Thank you for your effort in creating these videos. I have a question that I would appreciate if you could address. In the video, specifically from 29:10 to 30:00, you mentioned that the structure is weak in the y-axis, even after changing the direction of the slab. I found this statement a bit confusing, and I would be grateful if you could kindly clarify this misunderstanding for me. Thank you in advance for your time and explanation.
Hi there, thnx for the comment. I will try to give you a second by second break-down of that. Coz yep, it might be confusing. I quick note: The local coordinate system of the slab and the global coordinate system of the model are the same. So X is always X and Y is always Y. That is a good thing to start. so: in 28:55 I open the orthotropic definition and apply it on the slab. Note, the ribs direction is in the X direction. Since the ribs are in the x direction, this means that the inertia for a strip parallel to the x-axis is stronger than a strip parallel to the y axis. So the x-axis is strong, and the y axis is weak. This means that the lines parallel to x remain relatively unbent, and the lines parallel to y become bent, hence the deflection shape at 29:13 Then, at 29:34 I flipped the rib direction to y, so everything is now flipped, hence the deflection shape at 29:50 I can actually suggest a really cool experiment for you to do to visualize it. Imagine you take a piece of paper (A square one) and bend one direction in a zig-zag pattern. /\/\/\/\/\/\/\/\/\ and now support it on four fingers on four corners (you might need a friend for this). Look how the deflection shape behaves. It will be eye opening. I suggest of course to have a rather larger square, so that it would deflect under its own weight. Otherwise, you would have to put a small weight on it (without totally destroying it) Hope it was helpful. In case you have any further questions, please feel free to ask away. I will pin this comment because it might be helpful for future viewers. Thank you very much. It helps if you share this channel with your friends. Regards, CEE
Ok thank you I found this reply very helpful everything is clear when you flipped the ribs to the direction y then the slab is stronger in the y direction and weak in the x.
I don’t usually comment on TH-cam Vids, but this masterpiece really helped me alot. Thankyou so much and i really wish you the best luck in your channel. About suggestions maybe tutorials on basics for using Robot Structural Analysis
First of all, a huge thank you for your comment. It encourages me to give it my all. Sure, I would gladly cover the basics in more detail in robot. I do know that my videos are currently of intermediate level with some mentions of basics and some mentions of advanced stuff I have some videos talking about some basics, still, I am open for suggestions. Do you have any certain things you want me to cover? Regards, CEE
Thank you for making this video series, it’s incredibly informative! I’ve used robot for years but I’m picking up so many useful tips from you. Autodesk should be paying you for this
Hi there, Thnx a lot for your comment. I am happy that those videos helped you. Stay tuned for more content, and if you have any questions, feel free to ask. Regards, CEE
Hello, I am really happy you liked it. Yes, I will add the principles and complex results on my TODO list. I am planning something for that and for the wood and armer moments very soon. Stay tuned, and help the channel grow by suggesting it to your friends. Regards, CEE
Great video yet very educative. You really explained the alignment of the local slab coordinate with the global coordinate very well. It’s rarely explained in all videos on TH-cam I’d be keep my specific requests for later when we are done with this course. Thank you and God bless you immensely.
thnx a lot for your comment. It encourages me to continue doing my best. FYI: I am an Assistant Professor in Structural Analysis and that is the reason why there is a certain educative element in my explanations. As for future questions, just wait a little bit until the "elementary" tutorial is finished. It will be finished within 20 days when I explain a full structure from A to Z (importing, modeling, designing, exporting calculations and drawings) After that, I would start with some advanced topics and that is basically the perfect timing for any questions or requests.
@@CivilEngineeringEssentials that’s explains why your tutorials are educative and unique. The Structural Engineering profession and Robot Structural Analysis software needs more people like you to make the profession and the softwares appealing for practical use. I always look forward to seeing your post.
Hello. Great videos so far. I hope it continues and also for complex topics. a video about foundation slab (lets say mat or raft) with thicker areas where equipments are placed will be appreciated. (it is typically like a slab with drops but upside down). Also compatible nodes video will be good.
Hello there. Happy you liked it. Sure, gonna add it to my ToDo list. First, I have to do a simple video about rafts, then make a video about rafts with increased thickness in regions of higher loads such as columns or - as you have mentioned - machinery and equipment. Stay tuned.
Quick Update on the matter. I have filmed the tutorial on compatible nodes and am video editting it at the moment. you can expect it to be available Saturday (fingers crossed) Regards, CEE
Great suggestion. I think I made a video explaining the difference between wall and floor, but there is more as you stated. There are other models that may need to be explained, so I will keep this on my ToDo list. Stay tuned for more content, CEE
Thanks for the such a wonderful Video. It has very useful information I need your help in understanding the Principal stresses and complex stresses. Actually, I am working on steel bridge design which has two longitudinal box gliders and transverse girder above which I have a deck slab based on required of Client I have asked to model part of bridge with plate and shells and need to check location of stress concentration and stress variation to check fatigue failure. Can you make a video that explains what principal and complex stresses in detail and explain how we corelate for design of steel structures i.e plates.
Sure that is a good idea. I might be still - however - working on the bridge series on Midas, so it might take a little while Still, thnx a lot for your comment. I am really happy it helped. Regards, CEE
@@CivilEngineeringEssentials thanks a lot for such prompt reply 😊. I am bit hurry to show some progress on the work. It would be great help if you could share a document/link on the complex stress theory in autodesk robot manual. Also, is there any other way to connect with you to discuss on this further ?
Hi CEE, its a great video thank you, can i ask some question. Can you explain between Plate and Shell formula? Recently I read in online, RSA use thick plate formula but in SAP2000 can choose many option of the formula. So can we apply the shell thin formula to RSA? Thank you
Plate and shell are identical in Robot. It uses a Discrete Modified Kirchoff Triangle and Discrete Modified Kirchhoff Quad. RSA's model here works well for both thick and thin. There are other theories such as the mindlin theory, which only works for one type of plate. Here are the references for the DMKT and DMKQ www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/ROBOT-what-types-of-finite-elements-are-used-in-the-program.html
Hellow . Thanks ypu for this vidéo. I would like to explain a little bit Mises Stress. When should we use this type of stresses wile analysing strctucture.
Hello there. English: In my opinion, it is only used for steel plate elements, because the stresses are from 2 dimensions in addition to shear, so it would not be enough to consider moments and stresses form one direction only For beams, columns and connections, my humble opinion is to use the normal bending moment and axial force approaches as written in the code. العربية، من وجهة نظري، أعتقد إنه إجهادات فون ميزس تستخدم في تصميم البلاطات المعدنية فقط، حيث يوجد الإجهادات من كلا محوري السين والصاد والقص، وعليه لا أعتقد من وجهة نظري المتواضعة إنه التصميم من جهة واحدة مناسب، اما العناصر الخطية كالأحزمة والأعمدة، فمعادلات الأكواد مناسبة، German Von meiner Seite glaube ich, dass die von Mises Spannung nur im Fall einer Stahlplatte benutzt werden, da es ja Spannung aus der x und y richtung gibt. Fuer Balken und Saeulen, wuerde ich die normal Gleichung der EC oder DIN verwenden. Regards, CEE
I found your video very helpful. I learn a lot from it. I want to know if there is a way to model the partition walls not as load but wall. I want this beacause i'm using revit and i'm modeling my partition walls. If i can transfer the wall directly without trying to model load this will be very helpful.
you are most welcome. Partition walls as elements (not loads) is not directly possible in autodesk robot. Because it assumes those to be "shear walls" However, I can suggest a work-around (I have not tested this) In case you know the stiffness of the wall in the vertical direction (Force vs vertical displacement) then you could use it to modify the wall such that: AE/L of the shear wall is very close to AE/L of the brick wall. This does only work for purely axially loaded walls. Also note, I have not yet tested it, so I am pretty sure that there are some problems when it comes to shear and bending behavior. Sorry for the long answer.. The shorter TLDR version is: unfortunately, no. Regards CEE
Technically, there is no difference. And here is why: if you use the "floor command" to draw a slab, then it does two steps for you 1) It does create the contour 2) It does fill the contour with your slab if you use the panel command, then you have to click a contour that you already drew. So it is basically doing step 2 for you. if you want to use a panel command, you have to first draw the contour using Geometry -> Objects -> Contour then you go to panel and click inside the contour. It is important to make sure that you select the correct settings. Especially the model should be a shell or equivalent. Hope it helps, Regards, CEE
Thank you for jour job ! I have a question. Could write more about shear stress in part "principal" ? I cant find the formula how robot calculate it. I try to understand it, generally when i calculate shear stress in slab on piece of paper I calculate "just shear stress" to judge if it will be problem with punching or no and here i see txx and tyy and then in principal t. How to understand "txx" and "tyy" and how to connect it with "t"? I will be gratful for help :)
Hi there, thnx a lot for your comment. It is always a joy to me to know that those videos help ppl. The principal stress in shear is calculated via "Mohr's Circle" But not any "Mohr Circle", because: as you noted, t_xx and t_yy are there, and they should have a meaning, right? So here is the meaning of t_xx and t_yy t_xx is the shear stress due to the shear force Q_xx. so t_xx = Q_xx / Area
Hi, how can we apply an eccentricity/offset for a panel? I have a case of an wall having 100cm thickness and on top of it (linked) there is another wall of 50cm thickness. I saw that In SCIA Engineer there is the eccentricity function which that is applicable to panels. Thank you in advance!
Hello there and thnx for your comment. To be honest, I am not 100% sure that there is a "quick command" to do that. What I would do in RSA is to model both and connect them manually with rigid links. But a "full-automated" tool, not that I know to be honest. Regards, CEE
Thank you for you answer one more question, in the eurocode the shear needs to be verified and if necessary minimum shear reinforcement must be installed, is there a module to check and calculate the shear reinforcement in robot for slab design ? @@CivilEngineeringEssentials
Hello there. You cannot simply interface concrete with steel in robot. As for a shell element (plate element), only 1 material is used and its coefficients are calculated. Even in highly advanced research packages such as Ansys and Abaqus, researchers tend to "blend in" the characteristics by calculating a "smeared" material. This is - of course - not the only way. So I do not think a n interface is possible. What is possible - however - is carrying a concrete slab on steel. This is totally possible and can be done. Still, Robot cannot calculate the shear studs used to cause slab/steel composite action. Regards, CEE
Thank you very much for your explanation, and I benefited a lot from you, but excuse me. Can you explain to me the difference between no smoothing and the rest of the other three options, and what option should I choose for a flat slab. I am not good at English, so I did not understand this point in your explanation.
@@CivilEngineeringEssentials thanks sir IAM from Middle East. I noticed when I use no smoothing. It gives greater shear force as well as moment, but the moment increase only in the center of the column, while in the face of the column the moments remain the same, meaning they remain the same as in smoothing within a panel..and in the shear force do I use global smoothing?.
@@user-jk9kd6eb3z Well, short answer, you should use smoothing. Long answer: No smoothing gives the values of the plate itself. Now the calculation of those values is a really looooong story. Here are some insights: - The elements that are used in shells are DKMQ (Discrete Kirchhof Mindlin Quads), those are calculated using numerical integration at gauss points, whereas the stresses/shears/moments are calculated at the edge nodes. Here is an out-take of Daryl L Logan's book (A first course in the finite element) "Smoothing results in a pleasing, continuous plot which may not indicate some serious problems with the model and the results. You should always view the un- smoothed contour plots as well. Highly discontinuous contours between elements in a region of an unsmoothed plot indicate modeling problems and typically require ad- ditional refinement of the element mesh in the suspect region. If the discontinuities in an unsmoothed contour plot are small or are in regions of little consequence, a smoothed contour plot can normally be used with a high degree of confidence in the results. There are, however, exceptions when smoothing leads to erroneous results. For instance, if the thickness or material stiffness changes significantly between adjacent elements, the stresses will normally be different from one element to the next. Smoothing will likely hide the actual results. Also, for shrink- fit problems involving one cylinder being expanded enough by heating to slip over the smaller one, the circumferential stress between the mating cylinders is normally quite different [16]."
I am going to assume you speak arabic, so here are some arabic points to that regard فعليا، كل مربع أو عنصر من الشبكة له قيم مومنت أو شير على زواياه تختلف مع العنصر المجاور له. هذا طبعا يخلق مشكلة في قراءة النتائج، وحتى إنه أحيانا قد يكون غير منطقي، حيث إنه من المتوقع أن يكون المومنت والشير (مثله مثل البيمات) مستمرة وغير متكسرة، وبالتالي البرامج جميعها تقوم بعملية (تنعيم) النتائج، فيحسبون قيمة الشير والمومنت عند النقطة كمتوسط حسابي لجميع العناصر المشتركة في تلك النقطة، طبعا هذه الطريقة هي المستخدمة في الهندسة المدنية في كافة أنحاء العالم، فقط في حالة كنت تود إكمال دراساتك العليا (ماجستير ودكتوراة) ساعتها تضطر لأخذ هذه الأمور في نظر الاعتبار.. وقد أرفقت لك مقتطع من كتاب مشهور في طريقة العناصر المحددة،، I tried to write in arabic, hoping it is your native Language. I do speak German, too. It is actually my mother tongue. Good Luck, CEE
Thanks a lot dear for your help. I apologize for bothering you with so many questions. I'm left with two questions, how does the RSA take the shear force to calculate the punshing shear? The other question. I have the same columns, the same panles , and the same forces, but the program gives a different circumference (u) i use BS 8110 code
Hi there, you can design a 1 way slab as follows: When you draw your slab/floor, There is a (...) near the word (shell). Click on it, Define a new calculation model, call it shell1x (DO NOT OVERWRITE THE SHELL) then in the bottom side, you should select One Way then, use this model to draw your slab, do not forget to put beams around it, then it will calculate 1 way moments and you can design it. I made a quick example under this link: drive.google.com/file/d/1PsYdpfWY-lhD4xwlYDOz_GGZ60UWLGa3/view?usp=sharing Regards, CEE
Hi, which coefficient should I input in orthotropic stiffness reduction to account for 0.25 reduction for slabs covered in ACI code? Pretty unsure about f11, f12, f22, k11, k12, k22, v13, and v23 terms in Robot. In ETABS I usually reduce the f11, f22, f12, m11, m22 and m12 by 0.25. Which of those are equivalent in Robot? Thanks a lot
Thnx a lot for your comment. First, some basics (for others who read the comment): The stiffness reduction coefficient in the ACI code tries to account for the reduction in bending stiffness due to the cracking of the section under ultimate load conditions. This is used in various calculations, such as calculating the "k" coefficient used to determine if a column is long or short. With that being said, what would you modify in a column or beam? Well, you would modify the two bending inertias and maybe the torsional inertia. You may not deem it necessary to reduce the cross sectional area. Now this is in a column, what about a plate? ----- Here starts the answer portion to your question --- in a plate, you have a matrix for membrane force resistance, which can be reduced using the f factors, you also have a 3x3 bending resistance matrix, which is reduced by the k factors, you have a 2x2 (depending on the FEM assumption) matrix for shear resistance, which is reduced by the v factors. you also have weight and mass, but those do not need to be reduced. Based on my understanding of the "reason" behind the reduction, I would suggest reducing the ks and optionally the fs, but not the vs as in the assumption of shear resistance, the section is assumed to have cracked, and the resistance of concrete to shear is partially due to the friction of such cracked section. I hope it made sense. Regards, CEE
@@CivilEngineeringEssentials so f11=f22=f12=k11=k22=k12=0.25 in that case? What about the input bar beside the “symmetry” sign in the plate stiffness matrix in robot? It does not have any terms beside it, should it be left as 1?
I would keep it as 1.0 if you set f11 f22 f12 = 0.25, then you are also acknowledging that there is a reduction of 25% in the axial stiffness of the membrane. It was not specifically mentioned in ACI, but it does not hurt.
Not yet. I only show the deflection shape for the "sense" of the structure. I will provide more details about it later. However, it is VERY important to note the following about RC slabs: The deformation that you get from any FEM software using simple deformations are elastic deformations. However, design codes require you to check against long term deflections. It is calculated using a cracked section inertia and some modified factors. I will give detailed descriptions later. Thanks for your suggestion.
@@CivilEngineeringEssentials yeah thats an interesting topic too, but i was refering to the erratic deformation whereas a slab is being supported by beams and columns, have you ever noticed that in robot structural?
Hi there, The reason why your moments are in kN.m/mm rather than kN.m/m is because: Your structural dimensions are in mm. To fix this: Tools -> Job Preferences -> Units and Formats -> Dimensions -> Structure Dimensions -> Select m Hope it helps. Stay tuned for more contents, also, if possible, suggest this channel to your friends. It helps a lot. Regards, CEE
I think I had made a video about composite slabs on beams. But please note that Robot is a little bit limited when it comes to designing the panels To model those, you can easily apply the "zig-zaggi shape" of the panel by defining it via the "thickness definition window" Please feel free to ask follow up questions if need be, Regards, CEE
how to apply point load on surfaces (panels). ı tried adding a node and applying the load but the program gave me warning message that the load is applied on unconnected nodes
if you add a node to a plate, it should work. One important thing is: Check that Robot meshes the surface. If it does not mesh the surface, then make sure you selected the model "Shell" when you defined your floor/plate. Otherwise, the node will not connect to any Finite Element, and you get a warning about "Isolated nodes". Please try the suggestion. If it still does not work, please let me know. Regards, CEE
@@CivilEngineeringEssentials I don't want to analyze the surface. I am modelling a trapezoidal steel sheet roofing and applying a resultant force with 0.25 eccentricity.
If you do not want to analyze the surface, then a point load wont work because it would be floating in the air. In robot, you would need a plate to carry the load. Otherwise it will be counted as isolated node.
Hellow . Thanks ypu for this vidéo. I would like to explain a little bit Mises Stress. When should we use this type of stresses wile analysing strctucture.
Hello there. English: In my opinion, it is only used for steel plate elements, because the stresses are from 2 dimensions in addition to shear, so it would not be enough to consider moments and stresses form one direction only For beams, columns and connections, my humble opinion is to use the normal bending moment and axial force approaches as written in the code. العربية، من وجهة نظري، أعتقد إنه إجهادات فون ميزس تستخدم في تصميم البلاطات المعدنية فقط، حيث يوجد الإجهادات من كلا محوري السين والصاد والقص، وعليه لا أعتقد من وجهة نظري المتواضعة إنه التصميم من جهة واحدة مناسب، اما العناصر الخطية كالأحزمة والأعمدة، فمعادلات الأكواد مناسبة، German Von meiner Seite glaube ich, dass die von Mises Spannung nur im Fall einer Stahlplatte benutzt werden, da es ja Spannung aus der x und y richtung gibt. Fuer Balken und Saeulen, wuerde ich die normal Gleichung der EC oder DIN verwenden. Regards, CEE
Thank you for your effort in creating these videos. I have a question that I would appreciate if you could address. In the video, specifically from 29:10 to 30:00, you mentioned that the structure is weak in the y-axis, even after changing the direction of the slab. I found this statement a bit confusing, and I would be grateful if you could kindly clarify this misunderstanding for me. Thank you in advance for your time and explanation.
Hi there, thnx for the comment. I will try to give you a second by second break-down of that. Coz yep, it might be confusing.
I quick note: The local coordinate system of the slab and the global coordinate system of the model are the same. So X is always X and Y is always Y. That is a good thing to start.
so:
in 28:55 I open the orthotropic definition and apply it on the slab. Note, the ribs direction is in the X direction.
Since the ribs are in the x direction, this means that the inertia for a strip parallel to the x-axis is stronger than a strip parallel to the y axis. So the x-axis is strong, and the y axis is weak.
This means that the lines parallel to x remain relatively unbent, and the lines parallel to y become bent, hence the deflection shape at 29:13
Then, at 29:34 I flipped the rib direction to y, so everything is now flipped, hence the deflection shape at 29:50
I can actually suggest a really cool experiment for you to do to visualize it.
Imagine you take a piece of paper (A square one) and bend one direction in a zig-zag pattern.
/\/\/\/\/\/\/\/\/\
and now support it on four fingers on four corners (you might need a friend for this).
Look how the deflection shape behaves. It will be eye opening.
I suggest of course to have a rather larger square, so that it would deflect under its own weight. Otherwise, you would have to put a small weight on it (without totally destroying it)
Hope it was helpful. In case you have any further questions, please feel free to ask away.
I will pin this comment because it might be helpful for future viewers.
Thank you very much. It helps if you share this channel with your friends.
Regards,
CEE
Ok thank you I found this reply very helpful everything is clear when you flipped the ribs to the direction y then the slab is stronger in the y direction and weak in the x.
I don’t usually comment on TH-cam Vids, but this masterpiece really helped me alot. Thankyou so much and i really wish you the best luck in your channel. About suggestions maybe tutorials on basics for using Robot Structural Analysis
First of all, a huge thank you for your comment. It encourages me to give it my all.
Sure, I would gladly cover the basics in more detail in robot. I do know that my videos are currently of intermediate level with some mentions of basics and some mentions of advanced stuff
I have some videos talking about some basics, still, I am open for suggestions.
Do you have any certain things you want me to cover?
Regards,
CEE
Thank you for making this video series, it’s incredibly informative! I’ve used robot for years but I’m picking up so many useful tips from you. Autodesk should be paying you for this
Hi there,
Thnx a lot for your comment. I am happy that those videos helped you.
Stay tuned for more content, and if you have any questions, feel free to ask.
Regards,
CEE
Fantastic explanation, thank you
Most welcome.
Please suggest this channel to your colleagues. It helps a lot 🌹👍
alhamdulillah
Thank You
Civil Engineering Essentials
I am happy you liked the video, it encourages me to keep it up.
Really a great and concise video. I request you to explain the Wood & Armer moments of slabs.
Thanks for your comment. I have added the topic to my TODO list. Once I finish the basics I will start with the advanced topics.
@@CivilEngineeringEssentials I too look forward to this. Thanks in advance.
You videos and detailed explanation helped me progress by a 1000% about using this much complicated software. Thank you! More please !
Hi there,
I am happy it helps you ^_^ Stay tuned for more videos. Also consider suggesting this channel to your friends.
Regards,
CEE
@@CivilEngineeringEssentials you bet I will…keep on going !
Thank you! Your explanation is very helpful. Can you make another video that goes more detail on Principle and Complex tabs, sir.
Hello, I am really happy you liked it.
Yes, I will add the principles and complex results on my TODO list. I am planning something for that and for the wood and armer moments very soon.
Stay tuned, and help the channel grow by suggesting it to your friends.
Regards,
CEE
Great video yet very educative.
You really explained the alignment of the local slab coordinate with the global coordinate very well. It’s rarely explained in all videos on TH-cam
I’d be keep my specific requests for later when we are done with this course.
Thank you and God bless you immensely.
thnx a lot for your comment. It encourages me to continue doing my best. FYI: I am an Assistant Professor in Structural Analysis and that is the reason why there is a certain educative element in my explanations.
As for future questions, just wait a little bit until the "elementary" tutorial is finished.
It will be finished within 20 days when I explain a full structure from A to Z (importing, modeling, designing, exporting calculations and drawings)
After that, I would start with some advanced topics and that is basically the perfect timing for any questions or requests.
@@CivilEngineeringEssentials that’s explains why your tutorials are educative and unique. The Structural Engineering profession and Robot Structural Analysis software needs more people like you to make the profession and the softwares appealing for practical use.
I always look forward to seeing your post.
Hello. Great videos so far. I hope it continues and also for complex topics. a video about foundation slab (lets say mat or raft) with thicker areas where equipments are placed will be appreciated. (it is typically like a slab with drops but upside down). Also compatible nodes video will be good.
Hello there. Happy you liked it.
Sure, gonna add it to my ToDo list.
First, I have to do a simple video about rafts,
then make a video about rafts with increased thickness in regions of higher loads such as columns or - as you have mentioned - machinery and equipment.
Stay tuned.
@@CivilEngineeringEssentials awesome. looking forward to.
Quick Update on the matter. I have filmed the tutorial on compatible nodes and am video editting it at the moment. you can expect it to be available Saturday (fingers crossed)
Regards,
CEE
Hello can you make a video explaining each mode type of the slabs (the ones other than shells)
Great suggestion. I think I made a video explaining the difference between wall and floor, but there is more as you stated. There are other models that may need to be explained, so I will keep this on my ToDo list.
Stay tuned for more content,
CEE
Thanks for the such a wonderful Video. It has very useful information
I need your help in understanding the Principal stresses and complex stresses. Actually, I am working on steel bridge design which has two longitudinal box gliders and transverse girder above which I have a deck slab based on required of Client I have asked to model part of bridge with plate and shells and need to check location of stress concentration and stress variation to check fatigue failure.
Can you make a video that explains what principal and complex stresses in detail and explain how we corelate for design of steel structures i.e plates.
Sure that is a good idea. I might be still - however - working on the bridge series on Midas, so it might take a little while
Still, thnx a lot for your comment. I am really happy it helped.
Regards,
CEE
@@CivilEngineeringEssentials thanks a lot for such prompt reply 😊. I am bit hurry to show some progress on the work. It would be great help if you could share a document/link on the complex stress theory in autodesk robot manual. Also, is there any other way to connect with you to discuss on this further ?
@@chaiturishan4uWill prepare a video for you right now. Stay tuned ^_^
Also, yes
civ.eng.essentials@gmail.com
Hi CEE, its a great video thank you, can i ask some question. Can you explain between Plate and Shell formula? Recently I read in online, RSA use thick plate formula but in SAP2000 can choose many option of the formula. So can we apply the shell thin formula to RSA? Thank you
Plate and shell are identical in Robot.
It uses a Discrete Modified Kirchoff Triangle and Discrete Modified Kirchhoff Quad.
RSA's model here works well for both thick and thin.
There are other theories such as the mindlin theory, which only works for one type of plate.
Here are the references for the DMKT and DMKQ
www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/ROBOT-what-types-of-finite-elements-are-used-in-the-program.html
Thank you so much broo
yo, anytime ^_^ Stay tuned for more content.
Hellow . Thanks ypu for this vidéo. I would like to explain a little bit Mises Stress. When should we use this type of stresses wile analysing strctucture.
Hello there.
English:
In my opinion, it is only used for steel plate elements, because the stresses are from 2 dimensions in addition to shear, so it would not be enough to consider moments and stresses form one direction only
For beams, columns and connections, my humble opinion is to use the normal bending moment and axial force approaches as written in the code.
العربية،
من وجهة نظري، أعتقد إنه إجهادات فون ميزس تستخدم في تصميم البلاطات المعدنية فقط، حيث يوجد الإجهادات من كلا محوري السين والصاد والقص، وعليه لا أعتقد من وجهة نظري المتواضعة إنه التصميم من جهة واحدة مناسب،
اما العناصر الخطية كالأحزمة والأعمدة، فمعادلات الأكواد مناسبة،
German
Von meiner Seite glaube ich, dass die von Mises Spannung nur im Fall einer Stahlplatte benutzt werden, da es ja Spannung aus der x und y richtung gibt.
Fuer Balken und Saeulen, wuerde ich die normal Gleichung der EC oder DIN verwenden.
Regards,
CEE
I found your video very helpful. I learn a lot from it.
I want to know if there is a way to model the partition walls not as load but wall. I want this beacause i'm using revit and i'm modeling my partition walls. If i can transfer the wall directly without trying to model load this will be very helpful.
you are most welcome.
Partition walls as elements (not loads) is not directly possible in autodesk robot. Because it assumes those to be "shear walls"
However, I can suggest a work-around (I have not tested this)
In case you know the stiffness of the wall in the vertical direction (Force vs vertical displacement) then you could use it to modify the wall such that:
AE/L of the shear wall is very close to AE/L of the brick wall.
This does only work for purely axially loaded walls. Also note, I have not yet tested it, so I am pretty sure that there are some problems when it comes to shear and bending behavior.
Sorry for the long answer.. The shorter TLDR version is: unfortunately, no.
Regards
CEE
Perfect
thnx a lot. Stay tune for more content.
What the different between definition the slab by panel or by floor in Robot and what is the more suitable to be use in soild slabs
Technically, there is no difference. And here is why:
if you use the "floor command" to draw a slab, then it does two steps for you
1) It does create the contour
2) It does fill the contour with your slab
if you use the panel command, then you have to click a contour that you already drew. So it is basically doing step 2 for you.
if you want to use a panel command, you have to first draw the contour using Geometry -> Objects -> Contour
then you go to panel and click inside the contour. It is important to make sure that you select the correct settings. Especially the model should be a shell or equivalent.
Hope it helps,
Regards,
CEE
Thank you for jour job ! I have a question. Could write more about shear stress in part "principal" ? I cant find the formula how robot calculate it. I try to understand it, generally when i calculate shear stress in slab on piece of paper I calculate "just shear stress" to judge if it will be problem with punching or no and here i see txx and tyy and then in principal t. How to understand "txx" and "tyy" and how to connect it with "t"? I will be gratful for help :)
Hi there, thnx a lot for your comment. It is always a joy to me to know that those videos help ppl.
The principal stress in shear is calculated via "Mohr's Circle"
But not any "Mohr Circle", because:
as you noted, t_xx and t_yy are there, and they should have a meaning, right? So here is the meaning of t_xx and t_yy
t_xx is the shear stress due to the shear force Q_xx.
so t_xx = Q_xx / Area
I didn't imagine such a rich content
Thnx a lot for your comment ^_^
If possible, please share this channel with your friends. It helps a lot.
Regards,
CEE
@@CivilEngineeringEssentials already did dear engineer
Hi, how can we apply an eccentricity/offset for a panel? I have a case of an wall having 100cm thickness and on top of it (linked) there is another wall of 50cm thickness. I saw that In SCIA Engineer there is the eccentricity function which that is applicable to panels. Thank you in advance!
Hello there and thnx for your comment.
To be honest, I am not 100% sure that there is a "quick command" to do that. What I would do in RSA is to model both and connect them manually with rigid links. But a "full-automated" tool, not that I know to be honest.
Regards,
CEE
Hey, thank you for your video, the panel cut result gives kNm /m what does this mean why is it per m and not simply kNm ?
Hi there.
It means
Kn.m /m
Moment kn.m for a strip of 1m width
So
To read it more clearly you should say
Kn.m per 1m strip
Thank you@@CivilEngineeringEssentials
Thank you for you answer one more question, in the eurocode the shear needs to be verified and if necessary minimum shear reinforcement must be installed, is there a module to check and calculate the shear reinforcement in robot for slab design ?
@@CivilEngineeringEssentials
Not sure. It checks the shear and warns about it. But it does not provide extra shear reinforcement.
How to make concrete steel interface while doing non typical bracket analysis?
Hello there.
You cannot simply interface concrete with steel in robot. As for a shell element (plate element), only 1 material is used and its coefficients are calculated.
Even in highly advanced research packages such as Ansys and Abaqus, researchers tend to "blend in" the characteristics by calculating a "smeared" material. This is - of course - not the only way.
So I do not think a n interface is possible. What is possible - however - is carrying a concrete slab on steel. This is totally possible and can be done.
Still, Robot cannot calculate the shear studs used to cause slab/steel composite action.
Regards,
CEE
Thank you very much for your explanation, and I benefited a lot from you, but excuse me. Can you explain to me the difference between no smoothing and the rest of the other three options, and what option should I choose for a flat slab. I am not good at English, so I did not understand this point in your explanation.
Most welcome
Please use global smoothing for slabs.
Stay tuned for more content
CEE
@@CivilEngineeringEssentials thanks sir
IAM from Middle East.
I noticed when I use no smoothing. It gives greater shear force as well as moment, but the moment increase only in the center of the column, while in the face of the column the moments remain the same, meaning they remain the same as in smoothing within a panel..and in the shear force do I use global smoothing?.
@@user-jk9kd6eb3z
Well, short answer, you should use smoothing.
Long answer: No smoothing gives the values of the plate itself. Now the calculation of those values is a really looooong story. Here are some insights:
- The elements that are used in shells are DKMQ (Discrete Kirchhof Mindlin Quads), those are calculated using numerical integration at gauss points, whereas the stresses/shears/moments are calculated at the edge nodes.
Here is an out-take of Daryl L Logan's book (A first course in the finite element)
"Smoothing results in a pleasing, continuous plot which may not indicate some
serious problems with the model and the results. You should always view the un-
smoothed contour plots as well. Highly discontinuous contours between elements in
a region of an unsmoothed plot indicate modeling problems and typically require ad-
ditional refinement of the element mesh in the suspect region.
If the discontinuities in an unsmoothed contour plot are small or are in regions
of little consequence, a smoothed contour plot can normally be used with a high
degree of confidence in the results. There are, however, exceptions when smoothing
leads to erroneous results. For instance, if the thickness or material stiffness changes
significantly between adjacent elements, the stresses will normally be different from
one element to the next. Smoothing will likely hide the actual results. Also, for shrink-
fit problems involving one cylinder being expanded enough by heating to slip over the
smaller one, the circumferential stress between the mating cylinders is normally quite
different [16]."
I am going to assume you speak arabic, so here are some arabic points to that regard
فعليا، كل مربع أو عنصر من الشبكة له قيم مومنت أو شير على زواياه تختلف مع العنصر المجاور له.
هذا طبعا يخلق مشكلة في قراءة النتائج، وحتى إنه أحيانا قد يكون غير منطقي، حيث إنه من المتوقع أن يكون المومنت والشير (مثله مثل البيمات) مستمرة وغير متكسرة،
وبالتالي البرامج جميعها تقوم بعملية (تنعيم) النتائج، فيحسبون قيمة الشير والمومنت عند النقطة كمتوسط حسابي لجميع العناصر المشتركة في تلك النقطة،
طبعا هذه الطريقة هي المستخدمة في الهندسة المدنية في كافة أنحاء العالم، فقط في حالة كنت تود إكمال دراساتك العليا (ماجستير ودكتوراة) ساعتها تضطر لأخذ هذه الأمور في نظر الاعتبار..
وقد أرفقت لك مقتطع من كتاب مشهور في طريقة العناصر المحددة،،
I tried to write in arabic, hoping it is your native Language.
I do speak German, too. It is actually my mother tongue.
Good Luck,
CEE
Thanks a lot dear for your help. I apologize for bothering you with so many questions.
I'm left with two questions, how does the RSA take the shear force to calculate the punshing shear?
The other question. I have the same columns, the same panles , and the same forces, but the program gives a different circumference (u)
i use BS 8110 code
How can I design solid slab in one way direction?
Hi there,
you can design a 1 way slab as follows:
When you draw your slab/floor,
There is a (...) near the word (shell). Click on it,
Define a new calculation model, call it shell1x (DO NOT OVERWRITE THE SHELL)
then in the bottom side, you should select One Way
then, use this model to draw your slab, do not forget to put beams around it, then it will calculate 1 way moments and you can design it.
I made a quick example under this link:
drive.google.com/file/d/1PsYdpfWY-lhD4xwlYDOz_GGZ60UWLGa3/view?usp=sharing
Regards,
CEE
Hi, which coefficient should I input in orthotropic stiffness reduction to account for 0.25 reduction for slabs covered in ACI code? Pretty unsure about f11, f12, f22, k11, k12, k22, v13, and v23 terms in Robot. In ETABS I usually reduce the f11, f22, f12, m11, m22 and m12 by 0.25. Which of those are equivalent in Robot? Thanks a lot
Thnx a lot for your comment.
First, some basics (for others who read the comment):
The stiffness reduction coefficient in the ACI code tries to account for the reduction in bending stiffness due to the cracking of the section under ultimate load conditions. This is used in various calculations, such as calculating the "k" coefficient used to determine if a column is long or short.
With that being said, what would you modify in a column or beam?
Well, you would modify the two bending inertias and maybe the torsional inertia. You may not deem it necessary to reduce the cross sectional area.
Now this is in a column, what about a plate?
----- Here starts the answer portion to your question ---
in a plate, you have a matrix for membrane force resistance, which can be reduced using the f factors,
you also have a 3x3 bending resistance matrix, which is reduced by the k factors,
you have a 2x2 (depending on the FEM assumption) matrix for shear resistance, which is reduced by the v factors.
you also have weight and mass, but those do not need to be reduced.
Based on my understanding of the "reason" behind the reduction, I would suggest reducing the ks and optionally the fs, but not the vs as in the assumption of shear resistance, the section is assumed to have cracked, and the resistance of concrete to shear is partially due to the friction of such cracked section.
I hope it made sense.
Regards,
CEE
@@CivilEngineeringEssentials so f11=f22=f12=k11=k22=k12=0.25 in that case? What about the input bar beside the “symmetry” sign in the plate stiffness matrix in robot? It does not have any terms beside it, should it be left as 1?
I would keep it as 1.0
if you set f11 f22 f12 = 0.25,
then you are also acknowledging that there is a reduction of 25% in the axial stiffness of the membrane. It was not specifically mentioned in ACI, but it does not hurt.
@@CivilEngineeringEssentials Thanks for the reply, I guess I will also put 0.25 for the fs. Much appreciated.
🤩🧐🤯
🌹
Have you tried to analyze the deformation of a slab supported by beams?
Not yet. I only show the deflection shape for the "sense" of the structure.
I will provide more details about it later.
However, it is VERY important to note the following about RC slabs:
The deformation that you get from any FEM software using simple deformations are elastic deformations. However, design codes require you to check against long term deflections.
It is calculated using a cracked section inertia and some modified factors.
I will give detailed descriptions later.
Thanks for your suggestion.
@@CivilEngineeringEssentials yeah thats an interesting topic too, but i was refering to the erratic deformation whereas a slab is being supported by beams and columns, have you ever noticed that in robot structural?
I did. It is related to the meshing of robot. I think I should make a technical video about that soon.
@@CivilEngineeringEssentials that would be awesome, nobody has done it yet, thank you very much!
Best youtube channel to learn this software, ....um currently having my moments in kNm/mm2....how can i change this to kNm/m?
Hi there,
The reason why your moments are in kN.m/mm rather than kN.m/m is because: Your structural dimensions are in mm.
To fix this:
Tools -> Job Preferences -> Units and Formats -> Dimensions -> Structure Dimensions -> Select m
Hope it helps. Stay tuned for more contents, also, if possible, suggest this channel to your friends. It helps a lot.
Regards,
CEE
@@CivilEngineeringEssentials Thanks very much.... I will invite more friends from our firm.
How do you model composite insulated panels?
I think I had made a video about composite slabs on beams. But please note that Robot is a little bit limited when it comes to designing the panels
To model those, you can easily apply the "zig-zaggi shape" of the panel by defining it via the "thickness definition window"
Please feel free to ask follow up questions if need be,
Regards,
CEE
how to apply point load on surfaces (panels). ı tried adding a node and applying the load but the program gave me warning message that the load is applied on unconnected nodes
if you add a node to a plate, it should work.
One important thing is:
Check that Robot meshes the surface.
If it does not mesh the surface, then make sure you selected the model "Shell" when you defined your floor/plate.
Otherwise, the node will not connect to any Finite Element, and you get a warning about "Isolated nodes".
Please try the suggestion. If it still does not work, please let me know.
Regards,
CEE
@@CivilEngineeringEssentials I don't want to analyze the surface. I am modelling a trapezoidal steel sheet roofing and applying a resultant force with 0.25 eccentricity.
thank you very much
@@CivilEngineeringEssentials
If you do not want to analyze the surface, then a point load wont work because it would be floating in the air.
In robot, you would need a plate to carry the load. Otherwise it will be counted as isolated node.
Hi , as always very knowledgeable tutorial, I like your content. Have you got an email? I have one question. Thank you again for your hard work
Thnx a lot. I am happy my videos are beneficial for you.
Yep, my email is
Civ.eng.essentials@gmail.com
Thank you.I have sent email
didn't reach me yet. might be delayed or smthn.
civ.eng.essentials@gmail.com
I have resended it, let me know if you received it.Thank you
Hellow . Thanks ypu for this vidéo. I would like to explain a little bit Mises Stress. When should we use this type of stresses wile analysing strctucture.
Hello there.
English:
In my opinion, it is only used for steel plate elements, because the stresses are from 2 dimensions in addition to shear, so it would not be enough to consider moments and stresses form one direction only
For beams, columns and connections, my humble opinion is to use the normal bending moment and axial force approaches as written in the code.
العربية،
من وجهة نظري، أعتقد إنه إجهادات فون ميزس تستخدم في تصميم البلاطات المعدنية فقط، حيث يوجد الإجهادات من كلا محوري السين والصاد والقص، وعليه لا أعتقد من وجهة نظري المتواضعة إنه التصميم من جهة واحدة مناسب،
اما العناصر الخطية كالأحزمة والأعمدة، فمعادلات الأكواد مناسبة،
German
Von meiner Seite glaube ich, dass die von Mises Spannung nur im Fall einer Stahlplatte benutzt werden, da es ja Spannung aus der x und y richtung gibt.
Fuer Balken und Saeulen, wuerde ich die normal Gleichung der EC oder DIN verwenden.
Regards,
CEE