Hello Dr. CEE, First, thank you so much for continuing to fearlessly venture into unchartered corners of the civil and structural engineering realm; do not stop, you are doing remarkably well. You are not only making some of us smarter, but you are also making some of us that much more relevant and practical as well. Column base stiffness and its application (at least in my experience) is one of those topics that [as one subscribed have also noted in their comment to this video] “…nobody talks about…”. I have heard “it depends” before but never in a way that the CEE had just dissected this saying down on this video. In my region [and I am speaking of my own experience], there are those who probably know better and who most likely model and apply spring rotational stiffness to supports in their work. But for me, I had been stuck (until now 😊) with assuming the two extremes of either “pinned” or “fixed” and with complying to the conditioned acceptance that “bolts inside the section = pinned” and “bolts outside = fixed”. Before this video, my answer to the “grey-area” base plate that was presented in this video would have been that the base plate is fixed ☹. For me, the concept of base stiffness as I recall was solely focus on the empirical approach and only in relation to the modelling of nominal pinned bases in a portal frame, even then, I struggled to comprehend those assumptions then. In hindsight, these are the assumptions that the CEE has explained in this video at 15:41. I don’t recall recommendations for design stiffness of rigid bases then. I am so grateful to the CEE team for this video as it opens up a much better and holistic view of the topic. 14:31 Very good catch and well done to the CEE for spotting a possible error on the NCCI report regarding the definition of the lever arm. If (or when) the CEE do get a response from the NCCI, kindly share or update.This is a curious thing and sometimes if a reader or a user is not fully confident of their understanding of the principles of the subject, they may get significantly thrown off by such things or even driven to question their technical sanity. Now, back to 15:41 and for the case of using the empirical approach with an assumption of a “nominally pinned base plate”. My literal understanding of “…10% of column stiffness…” means that the modelled supporting spring stiffness (the value I would input in RSAP or in any other analysis software) = 0.1*E*Icolumn / Lcolumn and for 20% = 0.2*E*Icolumn / Lcolumn. However, I have seen text and references [particularly referring to bases of portal frames] that states that “…..10% of the column stiffness may be modelled by using a spring stiffness equal to 0.4*E*Icolumn/Lcolumn ….and 20% by using a spring stiffness equal to 0.8*E*Icolumn/Lcolumn….”. What am I missing here? How can 0.4EI/L be considered to be 10% and how can 0.8EI/L be considered to be 20%? Aren’t these values 40% and 80% respectively instead? 18:42 I envy your ability to seamlessly switch between multiple languages including your native language; you are truly an inspiration on many fronts. Thank you for sharing your preferred workflow and for the spreadsheet, it is always a treat (yummy) to hear your personal preferences and thoughts. 20:00 I understand the option of putting the bolts inside the section; with regard to the other option (20:06) of limiting the base plate stiffness to remain NOMINALLY PINNED and not to become SEMI-RIGID, how would one quantify this exactly? ….. I am asking this because the equations provided on Figure 2.2 of the NCCI are only dealing with the limits between RIGID and SEMI-RIGID. Does one simply assume the empirical 10% and 20% of the column stiffness above in order to quantify the limits between NOMINALLY PINNED and SEMI-RIGID or there is another way? I have enjoyed this video and I am looking forward to future videos by the CEE Keep well and kind regards, DK
Hi there Engr. DK, thank you very much for your comment. I am really honored. I am just trying to challenge the status quo of (this is a pin, that is a rigid/fix) by giving more details as to "why" that is. Oh I see that in your region, you have similar ways of dealing with the base plates. Either the pin/fix via bolt location, or the more sophisticated semi-rigid approach. I am very happy to learn about this. Thank you very much. To be honest, I am not a fan of the empirical approach, it kind of makes sense, but I rather feel more comfortable being surrounded by numbers and facts (I know those are not 100% facts, as uncertainties are always looming around, but at least, it is as good as it gets). The 14:31 equation took me some time to verify, I tried every single way of making sense of the figure, but it did not, so I mentioned this problem in my video. Oh, your comment about 0.4 EI/L and 0.8 EI/L surprised me really. Great attention to details! I also assumed in my mind the EI/L x ratio.. wow, this really surprised me. I am checking as I am writing the response... (long pause) after 10 mins (still long pause)... I FOUND IT!! after around 20 mins. I remember from the back of my mind the "moment redistribution method by hardy cross" and the "slope deflection method". OMG this is so cool (CEE is happy now) In the slope deflection method (Structural Analysis), let's say we have a beam AB, both ends fixed, then the moment generated at A is Ma = 4EI/L thetaA + 2EI/L theta B + something something Now the stiffness at A from a rotation at A is 4EI/L --> 10% 0.4 ---> 20% 0.8 That's it!!! THNX Engr. DK, you just made my day! You can find this in any structural analysis book, but here is a wikipedia page for easy access: en.wikipedia.org/wiki/Moment_distribution_method (Check out "determination of carry over stuff") Oh, for the nominally pinned vs semi-rigid, I think I had a comment somewhere either on this video or the implementation video, but still: the EN1993 code actually gives more details about when to consider nominally pinned. I missed saying this in the video. But still, in my humble opinion, semi rigid is the way to go if you would be ever in doubt. I am so happy by that column stiffness find that I might have missed smthn in your comment, plz feel free to ask away if I failed to answer anything. Stay tuned for more content, CEE
As a civil engineer I cannot thank enough for the efforts you put in these videos, treating details that nobody talks about but also not in a boring way.. It's the perfect formula.
Great work doctor , But at the end when you oppened the excel , i didn't understand or something missed me , you said the value is samller from those 2 values then it's semi rigid , but if you look to the graph that you have shown , you have 3 ares how did you know that the value you get first it's in the semi rigid and not in the fixed ?
That's is a very good point your raised. You are totally right and understood all well and good. Here is the thing: The "nominally pinned" region can be replaced with a semi rigid analysis. Because the stiffness of a semi rigid in those regions is "very small" you could apply a pin and no difference would be there (the stiffness is soooo weak so that it does not even matter anymore). I think the EC provides some more guidelines to find the stiffness of the "nominally pinned" base plate. For the rigid vs semi rigid, things are different. One of them (the solid lines) is for a certain type of frames, whereas the dashed line is for the other type. I think that the nominally pinned is valid for both types. I think I might have missed your question, so feel free to further clarify. Regards, CEE
@@CivilEngineeringEssentials doctor my question is the graph or your assumption i get it , but if we are going to reffer to the graph we can't because we didn't identify all the areas, I hope I'm not missing something .we still need more data so we identify it as the graph and then we can say this section is pinned , fixed or semirigid.
Oh I see. You are right. Now to be honest, I forgot to mention the fact that the graph is even more detailed in EN1993 So this unknown region is actually well phrased in the EN code. The drawing is also there.
Hi sir could clarify the 2D and 3D warehouse design? In our company we are following 2D analysis which is economic compare with 3D analysis. We are getting lesser profile. If you explain it it would be great. I have tried but still I couldn't find the answer. If possible to get your mail I can explain with more detail.
Sure, I always welcome suggestions like those. You can mail me on civ.eng.essentials@gmail.com But please note, my task list is currently filled to the brim, so it would take some time. Still, I hope that you find the videos on this channel beneficial> Regards, CEE
@@CivilEngineeringEssentials Hi thanks for your quick reply. I am grateful that which I was longing so long as a junior structural engineer to find a better guidance to learn better for Robot structural analysis finally I found you. I saw your video's regarding analysis and technically I learned a lot and understand that you are having more experience that you could solve my problem which will be more helpful. Tomorrow I will send you. Kindly help me this.
Hello Dr. CEE,
First, thank you so much for continuing to fearlessly venture into unchartered corners of the civil and structural engineering realm; do not stop, you are doing remarkably well. You are not only making some of us smarter, but you are also making some of us that much more relevant and practical as well.
Column base stiffness and its application (at least in my experience) is one of those topics that [as one subscribed have also noted in their comment to this video] “…nobody talks about…”. I have heard “it depends” before but never in a way that the CEE had just dissected this saying down on this video.
In my region [and I am speaking of my own experience], there are those who probably know better and who most likely model and apply spring rotational stiffness to supports in their work. But for me, I had been stuck (until now 😊) with assuming the two extremes of either “pinned” or “fixed” and with complying to the conditioned acceptance that “bolts inside the section = pinned” and “bolts outside = fixed”. Before this video, my answer to the “grey-area” base plate that was presented in this video would have been that the base plate is fixed ☹. For me, the concept of base stiffness as I recall was solely focus on the empirical approach and only in relation to the modelling of nominal pinned bases in a portal frame, even then, I struggled to comprehend those assumptions then. In hindsight, these are the assumptions that the CEE has explained in this video at 15:41. I don’t recall recommendations for design stiffness of rigid bases then. I am so grateful to the CEE team for this video as it opens up a much better and holistic view of the topic.
14:31 Very good catch and well done to the CEE for spotting a possible error on the NCCI report regarding the definition of the lever arm. If (or when) the CEE do get a response from the NCCI, kindly share or update.This is a curious thing and sometimes if a reader or a user is not fully confident of their understanding of the principles of the subject, they may get significantly thrown off by such things or even driven to question their technical sanity.
Now, back to 15:41 and for the case of using the empirical approach with an assumption of a “nominally pinned base plate”. My literal understanding of “…10% of column stiffness…” means that the modelled supporting spring stiffness (the value I would input in RSAP or in any other analysis software) = 0.1*E*Icolumn / Lcolumn and for 20% = 0.2*E*Icolumn / Lcolumn. However, I have seen text and references [particularly referring to bases of portal frames] that states that “…..10% of the column stiffness may be modelled by using a spring stiffness equal to 0.4*E*Icolumn/Lcolumn ….and 20% by using a spring stiffness equal to 0.8*E*Icolumn/Lcolumn….”. What am I missing here? How can 0.4EI/L be considered to be 10% and how can 0.8EI/L be considered to be 20%? Aren’t these values 40% and 80% respectively instead?
18:42 I envy your ability to seamlessly switch between multiple languages including your native language; you are truly an inspiration on many fronts.
Thank you for sharing your preferred workflow and for the spreadsheet, it is always a treat (yummy) to hear your personal preferences and thoughts. 20:00 I understand the option of putting the bolts inside the section; with regard to the other option (20:06) of limiting the base plate stiffness to remain NOMINALLY PINNED and not to become SEMI-RIGID, how would one quantify this exactly? ….. I am asking this because the equations provided on Figure 2.2 of the NCCI are only dealing with the limits between RIGID and SEMI-RIGID. Does one simply assume the empirical 10% and 20% of the column stiffness above in order to quantify the limits between NOMINALLY PINNED and SEMI-RIGID or there is another way?
I have enjoyed this video and I am looking forward to future videos by the CEE
Keep well and kind regards, DK
Hi there Engr. DK,
thank you very much for your comment. I am really honored. I am just trying to challenge the status quo of (this is a pin, that is a rigid/fix) by giving more details as to "why" that is.
Oh I see that in your region, you have similar ways of dealing with the base plates. Either the pin/fix via bolt location, or the more sophisticated semi-rigid approach. I am very happy to learn about this. Thank you very much.
To be honest, I am not a fan of the empirical approach, it kind of makes sense, but I rather feel more comfortable being surrounded by numbers and facts (I know those are not 100% facts, as uncertainties are always looming around, but at least, it is as good as it gets).
The 14:31 equation took me some time to verify, I tried every single way of making sense of the figure, but it did not, so I mentioned this problem in my video.
Oh, your comment about 0.4 EI/L and 0.8 EI/L surprised me really. Great attention to details! I also assumed in my mind the EI/L x ratio.. wow, this really surprised me. I am checking as I am writing the response... (long pause) after 10 mins (still long pause)... I FOUND IT!! after around 20 mins.
I remember from the back of my mind the "moment redistribution method by hardy cross" and the "slope deflection method". OMG this is so cool (CEE is happy now)
In the slope deflection method (Structural Analysis), let's say we have a beam AB, both ends fixed, then the moment generated at A is
Ma = 4EI/L thetaA + 2EI/L theta B + something something
Now the stiffness at A from a rotation at A is 4EI/L --> 10% 0.4 ---> 20% 0.8
That's it!!! THNX Engr. DK, you just made my day!
You can find this in any structural analysis book, but here is a wikipedia page for easy access:
en.wikipedia.org/wiki/Moment_distribution_method
(Check out "determination of carry over stuff")
Oh, for the nominally pinned vs semi-rigid, I think I had a comment somewhere either on this video or the implementation video, but still: the EN1993 code actually gives more details about when to consider nominally pinned. I missed saying this in the video. But still, in my humble opinion, semi rigid is the way to go if you would be ever in doubt.
I am so happy by that column stiffness find that I might have missed smthn in your comment, plz feel free to ask away if I failed to answer anything.
Stay tuned for more content,
CEE
As a civil engineer I cannot thank enough for the efforts you put in these videos, treating details that nobody talks about but also not in a boring way.. It's the perfect formula.
You are most welcome. Just trying to have a positive impact on the Civ. Eng. Society.
CEE
Dear CEE, Thanks for your VDO, Excel spreadsheet and well explanation.
Happy you liked it. Stay tuned for more content ^_^
Amazing work! Thank you from Sweden!
Hej! I am happy you liked it. Stay tuned for more content.
Another Top Video.Thank you CEE
You are most welcome. Stay tuned for more content ^_^
CEE
Excellent content. Very gratefull sir.
You are most welcome. Stay tuned for more contents.
Regards,
CEE
Great work doctor ,
But at the end when you oppened the excel , i didn't understand or something missed me , you said the value is samller from those 2 values then it's semi rigid , but if you look to the graph that you have shown , you have 3 ares how did you know that the value you get first it's in the semi rigid and not in the fixed ?
That's is a very good point your raised. You are totally right and understood all well and good. Here is the thing:
The "nominally pinned" region can be replaced with a semi rigid analysis. Because the stiffness of a semi rigid in those regions is "very small" you could apply a pin and no difference would be there (the stiffness is soooo weak so that it does not even matter anymore). I think the EC provides some more guidelines to find the stiffness of the "nominally pinned" base plate.
For the rigid vs semi rigid, things are different. One of them (the solid lines) is for a certain type of frames, whereas the dashed line is for the other type. I think that the nominally pinned is valid for both types.
I think I might have missed your question, so feel free to further clarify.
Regards,
CEE
@@CivilEngineeringEssentials doctor my question is the graph or your assumption i get it , but if we are going to reffer to the graph we can't because we didn't identify all the areas, I hope I'm not missing something .we still need more data so we identify it as the graph and then we can say this section is pinned , fixed or semirigid.
Oh I see.
You are right. Now to be honest, I forgot to mention the fact that the graph is even more detailed in EN1993
So this unknown region is actually well phrased in the EN code. The drawing is also there.
Could you please share the excel file ? thanks
Of course:
docs.google.com/spreadsheets/d/1Rrpc8efvFdbZLyzzNmQafQv6H4-hUgJ8/edit?usp=sharing&ouid=110241062538661131550&rtpof=true&sd=true
Hi sir could clarify the 2D and 3D warehouse design? In our company we are following 2D analysis which is economic compare with 3D analysis. We are getting lesser profile. If you explain it it would be great. I have tried but still I couldn't find the answer. If possible to get your mail I can explain with more detail.
Sure, I always welcome suggestions like those.
You can mail me on civ.eng.essentials@gmail.com
But please note, my task list is currently filled to the brim, so it would take some time.
Still, I hope that you find the videos on this channel beneficial>
Regards,
CEE
@@CivilEngineeringEssentials
Hi thanks for your quick reply. I am grateful that which I was longing so long as a junior structural engineer to find a better guidance to learn better for Robot structural analysis finally I found you. I saw your video's regarding analysis and technically I learned a lot and understand that you are having more experience that you could solve my problem which will be more helpful.
Tomorrow I will send you. Kindly help me this.
I received the email. I will check it asap
Regards,
CEE