Nonlinear P-Delta Analysis Principles in Autodesk Robot
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- เผยแพร่เมื่อ 24 ก.ค. 2024
- In this video, we'll explore the principles of nonlinear P-Delta analysis in structural design using Autodesk Robot. We'll cover the basics of P-Delta analysis, including what it is, how it affects the behavior of a structure, and why it's important to consider in the design process.
We'll cover the basics of creating a structural model in Autodesk Robot and how to define the properties of the structure, including its stiffness and load distribution.
Next, we'll dive into the specifics of nonlinear P-Delta analysis, including how it accounts for the effects of gravity and lateral loads on the structure. We'll provide step-by-step instructions and helpful tips to guide you through the analysis process.
Finally, we'll discuss the importance of considering nonlinear P-Delta analysis in the design process and how it can affect the safety and performance of a structure.
Whether you're a student, a practicing engineer, or simply interested in the behavior of structures, this video will provide you with valuable insights into the principles of nonlinear P-Delta analysis in structural design using Autodesk Robot.
Current Video Ideas for the Future:
- More details about modal participation / report?
- Masses and stiffnesses to control modes
- LL Reduction in ACI/ASCE (vertical and horizontal)
- Eurocode WL.
- A possible way to model columns with pressure areas
- Deeper dive into slab reinforcement.
- Raft with larger thickness and positions
- Robot - seemingly - erratic deformation when supported by beams and columns
- A way to manually “clean-up” simple mesh like the above
- EQ on Retaining Walls
- Wood and Armer Moments in Slabs and their meaning
- Complex and Principle results
- Reaponse spectrum analysis
- Simple TBM tunnel lining analysis in robot
Timestamps:
0:00 Introduction
0:30 Some Theoretical Background
8:00 Modeling a simple column
10:08 Setting up PD Analysis
11:03 Analysis (I) - No Change?
12:25 Applying a Horizontal Force
12:53 Analysis (II) - Discussion
16:18 Analysis (III) - 2D Frame
19:09 Outro
Hello CEE, Thank you for yet another great video. In my opinion, the theoretical aspects in this video were the right amount, they were NOT too much, in fact, they were summarized and simplified for the viewers and for time benefits. Without the background, it is like shooting in the dark.
Today access to powerful and “relatively easy-to-use” software is fairly common place. Engineers are supposedly less likely to make calculations errors or mistakes (there is of course the reality of unintended bugs within the software itself which if the engineer is unable to verify if the software results make sense or if the software results are of the correct order of magnitude or not, the engineer’s ignorance or inability in this regard can be catastrophic. The software developers are well shielded from liabilities associated with such errors, omissions, or mistakes, etc. through well-crafted legal disclaimers embedded on their software.
The above should also make it very clear why it is that much more important for the engineer to know and to appreciate the theoretical background before jumping into the software. Theory and theoretical background should always take precedence over software.
Most versions of earlier codes formulate an “envelope” within which most types of structures and elements that those code covers can be “safety designed”. The thresholds and limits of those envelopes are guided (amongst others) by research. Some of that research was conducted through the use of computer models and software. The envelope approach seeks to keep the calculations within bounds, to simply the calculations when done by hand, and to minimise or to eliminate errors.
In my opinion, If the engineer has readily available and reliable means and methods to conduct analysis which explicitly consider structural effects that are otherwise represented by envelopes and other equivalent factors on the codes, then the engineer should always conduct such additional analysis for their particular structure(s) so as to be able to confidently make engineering judgements and perhaps even more economical designs for their particular structure based on reasoned and logical facts. In doing this the engineer does not disregard the code, but they use the code as guidance, better still, they can also contribute to the revision and to the improvement of the code in this way.
I totally agree with the dangerous issue of access to easy softwares. On one hand, those tools are really great assets we engineers use to increase our efficiency and speed up our daily workflow. On the other hand, it seems that now-adays we started treating those as "black boxes".
As you noticed, the objective of CEE is not only to provide you with a "step by step" procedure to perform a certain task, but to actually let the viewer think about the process itself, and be able to predict some results to check if those "make sense". Thus, I agree with your point that our judgement is extremely important to detect any modeling errors that might occur.
A huge thank you for your comment. It really encourages me to do more.
As per the discussion with my other dear subscriber Nii Serpai, I am investigating how to model material non-linearity in Robot. Spolier alert: it is not easily possible... 😞
Regards,
CEE
Yes, that would be great!! Thank you very much. No worries, it’s not urgent.
I think this video is very benefical and clear for understanding nonlinearity
Thank you very much for your comment ^_^ stay tuned for more content.
Great tutorial CEE
I love the theoretical background to this topic. It’s greatly refreshing.
I usually consider Pdelta effect on a structure no matter how insignificant it may seem. Usually for Structures where lateral stability/Analysis is a must ( 4 storey and above per my local requirements).
I have come across references especially ( Modelling for structural analysis,by Graham Powell ), where the stability coefficient of less than 10% requires Pdelta analysis to be ignored in the analysis procedure.
I stand to be corrected.
I will probably have to read for more information as this topic is a broad one.
Are there any checks in RSA, to confirm stability coefficient of building structures?
You made mention of Plastic hinges for material nonlinearity modeling , is it impossible in Robot software to define, material nonlinear at the material stress-strain level?
These are really advance topics for your dear viewers and am sure we will enjoy it
Thank you
Regards
Hi there,
I am happy you liked the video. I will have to check the ACI code as there was something about the lateral stability of the structure. I think it was 5% or 10% in that case but my memory seems not to serve me with that regard.
As for direct stability checks, I do not think so. There is some advanced analysis types where it might be included, such as "pushover analysis", but I will have to personally dig deeper there to prepare something that can be presented in video form
as for material non-linearity, it totally can be modeled. But here you have to use something called "plastic hinges" to simulate this. It is a cool thing actually, you might just have given me the idea for the next video.
simulating this phenomenon.
Stay tuned for more videos,
regards,
CEE
@@CivilEngineeringEssentials it’s great to know you’d prepare a tutorial on material nonlinearity modelling using plastic hinges.
Thank you and God bless you immensely.
Great video….very informative 👍…an example of P delta effects on concrete frame comprising of slender walls would be good…..
Great suggestions. I will be adding having structures modeled in the future, so it might be interesting to stay tuned ^_^
Well done thanks
most welcome. Glad you enjoyed it.
Great video.
Do you know if it's posible to model the P-delta effect in which delta is the displacement of the nodes WITHIN the column, not the top node? i.e. a column with both ends pinned and an axial load, basically a buckling analyisis.
Thanks!
You could (hypothetically) model you column in two pieces. Still, it is not really a buckling analysis in a sense, but would only be a rough approximation to such a thing.
kindly do pile analysis using soil springs. a special request
Definitely an interesting idea. I will have it on my todo list after I finish my Warehouse series.
@@CivilEngineeringEssentials will be appreciated 👍
I understand that you want to be code-neutral, but, could you consider showing how Robot should be used for properly doing a eurocode-compliant analysis in EC3, EC2, and EC5? I feel a bit lost about how to consider imperfections, notional forces, alpha crit >10, and effective buckling lengths in a code-compliant way. And would it be possible to do some analysis similar to the DAM that Robot implements for AISC, but for Eurocodes instead? Given your skills, I sincerely believe you could do a great video on this topic, and incredibly helpful because nobody explains this, not even Autodesk.
Hello there,
first, thnx a lot for your comment.
I will keep it in mind and deal with it once my "structures" series reaches a certain amount. Indeed, I try to be "as far as I can" code neutral, but since it seems that some ideas behind EC are cryptic, I will take a look and prepare something, but of course after I finish the plan for the "Structures" series.
Regards,
CEE
الشكر الجزيل لك بروفسور..على ما اتوقع ف ان حالة Large displacement لا تطلب كثيرا في المنشآت
و يكفي القيام بتحليل p-delta
سؤالي برنامج روبوت لن يقوم بهذا التحليل الا اذا كانت القوتين الجانبية و الشاقولية في نفس حالة التحليل the same case
اي هل سوف يقوم بهذا اذا كان لدي قوى زلزالية مثلا في حالة تحميل مختلفة عن القوى الشاقولية او قوى الجاذبية؟؟
هل هنالك طريقة لعمل ذلك؟؟
Large displacements
نادرة الحدوث، لأن منشآتنا عادة صلدة وهدفنا أساسا تقليل هذه الهبوطات والإزاحات،
الفكرة العلمية وراءها إنه حساباتنا
for stress and strain
نحن نفترض فرضية الإزاحة الصغيرة،
أتفق مع،
p-delta
كافي،
بخصوص وجود حالتين منفصلتين، ورغبتك بحسابهم مع بعض،
نعم، هناك طريقة "فخيمة" لعملها
افتح
combination
وخلي المعاملات الخاصة بكل حالة = 1
لأن حسب ما فهمت، حابب تشوف التأثير مع بعض من الناحية الحسابية، وليس من الناحية التصميمية، لأن كما تعلم، لو حبيت تصمم، بيصير عندك معاملات لكل حالة من حالات التحميل
أتمنى أكون أفدتك،
بالتوفيق.
Hello CEE, my comments are disappearing after posting them. In this and on the previous video.
For some reason, all the comments you write are "held for review"
but those new comments have not been shown anywhere. Not even "held for review". I am so sorry about this, sadly, it is not in my hands.
@@CivilEngineeringEssentials Thanks for the reply, I'll investigate from my end.