Science topic

# Earthquake Engineering - Science topic

Here you can discuss about any structural, risk analysis , geotechnical issues and whatever relates to earthquake engineering.
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The purpose of earthquake engineering is not to build strong and earthquake-resistant buildings that do not experience the slightest damage in rare and severe earthquakes. The cost of such structures for the vast majority of users will have no economic justification.
Instead, engineers focus on buildings that resist earthquakes' effects and do not collapse, even in severe external excitations. It is the most important goal of international standards in the seismic design of buildings.
Below I have mentioned some crucial points in reducing the seismic demand in reinforced concrete structures. If there is anything else that is not on the list, feel free to append:
1- Selecting suitable construction conditions with the desired soil type of seismic design
2. Avoid using unnecessary masses in the building
3- Using simple structural elements with minimal torsional effects
4. Avoid sudden changes in strength and stiffness in building height
5. Prevent the formation of soft-story
6. Provide sufficient lateral restraint to control drift through shear walls
7- Preventing disturbance in the lateral behavior of the structure by non-structural components
Allow me to present another of my own seismic design proposals that I hope will solve all the problems of structures in the great earthquake.
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I want to calculate maximum shear strain in a soil profile (10 layers), based on a half-space. I calculated deformation by the formula below, but I found a different shear straint by Deepsoil, Strata and shake. Although the amplification functions are the same, Figure (1)?
gama(i)(%)=100*(disp(i)-disp(i+1))/h(i)
disp(i): displacement in the top of layer (i)
disp(i+1): displacement in the top of layer (i+1) or displacement in the base of layer (i)
h(i) : thickness of layer (i)
Have you sorted out the reason?
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I need help modelling horizontal BNWF with axial, transverse, and vertical (bearing & uplift) springs and spring damper at the ends to simulate connectivity.
I want to know how I can model these on to the beam and assuming the pipeline segment is 1 kilometer in length, at what intervals should the soil springs be applied? Can we assign line springs in OpenSees?
Thank you
P.S I would like to validate my results through this paper "Seismic risk assessment of buried steel gas pipelines under seismic wave propagation based on fragility analysis - Vahid Jahangiri, Hamzeh Shakib" - DOI 10.1007/s10518-017-0260-1
Hi
Here is one approach to model a horizontal beam on nonlinear Winkler foundation (BNWF) with axial, transverse, and vertical springs in OpenSees:
1. Discretize the 1 km long beam into elements (say 100 10m long elements).
2. Use an ElasticBeamColumn element for each beam segment.
3. Attach zeroLength elements to each node:
- zeroLength in local x-direction for axial soil springs
- zeroLength in local y-direction for transverse soil springs
- zeroLength in local z-direction for vertical springs
4. Use a Parallel material to combine the elastic behavior with a Bilin/Quad nonlinearity for each spring.
5. Apply spring properties like stiffness, yield strength, post-yield stiffness.
6. For damping, attach zeroLength elements with a ViscousDamper material at the ends.
7. Apply restraints and prescribed displacement to beam ends to simulate boundary conditions.
8. For load, apply point loads, prescribed displacements, or ground motion acceleration to the model.
The spacing of the soil springs depends on the desired discretization accuracy. A spacing of 5-10m would likely be reasonable for this length of beam.
This assembles a beam on springs system with nonlinear material models and damping to capture soil-pipeline interaction effects under dynamic loading. The zeroLength elements conveniently allow applying 1D spring-damper behavior between nodes.
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I have modeled a two-dimensional plane strain embankment in Abaqus. I did not apply any forces, boundary conditions, or displacement to the infinite element, and I defined it as CINPE4. I defined two steps for the model: the first step is static to apply gravity load, and the second step is dynamic implicit. In the second step, I applied the time history of the Loma Prieta earthquake horizontally on the base of the model. Ultimately, I observe a concentration of shear strain at the boundary between the infinite and finite elements, as shown in the image below.
In addition, I have attached my model's .inp file to this question for reference.
Hi Amir,
I checked your input file and it seems that you are using MC material def. for your soil. So, my guess was that the strain concentration is caused by discontinuity in the material behavior. Your soil block is pulling the infinite region and since it is less deformable, you get the stress concentration and plasticity in the interface region. But I tried to run your input file and in fact, the plasticity already occurred during the static step.
So, there are 2 concerns here from my pov:
1. The way you create the model. First, there is no infinite elements in the bottom of the soil. I understand what you are trying to simulate but by modelling it this way, you have no representation of the static and dynamic behavior in the vertical direction.
2. The geostatic state is missing. As you know, the soil behavior is governed by its confining stress. And it is paramount in nonlinear soil simulation. In your static step, you apply the gravity loading to the soil but there is no predefined stress in the soil. This yields incorrect nonlinear behavior because the soil strength is underestimated. Any deformation beyond this point would be considered invalid. If you are unfamiliar with this, please check the abaqus manual regarding geostatic step.
So, for your model, I recommend to apply the infinite elements surrounding the main study area. You can imagine the interface to be like a half-ellipsoid. The interface here is the line between regular and infinite elements.
And then apply the correct geostatic step. I know it can be a challenge to implement a geostatic step on a model with irregular surface. How I usually solve it is by having a preliminary geostatic computation. In this preliminary model, I apply the geostatic computation while applying fixed boundary condition to all soil (finite) region and record the reaction forces. These reactions are then used as input in the true geostatic step in the main model to stabilize the result. I don't know whether you want to go this far, so I'll stop with the details.
Cheers and good luck with the model.
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I have performed a certain set of nonlinear dynamic analyses on an RC (Reinforced Concrete) frame that I designed on SAP2000 using the Indian Standard Codes. Since the numerical model is not based on any existing building, I fear that someone might ask me how I would validate my model, which on their part, is justified. What could I possibly say as a satisfactory response?
For some reason, many people are often reluctant to share their design details, so the question regarding validation seems a bit tricky.
Thank you Pavlo Pavliuchenko sir for this insightful answer. This does clarify a lot of things. Of course, covid induced restrictions did play a huge role in limiting us from going out to search for experimental data or real-world data that we could have used for our FE model. However, we can surely find some literature to validate the results. Thanks
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I want to use this attenuation relationship (suitable for central Italy) in probabilistic analysis therefore It must consider the soil type as a random variable with a certain probabilistic distribution.
Moreover, If there is any formula or methodology in which soil type from the epicenter to the target point is taken to account for obtaining an attenuation relationship, I would appreciate it if you introduce it.
Many thanks in advance.
Many thanks, anyway Gianluca Regina
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In his name is the judge
Hi
I think the best way to assign the nonlinear effect of steel components like beams that to model it with a plastic hinge.
So To build a nonlinear model of a one-story steel structure I use the Modified Ibarra – Krawinkler model to model my beam. In fact, I model a beam with two hing (zero length element) at the start and end and one elastic beam in the middle.
I used material developed by Lignos and Krawinkler named uniaxial material Bilin and here is more information about this material
After all, when I extract the output belonging to the stress-strain of this material under seismic loading like Kobe I get something like this diagram. (kobe0.5g) based on
"Ibarra L.F., and Krawinkler, H. (2005). “Global collapse of frame structures under seismic excitations”, Rep. No. TB 152, The John A. Blume Earthquake Engineering Center, Stanford University, Stanford, CA."
named article and this diagram (ref1) the stress-strain shows the right modeling and performance. consider that my record is near fault and the diagram of reference also belongs to near-fault loading.
If I use the 1g scale for the Kobe record I get this diagram (kobe1g) and here is the diagram of the 2g scale for the Kobe record (kobe2g) So my best shot is this when the record multiply and the ground accel become higher the material reaches the capacity of its deterioration very more quickly(In fact after a short time the strain of material switch between 1e10 an-1e10 and strain is between about -2 and 2) but it's a little non-sens for me in the other hand there is one benchmark( in the reference is named it before this benchmark is for standard loading) diagram for this material stress-strain (logos) and my diagram is different with it.
In the end here are the 1M\$ questions
1- why when I give more scale to record the diagram become like that?
2- and why my diagram is different from the benchmark stress-stress of material?
Any help is greatly appreciated.
Take refuge in the right.
Please note that pre-cap plastic deformation (rotation) capacity is relative, not absolute. It represents the distance between the yield and maximum moments. Although in the two diagrams the absolute maximums are different, the distance between the yield and maximum moments are the same.
Regarding your second question, please make sure you assigned monotonic backbone parameters with some cyclic deterioration. From the rapid in-cycle deterioration (softening) in the diagrams you have sent, I suspect you have assigned the first-cycle (cyclic) backbone parameters.
BR.
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In his name is the judge
I want to build some parametric structures. my objects is period of first mode, eccentricity and (frequency of torsional mode/frequency of transitional mode). So I decide to use NSGAII for make my parametric structure.
Inputs of optimization are transitional mass, rotational mass, length and width of structure and objects are period of first mode and (frequency of torsional mode/frequency of transitional mode) and in each one I assume eccentricity constant.
So I think there is a problem. I think there is a relation between rotational mass and transitional mass with respect to length and width of structure and eccentricity of mass.
If my guess is true I have to remove rotational mass from my inputs and use the relation instead.
So my big question is
Is there any formula to evaluate rotational mass based on dimension, eccentricity and transitional mass in rectangular plan?
wish you best
Take refuge in the right.
If your structure is an 'office' or 'hospital' type building with concrete floors, so that the floors form rigid diaphragms at each storey, mass is associated with the translational response, and mass moment of inertia (MMI) is associated with the torsional response. You need to study an appropriate text on this, or an ETABS program manual, etc. Attached are formulae for calculating the MMI for typical floor shapes, including how to allow for these shapes being offset from the overall centre of mass.
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I use OpenSees Navigator for finding mode shape and natural frequency.
After modeling, when I define line element, I want to use mass density, 7800 Kg/m^3. But, system of unit in OpenSees Navigator is different interational system of unit. Which unit should I convert Kg/m^3 to? kip/inch^3? or lb/ft^3?
t/m3
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While designing a model on SAP2000, post analysis when we perform the design check, there's a colour bar to the right hand side of the window with some values. I'm assuming that these may be the demand to capacity ratios because when these values are >1, the members become red (as indicated in the colour bar) and indicate a certain failure. Assuming I have dealt with all types of failure (as indicated in "Identify all failures"), which region should the members lie in? The answer can include suggestions where economical design is considered and ignored as well. I only wish to be clear with the underlying concept. I have attached an image of a frame I've designed for clarity.
You should look to the analysis result, by right click on the member
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In his name is the judge
Hi everyone
In order to use controller for structure with absorber, have to connect matlab and opensees in real time :
it means in each loop in opensees data must send to matlab and then matlab do some prossess with controller like fuzzy then send back data to opensees
Relying on researching and consulting the only way is use hybrid simulation (like openfresco),
do you have any other idea or way to connect these two programs without using openfresco?
Translation results
star_border
Consult
Wish you best.
Take refuge in the right.
Use TCP/IP communication.
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In his name is the judge
Hi
There is a fuzzy logic control system in python. The system contain 2 inouts and 18 outputs.
inference of system is mamdani and shape function used to be guassian.
Then in term of refine performance of the controller I need to optimize specifications belong to shape functions of both input and output. In order to that I need to use multi objective optimization.
We have 2 input and 1 output in case of this problem. I have developed 3 shape functions for each entrance and 3 for output and the shape function is gaussian so we have 18 parameters totally.
I defined my problem as a function in python. But notice this I there is not any clear relationship between input and output of function. It’s just a function which is so complicated with 2 inputs and 18 outputs.
I made my decision to use NSGAII algorithm and I really don't want to change the algorithm.
So I try every way to optimize my function but I didn’t find any success. By searching about python library which can do multiobjective optimization I find Pymoo as the best solution but I really failed to optimize my function which is complicated custom function, with it.
So It’s really my pleasure if you can introduce me a library in python or suggest me a way that I can use Pymoo in order to this aim.
wish you best
Take refuge in the right.
You can stick with Mamdani Fuzzy System if it is comfortable for you to design a "workable" FIS. You probably don't need optimization if your FIS works satisfactorily. From the "workable" FIS to the "satisfactory" FIS, you probably just need make minor adjustment to the design parameters. That's the Spirit of Engineering Design.
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Can we discuss the limitations of Performance-based Design? Does it really (in practice) deliver what it claims?
Short answer: I don't know.
Longer answer: There is potential for designs to be more physics or performance based than they have been in the past because there are less restrictions to fabricating buildings. The mathematics of optimization and solution of inverse problems is well established. The problem is that classical building doctrine is based on lots of experience, most of which is not encoded into the conclusions. To be superior, PBSD will have to optimize along several axes simultaneously, and the designer will have to capture all failure modes. I suspect there will be some (more) spectacular failures before the new design doctrine is established.
I will be starting a project soon on improving aerostructures using additive manufacturing and meta-materials, so I hope to be better informed in a year or so, but for now, I don't really know.
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I am doing my MTech thesis on topic “ANALYSIS OF SEISMIC SEPARATION GAP BETWEEN TWO ADJACENT REINFORCED CONCRETE BUILDING” and i am planning to use FVD250 between two adjacent buildings, so what will be the cost of one single viscous damper and is it good idea to use FVD between building?
Study the Petronas twin tower connections and you will understand the concept of connecting towers with dampers.
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When you speak of damage, is it the apparent cacking, residual, permanent distortions, the roof level drift, or the invisible concrete pulverisation, lap splice failure or rebar slippage or something else?
Damages in the structures are the result of distress due to bending, shear, bond, torsion, fatigue or any such action. The resulting phenomenon will be cracks and deformation which may become so significant that the stricture may not be serviceable. collapse in the structure is with large deformation which may not be recoverable. In fact in limit state design a structure will reach a collapse stage when it will have plastic hinges equal to its indeterminacy plus one that is becomes collapse mechanism (due to static mechanism or kinematic mechanism).
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In his name is the judge
Hi
I'm trying to make a fuzzy controller in order to optimize my absorber performance in opensees(in python).
I use adaptive neuro-fuzzy inference system (ANFIS) toolbox in matlab to make fuzzy system as controller.
input data for fuzzy logic system are acceleration and velocity of absorber and the output data is force wich controller send it to absorber for performance improvement.
in fact i want controller learn ,based on velocity and acceleration of a point of structure, how much force need for turn structure into it's balance position.
note that quantity of force determine by fuzzy controller system and applying force part of absorbr job.
logically we have to assign come load to the point of structure wich absorber locate there and then get acceleration and velocity of absorber as input training data of fuzzy logic system.
but i realy don't know how can i do this.
note that i want to give force to structure in balance position, in the otherwise i think make train data is possible when using dynamic loading so i entirely confused here
if you have any suggestion i realy eager to hear it.
wish you best
Take refuge in the right.
Mohammadhassan Eftekhar To train a fuzzy system utilizing neuro-adaptive approaches, input/output training data from experiments or simulations of the system to be modeled must be collected. In general, ANFIS training works successfully if the training data is completely reflective of the data characteristics that the trained FIS is meant to model.
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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.
dear Abolfazl Najafi thanks a lot for this suggestion
i think there is a lack time between opensees anb matlab run time it means when tcl try to write text file, matlab needs to read more data in text file and give error
after all i think working with python and openseespy library is the best choice for this goal.
wish you best
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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.
Gracias por su sugerencia
Definitivamente revisaré
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Hello,
I have recently started a Master course in Earthquake Engineering and I am new to research. I would like to choose a topic in the best area of research in this field of engineering but I am mostly getting confused with it. I was wondering if someone could give me some suggestions.
Regards,
I am sure that the best research topic in Earthquake Engineering for the developing world is providing resilience to the existing buildings. I, personally, recommend to use invented, designed and applied by me seismic (base or roof) isolation strategies for seismic retrofitting of the existing buildings. I have already implemented these strategies in several buildings without interruption of their use and without moving people out of the buildings.
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I am Abdollah, senior member of Engineering Seismology and Earthquake Engineering Research (eSEER) group, Universiti Teknologi Malaysia, leading by Prof. Azlan Adnan. Currently, we are working to propose Malaysian National Annex to BS EN 1998-2:2005, Eurocode 8: Design of structures for earthquake resistance -Part 2: Bridges.
In this regard, it would be appreciated if everyone could guide us on how to define the Distance (Lg) parameter beyond which the seismic ground motions may be considered as completely uncorrelated. Regarding the EC8-2, the parameter is defined based on the ground type. Now, we would like to know that how these values (e.g., 600 m for ground type A, or 500 m for ground type B) have been derived? We are waiting for your kind reply. Thank you very much for your contribution. Best Regards
Hi Abdollah
Answering your question is not that simple !
I do not know how these "Lg" values were derived in EC8, but from a physical viewpoint, they should be frequency dependent : the spatial correlation between the motion at two near-by sites is often characterized by the coherency, and all models and data show that this correlation is frequency and distance dependent: the longer the distance the lower the coherency for a given frequency; the higher the frequency the lower the coherency for a given distance. Moreover it also depends on the site properties : the softer the material the lower the wavelength at a given frequency and the lower the coherency for a given distance (see for instance the data in Imtiaz et al, BSSA2018, 108, 5A, pp. 2839–2853.
So I would recommend first to consider the frequency range of interest for the structure you have to deal with, and the corresponding site conditions. Then to look at the coherency predicted, in this frequency range, by the various models available in the literature – some are indicated in the above mentioned paper, but there are many more. If the predicted coherency is lower than 0.4-0.5 over the whole frequency range of interest, you might consider the motion as fully decorrelated. Beware also that the existing models may overestimate the coherency for very soft soils, especially above the site fundamental frequency.
Hoping it may help, best regards
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Dear colleagues,
I am working on a large landslide in the Caucasus region as part of my PhD and after extensive field work I am building a numerical model of the slope in RS2/RS3. As earthquakes are an important factor in the region I also want to make a pseudo-static seismic analysis for a slope stability analysis. I have PGA values from my study site, but I am not sure how to determine the seismic factors from them.
Rocscience support is more or less refusing to offer meaningful help and just refering to their program documentation and tutorials, which are basically useless for this topic...
According to Eurocode 8 seismic factors to be used in geotechnical design according to Eurocode 7 are calculated as:
kh=a(g)/g*S/r
kv=kh*0.33
with
kh: horizontal seismic coefficient
kv: vertical seismic coefficient
a(gR): reference peak acceleration
γ(l): coefficient for importance of buildings
a(g): design peak acceleration a(g) = a(gR) * γ(l)
g: 9,81 m/s2
S: value of factor for ground type
r: value of factor for type of retaining structure (if existing)
Depending on the various factors you can end up at about 0.4-2.1 * PGA.
Hynes-Griffin & Franklin (1984) recommend using half of the PGA value.
Marcuson (1981) assumes correct values to be in the range of 0.33-0.5 * PGA.
How do you approach this problem? What references do you use? What are your experiences?
Best,
Klaus
Dear Klaus,
Hynes-Griffin & Franklin approach (kh=0.50 PGA) is a very common and well-known approach for numerical analysis. I can say that considering kv will not cause any significant difference in results.
However, considering topographical state of the section may help you to come up with a precise solution. NCHRP advices a factor called as "fill-height dependent reduction factor" for the determination of the proper kh value. The soil class of the area is also critical for this approach. Maybe you can check this solution for your analysis. See attached file: Section 7.5 for more detailed information.
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I am modelling a L-shaped shear wall in ABAQUS for my project. I have applied a cyclic loading on top surface of my specimen. I have extracted the "base shear vs drift data" (and obtained a backbone envelope curve from the hysteresis). Apart from this load-deflection curve I wish to determine time and position when first cracking and crushing of concrete starts. And the same for the yielding of rebars. Can anyone help me with this ?
Some people here have suggested to plot ALLPD vs time (for whole model) and note down the time when curve becomes non-zero, that's when cracking of concrete has initiated. What's the logic behind that? And what about crushing of concrete and yielding of rebars?
Note: There are many rebars, so practically impossible to compare all rebar nodes time history to determine the first yielding point.
Hello,
First, you need to know what your damage initiation criterion is? After completing your job, select the damage initiation criterion from the Field Output dialog box. Check the frames and legend. Find out when the first point value is greater than one. You can read the time from the step time. To find the point location, select the Contour from the options menu, then go to the Limits tab, and toggle on the Show location to observe the location of the point.
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I am interested in learning a bit about the background of how the behaviour factors, which are used in Eurocode 8 to calculate the design base shear for a structure, were developed. As I understand it, and please correct me if I am wrong, the factors implcitly comprise several different components:
- first, a reduction in seismic forces to account for system ductility in accordance with the equal displacement principle,
- secondly, a further reduction to account for overstrength of the structural elements,
- and thirdly, some component that accounts for the performance for the structural system.
Can anyone enlighten me as to how the values in the Eurocode were obtained and/or point me towards some appropriate literature. I would also be content with information pertaining to the R valued used in the US as this is somewhat similar.
You may also find more information in this paper
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In his name is the judge
Hi
In order to design controler for my damper ( wich is tlcgd), i want to use fuzzy system.
So i have to optimize rules for fuzzy controler. i want to know for optimizition rules of fuzzy systems wich one is the best genetiz algorithm or Artificial neural network?
Wish you best
Take refuge in the right.
I strongly recommend the usage of a floating fuzzy control algorithm since it allows you to change the range of your membership function in real-time so you can adapt your controller at each time step.
Regards.
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I made a numerical model of a reinforced concrete frame in ANSYS APDL software in order to perform a PUSHOVER analysis, but the only experiment results that I got from the literature are obtained from a cyclic load experiment. However, the results are illustrated in terms of Base reaction versus roof displacement.
My question is, can I validate my numerical model with the envelope of the experimental cyclic results?
Nowadays, a variety of pushover analysis methods have been developed, including Modal pushover, Adaptive pushover, and Cyclic pushover, in which some weaknesses of the conventional pushover method have been rectified. In the conventional pushover analysis method, the effects of cumulative growth of cracks are not considered on the reduction of strength and stiffness of RC members that occur during the earthquake or cyclic loading.
I think these papers will help you:
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I need to perform a nonlinear Time History analysis on 7 ground motions. How do I apply the scale factor so that these ground motions are scaled to PGA like 0.1g, 0.2g. I am using PEER ground motion database wherein the acceleration time history data is "in units of g"
in the load case, choose time history and then you get the command scale factor by which you can scale the accelerograms according to the desired value of PGA.
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Of course, set the damping ratio of a structure to 5% will simplify the dynamic calculation. However, we all know it is just an assumption and since structures are quite sensitive to their "real" damping ratio, especially when the frequency ratio is near the unit. I wonder how we can achieve an actual damping coefficient numerically?
First you should find the mass matrix and the stiffness matrix. Afterwards, you should solve the eigenvalue problem associated with the problem at hand and these specific matrices. The structural damping coefficient is equivalent to the fraction of Im(lambda) over Real(lambda), where lambda is the complex eigenvalue and Im and real, respectively denote imaginary part and real part of the eigenvalue. I have attached a triple of screenshots to my comment for your perusal.
For forced vibration (for example in presence of air dynamic pressure), the solution of the eigenvalue problem is a bit harder than to find a solution to an ordinary eigenvalue problem. For concreteness, in this regard, I have attached a PDF of my own original idea to this comment. The PDF is also available in my ResearchGate project:
Linear Aeroelastic Analysis of Laminated Composite Plates with Fully Elastic Boundaries
Under the title:
Eigenvalue problem for aeroelastic vibrations: The solution
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I am working on seismic analysis of shear walls. So I am trying to calibrate CDP parameters for my further research by comparing load-Disp hysteresis (experimental and ABAQUS analysis) of U wall under cyclic loading.
For Experimental data I am referring this article:
I have attached an image showing best match (along with CDP parameters) which I could get for E=7000 MPa, which is very less than usually taken values like 25MPa. Is this normal when doing nonlinear cyclic analysis?
And how can I make my curve look similar to experimental one (there is huge difference in peak values and shape of cycles - experimental result shows narrow cycles whereas my ABAQUS analysis is resulting in wider cycles)
In the ABAQUS program, you need to select one hysteresis models which have similarities to your experimental curve.
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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.
I think that's the best answer
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hello
In order to do my thesis, I need to place the damper I developed at OpenSees on several asymmetric steel benchmarks. For this purpose, to develop asymmetric one- and nine-story structures, I decided to use the method given in the above article, but unfortunately in the article, the structures are parametric and I do not realize this.
Here are some basic questions for me.
One, how the mass and structural members of these structures are defined and modeled.
Second, how can a find period for these structures?
And finally, how is it possible to get the response of these structures under the earthquake record?
My strongest guess is that it is to define stiffness of each structural member as a coefficient of mass or vice versa.
Any help is greatly appreciated.
Take refuge in the right.
In his name is the judge
thank all of you Juan Pablo Peñaloza & Kan-Jen Liu & Paul Mathew
Vizhalil my dear friends.
I think found my answer. for researching about kind of structure we use parametric structure to do complete research. for example to see affect of torsionally assymetry structures we develope parametric structures.
It means we Generate structure in 3 diffrent periods like 0.5,0.75,1 second. mass, dimension and stiffness of structure are not important in this case what is important is period only. in the second step we Generate 3 structures which have 3 diffrent torsional ratio (torsional ratio = (period of torsional mode)/(period of Transitional mode)) 0.5,1,1.5 for each single period. so totaly we build 27 diffrent structres which their elements, dimension or materials and etc are not important at all the only main things about them are periods and torsional ratio.
We call these structures parametric and we can use them for Exhaustive research about torsionally assymetry structure in our Purpose. i used parametric structures in case of see tlcgd affect on torsionally assymetry structure.
Take refuge in the right.
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Dear Researchers,
Are there any references or standards regarding the allowable deformations of buried structures (e. box culvert) in either seismic or service conditions?
When designing this type of structure, at least 2 issues are important:
- structural integrity: the (differential) settlements have to be low enough to avoid structural damage to the structure.
- hydraulic functionality: possible settlements should not affect hydraulic (or other) functionality of the structure.
I am not aware of any specific standard, but a rational approach as described above can always be used to show adequate/inadequate design.
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Initial surface absorption test
This is a good question.
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.How to calculate the shear strain in a multilayer soil profile based on a half-space under a seismic action?
This is a good question.
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While adding dashpots error i am getting is the spring/dashpot element is not available.
And should I provide space for soil to flow to other region. I am considering very thin strip of soil and providing earthquake load to it.
And if I am assigning dashpots I would have to assign it to every node(except surface since it's open to air) So what size should I take for the mesh.
That is a good question.
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How can I appling non-axisymmetric loads or displacement to an axisymmetric model? I use bilinear asymmetric-axisymmetric elements (CAXA4N), but I also want to impose the asymmetry to the loads. (I'm using ABAQUS)
CAXA4N are not supported by Abaqus/CAE. You must include them in .inp file. The main limitation is that deformation must be symmetric with respect to the r–z plane at θ=0,π. Look at the sect. Axisymmetric elements with nonlinear, asymmetric deformation: https://abaqus-docs.mit.edu/2017/English/SIMACAEELMRefMap/simaelm-c-dimension.htm#simaelm-c-dimension-t-AxisymmetricElementsWithNonlinearAsymmetricDeformation-sma-topic11__simaelm-c-axisolid-fourier-modes
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i am trying to simulate the flat slab with equivalent frame method with ETABS software to conduct the pushover analysis, for modeling the rigid torsional member I adjust the torsional constant modifier to a very high value (1+e15). am I correct? if not what is the suitable way to simulate the rigid torsional member?. Thanks in advance.
Do you want to eliminate the torsion effects of slabs on beams? You can define a weightless rigid diaphragm (slab) and apply its weight manually on all beams.
If this is not the case you are looking for, please elaborate more.
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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
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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Dear researchers
What is your opinion about the criterion recommended in seismic codes for determining scaling period, which are used to scale ground motion records?
As you know, the mentioned criterion is the period of the structure’s dominant mode, which has the largest modal participating mass ratio (usually the first vibration mode). Hence, the period of the mode with the second largest modal participating mass ratio is not considered in the scaling process. Consequently, although this criterion usually results in the largest value of scaling period, it is not logical ones.
This is especially important when Tuned Mass damper (TMD) or Base-Isolation system is utilized, which cause the modal properties of the structures to change.
I used a new criterion based on the weighted mean value of the periods for the structures equipped with TMD.
Have you used any criteria other than the criterion mentioned in the seismic codes?
Dear Mikayel Grigor Melkumyan , it is my pleasure if u can read my latest article
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hello everyone, i'm trying to model a 3D one story buiding with mass IIrregularity, the model has 4 elastic columns and rigid diaphragm. the model has no beam, so i used rigid diaphragm to equal dof of top nodes of columns. i use a model from a reasercher's article, he note that the modal frequences of first three mode is 1.16 , 1.96 , 2.37 HZ respectively. i builded the model in etabs and can verify my model with 0.33% error, but i couldn't verify model in opensees. i trying almost everythings to verify it but Unfortunately all my work was unsuccsesfull. in my reaserch i found that mass moment of inertia is principle parameter in model with mass IIrregularity, so i try figure out how modal analysis run in etabs and opensees and what difference between them. i found that etabs centeralized all masses in center of mass and then make mass matrix with 3 parameters like that [mass in x direction 0 0 0 mass in y direction 0 0 0 mass moment of inertia about hight axis ] but i wondering opensees generate mass matix for each node(also we can use center of mass for assigne mass) and also mass matrix for 6 dof model with 3 limited dofs (dofs limited in z direction and rotation about x ,y axis) is 6*6, so i'm confused to understad how opensees derrive mass matix and calculate modal frequences. i try both assigning mass to nodes and center of mass. in first condition i assigned mass moment of inertia like that mass n "mass in x direction" "mass in y direction" 0. 0. 0. "mass moment of inertia about height axis" etabs calculate mass moment of inertia with multiple each mass of nodes by distance of node from center of mass then sum these valus and attain mass moment of inertia abuot height axis. also we can use another formula for it. i try all patterns i found but i can't verify my model because i can't understand how opensees run modal analysis and make eigen values. for best understanding i upload my model in opensees and etabs. I'm so thankful if you can help me. with best regard
I hope my research will be of use to you
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I am looking for the latest approaches to find the band-gap of Phononic / Periodic materials. In this regard, if anyone knows a reference (in detail) for Finite Difference Time Domain (FDTD) theory along with the Bloch method, please share.
I really appreciate any help you can provide.
For arbitrary unit cells, your best bet is an eigenmode simulation. Sweep the Bloch phase shifts across the various axes from 0 to pi and solve for the eigenfrequencies. The regions in which there are no found eigenfrequencies are your band gaps.
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Hi
I know the procedure of modeling modal analysis to obtain natural frequencies(I mean using Linear perturbation step>>frequency and without defining any other loading....) but the problem is all examples I have seen is just for model made of just one material(most examples for cantilever beam) but my model is consist of two or more material( 2layer soil and layer of polymer between these soil layers), for obtaining natural frequencies in this case, my exact question is: I have to run modal analysis for each material separately or all together?!
I should mention that the polymeric membrane part does not have any type of support and its just in interaction with soil( normal and tangential behaviour), and if I run the modal analysis for this part alone natural frequencies for polymeric membrane is zero. while the soil is fixed at bottom and sides and by running modal analysis once for soil alone and another time soil with polymer,the natural frequencies are the same for both conditions. so i'm willing to know any advise and special point to obtain natural frequencies procedure for model consist of two or more materials in abaqus.
Interesting
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Hi researchers
Im trying to model dense sand which has peak friction angle and constant volume friction angle . As you k now if we plot shear stress - shear displacement(strain) of dense sand till reaching specific displacement curve ascends to the peak point(peak friction angle)and after that with slight reduction becomes constant(constant volume or residual friction angle). I wanna model the behaviour of soil accurately so my purpose is to define friction angle as a function of shear displacement. I searched and understood using SUBROUTINE (specially USDFLD) may help me but I have not work with subroutines at all and this is my first time however I linked vs code and intel R with abaqus and its completely ready for working.
I will be thankful to hear your helps and advises.
Thank you so much dear chen, could you please guide me more about fist way( using field variable in abaqus) or suggest me any video or article related to this title?
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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
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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Both of these standards are relevant to testing materials at high temperatures.
When can we use ISO 834 and when can we use Standard ASTM E119?
What is the main difference between them? Is Fire Curve similar in them?
Using specimens similar to those described in the draft revision of ASTM E 119, tests were conducted in floor and wall fire test furnaces. The tests were designed to compare the practical consequences of following the ASTM E 119 and ISO 834 specifications for measuring and controlling the nominal furnace temperature. It has been found that in fire tests of shorter duration, perhaps up to 1.5 h, the ASTM test is slightly more severe than the ISO test. In longer tests the difference in severities is negligible.
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Hi everyone,
to calculate the prying forces in the column base plate connections, we need to get the contact reaction between the plate and the concrete, but in my model, I have a part in compression and another one in tension. so how can I evaluate the surface of the plate in tension under the cyclic load ?
Dear Aichouche
If I were you, I would forget the Castem and go for SolidWorks Simulation . it's more easier, faster, and efficient.
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When it comes to placing the column longitude bars in a foundation, an old wrong belief says that a column's longitude bars should be bent outward (like Figure 1). However, due to the force transmission mechanism and the cohesion stress in the bent part of longitude bars, in my opinion, It makes perfect sense to bend the column's longitudinal bars inward (like Figure 2).
The argument of those who consider Figure 1 to be correct usually refers to the roots of trees in nature.
Is this argument correct?
It was always a question for me until I found out that the new ACI 318 code says the figure 2 is correct.
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Do you admit that there must be a seismic culture among inhabitants and individuals to manage seismic risk?
I agree with you Amira. It would great if we could conceive what would be a seismic culture.
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The summary can be accessed from the link below:
Please let me know whether the information that has been gathered in the summary file is informative or not.
If the summary description is not clear enough, any suggestions will be welcome.
Thanks a lot, Dear Armin Huß
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For instance, while comparing the response spectrum curve in IS 1893-2002 with that of ATC-40, Ca = Z/2 and Cv is either of Z/2, 1.36·Z/2 and 1.67·Z/2 for hard, medium and soft soils respectively for DBE.
While doing the pushover analysis using capacity spectrum method (ATC 40), what would be the values for Ca and Cv with respect to the response spectrum curve given in NBC 105:1994???
As the values are expressed in terms of coefficients, it's rather confusing to figure out the value of intensity of ground acceleration.
I agree with the statement of DR. Karim
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Earthquake Engineering data
By signing up at the following link, you can get data according to your needs:
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I would appreciate some insights.
I also worked at chimneys on ANSYS.
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Dear all,
I'm trying to design the Rocking frame structure in Sap 2000 with an Energy dissipation element ''Shear Fuses'' at the base of the structure.
Would you please suggest how to model an element that has the same properties as a shear fuse?
Thank you,
You may be able to do that with link elements.
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Dear researchers
I modeled a specified structure with the same properties (mass and stiffness) (apply mass through defining nodal masses instead of calculating from gravity loads) in both Etabs and Sap2000 software and observed differences between the modal results of the structure (the value of natural frequencies). After various investigation (all factors affecting the stiffness of the structure), I have found that the mentioned differences are arisen from difference between the mass matrices created in Sap2000 and Etabs software.
Since, unlike SAP2000, it is not possible to output the mass matrix and nodal masses of the structure in Etabs, the reason for the difference in mass matrices cannot be identified.
In your opinion, what is the reason for the difference in the mass matrices created in Sap2000 and Etabs? And which one is more correct?
Hi,
OAPI is useful to extract the stiffness and mass matrices from SAP2000.
Let try to do it in Etabs to recognize where are the differences.
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The plate/mirror 4km far from the laser beam could shift when earthquake waves reach the observatory. Could it be useful to investigate the high-frequency content of very deep or teleseismic earthquakes ???
Dear Alexandro,
Yes,
You will understood why I responded this:
Laszlo
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Dear researchers
The provisions of ASCE 7-10 states that New Next Generation Attenuation Relationships (NNGAR) has been used in the process of Probabilistic Seismic Hazard Analysis (PSHA) to prepare seismic hazard maps provided in United State Geologic Survey (USGS).
Now, I want to know what is new next generation attenuation relationships and how are they different from other typical attenuation relationships such as Campbell, Douglas, Godrati, BJF, etc?
Hello Majid
Just a few words to answer you, although I was not part of the NGA / NGA2 projects. Essentially, from a methodological viewpoint, these NGA GMPE are not different from the previous ones you quote. They may however considered are significant improvements for several reasons :
- very careful gathering of a common set of high quality strong motion data from various parts of the world, and covering an as brand as possible range of magnitude and distances, together with the corresponding Metadata regarding the source characteristics (rupture extension, fault orientation, moment magnitude, etc.), the propagation characteristics (different source-receiver distance metrics, potentiality of source- receiver configurations), and the site characteristics (the poorest though in my opinion, with only VS30, and most often only inferred and not measured - but with a clear indication of the origin of VS30 value). Personally I do no trust that much the Z1 / Z2.5 values (depth at which the S-wave velocity exceeds 1 or 2.5 km/s).
- derivation of a parallel set of numerical simulation results (with 1D codes for horizontally layered media) in order to constrain the non-linear part of the site response
- on this common data set, several groups of authors have made their own section, and developed their own a priori models for the source, path and site effects, with for some of them very sophisticated models to (try to) account for peculiar effects (directivity, rupture mechanism, NL site response, + what is ambiguously called "basin effect" corresponding indeed to deep deposits effects, etc.)
- a very careful estimation of the aleatory variability and its systematic separation in two terms ( within and between-event), with or without additional dependence on magnitude / distance / site conditions.
These NGA were developed over several years with extensive discussions between many participants, and can thus be considered as being the best State-of-the-art at the time they were developed.
Hoping to have brought useful answers, and hoping also NGA/NGA2 authors will complement and correct me !
pyb
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Dear researchers
Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion, which considers structural collapse risk of each site in seismic hazard analyses, is used to prepare seismic hazard maps provided in United State Geologic Survey 2010 (USGS 2010).
The mentioned collapse risk are considered in MCER through risk coefficients and applying to Maximum Considered Earthquake Geometric Mean (MCEG).
How these coefficients are calculated and applied to seismic hazard maps?
Dear Majid,
The answer to your question is very long. You will find your answer in the following papers.
- Risk-targeted versus current seismic design maps for the conterminous United States (Luco et al. 2007)
- Risk-targeted seismic design maps for mainland France (Douglas et al. 2003)
Let me know if you need more information.
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During my research, I have read the concept that unbalanced moments in flat slabs being transferred partly by flexure and vertical shear, and it is the basis for ACI code in recommendations on flat plates transferring combined shear and moments. What I want to know is how was the model conceived? ( I mean what made the developers come up with that idea?) what makes the concept valid or how was it proved? Why didn't they make the moment transferred solely by flexure?
I would be happy if someone attaches the original research for the concept?
Because a Part of the unbalanced moment is transmitted by punching shear.
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Dear researchers
The equivalent frame method can be used for macro modeling of masonry structures in order to seismic evaluation and retrofit according to ASCE 41 provisions. But, this method is not applicable in SAP2000 and faces many problems in modeling and analysis results because the mentioned software is not really for modeling masonry structures.
Now, I want to know about 3Muri software for modeling and analysis of masonry structures and whether there are the mentioned problems in this software?
Hello everybody,
A 2D macro-model, alternative to the equivalent frame model, is represented by the Discrete Macro-Element Model (DMEM), implemented in the software 3DMacro (www.grupposismica.it). This model can be efficacy used to simulate both URM and mixed masonry-reinforced concrete structures, such as confined masonry or infilled frames. I attach below some references. In [5], an attempt to develop the DMEM model in SAP2000, for the simulation of infill frames, is reported.
Best Regards,
Bartolomeo
1- Caliò, I., Marletta, M., & Pantò, B. (2012). A new discrete element model for the evaluation of the seismic behaviour of unreinforced masonry buildings. Engineering Structures, 40, 327-338.
2- Caliò, I., & Pantò, B. (2014). A macro-element modelling approach of Infilled Frame Structures. Computers & Structures, 143, 91-107.
3- Pantò, B., Cannizzaro, F., Caliò, I., & Lourenço, P. B. (2017). Numerical and experimental validation of a 3D macro-model for the in-plane and out-of-plane behavior of unreinforced masonry walls. International Journal of Architectural Heritage, 11(7), 946-964.
4- Pantò, B., Caliò, I., & Lourenço, P. B. (2018). A 3D discrete macro-element for modelling the out-of-plane behaviour of infilled frame structures. Engineering Structures, 175, 371-385.
5- Kareem, K. M., & Pantò, B. (2019). Simplified macro-modelling strategies for the seismic assessment of non-ductile infilled frames: a critical appraisal. Journal of Building Engineering, 22, 397-414.
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Dear Research scholars,
I was doing my MTech thesis on pendulum based TMD and I was having trouble defining the link properties. I even followed the tutorials put on CSI website. still, I wasn't able to properly do that.I would be very grateful if anyone helped me with this.
Thank you
Dear Yathish
Within SAP2000 or ETABS, a TMD may be modeled using a spring-mass system with damping. Guidelines for this subsystem are described in the following link:
Regards,
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Dear researchers
As you know, one of the challenges of using nonlinear procedures is to determine the behavior of plastic hinges of members with deformation controlled action that this behavior is assigned to the plastic hinge by a force-deformation curve and its relations using parameters modeling. various researches has shown that the uncertainties in these modeling parameters significantly affect the structural responses.
Also, the acceptance criteria of different performance levels relating to the mentioned force-deformation curve are needed for performance-based design of structures.
There are two questions now:
1- Are force-deformation curves presented in ASCE 41-13 suitable only for nonlinear static analysis (push over)? or also is applicable for nonlinear dynamic analysis?
2- Given that the acceptance criteria presented in ASCE 41-13 are derived based on the mentioned force-deformation relations in this code (a, b and c modeling parameters), what acceptance criteria can be used to evaluate the structure at the IO, LS and CP performance levels if the other force-deformation relations presented in the technical literature (such as Lignos and Hartloper relations for beams and columns of moment frames, respectively) are utilized for concentrated plasticity modeling?
The mentioned curves (Lignos and Hartloper relations) are mostly used in structural modeling to study the structural collapse, in which the collapse is determined by the criteria mentioned in FEMA p-695 and as a result, acceptance criteria in accordance with these behavior curves have not been researched.
2. Uncertainties about deformation capacity are high beyond the point C of the F-δ curve. Even in the Collapse Prevention performance level (before point C), the ultimate deformations shows significant dispersion in experimental cyclic tests (e.g. reinforced concrete). Consequently, appropriate acceptance criteria for different performance levels and for different materials can be found in seismic codes (ASCE 41-13, FEMA, Eurocode, EN 1998-3, etc) or in other technical literature using model safety factors to scale down the proposed mean values to mean plus standard deviation ones.
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Hello,
I have a technical question about the selection of steel frame sections in the designing of steel frame structure i.e W16x48 etc. The common practice I have seen is the trial and error method for beginners, which is time-consuming for multi-story buildings.
My question is do we have a convenient method in the selection of frame section?
TIA
Warm Regards,
Hi.
In Define/Frame section you can define auto-select frame sections for steel sections only. An auto-select section is a group containing every section you prefer to assign to the elements. You can modify this group and add or remove sections to it. At the end you can assign this auto-select section name to all of the beams or columns or ...
After running the model and designing it, iterations are made and the optimum section is assigned to the elements with automatic try and error.
Hope this would help...
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Dear researchers
The modeling of P-Delta for the structural elements (specially columns) reduce the stiffness of the structure and consequently increase the period of vibration. Now, these changes are negligible when the structure and P-Delta effects are modeled in OpenSees software. Instead, the mentioned changes are more noticeable when modeling is perform in the softwares such as Etabs and Sap2000.
How to apply P-Delta effects is the reason for difference changes due to P-Delta modeling in different softwares.
Now with all these interpretations, what is the most accurate method for modeling P-Delta effects? In other words, In which software are stiffness changes calculated more correctly due to modeling of P-Delta effects?
As you know, In Etabs and Sap2000 software, P-delta effects are applied to the structure by defining a gravity load combination, while this procedure is performed in OpenSees using geometric transformation (second-order P-Delta effects) and its effects on stiffness matrix.
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When calculating Gmax of soils by ρ*Vs^2. Does this value reduce or increase if the soil is below or above water table?
Thank you
Najam Wani
I will check on it.
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FEMA P695 recommended 22 far-field earthquake records and 28 near-field earthquake records. I can searth and download the far-field records in peer database using RSN, but I can not find the near-field records in peer database. Can anyone help? Thanks!!
Dear Yang Liu
In general, you can download the acceleration records of the earthquakes recommended in FEMA p965 using their listed Record Sequence Number (RSN) from PEER web site.
But, The downloaded acceleration (time history) are slightly different from those of recommended in FEMA p695 and consequently, their properties such as PGA etc. has some difference.
This is because of the modification of the acceleration records presented in PEER web site compared to the earlier ones. The properties of earthquake records presented in FEMA p695 are based on the earlier records presented in PEER web site.
You can achieve the earlier records from researchers who works with them.
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