Hello all, Please keep in mind that you would still have to check the concrete of the support, and if it is able to hold the reactions, namely: 1) Vertical downward load. (Reaction Fz) 2) Horizontal shear load. (Reaction Fx) 3) Bending moment. (Reaction My). This may need you to adopt a larger foundation and/or apply some eccentricity to the foundation. Please have a look at my foundation videos with moments for more context. If you have a mat foundation, then you would have to apply the reactions (Fz, Fx, My and others if applicable) as actions (loads) on the mat at the location of the column. Or just model the mat foundation below the frame and it will be almost a fixed support. Hope this helps. Please feel free to ask any questions. I will do my best to answer them as soon as I can. Regards, CEE
Hello CEE, I’d be lying if I say that I did not enjoy the sheer torture and frustrations of the recorder guy at the end when connections designs were not readily working out. I think that the CEE editor was having a blast throughout those moments, and in a small way, I feel equally guilty by association in that regard. I would like to be crystal clear that I was not relishing because I wanted the CEE to suffer, no, that is far from what triggered my amusement. I often experience similar frustrations during design and it is strangely comforting to know that I am not alone and this is why I could relate and was triggered by the frustrations at the end. I admire the fact that the CEE did not edit the frustrations out and has kept the whole thing real and for that I thank you. Honestly, there is even more that one could learn from the various attempts that were made to try and make things work out. I can also say without any doubts that, the key principles and concepts showing what exactly needs to be done throughout the video from the very beginning to the end were provided and those principles are priceless, thank you so much for this. I suppose that the shape and type of the final design solution(s) “depends” on the designer and on how far and how many options the designer is able and is willing to explore. I have enjoyed this video and I am looking forward to future videos by the CEE Kind regards, DK
Hey there Engr. DK, By the way, you hit the nail on its head. The reason why the editor keeps those frustrating parts is to show people that: hey! this happens to every single one of us. I just want to be honest in my videos, and not always show things to be "perfect", because they are not. I'm just a human, after all ("so don't put the blame on me?.. ^_^") Yes, I 100% agree. Despite the fact that I try not to simply say "it depends", but in all honesty, it really depends ^_^ Thank you very much for your input. I really appreciate it. Also, sorry for being late (the members post already explains what I was doing during this delay) I am really inclined to pin your comment, but I already pinned my own as I had a very important clarification to make. Stay tuned for more content, CEE
Thank you. I've got two questions: 1. Could you please provide an example plate girder model and design? 2. If all of the joints in a truss are welded together, how do you model the joints in Robot? Do you specify the joints as fixed or pinned, or you just use the default specification in Robot?
If the truss joints are welded together, I would still assume them to be pinned (with a twist). I will show you why in a video ^_^ that is a great video idea. Because the loads are applied at the nodes, the components of moments may be less than what you would expect and would not affect the design. The twist is: I would assume the top chord and bottom chord to be continuous (so one full piece with no hinges). This would be more accurate. Here is a quote from the book: William T. Segui - Steel Design - 5th ed - Section 3.8 - Page 79 "Ideally, purlins are located at the truss joints so that the truss can be treated as a pin-connected structure loaded only at the joints. Sometimes, however, the roof deck cannot span the distance between joints, and intermediate purlins may be needed. In such cases, top chord members will be subjected to significant bending as well as axial compression and must be designed as beam-columns (Chapter 6)." What he means here: because purlins are connected to the truss at the joints, we can treat those as pin connected elements. if you would have a purlin in the middle of a truss element, then you would have a beam column. Now I know this sounds crazy, but the codes do actually account for "Modeling accuracy" in their factors of safety. I am really thinking of making a truss design video on this channel, and maybe show a "what if" scenario where I remove the releases, so that you would see that the changes may be minimal. But who knows? Thnx a lot for your comment. Oh, also nice suggestion with the plate girder video. I will think about it and if RSA does support those design checks. Anyways, stay tuned for more content, CEE
Thank you very much for your kind input to the matter. It totally slipped my mind discussing this. Thank you for real. My plan actually included a braced frame for comparison (only artificially braced with a roller that prohibits side-ways movement), but the video length really ran away from me. The video length is waaaaay longer than what you see here, with a lot of time having me pondering about what to do with the rigid base plate (that shows how complicated it can get). You can even see that I added a pinned comment about the foundations. Anyways, I am always happy to see any comment and question, and will do my best to reply to those as soon as I can. I wish you all the best, CEE
Hi there and thnx for your comment. Unfortunately, Autodesk Robot does not have any AISC/LRFD codes or American conforming codes in its connection database. Thus, it is not possible to design connections conforming to American codes. Regards, CEE
Thanks for all these videos, I have followed your videos to design i still hv one issue is to check the design and confirm the sections i hv choosed ( eurocode user). Any advices will be appreciated 😊
so basically you followed the video step by step and you did not get the same answer? that is really odd. Can you send me the file? I will take a look at it as soon as I have time. Email: civ.eng.essentials@gmail.com Regards, CEE
Referring to the base plate design in the code parameters tab, there is a concrete "check". When I have it clicked and active is almost impossible to pass the check and the connection is unrealistic. If I switch it off, it seems more normal, the connection passes the check and the design is realistic. If I have a mate foundation and a pier where my base plate is fixed, is it legit to uncheck this option?
Hello all, Please keep in mind that you would still have to check the concrete of the support, and if it is able to hold the reactions, namely: 1) Vertical downward load. (Reaction Fz) 2) Horizontal shear load. (Reaction Fx) 3) Bending moment. (Reaction My). This may need you to adopt a larger foundation and/or apply some eccentricity to the foundation. Please have a look at my foundation videos with moments for more context. If you have a mat foundation, then you would have to apply the reactions (Fz, Fx, My and others if applicable) as actions (loads) on the mat at the location of the column. Or just model the mat foundation below the frame and it will be almost a fixed support. Hope this helps. Please feel free to ask any questions. I will do my best to answer them as soon as I can. Regards, CEE
@CivilEngineeringEssentials Thanks a lot for the answers. My model is a 4 steel columns structure fixed with base plates into short concrete piers. Those piers (saddles) are connected to a mat foundation as a whole unit. [will be casted together] I modeled the raft slab as a shell, the four saddles as columns (calculating bending and shear reinforcement) and each one sharing a point with the steel columns. This concrete-steel connection I modeled it as a base plate connection. The forces are transferred correctly and the analysis shows no errors. My question is if the connection check is legit?
Hello all,
Please keep in mind that you would still have to check the concrete of the support, and if it is able to hold the reactions, namely:
1) Vertical downward load. (Reaction Fz)
2) Horizontal shear load. (Reaction Fx)
3) Bending moment. (Reaction My).
This may need you to adopt a larger foundation and/or apply some eccentricity to the foundation.
Please have a look at my foundation videos with moments for more context.
If you have a mat foundation, then you would have to apply the reactions (Fz, Fx, My and others if applicable) as actions (loads) on the mat at the location of the column. Or just model the mat foundation below the frame and it will be almost a fixed support.
Hope this helps. Please feel free to ask any questions. I will do my best to answer them as soon as I can.
Regards,
CEE
Hello CEE,
I’d be lying if I say that I did not enjoy the sheer torture and frustrations of the recorder guy at the end when connections designs were not readily working out. I think that the CEE editor was having a blast throughout those moments, and in a small way, I feel equally guilty by association in that regard.
I would like to be crystal clear that I was not relishing because I wanted the CEE to suffer, no, that is far from what triggered my amusement. I often experience similar frustrations during design and it is strangely comforting to know that I am not alone and this is why I could relate and was triggered by the frustrations at the end. I admire the fact that the CEE did not edit the frustrations out and has kept the whole thing real and for that I thank you. Honestly, there is even more that one could learn from the various attempts that were made to try and make things work out.
I can also say without any doubts that, the key principles and concepts showing what exactly needs to be done throughout the video from the very beginning to the end were provided and those principles are priceless, thank you so much for this.
I suppose that the shape and type of the final design solution(s) “depends” on the designer and on how far and how many options the designer is able and is willing to explore.
I have enjoyed this video and I am looking forward to future videos by the CEE
Kind regards, DK
Hey there Engr. DK,
By the way, you hit the nail on its head. The reason why the editor keeps those frustrating parts is to show people that: hey! this happens to every single one of us. I just want to be honest in my videos, and not always show things to be "perfect", because they are not. I'm just a human, after all ("so don't put the blame on me?.. ^_^")
Yes, I 100% agree. Despite the fact that I try not to simply say "it depends", but in all honesty, it really depends ^_^
Thank you very much for your input. I really appreciate it.
Also, sorry for being late (the members post already explains what I was doing during this delay)
I am really inclined to pin your comment, but I already pinned my own as I had a very important clarification to make.
Stay tuned for more content,
CEE
Sir pls make video on design of composite structure on basis of eurocode.
Oh that is an interesting idea. Now RSA is not that good in composite structures. I will see what I can do about it.
Thank you. I've got two questions:
1. Could you please provide an example plate girder model and design?
2. If all of the joints in a truss are welded together, how do you model the joints in Robot? Do you specify the joints as fixed or pinned, or you just use the default specification in Robot?
If the truss joints are welded together, I would still assume them to be pinned (with a twist). I will show you why in a video ^_^ that is a great video idea.
Because the loads are applied at the nodes, the components of moments may be less than what you would expect and would not affect the design.
The twist is: I would assume the top chord and bottom chord to be continuous (so one full piece with no hinges). This would be more accurate.
Here is a quote from the book: William T. Segui - Steel Design - 5th ed - Section 3.8 - Page 79
"Ideally, purlins are located at the truss joints so that the truss can be treated as a
pin-connected structure loaded only at the joints. Sometimes, however, the roof deck
cannot span the distance between joints, and intermediate purlins may be needed. In
such cases, top chord members will be subjected to significant bending as well as
axial compression and must be designed as beam-columns (Chapter 6)."
What he means here: because purlins are connected to the truss at the joints, we can treat those as pin connected elements. if you would have a purlin in the middle of a truss element, then you would have a beam column.
Now I know this sounds crazy, but the codes do actually account for "Modeling accuracy" in their factors of safety.
I am really thinking of making a truss design video on this channel, and maybe show a "what if" scenario where I remove the releases, so that you would see that the changes may be minimal. But who knows?
Thnx a lot for your comment.
Oh, also nice suggestion with the plate girder video. I will think about it and if RSA does support those design checks.
Anyways, stay tuned for more content,
CEE
@@CivilEngineeringEssentials Great. Thanks for the response.
Hi there, one thing to add, portal frames are susceptible to sway effects i.e. global stability .... nothing is perfect in this world ;) cheers
Thank you very much for your kind input to the matter. It totally slipped my mind discussing this. Thank you for real.
My plan actually included a braced frame for comparison (only artificially braced with a roller that prohibits side-ways movement), but the video length really ran away from me. The video length is waaaaay longer than what you see here, with a lot of time having me pondering about what to do with the rigid base plate (that shows how complicated it can get). You can even see that I added a pinned comment about the foundations.
Anyways, I am always happy to see any comment and question, and will do my best to reply to those as soon as I can.
I wish you all the best,
CEE
Thank you
It is possible to design the connection as per American code
Hi there and thnx for your comment.
Unfortunately, Autodesk Robot does not have any AISC/LRFD codes or American conforming codes in its connection database.
Thus, it is not possible to design connections conforming to American codes.
Regards,
CEE
Thanks for all these videos,
I have followed your videos to design i still hv one issue is to check the design and confirm the sections i hv choosed ( eurocode user).
Any advices will be appreciated 😊
so basically you followed the video step by step and you did not get the same answer? that is really odd. Can you send me the file? I will take a look at it as soon as I have time.
Email: civ.eng.essentials@gmail.com
Regards,
CEE
@@CivilEngineeringEssentials Sorry I haven't finished the video yet😊, apologize
I'll send you one of my projects,
Referring to the base plate design in the code parameters tab, there is a concrete "check". When I have it clicked and active is almost impossible to pass the check and the connection is unrealistic.
If I switch it off, it seems more normal, the connection passes the check and the design is realistic.
If I have a mate foundation and a pier where my base plate is fixed, is it legit to uncheck this option?
Hello all,
Please keep in mind that you would still have to check the concrete of the support, and if it is able to hold the reactions, namely:
1) Vertical downward load. (Reaction Fz)
2) Horizontal shear load. (Reaction Fx)
3) Bending moment. (Reaction My).
This may need you to adopt a larger foundation and/or apply some eccentricity to the foundation.
Please have a look at my foundation videos with moments for more context.
If you have a mat foundation, then you would have to apply the reactions (Fz, Fx, My and others if applicable) as actions (loads) on the mat at the location of the column. Or just model the mat foundation below the frame and it will be almost a fixed support.
Hope this helps. Please feel free to ask any questions. I will do my best to answer them as soon as I can.
Regards,
CEE
@CivilEngineeringEssentials
Thanks a lot for the answers.
My model is a 4 steel columns structure fixed with base plates into short concrete piers. Those piers (saddles) are connected to a mat foundation as a whole unit. [will be casted together]
I modeled the raft slab as a shell, the four saddles as columns (calculating bending and shear reinforcement) and each one sharing a point with the steel columns. This concrete-steel connection I modeled it as a base plate connection.
The forces are transferred correctly and the analysis shows no errors.
My question is if the connection check is legit?