Science topic

Structural Analysis - Science topic

Structural analysis is the determination of the effects of loads on physical structures and their components. Structures subject to this type of analysis include all that must withstand loads, such as buildings, bridges, vehicles, machinery, furniture, attire, soil strata, prostheses and biological tissue.
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In his name is the judge
Hi
for using matlab facilities especially matlab controller like fuzzy have to sending and receiving data between matlab and opensees, in fact i want send two data as fuzzy controller form opensees to matlab after each time history step in opensees and then matlab send back one output to opensees.
to achieve this i have to connect matlab and opensees with openfresco it means i do hybrid simulation.
first is this possible to do this?
second is there any one do work like this, do hybrid simulation generally or specifically do hybrid simulation between matlab and opensees. if yes i am very thankful to share work with me or for some aim.
have to say i prefer not to use openseespy and i almost read all example and guide in openfresco site and even on each site but i cant do this right.
Any help is greatly appreciated.
Take refuge in the right.
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Dear Eftekhar,
I have a suggestion, you can simply write OpenSees outputs to a text file using TCL commands, and then your MATLAB code can read the inputs written in that text file, doing it's processes and finally send back output by writing it in another text file,
Now you have to write a while loop in your TCL script that check Matlab output file for every n second (Based on the time that MATLAB prepares the results), if the MATLAB output for that specific time step exists, OpenSees can proceed to the next time step, and this process can continue until the end of analysis.
I hope this can work for you.
Regards
Abolfazl Najafi
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The psychological, inner mental activity, is a process. Usually it is hard approaching dynamic phenomenons by means of structural analysis, where intuitively things are seen in some static way. On the other hand, psychological activity is a very complex issue, and complexity can be frequently managed by systemic structural methods.
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Ken Wilber's Integral Psychological Maps are the most comprehensive
See Wilber, K. (2000). Integral Psychology. Boston, MA: Shambhala. PMCid:PMC1885698.
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I am currently testing a basic design for my research topic with a hollow cylinder.
The displacement was set as 0 on one end as a fix support and -5 in Y direction on another end.
The reaction solution i had is different from in Ansys Mechanical and i believe that the result generated from APDL was wrong.
The last screenshot is the result from APDL using .cbd file from Workbench mechanical
The result is still incorrect comparing to the result from Workbench Mechanical.
What is my mistakes here or any suggestion ?
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Please select all the nodes.
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To whom it may concern...
Case shown in pictures below need to stop in front of it...
Starting with the way of supporting slab before casting.. the question appear...
Based on your engineering opinion, and supporting method that you might used... is what shown in pictures attached ,.. enough.. ?
Then... whom responsibility is that... if slab fail during casting process, as there will be additional loading of pumped concrete and labors also ...? where that will be the most important question....
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Dear Sir,
supervision consultant needs to verify the scaffolding design which considers all loads of concrete and labors, usually the scaffolding specialist to provide full calculations, this specialist works under the contractor umbrella, both of contractor and supervision consultant did not perform well
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To whom it may concern...
Case shown in pictures below need to stop in front of it...
What the mean of overload... What will be the meaning of calculated loading before design... and.... What really mean the structural design based on submitted data..
All, in general,.. knows that.. design start with converting functional use of the building to loading on structural element... then start design element by element ...
So, what might be the supposed loading to one story house... based on all adopted code... ? this is the first question..
Then what you think, .. or what the supervisor engineer might think the value of such loading on that slab shown in pictures attached... ? this is the second question...
Then at last... whom responsibility is that... if failure occur...? where that will be the most important question....
Limited education with low experiences causes such cases, ... or... we need to ask the supervised engineer if he care...
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Invariably the loading on one storey building roof with access is only `1.5 to 2 kN/m2 . and this is uni-formally distributed load. But if you pile up load in a small area more than the failure load of slab with concentrated load then the failure is imminent. this failure load can be calculated using yield line theory or by Hillerborg Strip method.
If you have this kind of loading then keep your props intact before you finish roof top work
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In his name is the judge
Hi
I want design cotroller in to control active force of damper.
On this purpose, i analyzed structure with damper, wich is tlcdg, and get data whic use for generate controller. data are accleration and velocity of damper as input and dampers force as output ( i mean force wich made by own damper under earthquake excitation, not active force).
here is anfis properties :
number of inputs are 2
number of outputs is 1
generate fis method is grid partition
number of membership function are 4 for each input
input membership function type is guass2mf
output membership function type is linear
opt method is "hybrid".
(have to say i tried different epochs membership function , .....)
Unfortunately anfis toolbox in matlab refuse to train and build Suitable fuzzy controller wich means error is too much in training, so this answer is not acceptable.
i have some idea for make it true but i'm not sure.
here is my ideas :
* first i think train controller with more or less data ( training data are about 2000 wich is under 100s earthquake excitation but when i reduce earthquake excitation to 10 or 15 seconds the error is acceptable however i think this solution is not good.)
* second maybe i must try one damper for training.
* the last idea is to assign force on the damper location and get acceleration and velacity for generate trianing data.
here is my data and shot frome my try.
Any help is greatly appreciated.
Take refuge in the right.
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Get your data into excel and see if there will be marked inputs that show wrong annotations, which will not allow computing interface to run. Just a comma in place of a dot can through you off the rail. If this pulls through, then follow with Dr Emmanuel Arinze"s suggestion. I'm sure by the time you walk through these steps, you will overcome your challenge.
Good luck
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I am currently solving a static structural problem using ansys. I have given all the inputs but stress is not transmitting across the body. I have attached the files and I am bit new to ansys. Please guide me through the problem.
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It is not true that stress is not transmitting across the body. The results show a max von Mises stress of 1694 MPa, which is a sign of very localised stress singularity, perhaps at a sharp notch or edge. Such a high max value in the color band makes your whole body appear in blue color. Simply change the maximum scale value in your color band (e.g. 500 MPa).
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Dear all,
I would like to do a welding heat transfer analysis in 2D and map these results to a 3D model for conducting structural analysis. Is there any way to do the same?
Can any one suggest references for the same?
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I think one way to do that is to get the results from the 2D model and assign them as the initial conditions to the nodes having the exact coordinates( in just two directions (x and y)).
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There is nothing worse for curb appearance than chipped and cracked concrete, particularly in steps. But you don’t have to put up with that blight any longer. By the result of weather changes exerted on an existing construction for prolonged time, it causes contraction and expansion those gradually results concrete steps cracks and break up with time.
Dear researchers, I would like to get expert opinions on how to fix this issue with,
optimum efficiency
low cost
prolonged sustainability .
Your answers are highly welcomed.
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En mi pais, hay material especial para tratar estos casos y otros mas; por ejemplo selladores, alquitranes, y otros.
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I am doing a 2D pure shear isochoric strain analysis with 20% pure shear in ansys workbench using ansys static structural in ansys workbench. Previously in ansys mechanical apdl, there is a scope to enter displacement as a function of coordinates of nodes. The equations of my constituting boundary condition are
U = 0.2 *X and V = (-20/120)* Y. Here X and Y are the coordinates of the concerned node. How do I use them in ansys static structural analysis? Please guide.
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You can write a APDL script to do that. You need to write a loop (*DO) on your nodes, read coordinates and apply your desired load as a displacement.
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Hello,
I am studying the performance of 2 wing models (with the same size, constraints, loading and material properties but different material distribution) using Nastran. Wing A is lighter and 24% stiffer than wing B and that is demonstrated in the static analysis (under a distributed load on the top skin).
The two wings have about the same fundamental frequency (34.25Hz and 34Hz). Using the relationship f=sqrt(K/m), the difference between the two frequencies should be significant.
Also, the divergence analysis yields exactly the same displacement for the two wings.
Does any one know what could be causing such results? why the divergence displacement is not smaller for wing A (since it is stiffer) and its frequency is not much higher than wing B?
Thank you in advance for your input.
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Rossana Fernandes Can you share the two Nastran models (.bdf)?
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Dear researchers.
I am studying one way FSI using fluent and transient structural, my problem is that when I transfer the result directly from the fluent, I can not observe the correct deflection as the response should be a stepped as the excitation is a step function.
The relative total pressure on the structure surface is correct and I verified the plot.
I think that in transient I could not read the time steps even that I followed the correct step.
one of the solution I crossed with during web searching is to use external data transfer.
I know how to export pressure time value yet how to make the solver know that the pressure zone is as described in the attached picture?
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Long Chen first I tried to transfer the load directly to the structural solver yet the problem was that the feedback does not match with the input force, I had only one point, so I tried external data but I had a weighting error as I think I should also export the pressure coordinate but in that case we can not as I could not find any way how to export the pressure profile so I thought I may have an error in the simulation, I am doing it again.
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In recent years, there has been development of some innovative construction technologies that are changing the way we build. There are many new technologies that will have a significant impact on the future of the construction industry.
Today, construction companies are able to complete projects more quickly and efficiently than ever before. There are new technologies in demand for the future that will help with accuracy, sustainability and faster construction.
Based on your point of view, what are the types of construction that can be used in future?
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I suppose something like that would be a future:
So its all about local materials, somehow tranformed in structural elements.
Its probably not, what you are looking for, but I m working on several ideas, how to construct partially underground cities. Let me know, if you are interesting in such stuff. best regards. J.
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I will really appreciate if anyone could give some tips on the use of Lusas and SAP 2000 software for modeling and structural analysis. Thanks
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You can download the trial version and read user manual to practice the software.There are various online platforms offering a shirt term course for beginners like CAD Academy
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Can anyone suggest to me method to design fuzzy inference system (FIS) for MIMO structural damage detection (i.e. data distribution on the membership function, parameters of MF, Generate rules ... etc )
In my system there are 3 inputs and 2 outputs:
Inputs: Relative 1st Natural frequency , Relative 2nd Natural frequency , Relative 3rd Natural frequency
Outputs: Crack depth ratio , Crack Length
Note: I tried to use "genfis" By MATLAB it didn't give me reasonable results.
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Hi Murana Awad
Is it possible for you to share your data with me? I have some idea to solve your problem but I need your data.
I'm in touch by : ahmadi.v.1380@gmail.com
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Data science is a growing field of technology in present context. There have been notable applications of data science in electronic engineering, nanotechnology, mechanical engineering and artificial intelligence. What kind of future scopes available for data science at civil engineering aspects in the field of structural analysis, structural design, geotechnical engineering, hydrological engineering, environmental engineering and sustainable engineering?
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Complex graphical sketches are highly involved in Culmann's methods. Therefore, it is highly prone for getting deviations in magnitudes for resultant pressure on retaining wall. I would like to get suggestions from RG colleagues on why Culmann's graphical approach is mostly preferred in many research papers albeit Rankine's method is easy and precise in terms of equations and substitutions. I would welcome answers from both theoretical and practical perspectives.
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Perhaps this is due to the fact that the graphical method makes it possible to "see" the calculation. Psychological factor in choosing a method.
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Hello Researchers,
The FEM discretized (meshed) geometry/domain is considered stiffer than the actual geometry/domain due to the assumption of variation of the displacement within each element. This is analogous to the displacement being constrained to vary in a particular fashion within each of the elements. This results in the stiffness of the discretized domain being greater than the actual domain. As the element size decreases (or the number of elements increases), the constraint on the displacement loosens due to the smaller size of the element and hence, the smaller constraint zone. Thus, the stiffness of the meshed domain decreases and approaches that of the actual domain as the number of elements is increased.
Based on the above reasoning, the natural frequencies (on increasing the number of elements) must converge from above to the actual value (i.e. converge from higher values to the actual value).
  1. Can this be considered to be strictly true?
  2. Has any deviation from it been observed (i.e. convergence from below or lower values to the actual value) and if so how can that trend be physically explained/interpreted?
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Dear Jatin,
Not always does a finer mesh result in a more exact solution. A mesh convergence study should always be performed to guarantee the descending trend of the error as the mesh size gets smaller.
Having this verified, yes, a finer mesh reduces the stiffness of the model. Because FE approximates the the PDE solution by forcing the element into specific modes of displacement which yields a stiffer element. But as the element size decreases, the FE solution converges to the analytical solution of PDE.
Eigenvalue can be physically interpreted as how stiff the structure is in the eigenvector direction. So it follows the same pattern as stiffness.
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I am looking for stress-strain data for steel to input for the plastic properties in Abaqus. However I cannot find any literature or experimental data on the matter. If full data is not available then the strain or deformation rate will also be helpful. Should I assume a 2% strain rate in the absence of other data?
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Is the data provided by Al Mouayed Bellah Nafeh of aluminum or stainless steel? As per the above draft, the yield stress is very high.
What would be the plastic strain-stress of structural steel ( Fe345, S275, S355)? Can I use the plastic stress-strain curve from material data provided by software SAP2000? Please make it clear. Thank you.
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How can I get the equivalent(effective) Young modulus and Poisson ratio of a multilayer structure? A structure like the below picture. the structure is consists of Si, Al2O3, and Al metal thin films. They must be simplified into one equivalent layer.
Thanks.
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So If a column isn't casted exactly in the intended location according to the structural drawings, and the centre of this column is moved 3 cm away from it's original location.now in the ACI code, accidental eccentricity is taken into account in the column design equation,so the question is how to check If that eccentricity is within the allowable range? According to the ACI?
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we can write the minimum eccentricity = 12D/500 + D/30 = 0.057D, which has been taken as 0.05D or 0.05b as the maximum amount of eccentricity of a short column.
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While doing profile matching in full prof chi-square value is stuck at 12. When I try to refine u,v,w parameters their value reaches up to 38. What might be the possible reasons for the non-refinement of these parameters?
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Typically chi^2 is expected to decrease upon refining further parameters, if the refinement is well-behaved. As chi^2 increases, this suggests that the refinement is NOT well behaved at that point. This suggests high correlation of the refined paramaters push the refinement into a direction where everything is even poorer (you should see than in the visible quality of the fit, which should get poorer.). It is typically a sign for high correlation of the refined parameters, which can well be for uvw. This is in particular the case, if other parameters are being refined which do the same on the calculated profile as uvw. This depends, of course, on the details of you profile function and its refined parameters, and the history of your refinement. Based on this, and in view of the quality of your refinement do YOU have the feeling that you should touch u, v, w? I do not mean chi^2 (The way how people deal with their counting statistics frequently makes this number meaningless, unfortunately), but I refer to the agreement between observed and calculated profile!
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Structural analysis and morphological analysis
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Yes you can
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in his name is the judge
hi
I wrot a sub code on opensees for active tlcd or tuned liqiud gass damper (tlcgd) and assign it to some structures, it seems worked correctly.
In next step i want to optimize tlcgds location on each story with some objects like max dislacement or torsion ratio and ... so i have to use multi objective optimization (which may NSGAII algorithm is the best choice) code or toolbox on matlab and simulink. For this purpose i want to run NSGAII algorithm in matlab, then algorithm Calling my code in opensees (tcl) and run it, after that NSGAII algorithm modify damper location (in opensees code) after each timehistory analysis In order to improve objectives and then analysis my code again and again until find best location for dampers.
Note that I actually want to changing dampers location be part of the NSGAII algorithm and the algorithm itself automatically relocation the dampers to get the best answer.
one best solution may use openseespy but i think it's not free access and i can't get it from iran, So i think realyhead Over heels in this case.
Any help is greatly appreciated.
Take refuge in the right.
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I think that's the best answer
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What can cause severe bending conditions on the wind power plant's tower(only the tower part)? I assume that as the wind hits the blades it create a bending moment which vary linearly from wing tip to wing base. This moment will be transferred from blade's base to the top of the tower ( we have then a model like a beam with one end fixed and a bending moment on top). And I think that this moment has larger condtribution to tower's bending than the force coming from the wind as it hits the structure. Correct If I am wrong.
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Your interpretation is correct. The lateral loading due to wind and the moments due to rotating blades result in the problem.
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Hi,
Can any one please let me know how to configure ABAQUS solver for ANSYS workbench? So I can run simulations using ABAQUS solver which are pre-processed in ANSYS.
I read the help file, but I'm bit unclear what to do!
Thanks in Advnace!
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use an FEA modeler or external model then connect it to your step
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Hello friends
Nowadays I am trying to use Code_Aster to simulate CABLE . I want to know how to add a force like this F=0.5*velocity^2 on selected nodes?
And how can people add a triangle distributed force on a moving cable whose coordinate is changing with time .
Thanks for your help in advance.
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if you have a time-dept simulation, you can create a multiplyiting function with LIST_REEL and DEFI_FONC.
Franco
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Is the only way to differentiate between short and long coloums according to ACI is through slendeness ratio? Is there an easier approach?
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Dear Ali,
Columns can be broadly classified as short and slender columns based on their slenderness ratio. The slenderness ratio of a concrete column is defined as the ratio of its effective length le to its least lateral dimensions. The effective length is the unsupported length multiplied by a factor usually specified in the design codes depending on the end conditions of the column. Each code has its own criteria for classifying columns as either short or slender.
In this regard, I am attaching a thesis, where all the details have been given in more detail. I hope this will help.
Regards,
Pravin
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Structure Erection and Civil Works
1)Brief on civil foundation and, erection of supporting structures.
2) Fixing the foundation of the structure and, the grounding considerations.
3) Installation of mechanical structure
4) Foundation: Reinforcement and Shutting other balance of systems
5) Mechanical safety aspects.
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This is a good question.
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What should be done if items did not load in EFA?
should they be discarded? Or that means that they are unique and do not have partners?
What if these items are important or represent our dependent variables ? Can we include them as single items?
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Faten Amer, Usually items not loading on their respective constructs are discarded. However, at times discarded items can be combined to make a new construct.
Robert has already given you advice regarding single items.
Can you share a little more information regarding the EFA, so that we could together see what you have done and how could we help you further? Information such as:
- Which extraction method are you using?
- How the number of factors was identified?
- and, which rotation method was employed?
There is a common misconception between PCA and EFA, and at times right parameters (above) not selected. Consider reading the following article, if not already done:
Costello, A. B., & Osborne, J. (2005). Best practices in exploratory factor analysis: Four recommendations for getting the most from your analysis. Practical assessment, research, and evaluation, 10(1), 7.
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What are the programs which can be used for structural modeling?
I have used an AMOS previously but the trial period had run off, so are there any other available programs for the use which are free of charge?
thanks
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JASP is one of the latest software and it is free. If you need any assistance you can contact
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Hello everyone,
My dependent and independent variables are loading on the same component when performing EFA, Also CFA does not show a good fit when they are combined in one model but separated into different components.
I think this is due to the high correlation between them. So should I separate the questionnaire into different scales and perform EFA/CFA for each scale independently. Then combine them together in a path analysis later?
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Christian
thank you
yes i believe this is the problem
However, i am validating the Balanced scorecard which has 5 perspectives, under each perspective i could identify different constructs
actually i find it hard to delete or ignore any perspective
so i thought why not to split items depending on patient real experience items and the patient attitude items then to identify the constructs of each scale alone
the cfa and efa results became much better, also the constructs became more logic
my theory is that the 5 perspectives of balanced scorecard ( financial, customer, internal, external, and innovation and knowledge) experiences have effect on the balanced scorecard 5 perspectives images, which lead to patient satisfaction and loyalty.
so do you think it is not a good idea to plit the item based on dependent and independent items then to perform the construct validation for each separately?
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How can I validate a questionnaire for a small sample of hospitals' senior executive managers?
Hello everyone
-I performed a systematic review for the strategic KPIs that are most used and important worldwide.
-Then, I developed a questionnaire in which I asked the senior managers at 15 hospitals to rate these items based on their importance and their performance at that hospital on a scale of 0-10 (Quantitative data).
-The sample size is 30 because the population is small (however, it is an important one to my research).
-How can I perform construct validation for the items which are 46 items, especially that EFA and CFA will not be suitable for such a small sample.
-These 45 items can be classified into 6 components based on literature (such as the financial, the managerial, the customer, etc..)
-Bootstrapping in validation was not recommended.
-I found a good article with a close idea but they only performed face and content validity:
Ravaghi H, Heidarpour P, Mohseni M, Rafiei S. Senior managers’ viewpoints toward challenges of implementing clinical governance: a national study in Iran. International Journal of Health Policy and Management 2013; 1: 295–299.
-Do you recommend using EFA for each component separately which will contain around 5- 9 items to consider each as a separate scale and to define its sub-components (i tried this option and it gave good results and sample adequacy), but am not sure if this is acceptable to do. If you can think of other options I will be thankful if you can enlighten me.
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Faten Amer , sample size it is not a problem at al in Bayesian Factor Analysis, see for example:
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How can i validate a questionnaire for hospitals' senior managers?
Hello everyone
-I performed a systematic review for the strategic KPIs that are most used and important worldwide.
-Then, I developed a questionnaire in which I asked the senior managers at 15 hospitals to rate these items based on their importance and their performance at that hospital on a scale of 0-10 (Quantitative data).
-The sample size is 30 because the population is small (however, it is an important one to my research).
-How can I perform construct validation for the items which are 46 items, especially that EFA and CFA will not be suitable for such a small sample.
-These 45 items can be classified into 6 components based on literature (such as the financial, the managerial, the customer, etc..)
-Bootstrapping in validation was not recommended.
-I found a good article with a close idea but they only performed face and content validity:
Ravaghi H, Heidarpour P, Mohseni M, Rafiei S. Senior managers’ viewpoints toward challenges of implementing clinical governance: a national study in Iran. International Journal of Health Policy and Management 2013; 1: 295–299.
-Do you recommend using EFA for each component separately which will contain around 5- 9 items to consider each as a separate scale and to define its sub-components (i tried this option and it gave good results and sample adequacy), but am not sure if this is acceptable to do. If you can think of other options I will be thankful if you can enlighten me.
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After the survey is completed..but it is better to increase the number of studied samples..so that the result will be bette
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Hi
I had a questiones about the operation of the Riley damping command in Opensees.
First, how does the Rayleigh Damping Command affect the damping in any structural mode?
Second, can the Rayleigh Damping Command be set to affect only certain modes of the structure?
Any help is greatly appreciated
I wish you all the best
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Rayleigh damping is defined as a linear combination, i.e.
D ='alpha M + beta K
also known as "Bequemlichkeitshypothese".
The mode shapes of the undamped system simultaneously decouples M, D and K. That means that all modes are damped by using this approach.
You might consider modal damping if only a subset of modes should be damped.
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I am doing Response spectrum and  Linear time history analysis in RC building for my project. I have to consider infill consideration in the building, So i have calculated Strut width as per FEMA 356, using masonry property of Indian Standard. I have modeled strut assuming pinned jointed frame element having material properties as per masonry property as per Indian Standard. BUT i am unable making it not to take Tension in strut when running the analysis. And i am not able to make it not to take Dead and live load response,as infill should not take any dead and live load from the structure. So , how should i  model strut so that it will be  tension free  and it takes only compression? how can I model it in ETABS so that it will not  take any live and dead load from the structure? and i am not quit clear about that should strut is modeled for Nonlinear analysis( Pushover, nonlinear time history) only OR can it be modeled for Linear dynamic such (RESPONSE SPECTRUM, LINEAR TIME HISTORY ) analysis???  and how can i model it in Linear dynamic analysis??
Thank you!!!
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You can't do linear analysis of infill wall in etabs or any other software because linear analysis method is based on F=KU but the stiffness of infill wall showing non-linear behaviour it means ( As long as the wall does not crack, the wall contributes its stiffness to the frame,But when the wall is cracked at a small load then the wall does not contribute its stiffness, after cracking comes the stiffness becomes zero.So this is a nonlinear type of behavior.)
You can model the wall with the pushover analysis method or with the time history analysis method
.
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Hello everyone, I am designing a 7-story steel building using STAAD Pro software. I made it and when I saw it in render view, it showed intermixed I sections at column beam joints. What type of joint is that?
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It should be rigid joint. However, it all depends on structure designer.
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I am going to count the number of votes. So please select only: Concrete
or
Steel.
Just one word is enough.
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Steel
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Overall Sciences ... Overall Designs... Do we need always to consider Factor of Safety ... ?
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Yes we have to consider factor of safety depending on standards we are following and type of material and structure.
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Hello,
Could you please recommend me a good reference on the generalized theory of beams? In particular, I need one that includes the warping effects due to bending (7th DOF).
The only one I know is "Walter D. Pilkey (2002) - Analysis and Design of Elastic Beams: Computational Methods".
Kind regards,
Diego
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Which code are u using, this will assist in recommending suitable books and materials
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I'm trying to create a python script to get the "real" resistance of columns through Finite Element Analysis, and I wonder if there is any possible way to extract the eigenvalue in "Buckle" analysis automatically and then use it in Riks analysis (non-linear) without the need to do it manually.
In Abaqus command line interface, i usually use this script to manually extract the eigenvalue e.g. 1st:
>>> import odbAccess
>>> a1=odbAccess.openOdb('Buckle.odb')
>>> a1.steps['Step-1'].frames[1].mode
1
>>> a1.steps['Step-1'].frames[1].description
'Mode 1: EigenValue = 5.02675E+05'
But how can i automatize it in Python script and automatically insert the chosen eigenvalue in Riks script as the new load applied, see screenshot below:
Also added buckle script
and Riks script (-NL)
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Qamar Ul Islam Thanks, but that covers the first step, what I'm after is automatically insert these eigenvalues as a load in Riks which the second step
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Hello,
I am trying to preprocess DWI data for the first time in order to extract diffusion parameters and to perform tractography. I have watched all the tutorials provided by the Analysis Group (FSL), Andrew Jahn videos on Youtube and I have studied the DTI pipeline. However, I still have questions.
It is not very clear if I should preprocess my T1 data too. I am using it to perform registration with my diffusion images. I know that I should extract the brain (Bet function) but I was questioning about possible others steps I am missing? I am afraid it could bring artefacts onto my results.
Thank you for reading me,
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Yes you should correct your T1 images before doing anything with your DWI. Here are my recommendations, please keep in mind that this varies from person to person but the below mentioned steps I have seen most common in diffusion imaging papers.
1. Fixing the orientation i.e. Moving into standard space or center your brain to (0,0,0). You can use FSL's fslorient2std command to re-orient.
2. Denoising
3. Gibbs ringing correction
4. Bias field correction
5. Skull stripping
In case if your T1 data is not in isotropic voxel you may also need to resample it too.
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In your opinion which is the best software to analyse a 3D frame:
(a) STAAD
(b) ETABS
(c) ABAQUS
What are the merits of your answer?
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Dear Navin Ramroop
In general, ABAQUS is finite element analysis based software and generally used in research. However, STAAD and Etabs are used in analyze and design of structures in industry. So it depends on purpose.
Regards
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Hi there,
For defining damage variables in Abaqus, what stress-strain curve would be appropriate to use to define these two concrete damage variables?
Because some of the empirical concrete stress-strain curve give value of damage variables up to 0.7-0.8; I am looking to get at least damage variables of 0.9 (for dt & dc) when calculating these variables from the post-peak response of concrete curve. 
Cheers, 
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I am sharing the one of the best article related to ABAQUS published in Elsevier. It might be help all.
Genikomsou AS, Polak MA. Finite Element Analysis of Punching Shear of Concrete Slabs Using Damaged Plasticity Model in ABAQUS. Eng Struct 2015; vol. 98: pp.38-48.
Regards
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Dear
I am performing a series of structural analysis test through software, for some model I already have the experimental results so the selection of mesh is related to this results, the good mesh is the one who gives the best approximation to the desired results but....
In Case we are testing a new design or a new structure without any previous knowledge , how to know the correct mesh?
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Dear Mohammed Lamine Mekhalfia
The only way to find the correct mesh size is by doing sensitivity analysis. In which we decrease the mesh size and point where results will not change by further decreasing mesh size is correct or optimum mesh size. All researchers follows this method. You can find many research articles of FEM.
I hope this will helps you.
Regards
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Please compare various common programs, e.g., ETABS, TEKLA, etc. as well as the new generation of parametric ones, e.g., Karamba, Kangaroo, etc.
Please reply by referring to valid scientific papers.
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I think Etabs, SAP, STAAD Pro, SCIA Engineer are best for analyse and design. However, Abaqus, Ansys, ATENA are best for research.
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I'm trying to create a python script to get the "real" resistance of columns, and I wonder if there is any possible way to extract the eigenvalue in "Buckle" analysis automatically and then use it in Riks analysis (non-linear) without the need to do it manually.
Basically, extract the eigenvalue from Linear Petrubation - Buckle analysis, and use it in another model with Riks analysis to get LPF and automatically and plot Force-Displacement plots.
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Here is a tutorial on eigenmode imperfections and newton raphson which may be helpful:
here is a tutorial on extracting the load displacement curve via python:
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I performed transient structural analysis on a shaft geometry as a result I got the amount of thermal deformations. shaft geometry has different diameters on the surface, how to calculate the increased diameter or thickness for different areas of shaft i.e. after deformation.(without using code)
@
Claudio Pedrazzi
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I realized that you mentioned this question to Dr.
Claudio Pedrazzi
, I haven't seen any answers or comment from him for about a year and half, I hope he is doing well. He got many experience in Ansys specifically Ansys APDL. We miss him a lot here in RG. Thank you so much for your kind email, it is my pleasure that my answers here in RG helped you in the past.
Going back to your question, I think Dr. Victor J. Аdlucky already provided a very good guideline and this is the only thing you can do, if you don't want to use any kind of coding for that.
You can do the following steps for calculating radial deformations.
1. Insert a Cylindrical coordinate system in the center of your geometry.
2. Insert a directional deformation contour. Select the surface you are interested in and adjust the coordinate system to the one you just made. Then adjust the Orientation to reflect "X Axis".
3. Extract the result for this contour. Extracted results show you the radial deformation which you can add/subtract it to/from the original dimension for calculating final dimension.
Also, You can do the same thing with Cartesian coordinate system, however, you need to extract the result for X, Y and Z direction and then calculate the resultant vector.
Hope this answer helps.
Thanks,
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Is there any analytical formula that relates the longitudinal deformations to the transverse deformations of a cantilevered beam subjected to a transverse applied load?
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Some formulas can be found in sect. 20-21 of the book “Theory of Elasticity” by S. P. Timoshenko & J. N. Goodier.
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I am trying to simulate buckling phenomenon of ion source grids under thermal load in vacuum.Two grids namely screen grid and acceleration grid made of SS304 are mounted on a SS flange.The grids are electrically isolated from each other and SS flange by ceramic bushes.The inter grid spacing is maintained by brass spacers.I want to fix the grids at the bolting location so that it does not have any deflection there.A heat load of 300W is applied on the face of screen grid which faces the flange.There are no apertures in the model as it is just a preliminary study.The thickness of each grid is 1mm.
Following are my questions.
  • What kind of contact(bonded,rough,frictional etc) should i define between brass spacer and grid and brass spacer and ceramic bushes to get proper deflection results?
  • On what faces of the assembly should I define radiative boundary conditions? (Just 2 grids or even bolts,nuts, flange etc)
  • Which area of the assembly should contained the fine mesh size? Since I am using a regular 8GB desktop I am not able to make meshes <2mm element size.What is the criteria for choosing mesh size?
  • How can I know that the output by ansys is correct? (i.e the direction in which the grid buckles is right or wrong?).
I have attached picture of a sample run output for understanding.I have labelled all the components in the geometry.Please feel free to ask if you need any other details.
Thank you
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Hi Bharat,
Setting the boundary conditions will only be part of the solution. In the case that the grids are dished, when heated they will expand in the direction they are dished. When they are flat, they could buckle away from the heat, towards the heat, or just become wavy or a saddle shape, depending on which bolt lets the grid slip first.
You should try adding a very shallow dish to your grid model, and make sure that it buckles in the same direction as that dish when heated. (i.e. the radius of curvature of the spherical surface goes down)
-Charles
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I mean the mathematical component of said process.
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What exactly is not clear?
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I mean the use of the SQUG database to assess the seismic resistance of NPP equipment with the specified type of reactor.
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GIP - Generic Implementation Procedure
WWER - water-water energetic reactor
NPP - nuclear power plant
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I simulated a cylinder of length 75 and radius 2 in Abaqus using shell elements (S4R) for the cylindrical shell and solid elements (C3D10) for flanges. The connection between flanges and cylinder is done via shell-to-solid constraint. The thickness of the cylinder is varying from 0.03 at bottom to 0.013 at top. At top a concentrated lateral force of 100 is applied. Bottom edge is fixed.
I wanted to validate my results by comparing it with a beam. Thus, a beam is created of length 75. The thickness again is varying from 0.03 to 0.013. Same BC and load condtions are applied here. No influence of flanges here, just a straight beam divided into parts with different thickness. B31 elements are used.
A linear static analysis is followed. While displacements are close, I noticed something stange regarding Von Mises stresses. The location of S.Mises at both models is different. In cylindrical shell max Mises is at boundary while in beam model is above boundary. Any idea why is this happening? I was expecting also S.Mises for beam to be at boundary
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THE ANSWER BY SPYROS ARVANTIS APPEARS REASONABLE.
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Dear all,
I want to connect two parts in abaqus. One is a cylindrical shell and the other is a solid deformable ring. The ring will act as a stiffener for the cylindrical shell. My question is what is the appropriate way to connect them?
1) Should I connect the parts in Assembly modulus and then merge them together?
2) Should I design both in Part modulus?
3)Or should I tie them with a solid-to-shell constraint?
What is the best strategy? How the results will be affected by choosing one of these 3 methods?
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Anargyros A. Karakalas Thank you for your reply.Very helpful information
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I am studying the book "Structural Analysis with Applications to Aerospace Structures" by Craig. In Chapter 8 titled "Thin-Walled Beams", the authors derived the governing differential equation
dn / dx + df / ds = 0
where, n is the axial flow, f is shear flow, x is axial coordinate, and s is curvilinear coordinate along cross-section. Here we can substitute n = sigma * t where sigma is obtained from Euler-Bernoulli beam theory. Using this approach, we can determine shear flows and then shear stresses in each section of cross-section.
Another way to determine shear stress in a beam cross-section is to use Timoshenko beam theory.
Question: What are the difference between the shear stresses obtained from the two methods? Do both approach capture the same effect?
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The first one describes a single variable while the second case needs a couple.
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Dear all,
I want to use ring stiffeners in order to increase bending resistance of a cylinder. The rings has outer diameter R1 = 2 and inner diammeter R2 = 1.85. Their thickness is 0.12 . They will be attached in the inner of the cylinder.For modelling them in abaqus, solids or shells should be used and why?
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I would choose solid, although the shell option works too.
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Dear Scientists,
I have a question, we want to use the application of ANNs in regression analysis and this is some sort of easy utilization for ANNs, but the question is " how many samples do we need to training? using 12 samples could be enough? " I produced these 12 samples by Fractional Factorial Design (FFD) method and I need to be sure about this. Therefore, I would be grateful if you could provide me with any information about this subject.
Many thanks in advance for your time and kind consideration.
Regards
Mohsen
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Dear Mohsen, there is a rule of Thumb of Upadhyaya & Eryurec that says:
H= I * log2 N, where H is number of weights, I is the size of input vector and N is the number of trainning patterns. If you have 12 trainning patterns, and a input of size 1, you got only 3 weights. So its not possible to have a hidden layer. Hope it helps you.
References:
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HI,
can anyone explain me how to get modal mass coefficient and modal participation factor as per ATC 40 from SAP 2000?
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Hi
Modal analysis outputs can be found in the SM toolbox 6.0.4 instructions in the following sections:
74.29. ModalLoadParticipationRatios
74.30. ModalParticipatingMassRatios
74.31. ModalParticipationFactors
74.32. ModalPeriod
74.33. ModeShape
Best regards
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I am doing structural analysis of epoxy composite with natural filler. Facing problem in material selection. Because not available in engineering materia library of Ansys.
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I recently started using the Ansys workbench for my thesis project, and I would like to ask the best approach to show the post-processing results? For example, I had run a transient structural analysis simulation, and I got a result, i.e., deformed body, how we will compare the deformed body to the original geometry to find change in volume or diameter, etc.?
or is there any better way to show my results for people to understand in easier way
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Hi Aidin,
Can you explain it very clear? So that I can try this method.
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Is it right to face socioeconomic status as a latent variable? May you give an example?
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Hello Matheus,
in 2007, there was a whole special issue in Psychological Methods on formative variables that centered around the example of socio-economic status as a latent formative variable. It started with the very critical view by Howland and colleagues:
Howell, R. D., Breivik, E., & Wilcox, J. B. (2007). Reconsidering formative measurement. Psychological Methods, 12(2), 205-218.
The debate continued later with the same folks in the Journal of Business Research:
Wilcox, J. B., Howell, R. D., & Breivik, E. (2008). Questions about formative measurement. Journal of Business Research, 61, 1219-1228.
Best,
--Holger
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Dear all ,
I have a one fixed-end cylinder under bending force simulated in Abaqus. I run a geometric non-linear analysis and now I want to find the curvature at some specific point across the length. I want to measure the curvature ( κ ) at a portion of my model ( dz ) by applying κ = dθ/dz = (θc1-θc2 )/dz ,where θ is the rotation around y-axis and θc1,θc2 is the rotation of the center of the portion dz. Is it possible to find these rotations at the center c1,c2 of a portion of my model? Is any other way to find the curvature?
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This was my suggestion:
The formulation that you wrote is theta1 – theta2 /z1 – z2
So in your odb, for the theta you can get the rotation with Query/Probe values. Depending on which rotation you want you can extract UR1, UR2 or UR3. Also, for the value of the z1 and z2 you can get the COORD3 for those two points of C1 and C2. (don’t forget to active COORD in the step).
If you want to compute it through the whole cylinder you may need to write a python script to extract these values for all nodes and then compute it or plot it.
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I am studying the behaviour of cylindrical shells under bending loads. I simulated in Abaqus a straight cylinder of length = 100 , radius = 2 and thickness =0.05 . S4R elements are used. The cylinder has one end fixed and the other is free. (Rigid body kinematic conditions are applied in a reference point in middle of cross section at both ends). A displacement load is applied at free end and a geometric non-linear analysis is followed.
The model under bending load is subjected to ovalization of its cross section. My question is how can I measure this ovalization and how can I find the moment distribution across the cylinder in order to find at which moment the collapse occurs?
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For moment formula, you need to take the normal stress component
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I simulated the same problem using both wire beam and shell elements. The model is a cylinder of length = 100 , thickness = 0.05 and radius = 2. One end is fixed and the other is free. A displacement load in x-direction of 27 is applied on free edge. For shell element S4R elements are used and for the beam element quadratic beam elements. My goal is to check if these two formulations give the same results. However , I created free body cut ( at half of the length) to check if moment and reaction forces are the same. There is a difference between 2 models. Why shell formulation is not close to the beam one?
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Good work. I appreciate your research efforts and team work. Congratulations to all authors.
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in structural analysis, I would like to know what is the real physical meaning of having a low and high natural frequencies?
which is better to avoid structure with low or high natural frequencies?!!
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Interesting question!
In general and roughly speaking, for the same object (to be designed and/or tested=, there are many natural frequencies. Not all of them are equally important. Which ones will be important, depends on your problem.
Example 1- Frequency spectrum. If no external excitation are acting, the "free" or "natural" movement of your structure is the linear super-position of all the modes, meaning all modes participate. Generally, the lower the mode, the higher the participation. So you can say, low-frequency modes are "more important" in that sense.
Example 2- Resonance avoiding. Do you want to avoid vibration at a specific frequency? Then make sure your exciting frequency and the nearest natural frequency are sufficiently far from one another. This is called "separation margin" and should be 10-20% to design in a comfort zone, i.e. far from resonance. Resonance is when exciting frequency and natural frequency match. Although design engineers always try to avoid, test engineers know that it's not necessarily the worst-case scenario for your structure. If excitation magnitude is low, or acts close to a nodal point of your mode, or if there is enough damping to dissipate vibrating energy, the structure can operate in a resonant condition without too much pain.
Example 3 - If your problem is to compare natural frequencies on structures of different sizes, than you should define which order are you interested in, e.g. 1st bending mode. In general the smaller the structure, the higher is the mode.
I hope the three examples above help you a little bit.
Regards
Maurizio
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Good day Sir/Ma'am, anyone here knows how to extract data from structural analysis software specifically from ETABS to MS Excel. Thank you and God bless!
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Mehran Shahpari thanks, but I want to make a program that can easily check the analyzed structures without exporting the data to excel manually.
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I've done the Modal Analysis followed by Structural analysis in Ansys Mechanical & now I want to export my model in State Space Form. So that i can use it in Matlab.
Everything works well except loading of input vectors, I've followed guidelines from the link below:
example:
my query is that the given link provides accessibility to define DOFs in ux, uy & uz. However, I want to Include variable forces in x,y & z direction that will be controlled by my Control Algorithim in Matlab. how can I add forces as input?
The link also says if i don't define any input array it will define all the Loading vectors in the system as Inputs(by Default). But it's not working as it says.
Note: I've defined "Nodal forces" using "Named Selection"
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The page you requested is unavailable and will not be restored. For documentation please contact your software provider.
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Hi everyone.
I'm currently working on replicating the load-displacement backbone curve result from an experiment of a simple circular column subjected to slow-cyclic loading. The specimen is subjected to a constant axial load of 890 KN and a lateral load with a 978 KN servo-controlled hydraulic actuator. The column has couplers placed near the support.
I modeled the column with couplers using SAP2000 with auto hinge property ( P-M-M). The axial load is assigned as nonlinear static ( zero initial conditions ) while a displacement controlled static nonlinear load case for the lateral load ( continue from state at end of NL case "axial" ). My column eventually failed at step 27 of the displacement-controlled load case.
The results between the 2 are quite the same for the yielding load and displacement, however, drastic changes can be seen in terms of ultimate load and strain. Kindly see photos attached for comparison.
What seems to be the problem? Any suggestions Re: use user-defined hinge properties generated from other software.
Thanks!
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I think in experimental work you measured displacement by millimeters while in program it's too small (may be in meter).
Furthermore, in experiment you had data only for the end of plastic stage while program provides post failure behavior. You need to match every units
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I am interested to perform spectral analysis of a structure under random waves. could anyone suggest me a book or an example that starts from wave spectrum (such as
JONSWAP spectrum , P-M etc) to RAO. A complete example from formulation to numerical evaluation.
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