]

Most welcome. It is really good to know that this video helped you, stay tuned for more content.

[@JPedroso62]

In tems of foundations You pinned the columns why you didn't fixed them?

[@CivilEngineeringEssentials]

That is a very good question. You see, fixed vs pinned is determined by the engineer. To explain what I mean, here is the theoretical background: Fixed supports mean that the support is strong enough to stop any rotation Pinned supports mean that the support might allow some rotation. In reality, supports are neither fixed nor pinned, but somewhere in between. Some people like to put a "ground elasticity" by adding springs to the foundation. So, the decision of pinning vs fixing is left to the engineer's discretion. Here is what I usually have in mind: Pinned supports mean that: 1) The moment would be higher 2) the moment would be a single curvature moment So, it is a little bit more conservative when designing columns. Hope it helped, Regards, CEE

[@manueldario3755]

the rebars in this column are absurd

[@CivilEngineeringEssentials]

I respectfully disagree. The controling case was dominated by bending moment.