Science topic

# Earthquake Engineering - Science topic

Here you can discuss about any structural, risk analysis , geotechnical issues and whatever relates to earthquake engineering.

Questions related to Earthquake Engineering

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

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)

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

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.

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.

Thanks in advance.

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.

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.

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.

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?

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.

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

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Consult

Wish you best.

Take refuge in the right.

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.

Can we discuss the limitations of Performance-based Design? Does it really (in practice) deliver what it claims?

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?

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?

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.

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.

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.

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 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

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

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.

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.

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 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?

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"

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?

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 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.

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.

Dear Researchers,

Are there any references or standards regarding the allowable deformations of buried structures (e. box culvert) in either seismic or service conditions?

.How to calculate the shear strain in a multilayer soil profile based on a half-space under a seismic action?

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.

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)

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.

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

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?

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 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.

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.

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.

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

Reference for FFD method: https://en.wikipedia.org/wiki/Fractional_factorial_design

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?

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 ?

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?

Please share your opinion about this with others.

Do you admit that there must be a seismic culture among inhabitants and individuals to manage seismic risk?

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.

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.

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,

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?

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 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?

Dear researchers

Risk-Adjusted Maximum Considered Earthquake (MCE

_{R}) 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 MCE

_{R }through risk coefficients and applying to Maximum Considered Earthquake Geometric Mean (MCE_{G}).How these coefficients are calculated and applied to seismic hazard maps?

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?

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?

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 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.

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,

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.

When calculating Gmax of soils by ρ*Vs^2. Does this value reduce or increase if the soil is below or above water table?

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!!

I am doing my MSc thesis on base isolation of structures with variable curvature friction pendulum systems. I have downloaded the benchmark problem for base isolated buildings and everything is fine. However, the file which contains the nonlinear analysis algorithm of the building is in DLL format and I cannot open and edit it for my new bearing type.

My Matlab version is R2013b. I also tried some lower versions, but that did not work.

Please let me know how I can solve this problem. I really appreciate your assistance.