Zemestrīču inženierija is an starpdisciplinārs branch of engineering that designs and analyzes structures, such as buildings and bridges, with zemestrīces 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 seismiskais risks to sociāli-ekonomiski acceptable levels.1 Traditionally, it has been narrowly defined as the study of the behavior of structures and geo-structures subject to seismiskā slodze; it is considered as a subset of konstrukciju inženierija, ģeotehniskā inženierija, mehāniskā inženierija, ķīmiskā inženierija, lietišķā fizika, 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 civilā inženierija, mehāniskā inženierija, kodoltehnika, and from the sociālās zinātnes, especially socioloģija, politikas zinātne, ekonomika, and finanses.2
Galvenie zemestrīču inženierijas mērķi ir:
Foresee the potential consequences of strong zemestrīces on pilsētu teritorijās and civil infrastructure.
Design, construct and maintain structures to veikt at earthquake exposure up to the expectations and in compliance with būvnormatīvi.3
A pareizi izstrādāta struktūra 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.
Seismiskā slodze
Seismiskā slodze 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 gravitācijas viļņi from cunami. The loading that is expected at a given location on the Earth's surface is estimated by engineering seismoloģija. It is related to the seismisks apdraudējums of the location.
Seismiskā veiktspēja
Zemestrīce or seismiskā veiktspēja defines a structure's ability to sustain its main functions, such as its drošību and izmantojamība, plkst and pēc a particular earthquake exposure. A structure is normally considered droši if it does not endanger the lives and labsajūtu- of those in or around it by partially or completely collapsing. A structure may be considered apkalpojams if it is able to fulfill its operational functions for which it was designed.
Zemestrīču inženierijas pamatjēdzieni, kas ieviesti galvenajos būvnormatīvos, paredz, ka ēkai vajadzētu pārdzīvot retu, ļoti smagu zemestrīci, nodarot ievērojamus bojājumus, bet bez globālas sabrukšanas.7 On the other hand, it should remain operational for more frequent, but less severe seismic events.
Seismiskā veiktspējas novērtējums
Inženieriem ir jāzina faktiskās vai paredzamās seismiskās veiktspējas kvantitatīvais līmenis, kas saistīts ar tiešajiem bojājumiem atsevišķai ēkai, kas pakļauta noteiktai zemes satricināšanai. Šādu novērtējumu var veikt vai nu eksperimentāli, vai analītiski.
Eksperimentāls novērtējums
Experimental evaluations are expensive tests that are typically done by placing a (scaled) model of the structure on a kratīt-galdu 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.
Tā kā šādi testi ir dārgi, tos galvenokārt izmanto, lai izprastu struktūru seismisko uzvedību, apstiprinātu modeļus un pārbaudītu analīzes metodes. Tādējādi, ja tie ir pareizi apstiprināti, skaitļošanas modeļi un skaitliskās procedūras parasti uzņemas lielāko slogu konstrukciju seismiskās veiktspējas novērtējumam.
Analītiskais/skaitliskais novērtējums
Seismiskā veiktspējas novērtējums or seismiskā struktūras analīze 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 ne-ēku konstrukcijas. Tehnika kā formāls jēdziens ir salīdzinoši nesen izstrādāts.
In general, seismic structural analysis is based on the methods of strukturālā dinamika.10 For decades, the most prominent instrument of seismic analysis has been the earthquake reakcijas spektrs 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{0}}linearitāte) appears. Numerical soli{0}}pa-integrācija proved to be a more effective method of analysis for multi-degree-of-freedom strukturālās sistēmas with significant ne{0}}linearitāte under a pārejošs process of ground motion excitation.12 Use of the galīgo elementu metode is one of the most common approaches for analyzing non-linear augsnes struktūras mijiedarbība computer models.
Pamatā tiek veikta skaitliskā analīze, lai novērtētu ēku seismiskos rādītājus. Veiktspējas novērtējums parasti tiek veikts, izmantojot nelineāru statisku nobīdes analīzi vai nelineāro laika{0}}vēstures analīzi. Šādās analīzēs ir svarīgi panākt precīzu ne-lineāru strukturālo komponentu modelēšanu, piemēram, sijas, kolonnas, siju -kolonnu savienojumus, bīdes sienas utt. Tādējādi eksperimentālajiem rezultātiem ir liela nozīme, nosakot atsevišķu komponentu modelēšanas parametri, īpaši to, kas ir pakļauti ievērojamām nelineārām deformācijām. Pēc tam atsevišķie komponenti tiek montēti, lai izveidotu pilnu ne{4}}lineāru struktūras modeli. Šādi izveidoti modeļi tiek analizēti, lai novērtētu ēku veiktspēju.
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, ABAKUSA, 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 MOOSE Framework, RUAUMOKO un vecākais DRAIN-2D/3D, no kuriem vairāki tagad ir atvērtā koda.
Zemestrīču inženierijas pētījumi
Zemestrīču inženierijas pētījumi nozīmē gan lauka, gan analītiskus pētījumus vai eksperimentus, kas paredzēti ar zemestrīču inženieriju saistītu faktu atklāšanai un zinātniskai skaidrošanai, konvencionālo koncepciju pārskatīšanai, ņemot vērā jaunus atklājumus, un izstrādāto teoriju praktiskai pielietošanai.
The Nacionālais zinātnes fonds (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 Zemestrīču inženierzinātņu pētniecības institūts (EERI) is a leader in dissemination of zemestrīču inženiertehniskie pētījumi related information both in the U.S. and globally.
A definitive list of earthquake engineering research related kratot galdus 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 Japāna.
Galvenās ASV pētniecības programmas
NSF also supports the George E. Brown, Jr. Zemestrīču inženierijas simulācijas tīkls
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 analīze and model based simulation of structural behaviour and response including soil-structure interaction; design concepts that improve struktūras veiktspēja and flexibility; and application of new control techniques for structural systems.16
(NEES) that advances knowledge discovery and innovation for zemestrīces and cunami loss reduction of the nation's civil infrastructure and new experimental simulation techniques and instrumentation.17
NEES tīklā ir 14 ģeogrāfiski-izplatītas, dalītas-lietošanas laboratorijas, kas atbalsta vairāku veidu eksperimentālo darbu:17 geotechnical centrifuge research, kratīt-galdu tests, large-scale structural testing, tsunami wave basin experiments, and field site research.18 Participating universities include: Kornela universitāte; Lehigas universitāte; Oregonas štata universitāte; Renselera Politehniskais institūts; Bufalo universitāte, Ņujorkas štata universitāte; Kalifornijas Universitāte, Bērklija; Kalifornijas Universitāte, Deivisa; Kalifornijas Universitāte, Losandželosa; Kalifornijas Universitāte, Sandjego; Kalifornijas Universitāte, Santa Barbara; Ilinoisas Universitāte, Urbāna{0}}Šampena; Minesotas Universitāte; Nevadas Universitāte, Reno; and the Teksasas Universitāte, Ostina.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 Purdjū universitāte for nanoHUB specifically to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internets 2, nodrošina interaktīvus simulācijas rīkus, simulācijas rīku izstrādes zonu, kurētu centrālo datu krātuvi, animētas prezentācijas, lietotāju atbalstu, telepresence, resursu augšupielādes un koplietošanas mehānismu, kā arī statistiku par lietotājiem un lietošanas modeļiem.
Šī kiberinfrastruktūra ļauj pētniekiem: droši uzglabāt, kārtot un koplietot datus standartizētā sistēmā centrālā vietā; attālināti novērot un piedalīties eksperimentos, izmantojot sinhronizētus{0}}reāllaika datus un video; sadarboties ar kolēģiem, lai atvieglotu pētījumu eksperimentu plānošanu, veikšanu, analīzi un publicēšanu; un veikt skaitļošanas un hibrīda simulācijas, kas var apvienot vairāku izkliedētu eksperimentu rezultātus un saistīt fiziskos eksperimentus ar datorsimulācijām, lai varētu izpētīt kopējo sistēmas veiktspēju.
Šie resursi kopā nodrošina līdzekļus sadarbībai un atklāšanai, lai uzlabotu civilās un mehāniskās infrastruktūras sistēmu seismisko dizainu un veiktspēju.
Zemestrīces simulācija
The very first zemestrīču simulācijas were performed by statically applying some horizontālie inerces spēki based on mērogots maksimālais zemes paātrinājums to a mathematical model of a building.19 With the further development of computational technologies, statisks approaches began to give way to dinamisks ones.
Dynamic experiments on building and non-building structures may be physical, like sakrata{0}}galda testēšana, vai virtuālās. Abos gadījumos, lai pārbaudītu paredzamo struktūras seismisko veiktspēju, daži pētnieki dod priekšroku tā sauktajām "reālā laika{0}}vēstures datiem", lai gan pēdējā nevar būt "reāla" hipotētiskai zemestrīcei, kas noteikta ne būvnormatīvā, ne dažas īpašas pētniecības prasības. Tāpēc ir spēcīgs stimuls iesaistīties zemestrīces simulācijā, kas ir seismiskā ievade, kurai piemīt tikai būtiskas reāla notikuma pazīmes.
Dažkārt zemestrīces simulācija tiek saprasta kā spēcīgas zemes trīcēšanas{0}}vietējo seku radīšana.
Struktūras simulācija
Theoretical or experimental evaluation of anticipated seismic performance mostly requires a struktūras simulācija which is based on the concept of structural likeness or similarity. Līdzība is some degree of līdzība or līdzība between two or more objects. The notion of similarity rests either on exact or approximate repetitions of modeļiem in the compared items.
In general, a building model is said to have similarity with the real object if the two share ģeometriskā līdzība, kinemātiskā līdzība and dinamiskā līdzība. The most vivid and effective type of similarity is the kinemātiskā one. Kinemātiskā līdzība exists when the paths and velocities of moving particles of a model and its prototype are similar.
The ultimate level of kinemātiskā līdzība is kinemātiskā ekvivalence when, in the case of earthquake engineering, time-histories of each story lateral displacements of the model and its prototype would be the same.
Seismiskās vibrācijas kontrole
Seismiskās vibrācijas kontrole is a set of technical means aimed to mitigate seismic impacts in building and ne-ēka structures. All seismic vibration control devices may be classified as pasīvs, aktīvs or hibrīds21 where:
pasīvās kontroles ierīces have no atsauksmes capability between them, structural elements and the ground;
aktīvās vadības ierīces incorporate real-time recording instrumentation on the ground integrated with earthquake input processing equipment and izpildmehānismi within the structure;
hibrīda vadības ierīces have combined features of active and passive control systems.22
When ground seismiskie viļņi 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 virsbūve, ir vairāki veidi, kā tos kontrolēt, lai mazinātu to kaitīgo ietekmi un uzlabotu ēkas seismiskos rādītājus, piemēram:
to izkliedēt the wave energy inside a virsbūve with properly engineered amortizatori;
izkliedēt viļņu enerģiju starp plašāku frekvenču diapazonu;
to absorbēt the rezonanses portions of the whole wave frequencies band with the help of so-called masas slāpētāji.23
Pēdējā veida ierīces, attiecīgi saīsinātas kā TMD noregulētajam (pasīvs), as AMD for the aktīvs, and as HMD for the hibrīda masas amortizatori, have been studied and installed in augstceltnes{0}}, pārsvarā Japānā, ceturtdaļgadsimtu.24
However, there is quite another approach: partial suppression of the seismic energy flow into the virsbūve known as seismic or bāzes izolācija.
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 virsbūve from its apakšstruktūra resting on a shaking ground.
The first evidence of earthquake protection by using the principle of base isolation was discovered in Pasargadae, pilsēta senajā Persijā, tagadējā Irānā, un tā aizsākās 6. gadsimtā pirms mūsu ēras. Zemāk ir daži mūsdienu seismisko vibrāciju kontroles tehnoloģiju paraugi.
Sausas{0}}akmens sienas Peru
Peru is a highly seismisks land; for centuries the dry-stone celtniecība proved to be more earthquake-resistant than using mortar. People of Inku civilizācija were masters of the polished 'dry-stone walls', called ashlar, where blocks of stone were cut to fit together tightly without any java. Inki bija vieni no labākajiem akmeņkaļiem, kādu pasaule jebkad ir redzējusi25 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 strukturālā kontrole technique employing both the principle of energy dissipation (coulomb damping) and that of suppressing rezonanses amplifications.26
Noregulēts masas slāpētājs
Typically the noregulēti masas amortizatori are huge concrete blocks mounted in debesskrāpji or other structures and move in opposition to the rezonanses frekvence oscillations of the structures by means of some sort of spring mechanism.
The Taipeja 101 skyscraper needs to withstand taifūns winds and earthquake trīce common in this area of Asia/Pacific. For this purpose, a steel svārsts 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 brāzmas.
Histerētiski amortizatori
A histērisks slāpētājs is intended to provide better and more reliable seismic performance than that of a conventional structure by increasing the dissipation of seismiskā ievade energy.27 There are five major groups of hysteretic dampers used for the purpose, namely:
Šķidruma viskozi slāpētāji (FVD)
Viskozajiem amortizatoriem ir priekšrocība, ka tie ir papildu amortizācijas sistēma. Tiem ir ovāla histerētiskā cilpa, un amortizācija ir atkarīga no ātruma. Lai gan, iespējams, ir nepieciešama neliela apkope, viskozi slāpētāji parasti nav jāmaina pēc zemestrīces. Lai gan tie ir dārgāki par citām slāpēšanas tehnoloģijām, tos var izmantot gan seismisko, gan vēja slodžu gadījumā, un tie ir visbiežāk izmantotie histerētiskie slāpētāji.28
Berzes slāpētāji (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 kulona slāpētājs. Depending on the design, friction dampers can experience stick{0}}slīdēšanas parādība and Aukstā metināšana. Galvenais trūkums ir tas, ka berzes virsmas laika gaitā var nolietoties, tāpēc tās nav ieteicamas vēja slodzes izkliedēšanai. Lietojot seismiskos lietojumos, nodilums nav problēma un nav nepieciešama apkope. Viņiem ir taisnstūra histerētiska cilpa, un, kamēr ēka ir pietiekami elastīga, tie pēc zemestrīces mēdz atgriezties sākotnējā stāvoklī.
Metāla amortizatori (MYD)
Metāla amortizatori, kā norāda nosaukums, dod spēku, lai absorbētu zemestrīces enerģiju. Šāda veida amortizatori absorbē lielu enerģijas daudzumu, taču tie ir jānomaina pēc zemestrīces, un tie var neļaut ēkai nostādināties atpakaļ sākotnējā stāvoklī.
Viskoelastīgie amortizatori (VED)
Viskoelastīgie amortizatori ir noderīgi ar to, ka tos var izmantot gan vēja, gan seismiskiem lietojumiem, parasti tie ir ierobežoti ar nelielu nobīdi. Pastāv zināmas bažas par tehnoloģijas uzticamību, jo dažus zīmolus ir aizliegts izmantot ēkās Amerikas Savienotajās Valstīs.
Pārvietojamie svārsta amortizatori (šūpošanās)
Bāzes izolācija
Bāzes izolācijas mērķis ir novērst zemestrīces kinētiskās enerģijas pārnešanu uz elastīgo enerģiju ēkā. Šīs tehnoloģijas to dara, izolējot konstrukciju no zemes, tādējādi ļaujot tām pārvietoties zināmā mērā neatkarīgi. Pakāpe, kādā enerģija tiek pārnesta uz struktūru un kā enerģija tiek izkliedēta, atšķiras atkarībā no izmantotās tehnoloģijas.
Svina gumijas gultnis
Lead rubber bearing or LRB is a type of bāzes izolācija employing a heavy amortizācija. It was invented by Bils Robinsons, jaunzēlandietis.29
Heavy damping mechanism incorporated in vibrācijas kontrole 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 Parlamenta ēkas have been fitted with the bearings. Both are in Velingtona which sits on an aktīva vaina.29
Atsperes-ar-amortizatora pamatnes izolatoru
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 Northridge zemestrīce exposure. It is a bāzes izolācija device conceptually similar to Svina gumijas gultnis.
One of two three-story town-houses like this, which was well instrumented for recording of both vertical and horizontal paātrinājumus on its floors and the ground, has survived a severe shaking during the Northridge zemestrīce and left valuable recorded information for further study.
Vienkāršs rullīšu gultnis
Simple roller bearing is a bāzes izolācija device which is intended for protection of various building and non-building structures against potentially damaging sānu triecieni 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 metāla rullīšu gultnis for a housing complex (17 stories) in Tokija, Japāna.31
Berzes svārsta gultnis
Friction pendulum bearing (FPB) is another name of berzes svārsta sistēma (FPS). It is based on three pillars:32
šarnīrveida berzes slīdnis;
sfēriska ieliekta slīdvirsma;
aptverošs cilindrs sānu nobīdes ierobežošanai.
Snapshot with the link to video clip of a kratīt-galdu testing of FPB system supporting a rigid building model is presented at the right.
Seismiskais dizains
Seismiskais dizains is based on authorized engineering procedures, principles and criteria meant to dizains or modernizēšana structures subject to earthquake exposure.19 Those criteria are only consistent with the contemporary state of the knowledge about zemestrīces inženierbūves.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 izmēģinājums un kļūda process whether it was based on physical laws or on empirical knowledge of the strukturālā veiktspēja of different shapes and materials.
To practice seismiskais dizains, seismic analysis or seismic evaluation of new and existing civil engineering projects, an inženieris should, normally, pass examination on Seismiskie principi35 which, in the State of California, include:
Seismiskie dati un seismiskās konstrukcijas kritēriji
Inženiertehnisko sistēmu seismiskie raksturlielumi
Seismiskie spēki
Seismiskās analīzes procedūras
Seismiskās detaļas un būvniecības kvalitātes kontrole
Lai izveidotu sarežģītas strukturālās sistēmas,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.
Parasti saskaņā ar būvnormatīviem konstrukcijas ir veidotas tā, lai "izturētu" lielāko noteiktas varbūtības zemestrīci, kas varētu notikt to atrašanās vietā. Tas nozīmē, ka dzīvību zaudējums jāsamazina, novēršot ēku sabrukšanu.
Seismic design is carried out by understanding the possible atteices režīmi of a structure and providing the structure with appropriate spēks, stīvums, plastiskums, and konfigurācija37 to ensure those modes cannot occur.
Seismiskā dizaina prasības
Seismiskā dizaina prasības 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, Kalifornijas Transporta departaments's requirements called Seismiskā dizaina kritēriji (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 uz spēku{0}}pamatotu novērtējumu of seismic demand to a pārvietošanās{0}}novērtējums of demand and capacity. Thus, the newly adopted displacement approach is based on comparing the elastīga nobīde demand to the neelastīga nobīde 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 zemes stabilizācija 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
Kodolobjekti 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 Fukušimas I kodolavārijas and bojājumiem citiem kodoliekārtām that followed the 2011 Tōhoku earthquake and tsunami have, however, drawn attention to ongoing concerns over Japānas kodolseismiskās projektēšanas standarti and caused many other governments to atkārtoti{0}}novērtēt savas kodolprogrammas. Doubt has also been expressed over the seismic evaluation and design of certain other plants, including the Fesenheimas atomelektrostacija in France.
Kļūmes režīmi
Neveiksmes režīms 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 seismiskais dizains methods. Below, some typical modes of earthquake-generated failures are presented.
The lack of pastiprinājums coupled with poor java and inadequate roof-to-wall ties can result in substantial damage to an nepastiprināta mūra ēka. Smagi saplaisājušas vai slīpas sienas ir daži no visizplatītākajiem zemestrīces bojājumiem. Bīstami ir arī bojājumi, kas var rasties starp sienām un jumta vai grīdas diafragmām. Atdalīšana starp karkasu un sienām var apdraudēt jumta un grīdas sistēmu vertikālo atbalstu.
Mīksta stāsta efekts. 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 ķieģeļu finieris, has been completely dismantled from the studwall. Only the stingrība 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.
Augsnes sašķidrināšana. 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, sašķidrināšana of those loose saturated deposits may result in non-uniform apmetnes and tilting of structures. This caused major damage to thousands of buildings in Niigata, Japan during the 1964. gada zemestrīce.43
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Zemes nogruvums klinšu kritums. A nogruvums is a geological phenomenon which includes a wide range of ground movement, including klinšu kritumi. Typically, the action of smagums is the primary driving force for a landslide to occur though in this case there was another contributing factor which affected the original slīpuma stabilitāte: the landslide required an zemestrīces izraisītājs before being released.
Sitiens pret blakus ēku. This is a photograph of the collapsed five-story tower, St. Joseph's Seminary, Los Altosa, Kalifornija which resulted in one fatality. During Loma Prieta zemestrīce, tornis atsitās pret neatkarīgi vibrējošo blakus ēku aiz muguras. Sagrūšanas iespēja ir atkarīga no abu ēku sānu nobīdēm, kas ir precīzi jānovērtē un jāņem vērā.
At Northridge zemestrīce, the Kaiser Permanente concrete frame office building had joints completely shattered, revealing neatbilstošs tērauds, which resulted in the second story collapse. In the transverse direction, composite end bīdes sienas, consisting of two wythes of brick and a layer of skrotis betons that carried the lateral load, peeled apart because of neadekvāti, izmantojot-saites and failed.
Improper būvlaukums on a pakājē.
Poor detailing of the pastiprinājums (lack of concrete confinement in the columns and at the beam-column joints, inadequate splice length).
Seismically weak maigs stāsts at the first floor.
Long konsoles with heavy tukšā slodze.
Tonālo krēmu noslīdēšanas efekts of a relatively rigid residential building structure during 1987. gada Whittier Narrows zemestrīce. The magnitude 5.9 earthquake pounded the Garvey West Apartment building in Monterey Park, California and shifted its virsbūve about 10 inches to the east on its foundation.
If a superstructure is not mounted on a bāzes izolācija system, its shifting on the basement should be prevented.
Dzelzsbetons column burst at Northridge zemestrīce due to nepietiekams bīdes pastiprināšanas režīms which allows main reinforcement to sprādze outwards. The deck unseated at the vira and failed in shear. As a result, the La Cienega-Venice pazemes pāreja section of the 10 Freeway collapsed.
Loma Prieta zemestrīce: side view of reinforced concrete atbalsta-kolonnu kļūme which triggered augšējais klājs sabrūk uz apakšējā klāja of the two-level Cypress viaduct of Interstate Highway 880, Oakland, CA.
Atbalsta sienas bojājums at Loma Prieta zemestrīce 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 abatments.
Ground shaking triggered augsnes sašķidrināšana in a subsurface layer of smiltis, producing differential lateral and vertical movement in an overlying karapuce of unliquified sand and dūņas. This zemes atteices veids, termed sānu izkliedēšana, ir galvenais ar sašķidrināšanu{0}}saistīto zemestrīču cēlonis.44
Severely damaged building of Agriculture Development Bank of China after Sičuaņas zemestrīce 2008: most of the sijas un piestātnes kolonnas ir nocirptas. Large diagonal cracks in masonry and veneer are due to in-plane loads while abrupt norēķinu of the right end of the building should be attributed to a poligons which may be hazardous even without any earthquake.45
Divkārša cunami ietekme: jūras viļņi hydraulic spiedienu and applūšana. Thus, Indijas okeāna zemestrīce of December 26, 2004, with the epicentrs off the west coast of Sumatra, Indonesia, triggered a series of devastating tsunamis, killing more than 230,000 people in eleven countries by appludinot apkārtējās piekrastes kopienas ar milzīgiem viļņiem up to 30 meters (100 feet) high.47
Zemestrīcēm{0}}izturīga konstrukcija
Zemestrīces celtniecība means implementation of seismiskais dizains to enable building and non-building structures to live through the anticipated earthquake exposure up to the expectations and in compliance with the applicable būvnormatīvi.
Dizains un būvniecība ir cieši saistīti. Lai panāktu labu darbu, dalībnieku un to savienojumu aprakstam jābūt pēc iespējas vienkāršākam. Tāpat kā jebkura būvniecība kopumā, zemestrīces celtniecība ir process, kas sastāv no infrastruktūras izveides, modernizācijas vai montāžas, ņemot vērā pieejamos celtniecības materiālus.48
The destabilizing action of an earthquake on constructions may be tiešā veidā (seismic motion of the ground) or netiešs (earthquake-induced landslides, augsnes sašķidrināšana and waves of tsunami).
Struktūrai var būt viss stabilitātes izskats, taču zemestrīces gadījumā tā var radīt tikai briesmas.49 The crucial fact is that, for safety, earthquake-resistant construction techniques are as important as kvalitātes kontrole and using correct materials. Zemestrīces darbuzņēmējs should be reģistrēts in the state/province/country of the project location (depending on local regulations), saistīts and apdrošinātsnepieciešama atsauce.
To minimize possible zaudējumiem, būvniecības process jāorganizē, paturot prātā, ka zemestrīce var notikt jebkurā laikā pirms būvniecības beigām.
Each būvprojekts requires a qualified team of professionals who understand the basic features of seismic performance of different structures as well as būvniecības vadība.
Adobe struktūras
Apmēram trīsdesmit procenti pasaules iedzīvotāju dzīvo vai strādā zemes{0}}celtniecībā.50 Adobe type of dubļu ķieģeļi 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.
Adobe ēkas tiek uzskatītas par ļoti neaizsargātām spēcīgu zemestrīču gadījumā.51 However, multiple ways of seismic strengthening of new and existing adobe buildings are available.52
Galvenie faktori, kas uzlabo Adobe konstrukcijas seismisko veiktspēju, ir:
Būvniecības kvalitāte.
Kompakts, lodziņa{0}}tipa izkārtojums.
Seismiskā pastiprināšana.53
Kaļķakmens un smilšakmens konstrukcijas
Kaļķakmens 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 kaļķakmens and smilšakmens 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 Soltleiksitijas un apgabala ēka in Juta 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.
Koka karkasa konstrukcijas
Koka karkass 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 koka karkasu in buildings provides their complete skeletal framing which offers some structural benefits as the timber frame, if properly engineered, lends itself to better seismiskā izdzīvošana.54
Vieglas{0}}rāmju struktūras
Vieglas{0}}rāmju struktūras usually gain seismic resistance from rigid saplāksnis shear walls and wood structural panel diafragmas.55 Special provisions for seismic load-resisting systems for all inženierijas koks structures requires consideration of diaphragm ratios, horizontal and vertical diaphragm shears, and savienotājs/stiprinājums values. In addition, collectors, or drag struts, to distribute shear along a diaphragm length are required.
Pastiprinātas mūra konstrukcijas
A construction system where tērauda stiegrojums is embedded in the javas šuves of mūra or placed in holes and that are filled with betons or javu is called pastiprināts mūris.56 There are various practices and techniques to reinforce masonry. The most common type is the reinforced dobu mezglu mūris.
To achieve a elastīgs behavior in masonry, it is necessary that the bīdes spēks of the wall is greater than the lieces spēks.57 The effectiveness of both vertical and horizontal reinforcements depends on the type and quality of the masonry units and java.
The devastating 1933. gada Longbīčas zemestrīce revealed that masonry is prone to earthquake damage, which led to the Kalifornijas štata kodekss making masonry reinforcement mandatory across California.
Dzelzsbetona konstrukcijas
Dzelzsbetons is concrete in which steel reinforcement bars (armatūras stieņi) or šķiedras have been incorporated to strengthen a material that would otherwise be trausls. It can be used to produce sijas, kolonnas, grīdas vai tilti.
Spriegots betons is a kind of dzelzsbetons used for overcoming concrete's natural weakness in tension. It can be applied to sijas, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing cīpslas (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a spiedes spriegums that offsets the stiepes spriegums that the concrete kompresijas elements 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 elastīgs 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.
Iepriekš nospriegotas konstrukcijas
Iepriekš nospriegota struktūra is the one whose overall integritāte, stabilitāte and drošību depend, primarily, on a iepriekšēja nospriegošana. Iepriekšēja nospriegošana means the intentional creation of permanent stresses in a structure for the purpose of improving its performance under various service conditions.58
Ir šādi pamata spriegojuma veidi:
Iepriekšēja-saspiešana (galvenokārt ar pašas struktūras svaru)
Priekšspriegošana with high-strength embedded tendons
Pēc-spriegošana with high-strength bonded or unbonded tendons
Today, the concept of iepriekš nospriegota struktūra is widely engaged in design of ēkas, underground structures, TV towers, power stations, floating storage and offshore facilities, kodolreaktors vessels, and numerous kinds of tilts systems.59
A beneficial idea of iepriekšēja nospriegošana was, apparently, familiar to the ancient Rome architects; look, e.g., at the tall Bēniņi wall of Kolizejs working as a stabilizing device for the wall piestātnes beneath.
Tērauda konstrukcijas
Tērauda konstrukcijas are considered mostly earthquake resistant but some failures have occurred. A great number of welded tērauda moment{0}}izturīgs rāmis buildings, which looked earthquake-proof, surprisingly experienced brittle behavior and were hazardously damaged in the 1994. gada Northridge zemestrīce.60 After that, the Federālā ārkārtas situāciju pārvaldības aģentūra (FEMA) initiated development of repair techniques and new design approaches to minimize damage to steel moment frame buildings in future earthquakes.61
For strukturālais tērauds seismic design based on Slodzes un pretestības faktoru dizains (LRFD) approach, it is very important to assess ability of a structure to develop and maintain its bearing resistance in the neelastīgs range. A measure of this ability is plastiskums, which may be observed in a pats materiāls, in a strukturālais elements, or to a visa struktūra.
As a consequence of Northridge zemestrīce 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 Tērauda momentizturīgi rāmji employ either connections contained in AISC 358, or the use of connections that have been subjected to pre-qualifying cyclic testing.62
Zemestrīces zaudējumu prognozēšana
Zemestrīces zaudējumu aplēse is usually defined as a Bojājumu attiecība (DR) which is a ratio of the earthquake damage repair cost to the kopējā vērtība of a building.63 Iespējamais maksimālais zaudējums (PML) ir plaši izplatīts termins, ko izmanto zemestrīces zaudējumu aplēsei, taču tam trūkst precīzas definīcijas. 1999. gadā tika izstrādāta ASTM E2026 “Standarta rokasgrāmata ēku bojājumu novērtējumam zemestrīču gadījumā”, lai standartizētu seismisko zudumu aplēšu nomenklatūru, kā arī izstrādātu vadlīnijas par pārskatīšanas procesu un recenzenta kvalifikāciju.64
Earthquake loss estimations are also referred to as Seismiskā riska novērtējumi. Riska novērtēšanas process parasti ietver dažādu zemes kustību iespējamības noteikšanu kopā ar ēkas ievainojamību vai bojājumiem zem šīm kustībām. Rezultāti ir definēti kā procenti no ēkas aizstāšanas vērtības.65