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Seismic Design - Science topic
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Questions related to Seismic Design
If anyone has data on the issue, I would greatly appreciate it if you could share it with me.
KAGRA is said to be less sensitive to claimed LIGO type gravitational wave signals by two orders of magnitude as compared to the LIGO/VIRGO detectors. After KAGRA has substantially improved their seismic suspension systems it rather appears likely that KAGRA was successful in reducing the level of crackling noise* by two orders of magnitude and thereby increased the signal-to-noise ratio by two orders of magnitude.
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
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.
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.
When we put a large lateral force on the top level of a pillar it will be overturned.
When we put the same force on the top level of an elongated wall it will not be easily overturned. Here we see that the width of the wall reacts to the overturning more than the pillar.
Height is another factor. The higher we apply a force to a column, more easily the columns and walls are overturned.
The deformation of the trunk of the pillar due to bending is greater than that of the wall.
So a wall does not tip over easily and does not bend easily.
The wall does not intersect easily.
Its resistance to the shear of the base increases by 40% when we impose on its cross section compressive forces of the order of 70% of the breaking point.
The imposition of compressive stresses on the cross section increases the stiffness of the wall, ie the trunk does not bend or deform easily.
The overturning of the wall stops with the anchoring of all its sides to the ground.
The anchoring of all the sides of the walls to the ground and the imposition of compressive forces on its cross section ensures that the correct forces (N) (compressive and tensile) of the wall will be deflected into the ground.
The moments (M) in the cross sections around the nodes will be minimized.
The cross-sectional response to the base intersect will increase by 40% and the intersections (Q) will be eliminated.
Deformation and damage will be minimized and the bearing capacity of the construction will be increased.
We know that the potential difference, the critical failure area, as well as the extraction and detachment of the steel reinforcement bars, due to the reduced strength of the coating concrete in shear, and the ultra-tensile strength of the steel, are fragile properties of the concrete-steel cooperation mechanism, that of affinity. In pre-tensioning these brittle properties do not exist.
In prestressing, steel exerts only tensile forces and concrete compressive forces and there is no shear failure on the concrete and steel surface.
I also zeroed the eigenperiod after controlling the displacement of the floors in each seismic charge cycle using external forces coming from the ground.
The anchoring I ensure with deep ground anchorages and piles provide a stronger foundation.
In a few words I solved the problem of the earthquake.
Anyone who disagrees let me explain the reasons.
It will help me improve the seismic design.
Experiments
As I suggest the seismic design
As civil engineers plan, anti-seismic today
Can you suggest me the research gap for the further work in the seismic design and analysis of buildings in hilly region using STAAD Pro/SAP2000?
Good morning,
I am trying to analyze a 2D four-level frame structure that is formed by concrete columns and concrete beams. The original building from where I obtained the frame is a university structure here in Perú. I considered the sections and reinforcements according to constrution plans.
I used user defined hinges that were created by a moment-rotation analysis considerating concrete and steel models. I consider a certain level of axial load in order to obtain moment-rotation diagrams in columns. I didn´t use any automatic hinge definition (ASCE or FEMA) because I would like to obtain results acordding to my own constituve models. I created different hinges for columns and beams and I placed them in every extreme side in columns and beam and in the middle of beams.
The seismic record is Lima 1974 earthquake and I scaled it to a 0.45g aceleration that belong to the maximun aceleration in peruvian seismic resistant norm. The original unit of the seismic record is cm/seg2. I think this is a good level of earthquake in order to generated an inelastic response in the hinges. For that reason I used a scale factor of 0.0247 that means to convert the units cm/seg2 to m/seg2 (x 0.01) and I also considered the value of 2.47 to scale the maximun aceleration of the seismic record to the value of 0.45g. At the end, the scale factor results in 0.01 x 2.47 = 0.0247.
In the nonlinear time history case I also used a initial nonlinear case in order to obtain more degradation (Gravity loads). I also defined geometric nonlinearity parameters in order to obtain more displacements.
The problem is that I didn't obtain a good strength degradation of the hinges and they seem to have a elastic degradation response. For that reason, I ask for your help because I don´t find the problem in the model definition. I check my moment-rotation diagrams and don't have any problem or error.
I would apreciated some help and I share the model definition with all the things that I defined in the analysis.
Thanks.
In the seismic design phase of reinforced concrete buildings infilled with masonry either by brick (solid or hollow) or by concrete block (solid or hollow), with the existence of shear walls, we need to know the appropriate value of the behavior factor for this interaction of systems.
My question is what is the value to be taken for the behavior factor in case of seismic analysis of this type of buildings to evaluate their seismic response according to the famous world seismic codes.
Seismic design takes advantage of larger damping owing to structure ductility to reduce the design load by R factor (of 3 to 8 value). Apparently, both seismic and wind governing loads are derived from similarly rare event at about 500 years return period, although some recent codes use 2/3 of MCE 2500yrs for seismic. But why only seismic design allows some structural yielding and acceptable damage, while wind design should remain elastic? Is there some concept that I misunderstand?
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 tall building structures performance based design has been used. Which code provides performance based design more precisely seismic design of tall building structures with outriggers?
A scientific method must prove the results experimentally
The scientific method begins with the "observation" of one or more natural phenomena which are constantly repeated and we take them for granted.
The following is a hypothesis of a model based on the "observations" we have made before, examining new data resulting from the synthesis of the natural phenomena of the hypothetical model.
Then we examine <experimally> the data resulting from the synthesis of the natural pThe more experiments and hypotheses are repeated and agreed upon, the more the approach to reality and truth is enhanced.
I noticed that
1) If we screw an object on the floor it does not tip over.
2) If we compress a stack of unbound books then we can move them without breaking the stack even in a horizontal position.
3) I noticed that a part of an iron scaffolding alone can not even stand upright, while if we connect it to another with a cross link it is very difficult to overturn.
4) I noticed that when we lift a car with a mechanical jack on soft ground, first the ground recedes until it condenses and then lifts the car. I also noticed that as long as the jack lifts the car it is impossible to pull it out and take it out from under the car by hand.
5) I noticed that when the branches of the trees bend in the elastic area, one side of them stretches and grows and the other side of them compresses and shrinks. But I noticed that if you put a string in a shooting bow it loses its elasticity in one direction, and if you join the two bow bows together they become rigid.
6) I noticed that a wood rod before it breaks has an elastic deformation in which no cracks are observed, and if we remove the force that causes the deformation, the rod will return to its original form.
7) I noticed that the trains have front and rear springs or hydraulic systems to absorb the stresses that develop when they collide with each other.
I take these <observations> for granted because they are constantly repeated in our daily lives.
Based on the above data <observations> I constructed a <hypothetical> seismic model which mainly aims to stop the inelastic deformation of the vertical structural elements of the structures, as well as their total or partial overturning.
The constructions consist of the vertical and the horizontal structural elements of the bearing organism, which are joined in the nodes and necessarily the deformation of one is transferred to the other.
Deformation of the joints can occur either from the tendency of the columns to overturn, or from the bending of their trunk. If the bend is within the elastic range there is no problem, so we must prevent inelastic displacement and tipping moment if we do not want failures.
1) I stopped the overturning moment of the walls by joining their base to the ground.
2) In order not to cut their trunk near the base by the abrupt displacement of the ground (cutting base) I imposed compression on their cross section.
3) I used walls instead of pillars so that they do not tip over easily and put a lot of strain on the mechanism of the anchoring in the ground. To have a reversal reaction in both directions of displacement caused by the rocking of the earthquake, I anchored the sides of the wall to the ground on both sides.
4) I made a similar mechanism like the mechanical jack of the car, which under hydraulic traction expands and tightens firmly in the ground at the depths of a borehole to then anchor with the help of a tendon the base of the wall to the ground.
5) In the rigid wall, in which in its cross section there are imaginary, the two joined arches, I applied pressure on its two sides with tendons without relevance to stop its inelastic deformation.
6) By imposing compression on the cross section of the wall, its elasticity is not lost and it does not form cracks.
7) To help the cross-sections of the walls to receive part of the elastic stresses, removing these stresses from the anchoring mechanisms, and on the other hand to smoothly and not abruptly dampen the stresses of the mechanisms, I placed a hydraulic system on the upper part of the tendon. or a spring or a tire.
Experiments
I did two separate experiments with the same experimental model but under different conditions.
The first is prestressed and packed with the seismic base and the second simulates the current seismic design.
With my own design method
With the trampled method.
The conclusion is yours to make.
The strengths of the mechanism in different sizes, placed at different depths and types of soils, remain to be investigated.
Anchoring the mechanism to the rock is considered safe.
For the reduction of the deformation as well as for the cutting base, there are the very good results of simulation and numerical investigation which were done (and I have them) in the anti-seismic research laboratory at the Technical University of Athens by Professor Manolis Papadrakakis and his then assistant Vangelis Plevris.
According to modern regulations, the seismic design of buildings is based on the ability requirements of the correct design of the nodes and plasticity.
The (inevitable) inelastic behavior under strong seismic excitation is directed at selected elements and failure mechanisms.
In particular, the incorrect design of the nodes and the clearly limited plasticity of the components lead to major failures.
1) The philosophy of the correct design of the nodes of the regulations is characterized by the appropriate dimensioning of columns-beams so that we have plastic joints in the beams and not in the columns so that we do not have immediate collapse.
Question right or wrong?
Answer
Without the inelastic behavior the bearing would not show plastic joints in the beams.
I believe that displacement control is better than what they apply today which is nothing more than the management of inevitable inelastic displacement and failure.
Displacement control means no failure no plastic joint
It basically means controlling the deformation.
Deformation control also means control in failures since deformation and failures are directly connected.
If you do not have the ability to control the distortion then you manage it with the proper design of the nodes and that is good.
But being able to control the deformation of the construction is better.
2) The plasticity of structural elements and structures made of reinforced concrete is characterized by their ability to deform beyond the leakage limit, without significantly reducing their strength
According to § 5.2.1 of EC8 there is a design option of the available plasticity of the building.
Reinforced concrete buildings can be studied with two different design methods.
a) To be designed with the necessary ductility which means to have the required - necessary ability to consume seismic energy, but without losing their resistance to all loads during the rocking of the earthquake.
b) To be designed with low ductility, with low energy consumption, but with very high dynamics. The ductility or interoperability of the structural elements and nodes (exists) is achieved with the existence of the appropriate reinforcement, the construction devices, the proper dimensioning and the limitation of the axial loads to some limits.
Plasticity is a critical factor for seismic constructions for many reasons.
At the carrier level with inelastic analyzes you also find the levels of plasticity that the construction can develop.
Question right or wrong?
Answer
If the seismic energy (measured by ground acceleration) is too large, it will produce excessively large displacements that will cause a very high curvature in the vertical and horizontal elements.
If the curvature is too high, this means that the rotation of the sections of columns and beams will be well above the elastic area (Compressive concrete deformation over 0.35% and reinforcement fiber stresses over 0.2 %) beyond the leakage limit.
When the rotation exceeds this limit of elasticity, the structure begins to "dissolve the energy storage" through plastic displacement, which means that the parts will have a residual displacement that will not be able to be recovered (while in the elastic region all displacements are recovered).
Basically the design of the strength of a current building is limited to the limits of the elastic design range, and then passes to the default plastic leak areas, which are default areas of small and many leak failures, (usually designed to occur at the ends of the beams) so as not to collapse the structure.
This is the mechanism of plasticity that consumes seismic energy.
(Structure collapses when oblique / failed columns fail)
If the parts that experience the plastic deformations exceed the breaking point limit, and there are too many on the structure, the structure will collapse.
Basically, plasticity is achieved by placing a dense reinforcing connector at the ends of the elements because this helps to create many and small cracks, avoiding the creation of large catastrophic cracks.
Plasticity is directly related to the cooperation of concrete and steel (mechanism of relevance)
The most serious problem of relevance is created by the ultra-tensile strength of the steel, which turns the failure into a shear form, which is extremely brittle. When the shear stresses in the steel concrete interface reach their limit value, the correlation is destroyed in the form of concrete rupture.
Part of the reduction in stresses is achieved by increasing the overlap and reducing the diameter of the reinforcement bars. The increase of their limit value is achieved by increasing the strength of the concrete. The presence of transverse reinforcement acts favorably by restricting the opening of the developing cracks.
3) The columns or walls are rigid and flexible. It depends on the cross section in relation to the height and the beams that are connected etc. (Frames etc)
Question right or wrong?
Answer
Yes it is right ... the relationship between the height and the size of the cross section determines whether the elements are rigid or flexible.
But there are other factors such as the cross-sectional shape factor. A square column cross-section is more flexible than a cross-section of the same size which has the shape of a cross, angle or wall.
So we can design rigidly with walls if we want.
The walls may be located around the perimeter of the building (excluding shop facades) surrounding the stairwell and the elevator (strong cores) and may be internal walls (eg partition walls) throughout the height of the building. The installation of many strong walls implies, of course, due to their great rigidity, a significant reduction of the fundamental eigenperiod of construction. This, in combination with the view q = 1, leads to a correspondingly large increase in the seismic loads of the structure. However, it should not be overlooked that precisely because of the many and strong walls the strength increases more or conversely the cross-sectional loads decrease despite the increase of seismic loads.
Due to the fact that the wall has a double lever (that of height and that of width) the axial forces (kN) are smaller than they are in the column.
4) The diaphragm function ensures approximately the same movements of nodes in a plane (in a horizontal direction) which has the effect, among other things, to facilitate the analysis in space taking into account three degrees of freedom instead of six if you do not have a diaphragm. We should not confuse them with the walls. The coexistence of walls and columns is the most suitable formation for seismic structures made of reinforced concrete and especially for structures with many floors.
Question right or wrong?
Answer
Yes, correct for the diaphragm function of the plates.
The walls also have a diaphragm function under certain conditions. If the width and height do not have big differences then yes, and the walls are of diaphragm function. If they are both prestressed and anchored to the ground, then they are super diaphragmatic.
If you combine the diaphragm function of the slab and the compacted and prestressed walls, you have achieved complete rigidity, with zero same period and zero deformation which means zero failures.
Why Moment Resisting Frame Drift is more than Shear Wall Frame Drift, if they are in the same Seismic zone and the same quantity of material?
- Analyzing two Models ( Moment Resisting Frame and Shear Wall Frame) by Etabs.
- The same property and the same quantity of materials.
- Analyzing both Models in the same Seismic Zones.
- Both Models are the same geometry, the same height and Floors.
My question is:
Why Base Shear and Drift in Model of Moment resisting frame provided more than in Shear Wall Frame?
The current technology of seismic constructions likes to recycle the seismic rocking intensities, derived from the magnitude of the ground acceleration and the mass of the structure which generate the inertia intensities that cooperate with the seismic duration and the resonance multiplied in bearing elements and break them.
The big mistakes of modern seismic design are two.
1) They recycle the tensions of the earthquake on the cross sections of the bearing body
2) They send the intensities on the small cross sections instead of deflecting them on the large ones which are stronger.
A small cross section is one formed by the width and thickness of the element. A large cross section is one formed by the height and width of the element.
The design I suggest is different.
1) I use the large vertical and strong cross-section of the wall to transfer the compressive forces, deep into the ground through the anchoring mechanism of an anchor.
2) I use a tendon anchored to the ground and extended to the wall in order to deflect the tensile stresses of the other side of the wall into the ground.
3) I use concrete to receive compressive strengths whose specifications are excellent, and steel exclusively to receive tensile strengths.
This design deflects at each seismic load the inertia intensities (before being transferred to the small cross-sections of the beams and breaking them) into the ground, before they multiply over time and before construction and ground coordination occurs.
Plan
( Γ ) = Rolling torque
( A ) = Ground acceleration
( B ) = Inertia intensities
( 1 ) = Intensions compressive stresses
( 2 ) = Tensile strengths
( 3 ) = Diversion of tensile stresses in the ground, through the tendon 3
Άρθρωση = articulation
1 = Diversion of compressive stresses through the cross section of the wall and the anchoring mechanism, deep into the ground.
If there is no anchoring in the ground 3, then the wall rotates Γ, around the articulation, transferring the stresses to the beams where the walls are connected to them, through the nodes and break them.
Experiments.
When tensions are allowed in the ground no problem
When tensions are recycled around the nodes then big problem!
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.
How petrophysics can complement magnetic data discussing of structural geology, mineralisation, geology lithology
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.
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.
Based on ASCE7-10 provisions, seismic forces are calculated based on 2% probability of exceedance within a 50-year period (a mean recurrence interval of about 2475years). Due to the short remaining lifespan of the existing building which results in a relatively low probability of extreme load exposure, the use of these values for design may be excessively conservative.
I went through FEMA-356 and FEMA-440 for target displacement and I cam across the formula as well but it wasn't helpful as i'm not able to understand it completely and I wasn't able to find all of the coefficients. It would be great if i can get a solution for that.
Hi,
Equivalent viscous damping ratio is an indicator that is often used for the analysis of seismic performance of masonry walls.
Two definitions are frequently used (see attached figure) :
- Definition 1 (Priestley et al. 1996)
- Definition 2 (Magenes G, Calvi GM 1997)
Please, can someone explain the physical meaning and the difference between the two definitions?
Hello Khalil,
The common method for defining Equivalent viscous damping is to equate the energy dissipated in a vibration cycle of an actual structure and the energy dissipated by an equivalent viscous damper.
The energy dissipated in a vibration cycle of an actual structure will be the area under the hysteresis loop. Whereas, the energy dissipated by an equivalent viscous damper will be the area under the ellipse as shown in the attachment. In the attachment, I have assumed symmetrical behaviour in push and pull.
The concept of viscous damping is generally used to represent the energy dissipated by the structure in the elastic range. However, energy dissipated by the structure in the inelastic range have also been modeled as equivalent viscous damping in some research. That's why the definition varies.
My "Concrete Damaged Plasticity" model in ABAQUS can't simulate the behavior of reinforced concrete structures in cyclic loading.
In university sir gave me assignment to write proposal on this topic(Energy dissipation devices for seismic design).somebody help me
Does some have got the commentary of the American norm ANSI MH 16.1: 2012? according to this norm the seismic design of the steel rack could be performed using R=4 as behavior factor, this value seems to be too high. A rack structure should not have enough plastic resource. Should some over-strength factor be taken into account in the design of the connection?
waiting for your answer
thank you very much
best regards
I need to impose equivalent static seismic method to an structure landed on a soil block in abaqus. Does any one have idea how to do that? I am using some other load cases in a linear perturbation step and I'm intended to combine earthquake induced forces with these load cases. There are some other ways to do a seismic analysis: like extracting eigenfrequencies in a frequency step, followed by a response spectrum step and finally a dynamic analysis step. But as I said, I have some other load case in a linear perturbation step and in this step type there I could not find any way to impose earthquake load.
I need to asses what would be the consequences of earthquakes over a cylindrical water tank embedded in soil (roof is at the surface of the soil).
I was wondering to do a spectral response analysis but does this makes sense if the whole structure is below the surface?
What analysis can I do over the structure to asses seismic risk? Any recommendation is appreciated!
Most building codes require the following elements to be designed for VERTICAL seismic excitation:
1. Cantilever more than 5m span
2. Beams more than 20 m span
3. Pre stressed concrete
I can understand why the first two elements shall be designed for vertical excitation. What I want to understand is why pre stressed concrete is supposed to be designed for VERTICAL seismic excitation?
Please help me.
I am looking for a copy of the original Mainstone paper for masonry infill macro-modelling
"Mainstone 1971 - On the stiffnesses and strengths of infilled frames, Proceeding of the Institution of Civil Engineers, Supplement IV, pp. 57-90"
On the ICE website only the abstract/summary is available: https://www.icevirtuallibrary.com/doi/pdf/10.1680/iicep.1971.6267
The model is widely used and referenced to, however multiple versions and definitions of the equations can be found in the literature and it would be interesting to have a look at the original text.
Dear Colleagues,
I want to use a damper in order to reduce the effects of earthquake, blast or wind forces on the timber structures. However, I wish to use the most suitable damper in this regard. On the other hand, timber structures are usually susceptible to damage at their connections during strong forces. What kind of damper is the best choice and also what are the effects of using this damper on such connections?
to calculate the damage index, I need maximum and ultimate ductility but I don't know from which option in software ETABS I can find both the values.
the building model is following Eurocode EC8. The query is that by increasing the value of behavior factor, will the roof displacement of the model will decrease or increase?
Building exhibit torsional rotation under seismic loading due distance between the center of mass and center of rigidity. According to building codes, does this distance or torsional rotation have any limitations? And if not, how could I check the capacity of building for large torsional rotation?
Could the layout of the shear walls in multi story building induce torsional rotation due to dead load only?
I faced this problem when analyzing a building in Etabs.
Thanks
Seismic Design: How can I perform rigorously the SAP/ETABS analysis of the building constructed using "interlocking bricks technology"?
During earthquake,what mimimum value of Surface PGA can be expected to cause damage to any poorly constructed building in India?
hello
I need some information about the production process and material properties of seismic base isolators .e.g. LRBs (lead rubber bearings). I'd really appreciate it if you could share this kind of documents if you have any.
How can we apply earthquake time history, (time vs acceleration) non linear dynamic analysis on simple frame of steel to get the inter story drift.
while designing structures to Eurocode 1998( seismic design) the normalized axial load( Ned/fcd*b*h, where Ned is Axial load, fcd is design concrete strength, b and h are cross sectional dimensions of column) is limited to 0.65 and 0.55 for medium and high class ductility structures respectively.
What is not clear is, the axial load(Ned) should it be taken from factored gravity load combination(1.35Gk+1.5Qk) or seismic load combination( Gk+(phi)Qk+Ved(seismic load))?
Please clarify this for me.
In some tall building due to architectural aspects, some columns do not continue to the foundation. Hence, to transfer all force due to gravity and lateral loads to the base, application of concrete transfer slab is inevitable.
I would like to know if "2008 NYC DOT seismic design guidelines for bridges considering local site conditions" is implemented in practice or not. If anyone has some information regarding this it will be really helpful.
1. How can we develop diagonal strut in Sap2000 or etabs?
2. what are the basic to govern while conduction analytical method?
3. what properties are to be govern while examine the benefical effect of masonry infill?
Seismic researcher who using Etabs can give me a guide.
Hi there , want to ask why Etabs always get the same maximum story drift even if I changed the ground motion scale factor from 1 to 20 , or even i changed the other ground motion from PEER , is it I'm doing anything wrong or need to modified the stiffness , hope to get some guide from here.
Hi There.
It is of appreciation if you could provide us some references, underscoring that the drift ratio yardsticks for the different levels of performance, posited in TBI-V2.0-17, named "Guidelines for Performance-based Seismic Design of Tall Buildings", must be employed once dealing with the overall lateral deformation of a superstructure, including the structural distortion and the foundation rocking.
Regards,
Navid
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!!
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?
SeismoStruct and Opensees programs.
I am currently doing research on pipes subjected to a variety of static loadings and dynamic excitations. Do you know of any source to seismic design of above ground pipe?
Thanks
I have been working on Static Structural, I have my model, meshing and supports ready, but as design guide says I have to put on forces in each nodes associated to translational masses.
I think translational masses is not necessary because I already have the model as solid(with its mass), but I don't know how to put every force in each level nodes. Maybe I could create a distributed force. Make suggestions please.
thanks
The design response spectrum provides a general procedure to estimate the expected dynamic load on a structure which is expressed as a function of natural period. Thus knowing the period of the structure, design load could be calculated. It well known that the deterministic (DSHA) and probabilistic (PSHA) seismic hazard maps provide prediction of peak ground acceleration and ground motions for a specific site. As per NEHRP guidelines, design response spectrum is developed from the PSHA framework. The 2% pr 10% probability hazard level can be used for development of design response spectra which is actually satisfying a MCE level condition.
The accuracy in determination of PSA is very important in calculating the final shear load. Could you explain how to estimate such value for a given site?
How to calculate spectral acceleration (design acceleration) for the each type of site class?.
Read section 11.4 of ASCE 07-10. It is explained there clearly.
In following file you can see spectrum energy.
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.
In statistical and probabilty anslyses we are asked to compute error and uncertainty curves and values.
Do you think there are absolute fixed error or uncertainty? Do we reach the time to say what error exist in our answers?
all the codes that I could find, are usually talking about static loads, none of them is giving specifications about seismic loading. could you please suggest me how and where can I find the related content.
dear mohannad hussain
this Eurocode just gives the general guidelines about silos, not the specific ones. what actually is m searching for, is how to first calculate the time period of a particular silo and how to proceed thereafter. for example, if you see in IS1893: PART4 (2005), It asks to calculate the time period according to rayleigh's approximate formulation but that formulation given in IS is basically for the lumped mass system which is not the case for silos.
Please see the attached image of the excerpt from IS CODE.
without providing dampers , if one wants to use purely structural elements in tall building for seismic zone, & if architectural design is such that transfer plate is needed, how is the performance of such building ?
The value of amax/g can be computed using by the following methods
- basic seismic coeffiecient method
- Response Spectrum Method,
- IIT K -RDSO(Z*I*Sa/G),
- In explanatory note by IIT-K Z is used.Also Z for DBE is Z/2
Can all methods be used.Also it is written IITK-RDSO GUIDLINES are not binding for seismic design of bridges.
The value calculated by basic seismic coeffiecint is very less as given by IITK-RDSO Guidlines.
Also can liquefaction analysis be performed for DBE (DESIGN BASIS EARTHQUAKE)?
hi
I'm modeling a tank in ABAQUS under the earthquake excitation which is half filled with water. for verification purpose I have to compare my time history output with a paper. at the middle of the long side wall I've got sloshing height time history and on top of it acceleration time history. the sloshing height time history is correct according to the paper...but it is odd that acceleration is not...it has the same shape but its magnitude is half of the paper's time history
what could be wrong? could it be because of the damping? or maybe something els?
Why vertical ground motion is not used generally in time history analysis of the structure?
For instance, Uniform Code of Building Conservation (UCBC).
Dear Friends
How can I download the book "Seismic design of storage tanks: recommandations of a study group of the New Zealand National Society for Earthquake Engineering"?
I need it, but can not get it. please help me.
I am working on Intake tower which is 62.50 m height. I would like to calculate fragility parameters from push over analysis corresponding ultimate displacement. i have pushover curve of SAP 2000. Is there any tools (Excel or MATLAB or others) that can directly calculate the fragility parameters from pushover analysis?
Can we analyse the bridge using linear time history when base isolators are provided?
Working of Isolators and dampers sound very similar but in practice when are we supposed to use an isolator and when a damper. What is the exact difference between application of both.
Hello,
Please, share your experiences in microsesimic data acquisition with 'Model L-4 -3D Sensor Sercel Inc. Huston Texas.
The objective is the microsesimic monitoring of a field scale unstable slope.
I have a title for my report which is SELECTION OF GROUND MOTION INPUTS FOR SEISMIC DESIGN. I know that there are two different ways for example time history analysis and response specturm but there are some titles that I dont understand and I do not know if they are related to my topic or not such as collapse analysis, modal spectral analysis , mathematical fomulation based analysis , modal analysis and also linear and non linear analysis. if someone please can explain me the relationships of the keywords above and their connections together I will be thankfull.
I have to prepare a design manual for seismic resistant stone masonry school building with mud mortar and timber frame structure. Roofing will be wooden or steel truss with CGI roofing.
If you have/know such document and design calculations, please help me by sending it to me for reference.
Thank you all..
which generally produces torsional mechanism during EQ?
I can't use steel braces.As far I know the options are R.C jacketing,FRP wrapping and the addition of shear walls.Since its open front will retrofit of exterior columns will be enough for seismic improvement of the building.
My goal is to obtain the spectra of earthquakes: frequent, occasional, rare and very rare. The problem is that Latin American codes just define the spectrum of an earthquake with 10% probability of exceedance in 50 years, which would correspond to rare earthquake according to VISION 2000.
So, how can I get the remaining seismic spectras: frequent, occasional and very rare? Is it correct to scale the spectrum of the rare earthquake?. Conservatively, what scale factors would you suggest?
(Please mention your source, code or etc.)
Attached seismic performance objectives proposed by VISION 2000.
I am working on a project, and I have found that the displacement resulted from a high frequency earthquake is less than the displacement resulted from a low frequency earthquake. Does it make sense?, does it depend on the energy content?, and How?
Any literature on the the subject below?:
Effects on the responce of an Infilled RC structure (local or/and global) in case of placing horizontal zones of lightly-reinforced concrete in the middle height or near the top of the infill masonry wall, when subjected to seismic action.
As you know better ,ASCE -7 SEC. 12.4.4 says:
“In Seismic Design Categories D, E, and F, horizontal cantilevers are designed for an upward force that results from an effective vertical acceleration of 1.2 times gravity. This design requirement is meant to provide some minimum strength in the upward direction and to account for possible dynamic amplification of vertical ground motions resulting from the vertical flexibility of the cantilever. The requirement is not applied to downward forces on cantilevers, for which the typical load combinations are used.”
It is supposed that vertical acceleration is 1.20 g , my question is :
if this acceleration is upward and downward so why does not ASCE have this combo.
UP >>>>> 1.20g -1.0g = 0.20g
DOWN >>>>> -1.20g -1.0g = -2.20g
When we are considering the seismic response of vehicle, If we use the general equation of motion that we use during the analysis of structure with spring and dashpot, it will be the same result but I think for vehicles it will be different! The Orientation of the vehicle also plays the role on its' response!
Hello anyone!
I am reading some papers relative circular tunnel, but i don't know about no-slip and full-slip condition. Could anyone explain detail to me?
Thank in advance!
Some papers of Youssef M.A Hashash that I read:
1. Ovaling deformations of circular tunnels under seismic loading, an
update on seismic design and analysis of underground structures (page 347)
2. Seismic design and analysis of underground structures (page 270).
Which seismic parameters should I compare for building provided with composite and RC column with different cross section.
how can in simulate microseismic signal strength at different locations around a passive source in claly material using particle swarm optimization.
I am looking for a Canadian equivalent to the EPA document titled : "RCRA Subtitle D (258) Seismic Design Guidance for Municipal Solid Waste Langfill Facilities". If you have any other equivalent standard of pratice please write it down. The goal is to find the different static and seismic design parameters for waste landfill regarding slope stability and liquefaction assessment during filling and post-closure conditions.
Thanks for your help.
For seismic retrofitting, RC beams are retrofitted by external reinforced bars
How can they be placed?
Hi,
Our team of researchers are doing Linear Dynamic Analysis of Overground Water Tanks in SAP2000. We will be highly obliged if anyone can point out any issues that we need to address before and while doing such analysis in SAP2000. One issue that we are observing is the Mass Participation in the Modes and the total mass participating upto as high as 200 modes is still less than 85% of the total mass of some structures.
Thank you in advance.
Dear researchers;
Can any one suggest me some papers on the seismic retrofitting of damaged buildings using damping devices? I'm not finding a lot of papers on this problem.
Regards.
What is the accurate procedure to model or determine the minimum mass that a pile embedded in sand (with 3.65 m length and 0.9 m diameter) can support?, in order to obtain a lateral deformation less than 1 m, during lateral dynamic loading -under regular seismic acceleration values.
Is out there any software available to determine the resonance of a predetermined mass? In order to test different masses until we can get the desired deformation?
I will appreciate any information or advice that you can give me. Thank you very much for your help!
Best Regards.
Dear researchers;
if a structure is damaged by an earthquake, stiffness K and damping C parameters of some floors are reduced by 0.7 or 0.8.
how can I say that I retrofitted this structure to resist against a future earthquake ?
what should change between the damaged and the retrofitted responses of the structure ?
what are the parameters that the retrofitting should affect ?
Best regards
Take for instance an isolated structure.
1. I know the modal damping ratios of the corresponding fixed superstructure.
2. I know the equivalent damping ratio of the isolation system.
How do I combine this information to built the damping matrix of the isolated structure, which will be non-classical ?
Thank you in advance!
how can i measure the seismic capacity for a high rise building
How can I choose the moment for design the beam at support and midspan? and how is the reinforcement detailing?
for calculating the earthquake load of a steel structure I need to know the system of building. but how can I understand that is it MR frame or not?
What I'm searching for is some information/publications concerning the influence of the geometry (pier- / spandrel aspect ratios and opening sizes) on the seismic behavior of URM walls with openings under in-plane loading.
what is the precautions in analysis and design buried underground water tanks which will prevent uplift under seismic load ? with the effect of soil structure interaction ?
I’m modeling masonry infill panels with diagonal strut in order to study the seismic behavior of a frame building but I have some confusions. (I’m using sap2000)
When I want to run modal analysis I use just one diagonal strut to model the panel so as not to overestimate the global stiffness, then I use obtained modal displacements to distribute the lateral base shear (per mode) along the building height.
The problem is when I want to run analysis under lateral forces, it is necessary to replace the panel by two compression diagonal struts because the forces applied on floors have different signs. I wonder if calculated displacements can be correct even with two bars, because it seems that the global stiffness has changed so the displacements must be modified… Otherwise, is there any way to solve the problem when building is subjected to horizontal seismic forces with different signs?
my work is about seismic analysis and design for urban tunnel lining using Mida GTS , I didn't find any thing about Midas GTS as for unimerical analysis and monitoring for seismic design
I mean the beta which is popular in reliability-based designs. But I couldn't find any specific value for earthquake loads and different performance levels. It would be great kindness to introduce helpful references.
Thanks in advance
Does anyone have a reference about a matlab code for inelastic response spectra (nonlinear parameters)?
Dear researchers,
I'm using state space toolbox in Simulink to solve multi degrees of freedom equation of motion [multi story building under seismic excitation], and I'm introducing a MR damper force, I want to use multiple dampers this means multiple forces, but the state space toolbox admits only one values of the force as input !
Since the force given by the damper is specific to each floor, I can't apply the same force on all the floors [using a distribution vector], this means each floor needs to receive his specific force generated by his specific damper.
How can I do that? How can I input multiples forces in a state space resolution ?
Best regards
Thanks in advance for your replies.
Can we determine Yield Acceleration (Ay) or Ductility Reduction Factor (Rµ) without Pushover analysis?
I would like to determine these values by only using linear analysis...
