Inġinerija tat-terremoti is an interdixxiplinari branch of engineering that designs and analyzes structures, such as buildings and bridges, with terremoti 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 riskju sismiku to soċjo-ekonomikament acceptable levels.1 Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to tagħbija sismika; it is considered as a subset of inġinerija strutturali, inġinerija ġeoteknika, inġinerija mekkanika, inġinerija kimika, fiżika applikata, 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 inġinerija ċivili, inġinerija mekkanika, inġinerija nukleari, and from the Xjenzi soċjali, especially soċjoloġija, Xjenza politika, ekonomija, and finanzi.2
L-għanijiet ewlenin tal-inġinerija tat-terremoti huma:
Foresee the potential consequences of strong terremoti on żoni urbani and civil infrastructure.
Design, construct and maintain structures to twettaq at earthquake exposure up to the expectations and in compliance with kodiċi tal-bini.3
A struttura maħduma sew 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.
Tagħbija sismika
Tagħbija sismika 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 mewġ tal-gravità from tsunami. The loading that is expected at a given location on the Earth's surface is estimated by engineering siżmoloġija. It is related to the periklu sismiku of the location.
Prestazzjoni sismika
Terremot or prestazzjoni sismika defines a structure's ability to sustain its main functions, such as its sigurtà and servizz, fi and wara a particular earthquake exposure. A structure is normally considered sigur if it does not endanger the lives and -benessri of those in or around it by partially or completely collapsing. A structure may be considered servibbli if it is able to fulfill its operational functions for which it was designed.
Kunċetti bażiċi tal-inġinerija tat-terremoti, implimentati fil-kodiċijiet tal-bini ewlenin, jassumu li bini għandu jgħix minn terremot rari u sever ħafna billi jġarrab ħsara sinifikanti iżda mingħajr ma jiġġarraf globalment.7 On the other hand, it should remain operational for more frequent, but less severe seismic events.
Valutazzjoni tal-prestazzjoni sismika
L-inġiniera jeħtieġ li jkunu jafu l-livell kwantifikat tal-prestazzjoni sismika attwali jew antiċipata assoċjata mal-ħsara diretta lil bini individwali soġġett għal tħawwad tal-art speċifikat. Valutazzjoni bħal din tista' ssir jew b'mod sperimentali jew analitiku.
Valutazzjoni sperimentali
Experimental evaluations are expensive tests that are typically done by placing a (scaled) model of the structure on a ħawwad-mejda 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.
Minħabba n-natura għalja ta 'dawn it-testijiet, għandhom it-tendenza li jintużaw prinċipalment biex jifhmu l-imġiba sismika ta' strutturi, jivvalidaw mudelli u jivverifikaw metodi ta 'analiżi. Għalhekk, ladarba jkunu vvalidati sew, mudelli komputazzjonali u proċeduri numeriċi għandhom it-tendenza li jġorru l-piż ewlieni għall-valutazzjoni tal-prestazzjoni sismika tal-istrutturi.
Valutazzjoni Analitika/Numerika
Valutazzjoni tal-prestazzjoni sismika or analiżi strutturali sismika 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 mhux-strutturi tal-bini. It-teknika bħala kunċett formali hija żvilupp relattivament reċenti.
In general, seismic structural analysis is based on the methods of dinamika strutturali.10 For decades, the most prominent instrument of seismic analysis has been the earthquake spettru tar-rispons 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., non-linearità) appears. Numerical integrazzjoni pass-pass- proved to be a more effective method of analysis for multi-degree-of-freedom sistemi strutturali with significant non-linearità under a temporanju process of ground motion excitation.12 Use of the metodu ta' elementi finiti is one of the most common approaches for analyzing non-linear interazzjoni tal-istruttura tal-ħamrija computer models.
Bażikament, titwettaq analiżi numerika sabiex tiġi evalwata l-prestazzjoni sismika tal-bini. L-evalwazzjonijiet tal-prestazzjoni ġeneralment jitwettqu bl-użu ta' analiżi ta' pushover statika mhux lineari jew analiżi tal-istorja tal-ħin-nonlineari. F'analiżi bħal dawn, huwa essenzjali li jinkiseb mudellar preċiż mhux-lineari ta' komponenti strutturali bħal travi, kolonni, ġonot tal-kolonni tar-raġġ-, ħitan shear eċċ. Għalhekk, ir-riżultati sperimentali għandhom rwol importanti fid-determinazzjoni il-parametri tal-immudellar ta' komponenti individwali, speċjalment dawk li huma suġġetti għal deformazzjonijiet mhux-lineari sinifikanti. Il-komponenti individwali mbagħad jiġu mmuntati biex jinħoloq mudell sħiħ mhux-lineari tal-istruttura. Għalhekk mudelli maħluqa huma analizzati biex jevalwaw il-prestazzjoni tal-bini.
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 Qafas MOOSE, RUAUMOKO u l-anzjani DRAIN-2D/3D, li bosta minnhom issa huma sors miftuħ.
Riċerka għall-inġinerija tat-terremoti
Ir-riċerka għall-inġinerija tat-terremoti tfisser kemm investigazzjoni fuq il-post kif ukoll analitika jew esperimentazzjoni maħsuba għall-iskoperta u spjegazzjoni xjentifika ta 'fatti relatati mal-inġinerija tat-terremoti, reviżjoni ta' kunċetti konvenzjonali fid-dawl ta 'sejbiet ġodda, u applikazzjoni prattika tat-teoriji żviluppati.
The Fondazzjoni Nazzjonali tax-Xjenza (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 Istitut tar-Riċerka dwar l-Inġinerija tat-Terremoti (EERI) is a leader in dissemination of riċerka dwar l-inġinerija tat-terremoti related information both in the U.S. and globally.
A definitive list of earthquake engineering research related tħawwad imwejjed 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 Ġappun.
Programmi ewlenin ta' riċerka tal-Istati Uniti
NSF also supports the George E. Brown, Jr. Netwerk għas-Simulazzjoni tal-Inġinerija tat-Terremot
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 analiżi and model based simulation of structural behaviour and response including soil-structure interaction; design concepts that improve prestazzjoni tal-istruttura and flexibility; and application of new control techniques for structural systems.16
(NEES) that advances knowledge discovery and innovation for terremoti and tsunami loss reduction of the nation's civil infrastructure and new experimental simulation techniques and instrumentation.17
In-netwerk NEES fih 14-il laboratorju ta' użu-imqassam ġeografikament-li jappoġġaw diversi tipi ta' xogħol sperimentali:17 geotechnical centrifuge research, ħawwad-mejda tests, large-scale structural testing, tsunami wave basin experiments, and field site research.18 Participating universities include: Università ta’ Cornell; Università ta’ Lehigh; Università Statali ta' Oregon; Istitut Politekniku Rensselaer; Università f’Buffalo, Università Statali ta' New York; Università ta’ Kalifornja, Berkeley; Università ta’ Kalifornja, Davis; Università ta’ Kalifornja, Los Angeles; Università ta’ Kalifornja, San Diego; Università ta’ Kalifornja, Santa Barbara; Università ta' Illinois, Urbana-Champaign; Università ta' Minnesota; Università ta 'Nevada, Reno; and the Università ta’ 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 Università ta' Purdue for nanoHUB specifically to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internet2, jipprovdi għodod ta 'simulazzjoni interattivi, żona ta' żvilupp ta 'għodda ta' simulazzjoni, repożitorju tad-dejta ċentrali kkurat, preżentazzjonijiet animati, appoġġ għall-utent, telepreżenza, mekkaniżmu għat-tlugħ u l-qsim tar-riżorsi, u statistika dwar l-utenti u l-mudelli tal-użu.
Din iċ-ċiberinfrastruttura tippermetti lir-riċerkaturi: jaħżnu, jorganizzaw u jaqsmu d-dejta b’mod sigur f’qafas standardizzat f’post ċentrali; josserva mill-bogħod u tipparteċipa f'esperimenti permezz tal-użu ta' data u vidjo sinkronizzati f'ħin reali-; jikkollaboraw mal-kollegi biex jiffaċilitaw l-ippjanar, il-prestazzjoni, l-analiżi, u l-pubblikazzjoni ta 'esperimenti ta' riċerka; u twettaq simulazzjonijiet komputazzjonali u ibridi li jistgħu jgħaqqdu r-riżultati ta 'esperimenti distribwiti multipli u jgħaqqdu esperimenti fiżiċi ma' simulazzjonijiet tal-kompjuter biex jippermettu l-investigazzjoni tal-prestazzjoni ġenerali tas-sistema.
Dawn ir-riżorsi flimkien jipprovdu l-mezzi għall-kollaborazzjoni u l-iskoperta biex itejbu d-disinn sismiku u l-prestazzjoni ta 'sistemi ta' infrastruttura ċivili u mekkanika.
Simulazzjoni ta' terremot
The very first simulazzjonijiet ta' terremoti were performed by statically applying some forzi ta' inerzja orizzontali based on skalat l-ogħla aċċelerazzjonijiet tal-art to a mathematical model of a building.19 With the further development of computational technologies, statiku approaches began to give way to dinamiku ones.
Dynamic experiments on building and non-building structures may be physical, like ħawwad-test tal-mejda, 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.
Xi drabi s-simulazzjoni ta' terremot tinftiehem bħala ħolqien mill-ġdid ta' effetti lokali ta' tħawwad qawwi tad-dinja.
Simulazzjoni ta' l-istruttura
Theoretical or experimental evaluation of anticipated seismic performance mostly requires a simulazzjoni tal-istruttura which is based on the concept of structural likeness or similarity. Xebh is some degree of analoġija or xebh between two or more objects. The notion of similarity rests either on exact or approximate repetitions of mudelli in the compared items.
In general, a building model is said to have similarity with the real object if the two share xebh ġeometriku, xebh kinematiku and xebh dinamiku. The most vivid and effective type of similarity is the kinematika one. Xebh kinematiku exists when the paths and velocities of moving particles of a model and its prototype are similar.
The ultimate level of xebh kinematiku is ekwivalenza kinematika when, in the case of earthquake engineering, time-histories of each story lateral displacements of the model and its prototype would be the same.
Kontroll tal-vibrazzjoni sismika
Kontroll tal-vibrazzjoni sismika is a set of technical means aimed to mitigate seismic impacts in building and mhux-bini structures. All seismic vibration control devices may be classified as passiv, attiv or ibridu21 where:
apparat ta' kontroll passiv have no feedback capability between them, structural elements and the ground;
apparat ta' kontroll attiv incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and attwaturi within the structure;
apparati ta' kontroll ibridi have combined features of active and passive control systems.22
When ground mewġ sismiku 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 sovrastruttura, 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 tinħela the wave energy inside a sovrastruttura with properly engineered umidifikaturi;
biex tferrex l-enerġija tal-mewġ bejn firxa usa 'ta' frekwenzi;
to jassorbi the reżonanti portions of the whole wave frequencies band with the help of so-called umidifikaturi tal-massa.23
Apparat tal-aħħar tip, imqassar b'mod korrispondenti bħala TMD għall-irfinat (passiv), as AMD for the attiv, and as HMD for the umidifikaturi tal-massa ibridi, have been studied and installed in bini għoli-, l-aktar fil-Ġappun, għal kwart ta' seklu.24
However, there is quite another approach: partial suppression of the seismic energy flow into the sovrastruttura known as seismic or iżolament bażi.
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 sovrastruttura from its sottostruttura resting on a shaking ground.
The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, belt fil-Persja tal-qedem, illum l-Iran, u tmur lura għas-6 seklu Q.K. Hawn taħt, hemm xi kampjuni ta 'teknoloġiji ta' kontroll tal-vibrazzjoni sismika tal-lum.
-Ħitan tal-ġebel niexef fil-Perù
Peru is a highly sismiċi land; for centuries the dry-stone kostruzzjoni proved to be more earthquake-resistant than using mortar. People of ċiviltà Inca were masters of the polished 'dry-stone walls', called ashlar, where blocks of stone were cut to fit together tightly without any mehrież. L-Incas kienu fost l-aqwa ġebel tal-ġebel li qatt rat id-dinja25 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 kontroll strutturali technique employing both the principle of energy dissipation (coulomb damping) and that of suppressing reżonanti amplifications.26
Umidifikatur tal-massa sintonizzat
Typically the umidifikaturi tal-massa sintonizzat are huge concrete blocks mounted in skyscrapers or other structures and move in opposition to the frekwenza tar-reżonanza oscillations of the structures by means of some sort of spring mechanism.
The Tajpej 101 skyscraper needs to withstand tifun winds and earthquake rogħda common in this area of Asia/Pacific. For this purpose, a steel pendlu 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 buffuri.
Dampers isteretiċi
A umidifikatur isteretiku is intended to provide better and more reliable seismic performance than that of a conventional structure by increasing the dissipation of input sismiku energy.27 There are five major groups of hysteretic dampers used for the purpose, namely:
Umidifikaturi viskużi fluwidi (FVDs)
Umidifikaturi viskużi għandhom il-benefiċċju li huma sistema ta 'damping supplimentari. Huma għandhom linja isteretika ovali u d-damping huwa dipendenti fuq il-veloċità. Filwaqt li xi manutenzjoni minuri hija potenzjalment meħtieġa, umidifikaturi viskużi ġeneralment m'għandhomx għalfejn jiġu sostitwiti wara terremot. Filwaqt li jiswew aktar minn teknoloġiji oħra ta 'damping, jistgħu jintużaw kemm għal tagħbijiet sismiċi kif ukoll għar-riħ u huma l-umidifikatur isteretiku l-aktar użat komunement.28
Umidifikaturi tal-frizzjoni (FDs)
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 coulomb umidifikatur. Depending on the design, friction dampers can experience stick-fenomenu taż-żlieq and Iwweldjar kiesaħ. L-iżvantaġġ ewlieni huwa li l-uċuħ tal-frizzjoni jistgħu jilbsu maż-żmien u għal din ir-raġuni mhumiex rakkomandati biex ixerrdu tagħbijiet tar-riħ. Meta jintuża f'applikazzjonijiet sismiċi, l-ilbies mhuwiex problema u m'hemm l-ebda manutenzjoni meħtieġa. Għandhom linja isteretika rettangolari u sakemm il-bini jkun elastiku biżżejjed għandhom it-tendenza li joqogħdu lura għall-pożizzjonijiet oriġinali tagħhom wara terremot.
Umidifikaturi li joħorġu metalliċi (MYDs)
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.
Umidifikaturi Viscoelastic (VEDs)
Umidifikaturi viscoelastic huma utli peress li jistgħu jintużaw kemm għall-applikazzjonijiet tar-riħ u sismiċi, huma ġeneralment limitati għal spostamenti żgħar. Hemm xi tħassib dwar l-affidabbiltà tat-teknoloġija peress li xi marki ġew ipprojbiti mill-użu fil-bini fl-Istati Uniti.
Umidifikaturi tal-pendlu li jġorru fuq xulxin (swing)
Iżolament tal-bażi
L-iżolament tal-bażi jfittex li jipprevjeni l-enerġija kinetika tat-terremot milli tiġi trasferita f'enerġija elastika fil-bini. Dawn it-teknoloġiji jagħmlu dan billi jiżolaw l-istruttura mill-art, u b'hekk jippermettulhom li jiċċaqalqu b'mod kemmxejn indipendenti. Il-grad sa fejn l-enerġija tiġi trasferita fl-istruttura u kif l-enerġija tinħela se jvarjaw skont it-teknoloġija użata.
Ċomb tal-gomma li jkollhom
Lead rubber bearing or LRB is a type of iżolament bażi employing a heavy damping. It was invented by Bill Robinson, New Zealander.29
Heavy damping mechanism incorporated in kontroll tal-vibrazzjoni 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 Bini tal-Parlament have been fitted with the bearings. Both are in Wellington which sits on an tort attiv.29
Molol-b'-iżolatur tal-bażi tal-umidifikatur
Springs-with-damper base isolator installed under a three-story town-house, Santa Monika, California is shown on the photo taken prior to the 1994 Terremot Northridge exposure. It is a iżolament bażi device conceptually similar to Ċomb Lastiku Bearing.
One of two three-story town-houses like this, which was well instrumented for recording of both vertical and horizontal aċċelerazzjonijiet on its floors and the ground, has survived a severe shaking during the Terremot Northridge and left valuable recorded information for further study.
Roller bearing sempliċi
Simple roller bearing is a iżolament bażi device which is intended for protection of various building and non-building structures against potentially damaging impatti laterali 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 bering tar-rombli metalliku for a housing complex (17 stories) in Tokyo, il-Ġappun.31
Frizzjoni pendlu bearing
Friction pendulum bearing (FPB) is another name of sistema tal-pendlu tal-frizzjoni (FPS). It is based on three pillars:32
slider tal-frizzjoni artikolat;
wiċċ li jiżżerżaq konkavi sferiku;
ċilindru li jagħlaq għat-trażżin tal-ispostament laterali.
Snapshot with the link to video clip of a ħawwad-mejda testing of FPB system supporting a rigid building model is presented at the right.
Disinn sismiku
Disinn sismiku is based on authorized engineering procedures, principles and criteria meant to disinn or retrofit structures subject to earthquake exposure.19 Those criteria are only consistent with the contemporary state of the knowledge about strutturi ta' inġinerija tat-terremoti.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 prova u żball process whether it was based on physical laws or on empirical knowledge of the prestazzjoni strutturali of different shapes and materials.
To practice disinn sismiku, seismic analysis or seismic evaluation of new and existing civil engineering projects, an inġinier should, normally, pass examination on Prinċipji Siżmiċi35 which, in the State of California, include:
Dejta Sismika u Kriterji tad-Disinn Sismiku
Karatteristiċi Sismiċi ta' Sistemi ta' Inġinerija
Forzi Sismiċi
Proċeduri ta' Analiżi Siżmika
Dettal Sismiku u Kontroll tal-Kwalità tal-Kostruzzjoni
Biex jinbnew sistemi strutturali kumplessi,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 modi ta' falliment of a structure and providing the structure with appropriate saħħa, ebusija, duttilità, and konfigurazzjoni37 to ensure those modes cannot occur.
Rekwiżiti tad-disinn sismiku
Rekwiżiti tad-disinn sismiku 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, Dipartiment tat-Trasport ta' Kalifornja's requirements called Il-Kriterji tad-Disinn Sismiku (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 valutazzjoni bbażata-forza of seismic demand to a valutazzjoni bbażata fuq l-ispostament- of demand and capacity. Thus, the newly adopted displacement approach is based on comparing the spostament elastiku demand to the spostament inelastiku 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 stabbilizzazzjoni tal-art 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
Faċilitajiet nukleari 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 Inċidenti nukleari ta' Fukushima I and ħsara lil faċilitajiet nukleari oħra that followed the 2011 Tōhoku earthquake and tsunami have, however, drawn attention to ongoing concerns over Standards Ġappuniżi tad-disinn sismiku nukleari and caused many other governments to jerġa'-evalwa l-programmi nukleari tagħhom. Doubt has also been expressed over the seismic evaluation and design of certain other plants, including the Impjant tal-Enerġija Nukleari ta' Fessenheim in France.
Modi ta' falliment
Modalità ta' falliment 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 disinn sismiku methods. Below, some typical modes of earthquake-generated failures are presented.
The lack of tisħiħ coupled with poor mehrież and inadequate roof-to-wall ties can result in substantial damage to an bini tal-ġebel mhux rinfurzat. Ħitan kkrekkjati jew mimlijin ħafna huma wħud mill-aktar ħsarat komuni mit-terremoti. Perikoluża wkoll hija l-ħsara li tista 'sseħħ bejn il-ħitan u d-dijaframmi tas-saqaf jew tal-art. Is-separazzjoni bejn il-qafas u l-ħitan tista 'tipperikola l-appoġġ vertikali tas-sistemi tas-saqaf u tal-art.
Effett ta 'storja artab. 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 fuljetta tal-briks, has been completely dismantled from the studwall. Only the riġidità 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.
Likwefazzjoni tal-ħamrija. 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, likwefazzjoni of those loose saturated deposits may result in non-uniform insedjamenti and tilting of structures. This caused major damage to thousands of buildings in Niigata, Japan during the Terremot tal-1964.43
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Waqgħa tal-blat tal-landslide. A valanga is a geological phenomenon which includes a wide range of ground movement, including waqgħat tal-blat. Typically, the action of gravità is the primary driving force for a landslide to occur though in this case there was another contributing factor which affected the original stabbiltà tal-inklinazzjoni: the landslide required an grillu tat-terremot before being released.
Tħabbat kontra bini ta’ ħdejn. This is a photograph of the collapsed five-story tower, St. Joseph's Seminary, Los Altos, Kalifornja which resulted in one fatality. During Terremot ta’ 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 Terremot Northridge, the Kaiser Permanente concrete frame office building had joints completely shattered, revealing azzar ta 'konfinament inadegwat, which resulted in the second story collapse. In the transverse direction, composite end shear walls, consisting of two wythes of brick and a layer of shotcrete that carried the lateral load, peeled apart because of inadegwati permezz ta'-rabtiet and failed.
Improper sit tal-kostruzzjoni on a għoljiet.
Poor detailing of the tisħiħ (lack of concrete confinement in the columns and at the beam-column joints, inadequate splice length).
Seismically weak storja artab at the first floor.
Long cantilevers with heavy tagħbija mejta.
Effett tal-pedamenti li jiżżerżqu of a relatively rigid residential building structure during Terremot ta’ Whittier Narrows tal-1987. The magnitude 5.9 earthquake pounded the Garvey West Apartment building in Monterey Park, California and shifted its sovrastruttura about 10 inches to the east on its foundation.
If a superstructure is not mounted on a iżolament bażi system, its shifting on the basement should be prevented.
Konkrit rinfurzat column burst at Terremot Northridge due to mod insuffiċjenti ta' rinfurzar tal-shear which allows main reinforcement to bokkla outwards. The deck unseated at the ċappetta and failed in shear. As a result, the La Cienega-Venice sottopassaġġ section of the 10 Freeway collapsed.
Terremot ta’ Loma Prieta: side view of reinforced concrete appoġġ-falliment fil-kolonni which triggered il-kollass tal-gverta ta’ fuq fuq il-gverta t’isfel of the two-level Cypress viaduct of Interstate Highway 880, Oakland, CA.
Ħsara tal-ħajt ta 'żamma at Terremot ta’ Loma Prieta in Santa Cruz Mountains area: prominent northwest-trending extensional cracks up to 12 cm (4.7 in) wide in the concrete spillway to Austrian Dam, the north abutment.
Ground shaking triggered likwefazzjoni tal-ħamrija in a subsurface layer of ramel, producing differential lateral and vertical movement in an overlying karapace of unliquified sand and ħama. This mod ta 'falliment ta' l-art, termed tixrid laterali, hija kawża prinċipali ta' ħsara mit-terremot relatata ma' likwefazzjoni-.44
Severely damaged building of Agriculture Development Bank of China after Terremot ta’ Sichuan tal-2008: most of the travi u kolonni tal-moll huma mqaxxrin. Large diagonal cracks in masonry and veneer are due to in-plane loads while abrupt settlement of the right end of the building should be attributed to a terraferma which may be hazardous even without any earthquake.45
Impatt tat-tsunami doppju: mewġ tal-baħar hydraulic pressjoni and għargħar. Thus, it-terremot fl-Oċean Indjan of December 26, 2004, with the epiċentru off the west coast of Sumatra, Indonesia, triggered a series of devastating tsunamis, killing more than 230,000 people in eleven countries by għargħar komunitajiet kostali tal-madwar b'mewġ enormi up to 30 meters (100 feet) high.47
Kostruzzjoni reżistenti-terremoti
Kostruzzjoni ta' terremoti means implementation of disinn sismiku to enable building and non-building structures to live through the anticipated earthquake exposure up to the expectations and in compliance with the applicable kodiċi tal-bini.
Id-disinn u l-kostruzzjoni huma intimament relatati. Biex tinkiseb abbilità tajba, id-dettalji tal-membri u l-konnessjonijiet tagħhom għandhom ikunu sempliċi kemm jista 'jkun. Bħal kull kostruzzjoni b'mod ġenerali, il-kostruzzjoni tat-terremoti hija proċess li jikkonsisti fil-bini, ir-retrofitting jew l-assemblaġġ tal-infrastruttura minħabba l-materjali tal-kostruzzjoni disponibbli.48
The destabilizing action of an earthquake on constructions may be dirett (seismic motion of the ground) or indiretti (earthquake-induced landslides, likwefazzjoni tal-ħamrija and waves of tsunami).
Struttura jista 'jkollha l-apparenza kollha ta' stabbiltà, iżda ma toffri xejn ħlief periklu meta jseħħ terremot.49 The crucial fact is that, for safety, earthquake-resistant construction techniques are as important as kontroll tal-kwalità and using correct materials. Kuntrattur tat-terremot should be reġistrat in the state/province/country of the project location (depending on local regulations), magħqudin and assigurataċitazzjoni meħtieġa.
To minimize possible telf, il-proċess ta 'kostruzzjoni għandu jiġi organizzat b'kont meħud li t-terremot jista' jolqot kwalunkwe ħin qabel it-tmiem tal-kostruzzjoni.
Each proġett ta’ kostruzzjoni requires a qualified team of professionals who understand the basic features of seismic performance of different structures as well as ġestjoni tal-kostruzzjoni.
Strutturi Adobe
Around thirty percent of the world's population lives or works in earth-made construction.50 Adobe type of briks tat-tajn is one of the oldest and most widely used building materials. The use of adobe 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.
Bini Adobe huma kkunsidrati vulnerabbli ħafna fi terremoti qawwija.51 However, multiple ways of seismic strengthening of new and existing adobe buildings are available.52
Fatturi ewlenin għall-prestazzjoni sismika mtejba tal-kostruzzjoni tal-adobe huma:
Kwalità tal-kostruzzjoni.
Kompatt, tqassim tat-tip kaxxa-.
Tisħiħ sismiku.53
Strutturi tal-ġebla tal-ġir u tar-ramel
Ġebla tal-ġir 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 ġebla tal-franka and ġebel ramli 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 u Bini tal-Kontea 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.
Strutturi tal-qafas tal-injam
Gwarniċi tal-injam 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 qafas tal-injam in buildings provides their complete skeletal framing which offers some structural benefits as the timber frame, if properly engineered, lends itself to better sopravivenza sismika.54
Strutturi ta'-qafas ħfief
Strutturi ta'-qafas ħfief usually gain seismic resistance from rigid plajwudd shear walls and wood structural panel dijaframmi.55 Special provisions for seismic load-resisting systems for all injam inġinerija structures requires consideration of diaphragm ratios, horizontal and vertical diaphragm shears, and konnettur/qfil values. In addition, collectors, or drag struts, to distribute shear along a diaphragm length are required.
Strutturi rinfurzati tal-ġebel
A construction system where rinfurzar tal-azzar is embedded in the ġonot tat-tikħil of ġebel or placed in holes and that are filled with konkos or ħalib tat-tikħil is called ġebel rinfurzat.56 There are various practices and techniques to reinforce masonry. The most common type is the reinforced ġebel unità vojta.
To achieve a duttili behavior in masonry, it is necessary that the saħħa shear of the wall is greater than the saħħa tal-flessjoni.57 The effectiveness of both vertical and horizontal reinforcements depends on the type and quality of the masonry units and mehrież.
The devastating 1933 Terremot ta’ Long Beach revealed that masonry is prone to earthquake damage, which led to the Kodiċi tal-Istat ta' Kalifornja making masonry reinforcement mandatory across California.
Strutturi tal-konkrit rinfurzat
Konkrit rinfurzat is concrete in which steel reinforcement bars (rebars) or fibri have been incorporated to strengthen a material that would otherwise be fraġli. It can be used to produce travi, kolonni, artijiet jew pontijiet.
Konkrit prestressed is a kind of konkrit rinfurzat used for overcoming concrete's natural weakness in tension. It can be applied to travi, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing għeruq (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a stress kompressiv that offsets the tensjoni tat-tensjoni that the concrete membru tal-kompressjoni 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 duttili 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.
Strutturi prestressati
Struttura prestressata is the one whose overall integrità, stabbiltà and sigurtà depend, primarily, on a pretensjoni. Pretensjoni means the intentional creation of permanent stresses in a structure for the purpose of improving its performance under various service conditions.58
Hemm it-tipi bażiċi li ġejjin ta 'pretensjoni:
-kompressjoni minn qabel (l-aktar, bil-piż proprju ta' struttura)
Pretensjoni with high-strength embedded tendons
Post-tensjoni with high-strength bonded or unbonded tendons
Today, the concept of struttura prestressed is widely engaged in design of bini, underground structures, TV towers, power stations, floating storage and offshore facilities, reattur nukleari vessels, and numerous kinds of pont systems.59
A beneficial idea of pretensjoni was, apparently, familiar to the ancient Rome architects; look, e.g., at the tall attic wall of Kolossew working as a stabilizing device for the wall mollijiet beneath.
Strutturi tal-azzar
Strutturi tal-azzar are considered mostly earthquake resistant but some failures have occurred. A great number of welded mument tal-azzar-frejm li jirreżisti buildings, which looked earthquake-proof, surprisingly experienced brittle behavior and were hazardously damaged in the 1994 Terremot Northridge.60 After that, the Aġenzija Federali għall-Ġestjoni ta' Emerġenza (FEMA) initiated development of repair techniques and new design approaches to minimize damage to steel moment frame buildings in future earthquakes.61
For azzar strutturali seismic design based on Disinn tal-Fattur tat-Tagħbija u tar-Reżistenza (LRFD) approach, it is very important to assess ability of a structure to develop and maintain its bearing resistance in the inelastiku range. A measure of this ability is duttilità, which may be observed in a materjal innifsu, in a element strutturali, or to a struttura kollha.
As a consequence of Terremot 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 Gwarniċi li jirreżistu l-mumenti tal-azzar employ either connections contained in AISC 358, or the use of connections that have been subjected to pre-qualifying cyclic testing.62
Tbassir ta 'telf ta' terremoti
Stima tat-telf tat-terremot is usually defined as a Proporzjon ta' Ħsara (DR) which is a ratio of the earthquake damage repair cost to the valur totali of a building.63 Telf Massimu Probabbli (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 Valutazzjonijiet tar-Riskju Sismiku. Il-proċess tal-valutazzjoni tar-riskju ġeneralment jinvolvi d-determinazzjoni tal-probabbiltà ta 'diversi movimenti tal-art flimkien mal-vulnerabbiltà jew il-ħsara tal-bini taħt dawk il-movimenti tal-art. Ir-riżultati huma definiti bħala perċentwali tal-valur ta' sostituzzjoni tal-bini.65