Braces - Science topic

I am at the initial stage any suggestion or help will be highly appreciated.

I am reading two articles about the determination of equivalent viscous damping( 1. "Wijesundara KK, Nascimbene R, Sullivan T (2011) Equivalent viscous damping for steel concentrically braced frame structures" and 2. "Jayasooriya1 · D. W. U. Indika1 · K. K. Wijesundara1 · P. Rajeev Equivalent viscous damping for steel eccentrically braced frame structures with buckling restraint braces"). From the flowchart and description, I understand that we first determine the equivalent damping ratio ξeq = ξel + ξhyst (ξhyst form cyclic analysis in opensees). From ξ, we find the damped displacement spectrum. From this spectrum and for the plasticity we are examining, thus for the given horizontal displacement (Δtarget), we find the effective period Teff. Then, we determine the effective mass meff = (Keff * Teff^2) / (4π^2) and distribute the mass in the two nodes of the frame where we run the analysis in opensees. If the average horizontal displacement resulting from the inelastic time history analyses is close to the level of displacement we are examining (deviation less than 5%), then the ξ we took is accepted. If we have a greater deviation, we consider a new ξeq, resulting in a new spectrum, a new Teff, and a new mass (Keff remains the same from the initial hysteresis loop).

From the above, I deduce that if the displacement found is less than Δtarget in the time history analyses, the initial mass calculated is not sufficient and must be increased to increase the mass, thus increasing Teff. This means that for the same Δtarget, the spectrum must "drop," thus increasing the damping. In other words, a smaller Δ means that in the new approach, higher damping should be considered to increase meff and result in greater displacements (only ξel is defined as Rayleigh damping in the model). In the second paper, in paragraph 4, an example is mentioned where the correction is the opposite. That is, it starts with a high damping ratio with Δ < Δtarget and ends with a smaller one to approach Δtarget. If we look at the logic of the correction process described in both papers, smaller ξ would lead to a smaller Teff, smaller mass, and therefore smaller displacement. I suppose I have not understood something correctly in the iterative correction process.

Different clinicians follow different aligner wear protocols for their patients such as, 7,10 or 14 day protocol. What are your views?

Hi everyone, I want to model the shear links in an Eccentric Braced Frame Structural System. My problem is selecting the best element object in opensees/openseespy which can replicate the hysteretic behavior of its as the experimental test results show. I have found some papers: 1) 2018.05.22 - Experimental and numerical assessment of EBF structures with shear links (Silvia Caprili et al) 2) 2016.06.02 - Seismic Behavior of Direct Displacement-based Designed Eccentrically Braced Frames (Mohebkhah et al) I think the 1st one is more easier to model. Has anybody have any idea whether there are other object elements more straight forward to use instead while it can best replicate the hysteretic behavior? I also need an example of how to use that suggested approach if available (and also for any of the above mentioned models). Thanks, Husayn

I am currently working on my thesis in Retrofitting of soft story. At first step i am trying to validate a experimental test. There i need to model a bracing with gap in it. The bracing should act only in compression after the gap is closed and free in tension. For creating simplified model i tried to create compression only element with uniaxial non linear elasticity model available for steel in Diana where i gave input to stress-strain diagram with very small value in tension and in compression, i gave nearly 0 value upto strain when gap closes and after that normal stress strain value of steel. I got the hysterisis result where there is increases in lateral resistance as compared to test result. how an i fix this? Is there any approach to model gap element? i tried contact analysis too but could not make it out.I have attached hysteresis result of Experiment and Diana Modeling. The bracing should start working after 1% drift.

Thank you.

Hello researchers,

I have been modelling the cyclic behavior of bracings using ABAQUS. when I take the hysteresis loop once the model has run I get the graph with straight lines as shown in the first figure. Even though I have defined the plastic model for the material, I am unable to obtain the Bauschinger effect during load reversals. Can someone please help me out !

Thanks in advance !!

I am make a model of eccentric braced frame and I need to run it with FNA but no Plastic Hinges Results appear

For my graduation project I need to determine the cost of buckling restrained braces of different sizes and properties. Does anyone know how much is the approximate cost of each one and the cost of the tests required? For example, for the case of fluid viscous dampers, there are relationships in the literature of the type Cost = A*ForceDamper^b that allow estimating its cost.

Does anyone know if there are similar relationships exist for BRBs?

P.S. I have tried to contact some manufacturers but that kind of information is confidential

Thanks

I want to model the link-to-column connections in the ABAQUS program. But I need a sample resource.

How to assign force-deformation relationship and performance levels and parameters adopted from FEMA (2005) in SAP2000 or braces

I work on a model of steel frame of vertical and upper bracing in Abaqus... after run by dynamic explicit , I found 2 of the upper bracings and 4 of the vertical ones have got away from building... Although I tied them to columns

any one had similar problem could help?

Note :- the same model of all details did the run successfully in static...

The "two groups" will be in fact the same group of people. The first time they will not wear a brace while the second time they will wear one. The posttest measure will be after a fatigue protocol is executed.

If we consider corn, it has primary, seminal and crown roots. Primary and seminal roots are embryonic roots while crown (and brace) roots are post embryonic. I am wondering if hormonal release such as strigoractone release would be different in above mentioned root types of corn.

I am modelling a steel truss bridge with a steel deck for IRC Roadway vehicular loading. We know that the top chord (while in compression) is susceptible to buckling. Although there are members such as diagonals and verticals connecting the bottom chord with the top chord, which could offer some amount to lateral resistance, I am not able to find a solid way to account for that. How do I ensure lateral stability check in this case? Do I ignore the resistance offered by verticals and diagonals? Let me know if you need more details?

Dear All,

I have the MATLAB files of the isolated benchmark building. However, in those files the building is modeled using its eigenvalues and no information is given regarding the columns, beams, and braces section sizes, spaces, and other data so that someone can use to model the benchmark building in another software.

I would appreciate your assistance if someone can share this information or can guide on how to obtain the data.

Regards,

I want to design a building with BRB. for modeling BRB in it I have two kinds of sections ("core brace" and "star seismic") when I use "star seismic" and define "Area of yielding core", after design, I found that the area that used, is about 4 times bigger than that I define. Do you have any idea about this problem?

and

for defining inelastic data for BRB, in the picture that I send, I do not know how should I fill it? and what does this parameter means?

thank you for your help

According to Eurocode 3, multiplanar KK-Joints have to be prooven for shearing in the gap between the braces. Do i have to do the shearproof for each plane or for the whole connection, or both? If for the whole connection, what is V gap? Some literature only uses the maximum axial braceload multiplied by sin(brace angle) other use both loads in the braces. The second approach is very conservative isn't it? What happens if they are asymmetricaly loaded? 

Hi all,

I have been modeling Buckling Restrained Brace(BRB) for more than 2 months, the analysis is aborting every time with following errors and warnings:

warnings:

1. 2 unconnected regions in the model ( I have been seeing this warning right from the start).

2. The system matrix has negative eigenvalues

errors:

1. Time increment required is less than the minimum specified

2. The analysis has been terminated due to previous errors. All output requests have been written for the last converged increment.

The modeling details are:

1. The core and casing is completely made with steel, with the combined hardening plasticity model.

2. Their is a gap of 12 mm around the steel core and steel casing(please see the second photo) with surface to surface interaction with penalty of 0.1 frictional coefficient.

3. One end is fixed and at the other end subjected to axial displacement increments and analysis out is attached below (U1 in third photo is in mm).

What I observed was as soon as the core touching the casing, the analysis will continue for short time and gets aborted.

Any answer is helpful.

Thanks in advance.

Hello

I intend to model a diagonal steel brace in an experimental model using the finite element method. Can anyone introduce a valid experimental model?

The model must have details of the dimensions and specifications of the materials.

I want to model buckling restrained bracing in SeismoStruct software but i could not find any resource on this. What type of element should I use as there is no direct element for buckling restrained bracing.

Please help.

Compare the three systems ( Fixed base, Base isolation, and Fluid Viscous Damper of braces corner) I need someone to help me with this system.

On what basis are the section size of the chevron brace and the SR (The ratio of the stiffness of the brace and the damper to the stiffness of the story) determined in design of the TADAS damper?

I am doing a non-linear time history analysis of my structure in sap2000. so when I assign hinges to diamond bracing I am facing the below issue. kindly help me to how to solve it. Thank you

I have performed a nonlinear static analysis in etabs for a steel braced frame. The pushover curve is linear and the model has shown any yielding. But the analysis has stopped before reaching the target displacement. I do not know why?

Please suggest what to do. Why the analysis is stopping if there is no plastic hinge formed before reaching the target displacement?

I am performing pushover analysis in Etabs of a steel braced frame but oI do not know what value should I use for target displacement. The height of the building is 20m. I want to know what value should I use according to ASCE 41-17?

Please help me to solve this issue.

I am trying to model a concrete-filled steel tube as bracing in my work. I am confused about how to model the plastic hinge for the brace.

Which type of plastic hinge should I use for this purpose?

Please suggest how to do it in sap2000 / etabs ?

Dear researchers

What are the primary defects associated with welding druring construction-stages which might influence the capacity of the gusset-plate connections in concentrated braced frames? (Considering the fillet weld, for example, can one quantify the capacity reduction of gusset-plates due to the presence of those flaws?)

Any reference, guideline, or research regarding the above issue which clarify the following would be good

- Different types of defects associated with regular welding types

- Can the effect of defects be quantified?

- Is there any mathematical distribution for each defect?

I am trying to model the shear-link in etabs for nonlinear time history analysis.

I do not know how to model the nonlinear behavior of this link.

Please help.

I am trying to model the shear link in sap2000/ etabs by I do not know how to model the web stiffened beam in this software because for the shear link we have to use web stiffness.

Please suggest how to do it.

I want to perform a nonlinear dynamic analysis of this model.

Dear all,

I was wondering if anyone can tell me how to get the viscous story shear resulting from Rayleigh damping of a component ( e.g., a brace) in OpenSees?

Thanks in advance.

Dear colleagues

I have experimental tests databases for steel structures (bracing and outrigger). If any of you have interest and specialty in this area can join our research group. We decided to include artificial neural network (ANN) combined with metaheuristic algorithm to estimate the results of experimental test.

I can share more information if you are interested.

You may contact me here or my personal email address:

s.k.k-co@live.com

I modeled a bridge on ANSYS APDL and added cross bracings / diaphragms as shown below. The diaphragms are not straight along the x or y or z direction, they are inclides BEAM188 elements.

how can I get the axial stress for inclined Beam188 elements?

Eccentrically Braced Frame building of 6 story modeled in SAP 2000. Conducting a non-linear dynamic response to earthquakes.

During Pushover analysis, the curve doesn't reach defined target displacement and the curve becomes almost linear when bracing is provided on the top floor.

Any Idea how to fix this?

For the modelling of inverted V bracing, I need to provide node at the center of the beam to create the inverted V bracing but if I am providing the node as a hinge, the model is not running. However, if I am giving it as a fixed connection, the model is running but in actual fixity should not be there..

I have modelled a steel building according to example 5 given in opensees in which I have provided cross bracing on each storey and I am two applying earthquake force one having scaling factor of 0.1 and one having scaling factor of 1. after performing the analysis the difference in their displacement is coming out very less which should not be in real because the difference of magnitude of earthquake is very high. So how to check were the mistake has been made. If I am removing the bracings from ground floor or from middle floor, I am getting correct values.

Are there any commercially available test system/walking simulator to test

(1) ankle foot orthotics

(2) knee braces

(3) knee ankle foot orthosis

There is a steel pipe rack with normal framing system including horizontal and vertical bracing systems, all the connections of the horizontal bracing are defected, for some reasons it is nearly impossible to re-weld the connections without a shutdown for the operation. What are the alternatives for horizontal bracing system? For example adding new members and removing the horizontal bracing members completely as in the portal framing which is an alternative for vertical bracing.

Practically, how to retrofit existing building with:

- Shear walls

- Base isolation

- Viscous dampers

Lateral Bracing

Kind Regards.

Hi I'm modeling a structure in opensees. Static linear analysis is modeled in opensees. The question is can i consider imperfection and buckling for my braced members or in static linear analysis it's not necessary to consider buckling of braces?

Dear all,

Currently I am doing a performance based earthquake analysis for a braced steel structure in SAP2000 using the nonlinear time-history procedure.To obtain the storey shears, I am using the -section.-cut method available in post processing. However it is seen that the link element could not be selected during the section cut and hence the obtained resultant forces are not correct. Kindly suggest me how to include the links in a storey as well in the computation of storey shears.

Actually for a project of FEA class, I need to perform FEA analysis for braces application. Please guide from where could I get the CT scans files. Because CT scan files can be converted to CAD model.

I'm working with my senior design group to create a customizable brace for PCL injuries. We are able to find general specs for fitting. We are looking for screw hole sizes to give us a starting point to help us join the pieces together.

Hello everyone!

I am new to abaqus and i am trying to model buckling restrained braces. I am finding difficult in modeling brace. As we know that the brace is composed of core (restrained and yielding), transition (restrained and unyielding) and end section (unrestrained and unyielding). My doubt is how to define these three elements having difference behavior in abaqus.

Thank you!

I have to validate my project for finite element analysis.

Dear researcher

I need to design the shear plate metallic damper connected to chevron bracing for retrofitting the reinforced concrete frame, So could you please provide me any reference or design procedure for this type of dampers.

best regards

Hi,

Could you please advise how to model an X bracing, in which the diagonals are continuous for their full length and are not connected at the intersection point in ETABS?

Please see attached picture.

Thank you,

Linh

If designer has two options of selection of one X bracing in one span or two Z bracing in two spans in steel structures, what are the advantages/disadvantages of using one X bracing in one span compared to two Z bracing in two spans in steel structures?

I'm working on the RCC bracing concept to reduce the displacement. using push over analysis through  Etabs V13. Do the bracing required to be assigned with hinge, if yes which book could I refer?

Is there any relationship available to relate brace angles and lateral displacement in steel diagrid building ?

I am looking for possible optimum brace angle which result in low lateral displacement.

hi iwant to model sma braces in opensees ,

do you have any examples of modeling sma braces in opensees?

Orthodontic treatment

In designing high-rise buildings, the three parameters of strength, hardness and stability are very important, and the higher the building is built, the greater the impact of hardness and stability on the optimal design of the structure, and the effects of these two factors, designed to design against the lateral loads of wind and earthquake, dominate They go back. The best way to meet these two factors is to use the forms and models of the structures, which, while maintaining hardness, reduce the structural stability by reducing the deformations and drafts resulting from the lateral loads. The steel frame system with truss belt and hinged bracing is one of the innovative and new systems in long structures, which use a significant reduction in the amount of steel used and the cost of building a tall building.

For a Structure say 15 meters high, 12 meters long and 12 meters wide and has 200mm*100mm I-section column with lateral bracing. The stages should include things such as concrete footing casting and curing, steel material preparation, time for connecting each steel members, installation of roof truss etc. and the help i am seeking is name of each stages duration, each stages take.

I am doing a project on buckling restrained braces in SAP2000. Hope you could help me how to model a BRB in SAP2000?

Lately i have been reading a lot of papers about BRB and their optimum configuration, but i can´t seem to find an article which demonstrate the concept.

I'm hoping someone can point me in the right direction.

I'm will appreciate a lot any help!!

sometimes there is problems with compliance for the FAB after Ponseti. so is there any alternative of FAB. any suggesssions, ideas

Can anyone suggest papers or any source where I can find experimental results of cyclic loading test of concentrically braced frames with X bracings and I sections as braces?

Instead of modelling a BRB using the nonlinear link option, can it be modeled using a frame elements with cross sectional dimensions so as to produce the same elastic stiffness and with an axial plastic hinge? I will be doing a nonlinear time history analysis of a braced frame with BRB. I have assigned flexural plastic hinges at the ends of the beam and columns to study their damages if any.

Will brace or orthosis usage improve cosmetic result after resection of rib hump? In case of idiopathic scoliosis surgery with multilevel fusion, apical derotation and thoracoplasty. Do you have expirience of using brace after same surgery in adult patients (about 40 y.o.)? What type of brace or orthosis do you use?

I am working on modeling the dynamic response of a steel brace frame by applying ground motion acceleration using ABAQUS. For the most part, the response that is observed makes sense. However, at points where the braces rapidly go from yielding in tension to a compression state, unexpected results are observed. At this points, the brace's axial load exceeds the expected buckling load by as much as 2 times.

i have 4 storey SCBF in which i have to give to properties of brace section as round HSS elements in opensees.

can anyone help me with the command to give section properties

i have 4 storey SCBF. I want to analyse it by opensees. It has chevron brace in middle bay

I am currently modelling 15 storey steel structure of moment resisting frame, X bracing and V bracing in ETABS to generate the the fragility curve of these structures. I am not sure how it is possible to check that structure going to fail, therefore I came up with the idea that add plastic hinges to my beams and column to find out if structure withstand with conditions I provided

I am trying to do a time history analysis of a Buckling Restrained Braced Frame (BRBF) using SAP2000. For time history analysis SAP2000 provides two options namely modal i.e. Fast Non Linear Analysis (FNA) and Direct Integration. I am in a dilemma regarding which one to use for the analysis. On one hand, CSI Knowledge Base claims FNA to be "generally more accurate and efficient than direct-integration time-history analysis" and on the other, on another page for Hinge FAQ it says that "FNA is based upon the mode-superposition method, intended for primarily linear-elastic systems which may have a limited number of predefined nonlinear elements."

Now I find these statements to be quite ambiguous.

https://wiki.csiamerica.com/display/kb/Hinge+FAQ#HingeFAQ-Whyareplastic-hingecolorsnotdisplayedwhenviewingFNAdeformation?

Also I have analysed the same frame employing both the methods, thereby getting different results. Please help.

We have 4 frames including intermediate steel moment frames, special steel moment frames,braced steel frames and concrete moment frames, which are designed based on the current seismic design codes. which one of theme has more strength and stiffness degradation under seismic loads?

thanks for your answers.

What is your opinion regarding using a seismic proofing system such as fluid brace damper or base isolator for residential house either single story or and apartments?

I'm a student researching about damper application in small scale project such as residential house

Skeletal trauma leads to pain and discomforting positioning often with cumbersome braces/splints/plaster etc. How it affects sleep quality. That might also be contributing to various I'll effects in future.

I was recently trying to model a BRB using SAP2000 by defining axial plastic hinges at either ends of the brace. But the problem that I am facing while doing pushover analysis is that the brace is buckling in compression and hence achieving much lower axial strength than what it is having in tension. I have also referred to the paper : Karimi, M. R. B., Yaghin, M. A. L., Nezhad, R. M., Sadeghi, V., & Aghabalaie, M. (2015). Seismic Behavior of Steel Structure with Buckling-Restrained Braces. World Academy of Science, Engineering and Technology, International Journal of Civil, Environmental, Structural, Construction and Architectural Engineering, 9(4), 488-496. But could not solve the issue. Can anyone help?

in the PhD thesis (Tremblay, 1993), it is presented a brace frame that dissipate energy through friction instead of yielding and buckling, but in the literature such as in the book " Principles of Passive Supplemental Damping and Seismic Isolation" it is presented as a friction damper.

I tried shear hinge using FEMA 356 table parameters but my calibration with actual test experiment is off for cyclic loading. If I am concerned about nonlinear shear behavior of my member, still P-M3 Fiber hinge would work? I believe it takes shear behavior elastically if we assign fiber hinge. I tried this as well and assigned a moment - rotation curve but it its not calibrating. For example, if I am looking at shear link member in eccentrically braced frame. Do you have a recommendation to get good hysteresis using particular type of hinge in SAP 2000?

How can model the fracture of braced frames  in opensees by the picture attached?

I want to assign the fracture model in Fig.7 to the green and blue spring

I try to model the BRB in ABAQUS, and I now I get the results, but the hysteretic curve just looks like that of ordinary brace since the brace buckles when compressed. Do anyone know why? In the model, I use the surface to surface to represent the interaction between the core and the restrained segment,and when I use frictionless model the curve looks good while I use friction model with coefficient of 0.05, the curve implies that brace buckle when compressed. And I do not figure out why. Can anyone do me a favor to work this out? Of course, possibilities that many problems with my model needed to solve exist.

hello, am trying to model a braced frame which has columns and beams of shell elements(s4R) and the brace as a truss element(T3D2),  how can i connect them with a pinned condition at the end of the brace?

Present is a 6 mm overbite with one top incisor rotated due to overcrowding.  Bottom incisors are also overcrowded.  The mandibular arch has a deep curve of Spee.  No cross bite.  Currently using Damon III braces top an bottom with class iii elastic.