Ingineria cutremurelor is an interdisciplinară branch of engineering that designs and analyzes structures, such as buildings and bridges, with cutremure in mind. Its overall goal is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to construct structures that will not be damaged in minor shaking and will avoid serious damage or collapse in a major earthquake. Earthquake engineering is the scientific field concerned with protecting society, the natural environment, and the man-made environment from earthquakes by limiting the risc seismic to socio-economic acceptable levels.1 Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to încărcare seismică; it is considered as a subset of Inginerie structurală, Inginerie geotehnică, Inginerie Mecanică, Inginerie Chimica, fizică Aplicată, etc. However, the tremendous costs experienced in recent earthquakes have led to an expansion of its scope to encompass disciplines from the wider field of Inginerie civilă, Inginerie Mecanică, Inginerie Nucleara, and from the Stiinte Sociale, especially sociologie, Stiinte Politice, economie, and finanţa.2
Principalele obiective ale ingineriei cutremurelor sunt:
Foresee the potential consequences of strong cutremure on zonele urbane and civil infrastructure.
Design, construct and maintain structures to a executa at earthquake exposure up to the expectations and in compliance with codurile de constructie.3
A structură proiectată corespunzător does not necessarily have to be extremely strong or expensive. It has to be properly designed to withstand the seismic effects while sustaining an acceptable level of damage.
Încărcare seismică
Încărcare seismică means application of an earthquake-generated excitation on a structure (or geo-structure). It happens at contact surfaces of a structure either with the ground,5 with adjacent structures,6 or with unde gravitaționale from tsunami. The loading that is expected at a given location on the Earth's surface is estimated by engineering seismologie. It is related to the hazard seismic of the location.
Performanță seismică
Cutremur or performanta seismica defines a structure's ability to sustain its main functions, such as its Siguranță and utilitate, la and după a particular earthquake exposure. A structure is normally considered sigur if it does not endanger the lives and bunăstare{0} of those in or around it by partially or completely collapsing. A structure may be considered deservibil if it is able to fulfill its operational functions for which it was designed.
Conceptele de bază ale ingineriei cutremurelor, implementate în principalele coduri de construcție, presupun că o clădire ar trebui să supraviețuiască unui cutremur rar, foarte sever, suferind daune semnificative, dar fără a se prăbuși la nivel global.7 On the other hand, it should remain operational for more frequent, but less severe seismic events.
Evaluarea performanței seismice
Inginerii trebuie să cunoască nivelul cuantificat al performanței seismice reale sau anticipate asociat cu daunele directe aduse unei clădiri individuale supuse unei scuturi de sol specificate. O astfel de evaluare poate fi efectuată fie experimental, fie analitic.
Evaluare experimentală
Experimental evaluations are expensive tests that are typically done by placing a (scaled) model of the structure on a scuturați-masa that simulates the earth shaking and observing its behavior.8 Such kinds of experiments were first performed more than a century ago.9 Only recently has it become possible to perform 1:1 scale testing on full structures.
Datorită naturii costisitoare a acestor teste, acestea tind să fie utilizate în principal pentru înțelegerea comportamentului seismic al structurilor, validarea modelelor și verificarea metodelor de analiză. Astfel, odată validate corespunzător, modelele de calcul și procedurile numerice tind să suporte sarcina majoră pentru evaluarea performanței seismice a structurilor.
Evaluare analitică/numerică
Evaluarea performanței seismice or analiza structurală seismică is a powerful tool of earthquake engineering which utilizes detailed modelling of the structure together with methods of structural analysis to gain a better understanding of seismic performance of building and structuri non-de clădire. Tehnica ca concept formal este o dezvoltare relativ recentă.
In general, seismic structural analysis is based on the methods of dinamica structurală.10 For decades, the most prominent instrument of seismic analysis has been the earthquake spectrul de răspuns method which also contributed to the proposed building code's concept of today.11
However, such methods are good only for linear elastic systems, being largely unable to model the structural behavior when damage (i.e., ne-liniaritate) appears. Numerical integrare-cu-pas cu pas proved to be a more effective method of analysis for multi-degree-of-freedom sisteme structurale with significant ne-liniaritate under a tranzitoriu process of ground motion excitation.12 Use of the metoda elementului finit is one of the most common approaches for analyzing non-linear interacțiunea structurii solului computer models.
Practic, se efectuează analize numerice pentru a evalua performanța seismică a clădirilor. Evaluările de performanță sunt, în general, efectuate utilizând o analiză de tip pushover statică neliniară sau o analiză neliniară a istoricului de timp-. În astfel de analize, este esențial să se realizeze o modelare ne-liniară precisă a componentelor structurale cum ar fi grinzi, stâlpi, rosturi de grinzi-stâlpi, pereți de forfecare etc. Astfel, rezultatele experimentale joacă un rol important în determinarea parametrii de modelare ai componentelor individuale, în special a celor care sunt supuse unor deformații ne-liniare semnificative. Componentele individuale sunt apoi asamblate pentru a crea un model complet ne-liniar al structurii. Sunt analizate modele astfel create pentru a evalua performanța clădirilor.
The capabilities of the structural analysis software are a major consideration in the above process as they restrict the possible component models, the analysis methods available and, most importantly, the numerical robustness. The latter becomes a major consideration for structures that venture into the non-linear range and approach global or local collapse as the numerical solution becomes increasingly unstable and thus difficult to reach. There are several commercially available Finite Element Analysis software's such as CSI-SAP2000 and CSI-PERFORM-3D, MTR/SASSI, Scia Engineer-ECtools, ABAQUS, and Ansys, all of which can be used for the seismic performance evaluation of buildings. Moreover, there is research-based finite element analysis platforms such as OpenSees, MASTODON, which is based on the Cadrul MOOSE, RUAUMOKO și DRAIN-2D/3D mai vechi, dintre care câteva sunt acum open source.
Cercetare pentru ingineria cutremurelor
Cercetare pentru ingineria cutremurelor înseamnă investigații sau experimente atât pe teren, cât și analitice, destinate descoperirii și explicației științifice a faptelor legate de ingineria cutremurelor, revizuirea conceptelor convenționale în lumina noilor descoperiri și aplicarea practică a teoriilor dezvoltate.
The Fundația Națională de Știință (NSF) is the main United States government agency that supports fundamental research and education in all fields of earthquake engineering. In particular, it focuses on experimental, analytical and computational research on design and performance enhancement of structural systems.
The Institutul de Cercetare a Ingineriei Cutremurelor (EERI) is a leader in dissemination of cercetarea ingineriei cutremurelor related information both in the U.S. and globally.
A definitive list of earthquake engineering research related scuturarea meselor around the world may be found in Experimental Facilities for Earthquake Engineering Simulation Worldwide.14 The most prominent of them is now E-Defense Shake Table15 in Japonia.
Principalele programe de cercetare din SUA
NSF also supports the George E. Brown, Jr. Rețeaua de simulare a ingineriei cutremurelor
The NSF Hazard Mitigation and Structural Engineering program (HMSE) supports research on new technologies for improving the behaviour and response of structural systems subject to earthquake hazards; fundamental research on safety and reliability of constructed systems; innovative developments in analiză and model based simulation of structural behaviour and response including soil-structure interaction; design concepts that improve performanța structurii and flexibility; and application of new control techniques for structural systems.16
(NEES) that advances knowledge discovery and innovation for cutremure and tsunami loss reduction of the nation's civil infrastructure and new experimental simulation techniques and instrumentation.17
Rețeaua NEES are 14 laboratoare-distribuite geografic, cu utilizare partajată-care acceptă mai multe tipuri de lucrări experimentale:17 geotechnical centrifuge research, scuturați-masa tests, large-scale structural testing, tsunami wave basin experiments, and field site research.18 Participating universities include: Universitatea Cornell; Universitatea Lehigh; Universitatea de Stat din Oregon; Institutul Politehnic Rensselaer; Universitatea din Buffalo, Universitatea de Stat din New York; Universitatea din California, Berkeley; Universitatea din California, Davis; Universitatea din California, Los Angeles; Universitatea din California, San Diego; Universitatea din California, Santa Barbara; Universitatea din Illinois, Urbana-Champaign; Universitatea din Minnesota; Universitatea din Nevada, Reno; and the Universitatea din Texas, Austin.17
The equipment sites (labs) and a central data repository are connected to the global earthquake engineering community via the NEEShub website. The NEES website is powered by HUBzero software developed at Universitatea Purdue for nanoHUB specifically to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internet 2, oferă instrumente de simulare interactivă, o zonă de dezvoltare a instrumentelor de simulare, un depozit central de date, prezentări animate, asistență pentru utilizatori, teleprezență, mecanism de încărcare și partajare a resurselor și statistici despre utilizatori și modele de utilizare.
Această infrastructură cibernetică permite cercetătorilor: să stocheze, să organizeze și să partajeze în siguranță datele într-un cadru standardizat într-o locație centrală; observați de la distanță și participați la experimente prin utilizarea datelor și videoclipurilor sincronizate în timp real-; să colaboreze cu colegii pentru a facilita planificarea, performanța, analiza și publicarea experimentelor de cercetare; și efectuează simulări computaționale și hibride care pot combina rezultatele unor experimente distribuite multiple și pot lega experimente fizice cu simulări pe computer pentru a permite investigarea performanței generale a sistemului.
Aceste resurse oferă împreună mijloacele de colaborare și descoperire pentru a îmbunătăți proiectarea și performanța seismică a sistemelor de infrastructură civilă și mecanică.
Simularea cutremurului
The very first simulări de cutremur were performed by statically applying some forțe de inerție orizontale based on scalat accelerații de vârf ale solului to a mathematical model of a building.19 With the further development of computational technologies, static approaches began to give way to dinamic ones.
Dynamic experiments on building and non-building structures may be physical, like testare{0}}la masă, or virtual ones. In both cases, to verify a structure's expected seismic performance, some researchers prefer to deal with so called "real time-histories" though the last cannot be "real" for a hypothetical earthquake specified by either a building code or by some particular research requirements. Therefore, there is a strong incentive to engage an earthquake simulation which is the seismic input that possesses only essential features of a real event.
Uneori, simularea unui cutremur este înțeleasă ca o re-creare a efectelor locale ale unui puternic cutremur de pământ.
Simularea structurii
Theoretical or experimental evaluation of anticipated seismic performance mostly requires a simularea structurii which is based on the concept of structural likeness or similarity. Similitudine is some degree of analogie or asemănare between two or more objects. The notion of similarity rests either on exact or approximate repetitions of modele in the compared items.
In general, a building model is said to have similarity with the real object if the two share asemănarea geometrică, asemănarea cinematică and asemănare dinamică. The most vivid and effective type of similarity is the cinematic one. Asemănarea cinematică exists when the paths and velocities of moving particles of a model and its prototype are similar.
The ultimate level of asemănarea cinematică is echivalență cinematică when, in the case of earthquake engineering, time-histories of each story lateral displacements of the model and its prototype would be the same.
Controlul vibrațiilor seismice
Controlul vibrațiilor seismice is a set of technical means aimed to mitigate seismic impacts in building and fără{0}}cladire structures. All seismic vibration control devices may be classified as pasiv, activ or hibrid21 where:
dispozitive de control pasiv have no părere capability between them, structural elements and the ground;
dispozitive de control activ incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and actuatoare within the structure;
dispozitive de control hibrid have combined features of active and passive control systems.22
When ground unde seismice reach up and start to penetrate a base of a building, their energy flow density, due to reflections, reduces dramatically: usually, up to 90 percent . However, the remaining portions of the incident waves during a major earthquake still bear a huge devastating potential.
After the seismic waves enter a suprastructură, there are a number of ways to control them in order to soothe their damaging effect and improve the building's seismic performance, for instance:
to risipi the wave energy inside a suprastructură with properly engineered amortizoare;
să disperseze energia valurilor între o gamă mai largă de frecvențe;
to absorbi the rezonant portions of the whole wave frequencies band with the help of so-called amortizoare de masă.23
Dispozitive de ultimul fel, prescurtate corespunzător ca TMD pentru reglat (pasiv), as AMD for the activ, and as HMD for the amortizoare de masă hibride, have been studied and installed in clădiri{0}}înalte, predominant în Japonia, timp de un sfert de secol.24
However, there is quite another approach: partial suppression of the seismic energy flow into the suprastructură known as seismic or izolarea bazei.
For this, some pads are inserted into or under all major load-carrying elements in the base of the building which should substantially decouple a suprastructură from its substructură resting on a shaking ground.
The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, un oraș din Persia antică, acum Iran, și datează din secolul al VI-lea î.Hr. Mai jos, există câteva mostre de tehnologii de control al vibrațiilor seismice de astăzi.
Ziduri de-piatră uscată în Peru
Peru is a highly seismic land; for centuries the dry-stone constructie proved to be more earthquake-resistant than using mortar. People of civilizație incasă were masters of the polished 'dry-stone walls', called siliu, where blocks of stone were cut to fit together tightly without any mortar. Incașii au fost printre cei mai buni pietrari pe care i-a văzut vreodată lumea25 and many junctions in their masonry were so perfect that even blades of grass could not fit between the stones.
The stones of the dry-stone walls built by the Incas could move slightly and resettle without the walls collapsing, a passive control structural technique employing both the principle of energy dissipation (coulomb damping) and that of suppressing rezonant amplifications.26
Amortizor de masă reglat
Typically the amortizoare de masă reglate are huge concrete blocks mounted in zgârie-nori or other structures and move in opposition to the frecventa de rezonanta oscillations of the structures by means of some sort of spring mechanism.
The Taipei 101 skyscraper needs to withstand taifun winds and earthquake tremurături common in this area of Asia/Pacific. For this purpose, a steel pendul weighing 660 metric tonnes that serves as a tuned mass damper was designed and installed atop the structure. Suspended from the 92nd to the 88th floor, the pendulum sways to decrease resonant amplifications of lateral displacements in the building caused by earthquakes and strong rafale.
Amortizoare histeretice
A amortizor histeretic is intended to provide better and more reliable seismic performance than that of a conventional structure by increasing the dissipation of intrare seismică energy.27 There are five major groups of hysteretic dampers used for the purpose, namely:
Amortizoare vâscoase fluide (FVD)
Amortizoarele vâscoase au avantajul de a fi un sistem suplimentar de amortizare. Au o buclă histeretică ovală, iar amortizarea este dependentă de viteză. Deși poate fi necesară o întreținere minoră, amortizoarele vâscoase, în general, nu trebuie înlocuite după un cutremur. Deși sunt mai scumpe decât alte tehnologii de amortizare, acestea pot fi utilizate atât pentru sarcini seismice, cât și pentru eoliene și sunt amortizorul histeretic cel mai frecvent utilizat.28
Amortizoare de frecare (FD)
Friction dampers tend to be available in two major types, linear and rotational and dissipate energy by heat. The damper operates on the principle of a amortizor coulomb. Depending on the design, friction dampers can experience stick-fenomen de alunecare and Sudarea la rece. Principalul dezavantaj fiind că suprafețele de frecare se pot uza în timp și din acest motiv nu sunt recomandate pentru disiparea sarcinilor vântului. Când este utilizat în aplicații seismice, uzura nu reprezintă o problemă și nu este necesară întreținerea. Au o buclă histeretică dreptunghiulară și, atâta timp cât clădirea este suficient de elastică, au tendința de a reveni la pozițiile inițiale după un cutremur.
Amortizoare metalice de elasticitate (MYD)
Metallic yielding dampers, as the name implies, yield in order to absorb the earthquake's energy. This type of damper absorbs a large amount of energy however they must be replaced after an earthquake and may prevent the building from settling back to its original position.
Amortizoare vâscoelastice (VED)
Amortizoarele viscoelastice sunt utile prin faptul că pot fi utilizate atât pentru aplicații eoliene, cât și pentru aplicații seismice, ele fiind de obicei limitate la deplasări mici. Există o oarecare îngrijorare cu privire la fiabilitatea tehnologiei, deoarece unor mărci li s-a interzis utilizarea în clădirile din Statele Unite.
Amortizoare pendulare aflate în picioare (swing)
Izolarea bazei
Izolarea bazei urmărește să prevină transferul energiei cinetice a cutremurului în energie elastică în clădire. Aceste tehnologii fac acest lucru prin izolarea structurii de sol, permițându-le astfel să se miște oarecum independent. Gradul în care energia este transferată în structură și modul în care energia este disipată va varia în funcție de tehnologia utilizată.
Rulment din cauciuc cu plumb
Lead rubber bearing or LRB is a type of izolarea bazei employing a heavy amortizare. It was invented by Bill Robinson, un neozeelandez.29
Heavy damping mechanism incorporated in controlul vibrațiilor technologies and, particularly, in base isolation devices, is often considered a valuable source of suppressing vibrations thus enhancing a building's seismic performance. However, for the rather pliant systems such as base isolated structures, with a relatively low bearing stiffness but with a high damping, the so-called "damping force" may turn out the main pushing force at a strong earthquake. The video30 shows a Lead Rubber Bearing being tested at the UCSD Caltrans-SRMD facility. The bearing is made of rubber with a lead core. It was a uniaxial test in which the bearing was also under a full structure load. Many buildings and bridges, both in New Zealand and elsewhere, are protected with lead dampers and lead and rubber bearings. Te Papa Tongarewa, the national museum of New Zealand, and the New Zealand Clădirile Parlamentului have been fitted with the bearings. Both are in Wellington which sits on an defect activ.29
Arcuri-cu-izolator de bază a amortizorului
Springs-with-damper base isolator installed under a three-story town-house, Santa Monica, California is shown on the photo taken prior to the 1994 Cutremur Northridge exposure. It is a izolarea bazei device conceptually similar to Rulment din cauciuc cu plumb.
One of two three-story town-houses like this, which was well instrumented for recording of both vertical and horizontal acceleratii on its floors and the ground, has survived a severe shaking during the Cutremur Northridge and left valuable recorded information for further study.
Rulment cu role simplu
Simple roller bearing is a izolarea bazei device which is intended for protection of various building and non-building structures against potentially damaging impacturi laterale of strong earthquakes.
This metallic bearing support may be adapted, with certain precautions, as a seismic isolator to skyscrapers and buildings on soft ground. Recently, it has been employed under the name of rulment metalic cu role for a housing complex (17 stories) in Tokyo, Japonia.31
Rulment pendul de frecare
Friction pendulum bearing (FPB) is another name of sistem pendul de frecare (FPS). It is based on three pillars:32
glisor de frecare articulat;
suprafață de alunecare sferică concavă;
cilindru de închidere pentru reținerea deplasării laterale.
Snapshot with the link to video clip of a scuturați-masa testing of FPB system supporting a rigid building model is presented at the right.
Proiectare seismică
Proiectare seismică is based on authorized engineering procedures, principles and criteria meant to proiecta or modernizare structures subject to earthquake exposure.19 Those criteria are only consistent with the contemporary state of the knowledge about structuri de inginerie seismică.33 Therefore, a building design which exactly follows seismic code regulations does not guarantee safety against collapse or serious damage.34
The price of poor seismic design may be enormous. Nevertheless, seismic design has always been a încercare și eroare process whether it was based on physical laws or on empirical knowledge of the performanta structurala of different shapes and materials.
To practice proiectare seismică, seismic analysis or seismic evaluation of new and existing civil engineering projects, an inginer should, normally, pass examination on Principii seismice35 which, in the State of California, include:
Date seismice și criterii de proiectare seismică
Caracteristicile seismice ale sistemelor proiectate
Forțe seismice
Proceduri de analiză seismică
Detalierea seismică și controlul calității construcțiilor
Pentru a construi sisteme structurale complexe,36 seismic design largely uses the same relatively small number of basic structural elements (to say nothing of vibration control devices) as any non-seismic design project.
Normally, according to building codes, structures are designed to "withstand" the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings.
Seismic design is carried out by understanding the possible moduri de eșec of a structure and providing the structure with appropriate putere, rigiditate, ductilitate, and configurație37 to ensure those modes cannot occur.
Cerințe de proiectare seismică
Cerințe de proiectare seismică depend on the type of the structure, locality of the project and its authorities which stipulate applicable seismic design codes and criteria.7 For instance, Departamentul Transporturilor din California's requirements called Criteriile de proiectare seismică (SDC) and aimed at the design of new bridges in California38 incorporate an innovative seismic performance-based approach.
The most significant feature in the SDC design philosophy is a shift from a evaluare bazată{0}}forței of seismic demand to a evaluare bazată{0}}deplasării of demand and capacity. Thus, the newly adopted displacement approach is based on comparing the deplasare elastică demand to the deplasare inelastică capacity of the primary structural components while ensuring a minimum level of inelastic capacity at all potential plastic hinge locations.
In addition to the designed structure itself, seismic design requirements may include a stabilizarea solului underneath the structure: sometimes, heavily shaken ground breaks up which leads to collapse of the structure sitting upon it.40 The following topics should be of primary concerns: liquefaction; dynamic lateral earth pressures on retaining walls; seismic slope stability; earthquake-induced settlement.41
Instalații nucleare should not jeopardise their safety in case of earthquakes or other hostile external events. Therefore, their seismic design is based on criteria far more stringent than those applying to non-nuclear facilities.42 The Accident nuclear de la Fukushima I and deteriorarea altor instalații nucleare that followed the 2011 Tōhoku earthquake and tsunami have, however, drawn attention to ongoing concerns over Standarde japoneze de proiectare seismică nucleară and caused many other governments to re{0}}evaluează programele lor nucleare. Doubt has also been expressed over the seismic evaluation and design of certain other plants, including the Centrala nucleară Fessenheim in France.
Moduri de eșec
Modul de eșec is the manner by which an earthquake induced failure is observed. It, generally, describes the way the failure occurs. Though costly and time consuming, learning from each real earthquake failure remains a routine recipe for advancement in proiectare seismică methods. Below, some typical modes of earthquake-generated failures are presented.
The lack of armare coupled with poor mortar and inadequate roof-to-wall ties can result in substantial damage to an clădire din zidărie nearmată. Pereții crăpați grav sau înclinați sunt unele dintre cele mai frecvente daune cauzate de cutremur. De asemenea, periculoase este și deteriorarea care poate apărea între pereți și diafragmele acoperișului sau podelei. Separarea dintre cadru și pereți poate pune în pericol suportul vertical al sistemelor de acoperiș și podea.
Efect de poveste moale. Absence of adequate stiffness on the ground level caused damage to this structure. A close examination of the image reveals that the rough board siding, once covered by a furnir de cărămidă, has been completely dismantled from the studwall. Only the rigiditate of the floor above combined with the support on the two hidden sides by continuous walls, not penetrated with large doors as on the street sides, is preventing full collapse of the structure.
Lichefierea solului. In the cases where the soil consists of loose granular deposited materials with the tendency to develop excessive hydrostatic pore water pressure of sufficient magnitude and compact, lichefiere of those loose saturated deposits may result in non-uniform aşezări and tilting of structures. This caused major damage to thousands of buildings in Niigata, Japan during the cutremur din 1964.43
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Alunecare de teren cădere de stâncă. A alunecare de teren is a geological phenomenon which includes a wide range of ground movement, including căderi de stâncă. Typically, the action of gravitatie is the primary driving force for a landslide to occur though in this case there was another contributing factor which affected the original stabilitatea pantei: the landslide required an declanșator de cutremur before being released.
Lovindu-se împotriva clădirii adiacente. This is a photograph of the collapsed five-story tower, St. Joseph's Seminary, Los Altos, California which resulted in one fatality. During Cutremur Loma Prieta, the tower pounded against the independently vibrating adjacent building behind. A possibility of pounding depends on both buildings' lateral displacements which should be accurately estimated and accounted for.
At Cutremur Northridge, the Kaiser Permanente concrete frame office building had joints completely shattered, revealing oțel de izolare inadecvat, which resulted in the second story collapse. In the transverse direction, composite end pereți de forfecare, consisting of two wythes of brick and a layer of beton împușcat that carried the lateral load, peeled apart because of inadecvat prin-legături and failed.
Improper santier on a poalele dealului.
Poor detailing of the armare (lack of concrete confinement in the columns and at the beam-column joints, inadequate splice length).
Seismically weak poveste moale at the first floor.
Long consolele with heavy sarcină moartă.
Efectul de alunecare a fundațiilor of a relatively rigid residential building structure during Cutremurul de la Whittier Narrows din 1987. The magnitude 5.9 earthquake pounded the Garvey West Apartment building in Monterey Park, California and shifted its suprastructură about 10 inches to the east on its foundation.
If a superstructure is not mounted on a izolarea bazei system, its shifting on the basement should be prevented.
Beton armat column burst at Cutremur Northridge due to mod insuficient de armare prin forfecare which allows main reinforcement to cataramă outwards. The deck unseated at the balama and failed in shear. As a result, the La Cienega-Venice pasaj subteran section of the 10 Freeway collapsed.
Cutremur Loma Prieta: side view of reinforced concrete asistență-coloane eșec which triggered puntea superioară se prăbușește pe puntea inferioară of the two-level Cypress viaduct of Interstate Highway 880, Oakland, CA.
Defectarea zidului de sprijin at Cutremur Loma Prieta in Santa Cruz Mountains area: prominent northwest-trending extensional cracks up to 12 cm (4.7 in) wide in the concrete deversor to Austrian Dam, the north bont.
Ground shaking triggered lichefierea solului in a subsurface layer of nisip, producing differential lateral and vertical movement in an overlying carapace of unliquified sand and nămol. This modul de defectare la sol, termed răspândire laterală, este o cauză principală a daunelor cauzate de lichefiere-cutremurele.44
Severely damaged building of Agriculture Development Bank of China after Cutremur din Sichuan din 2008: most of the grinzile și stâlpii pilonului sunt forfecate. Large diagonal cracks in masonry and veneer are due to in-plane loads while abrupt aşezare of the right end of the building should be attributed to a groapa de gunoi which may be hazardous even without any earthquake.45
Impact dublu de tsunami: valurile marii hydraulic presiune and inundaţie. Thus, cutremurul din Oceanul Indian of December 26, 2004, with the epicentru off the west coast of Sumatra, Indonesia, triggered a series of devastating tsunamis, killing more than 230,000 people in eleven countries by inundând comunitățile de coastă din jur cu valuri uriașe up to 30 meters (100 feet) high.47
Construcție rezistentă la cutremur{0}
Construcție cutremur means implementation of proiectare seismică to enable building and non-building structures to live through the anticipated earthquake exposure up to the expectations and in compliance with the applicable codurile de constructie.
Proiectarea și construcția sunt strâns legate. Pentru a obține o manoperă bună, detalierea membrilor și a conexiunilor lor ar trebui să fie cât mai simplă posibil. Ca orice construcție în general, construcția cutremurului este un proces care constă în construirea, modernizarea sau asamblarea infrastructurii având în vedere materialele de construcție disponibile.48
The destabilizing action of an earthquake on constructions may be direct (seismic motion of the ground) or indirect (earthquake-induced landslides, lichefierea solului and waves of tsunami).
O structură poate avea toate aparențele de stabilitate, dar nu oferă decât un pericol atunci când are loc un cutremur.49 The crucial fact is that, for safety, earthquake-resistant construction techniques are as important as control de calitate and using correct materials. Antreprenor de cutremur should be înregistrat in the state/province/country of the project location (depending on local regulations), legat and asiguratcitare necesară.
To minimize possible pierderi, procesul de construcție ar trebui organizat ținând cont de faptul că un cutremur poate avea loc în orice moment înainte de încheierea construcției.
Each proiect de constructie requires a qualified team of professionals who understand the basic features of seismic performance of different structures as well as Managentul construcțiilor.
Structuri Adobe
Around thirty percent of the world's population lives or works in earth-made construction.50 Chirpici type of cărămizi de noroi is one of the oldest and most widely used building materials. The use of chirpici is very common in some of the world's most hazard-prone regions, traditionally across Latin America, Africa, Indian subcontinent and other parts of Asia, Middle East and Southern Europe.
Clădirile Adobe sunt considerate foarte vulnerabile la cutremure puternice.51 However, multiple ways of seismic strengthening of new and existing adobe buildings are available.52
Factorii cheie pentru performanța seismică îmbunătățită a construcțiilor din chirpici sunt:
Calitatea constructiei.
Aspect compact, tip-cutie.
Armare seismică.53
Structuri din calcar și gresie
Calcar is very common in architecture, especially in North America and Europe. Many landmarks across the world are made of limestone. Many medieval churches and castles in Europe are made of calcar and Gresie masonry. They are the long-lasting materials but their rather heavy weight is not beneficial for adequate seismic performance.
Application of modern technology to seismic retrofitting can enhance the survivability of unreinforced masonry structures. As an example, from 1973 to 1989, the Salt Lake City și clădirea județului in Utah was exhaustively renovated and repaired with an emphasis on preserving historical accuracy in appearance. This was done in concert with a seismic upgrade that placed the weak sandstone structure on base isolation foundation to better protect it from earthquake damage.
Structuri cu cadru din lemn
Structura din lemn dates back thousands of years, and has been used in many parts of the world during various periods such as ancient Japan, Europe and medieval England in localities where timber was in good supply and building stone and the skills to work it were not.
The use of încadrare din lemn in buildings provides their complete skeletal framing which offers some structural benefits as the timber frame, if properly engineered, lends itself to better supraviețuirea seismică.54
Structuri ușoare-cadru
Structuri ușoare-cadru usually gain seismic resistance from rigid placaj shear walls and wood structural panel diafragme.55 Special provisions for seismic load-resisting systems for all lemn prelucrat structures requires consideration of diaphragm ratios, horizontal and vertical diaphragm shears, and conector/dispozitiv de fixare values. In addition, collectors, or drag struts, to distribute shear along a diaphragm length are required.
Structuri de zidărie armată
A construction system where armătură din oțel is embedded in the rosturi de mortar of zidărie or placed in holes and that are filled with beton or chit is called zidărie armată.56 There are various practices and techniques to reinforce masonry. The most common type is the reinforced zidărie unitatea goală.
To achieve a ductil behavior in masonry, it is necessary that the rezistența la forfecare of the wall is greater than the rezistență la încovoiere.57 The effectiveness of both vertical and horizontal reinforcements depends on the type and quality of the masonry units and mortar.
The devastating Cutremur din 1933 din Long Beach revealed that masonry is prone to earthquake damage, which led to the Codul de stat al Californiei making masonry reinforcement mandatory across California.
Structuri din beton armat
Beton armat is concrete in which steel reinforcement bars (armaturi) or fibre have been incorporated to strengthen a material that would otherwise be fragil. It can be used to produce grinzi, coloane, podele sau poduri.
Beton precomprimat is a kind of beton armat used for overcoming concrete's natural weakness in tension. It can be applied to grinzi, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing tendoane (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a stresul de compresiune that offsets the efort de tracțiune that the concrete membru de compresie would, otherwise, experience due to a bending load.
To prevent catastrophic collapse in response earth shaking (in the interest of life safety), a traditional reinforced concrete frame should have ductil joints. Depending upon the methods used and the imposed seismic forces, such buildings may be immediately usable, require extensive repair, or may have to be demolished.
Structuri precomprimate
Structură precomprimată is the one whose overall integritate, stabilitate and Securitate depend, primarily, on a pretensionare. Pretensionare means the intentional creation of permanent stresses in a structure for the purpose of improving its performance under various service conditions.58
Există următoarele tipuri de bază de pretensionare:
Pre-compresie (în mare parte, cu greutatea proprie a unei structuri)
Pretensionare with high-strength embedded tendons
Post{0}tensionare with high-strength bonded or unbonded tendons
Today, the concept of structură precomprimată is widely engaged in design of cladiri, underground structures, TV towers, power stations, floating storage and offshore facilities, reactor nuclear vessels, and numerous kinds of pod systems.59
A beneficial idea of pretensionare was, apparently, familiar to the ancient Rome architects; look, e.g., at the tall pod wall of Colosseum working as a stabilizing device for the wall digurile beneath.
Structuri de otel
Structuri de otel are considered mostly earthquake resistant but some failures have occurred. A great number of welded cadru rezistent la moment{0}}de oțel buildings, which looked earthquake-proof, surprisingly experienced brittle behavior and were hazardously damaged in the Cutremur Northridge din 1994.60 After that, the Agenția Federală de Management al Urgențelor (FEMA) initiated development of repair techniques and new design approaches to minimize damage to steel moment frame buildings in future earthquakes.61
For otel de constructie seismic design based on Proiectare de sarcină și factor de rezistență (LRFD) approach, it is very important to assess ability of a structure to develop and maintain its bearing resistance in the neelastic range. A measure of this ability is ductilitate, which may be observed in a materialul în sine, in a element structural, or to a întreaga structură.
As a consequence of Cutremur Northridge experience, the American Institute of Steel Construction has introduced AISC 358 "Pre-Qualified Connections for Special and intermediate Steel Moment Frames." The AISC Seismic Design Provisions require that all Rame rezistente la momente din oțel employ either connections contained in AISC 358, or the use of connections that have been subjected to pre-qualifying cyclic testing.62
Predicția pierderilor cauzate de cutremur
Estimarea pierderilor de cutremur is usually defined as a Raportul de deteriorare (DR) which is a ratio of the earthquake damage repair cost to the Valoarea totală of a building.63 Pierderea maximă probabilă (PML) is a common term used for earthquake loss estimation, but it lacks a precise definition. In 1999, ASTM E2026 'Standard Guide for the Estimation of Building Damageability in Earthquakes' was produced in order to standardize the nomenclature for seismic loss estimation, as well as establish guidelines as to the review process and qualifications of the reviewer.64
Earthquake loss estimations are also referred to as Evaluări ale riscului seismic. Procesul de evaluare a riscurilor implică, în general, determinarea probabilității diferitelor mișcări ale solului cuplate cu vulnerabilitatea sau deteriorarea clădirii sub acele mișcări ale solului. Rezultatele sunt definite ca procent din valoarea de înlocuire a clădirii.65