CBS Põhja torn varises kokku

CBS Põhja torn varises kokku


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KELO-TV teenindab Ameerika Ühendriikide kõigi jaamade suurimat vaatamisala. Ta nimetab seda tohutut piirkonda - mis koosneb kogu Lõuna -Dakotast, samuti osadest Iowast, Minnesotast, Montanast, Nebraskast, Põhja -Dakotast ja Wyomingist - "KELOLAND". See hõlmab seda piirkonda kolme täisvõimsusega poolsatelliidi võrguga, mida tuntakse kui Meediakontsern KELOLAND (algselt tuntud kui "KELO-land teler"1954-1991 ja seejärel"KELOLAND Televisioon [võrk]"pärast seda kuni veebruarini 2020).

Tõlkijad Muuda

KCLO-TV Muuda

Kolmas poolsatelliit, KCLO-TV (kanal 15) Rapid City'is kustutab kõik emaprogrammi kaudu pakutavad võrguprogrammid ja simuleerib KELO-TV uudistesaateid (koos kohalike ilmateadetega), kuid eetris on eraldi sündikaatprogrammide pakkumine. Kuigi KCLO-TV peab Rapid Citys Canyon Lake Drive'il uudistebürood ja reklaamimüügibürood, on põhikontroll ja enamik sisemisi toiminguid KELO-TV stuudiotes. Kuna Rapid City asub mägede ajavööndis, algab KCLO-TV parim ajakava kell 18.00. pigem kui tavaline kell 19.00. alustada ülejäänud mäeaega või kesk -aega, kus asuvad KELOLAND Media Groupi teised jaamad.

KELO-TV allkirjastas eetris 19. mail 1953 Lõuna-Dakota esimese televisioonijaamana. See kuulus teatri- ja ringhäälingukonglomeraadile Midcontinent Media koos raadioga KELO (AM 1320 ja 92,5 FM). See oli peamine NBC sidusettevõte, kuid kandis ka programme ABC, CBS ja DuMont. Pärast KSOO-TV (nüüd KSFY-TV) sisselogimist 1960. aastal vahetas KELO-TV oma esmase sideme CBS-i vastu ja on sellest ajast saadik sellesse võrku jäänud.

Varsti pärast KELO-TV sisselogimist varises Federal Communications Commission (FCC) kokku Lõuna-Dakota idaosa, Minnesota edelaosa ja Iowa loodeosa üheks hiiglaslikuks teleturuks. Hiljem 1950ndatel hakkas Midcontinent allkirjastama KELO-TV satelliitjaamades, et teenindada oma suurt leviala. KDLO-TV Firenzes (algselt litsentsitud Garden City-le) oli esimene satelliitjaamadest, mis läks eetrisse 27. septembril 1955, millele järgnes KPLO-TV, mis oli litsentsitud Reliance'ile ja teenindas Lõuna-Dakota osariigi pealinna Pierre'i 15. juulil, 1957.

KELO-TV laienes Lõuna-Dakota lääneossa 1981. aastal, kui sõlmis KPLO-TV tõlkija K15AC (kanal 15) teenuse Rapid City teenindamiseks. 28. novembril 1988 täiendati see täisvõimsusega poolsatelliidiks kui KCLO. Rapid City oli üks väheseid riigi piirkondi, kus kolm peamist võrku ei saanud täisteenust.

KELO oli koduks Kapten 11, piirkonnas populaarne lastesaade, aastatel 1955–1996. Kapten 11 oli jaama kauaaegne ilmateadustaja Dave Dedrick. Ta oli enne KELO eetrisse minekut olnud populaarne raadiotegelane.

Kanal 11 edastas algselt 175-meetrist tornist Shindleri lähedal Lõuna-Dakotas. 20. septembril 1955 hävitati see tugeva tuule käes - arvatavasti tornaado. Jaamainsenerid tõid jaama eetrisse 48 tunni pärast - just World Seriesi ajaks. [1] Aastal 1956 püstitas jaam samasse kohta 1032 jala (315 m) torni, laiendades selle leviala enamikule Lõuna-Dakota idaosast. Aastal 1967 kolis KELO-TV uude 2019-meetrisesse (619 m) torni Rowena lähedal, mida jagati KSFY-ga. Shindleri torni kasutatakse endiselt tagavarana.

24. juunil 1968 lõikas Põhja-Kesk-reisilennuk aastasele Rowena tornile kuti traadi, tuues selle alla. Õnneks maandus lennuk ohutult, vigastusteta. KELO-TV insenerid tõid jaama eetrisse kolme päeva pärast Shindleri vanast tornist. Rowena torn ehitati kiiresti ümber. [1]

11. jaanuaril 1975 hävitas võimas talvetorm KELO-teletorni. Mõne tunni pärast oli jaam Shindleri eetris. [2] Torn ehitati Rowenas uuesti üles ja see hakkas tööle 19. detsembril 1975. Rowena ala nimetatakse arvukate varingute tõttu mõnikord tornikohtade "Bermuda kolmnurgaks".

Järgnevatel aastatel varises KDLO-TV torn kokku ja KELO-TV kaotas tormide ja muude põhjuste tõttu muud mikrolaineahi ja tõlkija saidid. [2] KPLO-TV torn varises 22. jaanuaril 2010 tugeva jäätormi tõttu kokku. See naasis eetrisse 19. märtsil 2010. Mõnda aega töötas see aga väikese võimsusega, mistõttu jäi Pierre ilma üle õhu signaalita. Seejärel andis FCC Pierre'i kanalis 29 välja ehitusloa väikese võimsusega täitetõlkijale.

25. novembril 1986 alustas KELO-TV oma saadete edastamist stereona. 1995. aastal müüs Midcontinent Media KELO-TV Young Broadcastingile. FCC kiitis müügi heaks 31. mail 1996. Jaam tähistas 19. mail 2003 oma 50. aastapäeva.

Hilishooaja jäätorm 6. aprillil 1997 põhjustas Põhja-Dakotas Trailli maakonnas KXJB-TV masti kokkuvarisemise. Seetõttu ei suutnud mitmed Põhja -Dakota idaosas ja Minnesota loodeosas asuvad kaablisüsteemid CBS -i programme vastu võtta. Mõned kaablisüsteemid asendasid KXJB-TV ajutiselt või püsivalt KDLO-TV-ga. (CBS-i programmeerimine Põhja-Dakota idaosas on sellest ajast kolinud KXJB-LD ja KVLY-DT2.)

1999. aastal anti raadiojaamale Rahvusringhäälinguorganisatsioonide liidu sõber sõbrale auhind silmapaistva teeninduse eest loodusõnnetuste korral. [3]

6. juunil 2013 teatas Young Broadcasting, et ühineb Media Generaliga. [4] Ühinemine kiideti heaks 8. novembril, pärast seda, kui Media General aktsionärid kiitsid ühinemise päev varem heaks [5], see viidi lõpule 12. novembril. [6]

Müüa Nexstar Editile

Nexstar Broadcasting Group teatas 27. KCAU-TV Sioux City's, Iowa. [8]


Sisu

Mast asub 4,8 km kaugusel Blanchardist lääne pool, Põhja -Dakotas, poolel teel Fargo ja Grand Forksi vahel. Sellest sai kõrgeim tehiskonstruktsioon ja esimene tehislik ehitis, mille kõrgus ületas 610 m, pärast ehituse lõpetamist 13. augustil 1963.

Torni ehitas Hamilton Erection Company of York, Lõuna -Carolina ja Kline Iron and Steel ning selle valmimiseks kulus kolmkümmend päeva ja see maksis umbes 500 000 dollarit [2] (täna ligikaudu 4,23 miljonit dollarit [3]). Ehitustööd lõpetati 13. augustil 1963. [4]

Torn kuulub Gray Televisioonile Atlanta, Georgia, ja see torn edastab 356 kW võimsusega kanalil 44 televisioonijaama KVLY-TV (kanal 11 PSIP, NBC/CBS sidusettevõte), mis asub Põhja-Dakotas Fargos. Torn annab leviala umbes 9 700 ruut miili (25 000 km 2), mis on umbes 55, 6 miili (89, 5 km) raadiuses. Spektri ümberpakkimise tõttu edastab KVLY UHF kanalil 36 ja kaardistab virtuaalsele kanalile 11 PSIP kaudu. CBS/CW+ sidusettevõte KXJB-LD tõlkija K28MA-D edastab sellel tornil ka 15 kW võimsusega UHF kanalil 28 (ka selle virtuaalsel kanalil).

Kui mast ehitati, muudeti telejaama, mille jaoks see ehitati, kõnetähed KTHI -ks, "HI" viitas masti kõrgusele. Tippu pääseb kahe inimese teenindusliftiga (ehitatud Park Manufacturing of Charlotte, Põhja-Carolina) või redeliga.

Torn koosneb kahest osast: võretornist, mille kõrgus on 590 m [5] ja mille ülaosas on edastava antenni massiiv, mis on 113 jalga (34 m). Mõlema kogukõrgus on 2063 jalga (629 m). Antenn kaalub 9000 naela (4,1 t), võretorn kaalub 855 500 naela (388,0 t), andes kogumassiks 864 500 naela (392,1 t). See võtab koos oma ankrutega 160 aakrit (65 ha) maad. [6] [7] Selle kõrgus keskmisest merepinnast on 3038 jalga (926 m).

Mõni aeg pärast selle valmimist kehtestasid Föderaalne Kommunikatsioonikomisjon (FCC) ja Föderaalne Lennundusamet (FAA) poliitika, mis sätestab: "Kuigi antennitornide absoluutset kõrgusepiirangut ei ole, on mõlemad asutused kehtestanud ümberlükatava eelduse üle 2000 jala pikkuste konstruktsioonide suhtes maapinnast kõrgemal. " FCC ja FAA võivad "erandjuhtudel" kõrgema struktuuri heaks kiita. [8]


Ajaskaala: rünnak Ameerikale

8.45 American Airlinesi lend 11, mis vedas 92 inimest Bostonist Los Angelesse, kukub Maailma Kaubanduskeskuse põhja torni.

9:03 United Airlinesi lend 175, mis vedas 65 inimest Bostonist Los Angelesesse, kukub Maailma Kaubanduskeskuse lõunapoolsesse torni.

9.31 President Bush nimetab õnnetusi "nähtavaks terrorirünnakuks meie riigi vastu".

9.40 Kauplemine Wall Streetil katkes.

9.43 Pentagoni lähedal kukkus alla American Airlinesi lend 77, mis vedas 64 inimest Washingtonist Los Angelesse.

Populaarsed uudised

9.48 Valge Maja Kapitoolium ja Lääne tiib evakueeritakse.

9.49 Föderaalne lennuamet takistab õhusõidukite tõusu kogu riigis. Käimasolevad rahvusvahelised lennud pidid maanduma Kanadasse.

9.50 Üks Maailma Kaubanduskeskus, põhja torn variseb kokku.

10:29 Kaks Maailma Kaubanduskeskust lõunapoolne torn varises kokku.

10.37 Ametnikud kinnitavad, et New Airlinesist New Yorgist San Franciscosse suunduv United Airlinesi lend 93 kukkus alla Pittsburghist 80 miili kagus. Ükski 45 pardal olnud inimesest ei jäänud ellu.

10-11: 30 Valitsushooned kogu riigis, sealhulgas Kapitoolium ja Valge Maja, evakueeritakse. ÜRO suleti. Väärtpaberite ja börside komisjon sulgeb selleks päevaks kõik USA finantsturud. New Yorgi linnapea Rudolph Giuliani nõuab Manhattani alaosa evakueerimist.

13:20 Bush lahkub Barksdale'i õhujõudude baasist, La., Turvalise ja avalikustamata asukoha jaoks.

14:51 Merevägi saadab raketihävitajad ja muu varustuse New Yorki ja Washingtoni.

17:25 Seitse maailmakaubanduskeskust varises kokku.

& copyMMI Associated Press. Kõik õigused kaitstud. Seda materjali ei tohi avaldada, edastada, ümber kirjutada ega ümber levitada

Esmakordselt avaldatud 11. septembril 2001 / 19:18

& koopia 2001 The Associated Press. Kõik õigused kaitstud. Seda materjali ei tohi avaldada, edastada, ümber kirjutada ega ümber levitada.


Miks WTC tornid kokku varisesid

Paks must suits voolab mürgistes pilvedes, kui Maailma Kaubanduskeskus on leekidest alla neelatud.

Nagu CBS News korrespondent Bob Orr tulekahju, põhjaliku torni tabamiskoha täpne taastamine, on kaks aastat kestnud uurimise keskmes, miks kaksiktornid kukkusid.

Samal ajal kui tuli põleb labori sees, asuvad väljas langenud pilvelõhkujate luustiku jäänused. Uurijad valisid tonnide kaupa vrakke, sobitasid armistunud seerianumbreid ja tuvastasid uskumatult lennukite tabatud veerud.

"Seda konkreetset tükki tabas kere ülemine osa," ütleb riikliku standardite ja tehnoloogia instituudi metallurg Frank Gayle. "Me näeme, kuidas poldid toimisid, kõik sellel joonel."

Nad on võtnud terasest pisikesi proove ja tulistanud neid läbi õhukahuri, et täpselt arvutada kaaperdatud reaktiivlennukite tekitatud kahju.

Katsed näitavad kindlalt, et lennukirünnakud ei toonud torne alla. Ja see ei olnud tuhandete gallonite reaktiivkütus, mida lennukid kandsid.

Populaarsed uudised

"Kütus ise sai tarbitud mõne minutiga," ütleb NISTi juhtiv uurija Shyam Sunder WTC sondis.

Nii et levinud arvamus, et kogu see kütus muutis hoone kokkuvarisemise vältimatuks, ei vasta tõele, ütleb Sunder.

Et teada saada, miks hooned tegelikult kokku varisesid, lõid NISTi teadlased uuesti 96. korruse koos arvutite, vaipade, mööbli ja paberiga. Siis panid nad selle põlema. Nüüd on uurijad peaaegu võimelised tõestama, et just see igapäevane kontorimaterjal, mis põles tulekahjus, mida toitis pidevalt purunevatest akendest hapnik, põhjustas lõpuks terase andmise.

"Teras kipub selle kuumutamisel pehmendama või nõrgenema ja muutuma Playdoughi sarnaseks," ütleb Sunder.

Uurijad esitavad oma lõpparuande sel sügisel. Nad esitavad põhjalikke soovitusi, mille eesmärk on muuta hooned katastroofilistele sündmustele paremini vastu, ja nõuavad evakueerimiste parandamist, pidades silmas mõeldamatu ellujäämist.


Sisu

1973. aastal valminud kaksiktornid olid lühidalt maailma kõrgeimad hooned ja terrorirünnakute ajal olid nad endiselt esiviisikus. Üks Maailma Kaubanduskeskus (WTC 1), "Põhja torn", oli 1,368 jalga (417 m) kuus jalga kõrgem kui kaks Maailma Kaubanduskeskust (WTC 2), "Lõuna torn", mille kõrgus oli 1362 jalga (415 m) . Rünnakute ajal olid kõrgemad vaid toona hiljuti valminud Petronase tornid Malaisias Kuala Lumpuris ja Chicagos asuv Willise torn (tuntud kui Searsi torn). [2] Uue disainiga, mis maksimeeris siseruumi, olid tornid kõrge tugevuse ja kaalu suhtega, kuna nad kasutasid uut "raamitud toru" disaini, mis nõudis 40 protsenti vähem terast kui traditsioonilised terasraamiga pilvelõhkujad. [3] Lisaks seisis WTC 1 kohal 1978. aastal püstitatud 1102 m (362 jalga) telekommunikatsiooniantenn, mis tõi torni üldkõrguseks 530 m (1730 jalga), kuigi mittekonstruktiivse lisandina ei olnud antenn ametlikult loetud.

Struktuurne disain

Tornid kujundati raamitud torukonstruktsioonidena, mis pakkusid üürnikele avatud põrandaplaane, mida ei katkesta veerud ega seinad. Hooned olid ruudukujulised ja mõlemal küljel 63 meetrit (207 jalga), kuid neil oli faasitud 2,11 meetri (6 jalga 11 tolli) nurki, mis muutis iga hoone välisilme ligikaudu 64 jala laiuseks. [4] Paljud tihedalt paiknevad perimeetrilised veerud andsid konstruktsioonile suure osa tugevusest koos gravitatsioonikoormusega, mida jagasid südamiku teraskastist veerud. [5] Kümnenda korruse kohal oli hoone mõlemal küljel 59 ümbermõõtu veergu, mille keskel oli 3 jalga 4 tolli (1,02 meetrit). [5] Kui tornid olid ruudukujulised, olid sisemised südamikud ristkülikukujulised ja neid toetas 47 veergu, mis kulgesid iga torni täiskõrguses. [4] Kõik liftid ja trepikojad asusid südamikus, jättes selle ja perimeetri vahele suure veeruvaba ruumi, mis oli ühendatud kokkupandavate põrandasõrestikega. [5] Kuna südamik oli ristkülikukujuline, tekitas see perimeetrilistest veergudest pika ja lühikese vahemaa.

Põrandad koosnesid 4-tollistest paksustest (10 cm) kergbetoonplaatidest, mis olid laotud terasest tekile. [4] Kergete sillafermide ja põhisõrestike võrk toetas põrandaid nihkeühendustega betoonplaadi külge komposiitmõju jaoks. [5] Fermide vahekaugus oli 18 meetrit (18 jalga) ja 35 jalga (11 meetrit) lühikeses piirkonnas. Fermid ühendati perimeetriga alternatiivsete veergude juures ja asusid seetõttu 2,1 m (6,8 jala) keskustes. Fermide ülemised akordid polditi perimeetri küljel asuvate spandrelide külge keevitatud istmete külge ja südamikupoolse sisekarbi veergude külge keevitatud kanaliga. Põrandad ühendati ümbermõõduliste plaatidega viskoelastsete siibritega, mis aitasid vähendada hoones viibijate õõtsumist. [5]

Tornid hõlmasid ka 107. ja 110. korruse vahel asuvat "kübarasõrestikku" või "tugiposti", mis koosnes kuuest sõrestikust piki südamiku pikitelge ja neljast piki lühikest telge. [4] See sõrestikusüsteem võimaldas põrandamembraanide optimaalset koormuse ümberjaotamist perimeetri ja südamiku vahel, parandades jõudlust painduva terase ja jäiga betooni erinevate materjalide vahel, võimaldades momendiraamidel südamiku surumist üle kanda, mis samuti enamasti toetas ülekandetorn. Need sõrestikud paigaldati igasse hoonesse tulevaste ülekandetornide toetamiseks, kuid lõpuks paigaldati ainult põhjatorn. [4]

Lennukite mõju hindamine

Kuigi tulekahjuuuringud ja isegi väikese kiirusega reaktiivlennukite löökide mõju analüüs oli tehtud enne nende valmimist, ei ole nende uuringute kogu ulatust enam olemas. Sellest hoolimata, kuna tulekahju polnud kunagi varem põhjustanud pilvelõhkuja kokkuvarisemist ja nende projekteerimisel oli arvestatud õhusõidukite löökidega, tuli nende hävitamine esialgu mõne insenerikogukonna jaoks üllatusena. [6]

Maailma Kaubanduskeskuses töötavad ehitusinsenerid kaalusid võimalust, et hoonesse võib kukkuda lennuk. 1945. aasta juulis oli udus eksinud pommitaja B-25 kukkunud Empire State Building'i 79. korrusele. [7] Aasta hiljem kukkus C-45F Expeditor vastu Wall Streeti 40 hoonet. Veel kord arvati, et udu mõjutas kokkupõrget. [8] Üks Maailma Kaubanduskeskuse projekteerimisega tegelevatest peainseneridest Leslie Robertson märkis, et arvestab Boeing 707 kokkupõrke stsenaariumiga, mis võib udus kaduma minna ja suhteliselt väikese kiirusega lennata. maanduda kas JFK või Newarki lennujaamades. [9] Kaks kuud pärast hoone varisemist BBC -le antud intervjuus väitis Robertson, et "707 -ga ei võetud projekteerimisel arvesse kütuse koormust, ma ei tea, kuidas seda oleks võinud arvestada". Intervjuus nentis Robertson, et peamine erinevus projekteerimisuuringute ja sündmuste vahel, mis lõppkokkuvõttes põhjustasid tornide kokkuvarisemise, oli tingitud löögi kiirusest, mis suurendas oluliselt neeldunud energiat ja seda ei arvestatud ehitusprotsessi käigus kunagi. [10]

Kokkuvarisemist uurides sai riiklik standardite ja tehnoloogia instituut (NIST) kolmeleheküljelise valge raamatu, milles öeldi, et hooned jäävad ellu Boeing 707 või DC 8 lennuki kokkupõrkel, mis lendab kiirusel 600 miili tunnis (970 km) /h). [11] 1993. aastal märkis WTC juhtivkonstruktsioonide insener John Skilling intervjuus pärast 1993. aasta Maailma Kaubanduskeskuse pommitamist: "Meie analüüs näitas, et suurim probleem oleks asjaolu, et kogu kütus (lennukist) hoonesse. Seal oleks kohutav tulekahju. Paljud inimesed saaksid surma, "ütles ta. "Ehituskonstruktsioon oleks alles." [12] NIST väitis oma aruandes, et tehniline võimekus õhusõidukite kokkupõrke ja sellest tulenevate tulekahjude ranget simulatsiooni teostada on hiljutine areng ning et sellise analüüsi tehniline võimekus oleks 1960. aastatel olnud üsna piiratud. [13] [märkus 1] Oma lõppkokkuvõtte kokkuvarisemiste kohta teatas NIST, et nad ei leia ühtegi dokumenti, mis uuriks suure kiirusega reaktiivlennuki ega lennuki kütusega töötava laiaulatusliku tulekahju mõju. [14]

Tulekindlus

Kuni 1970ndate keskpaigani oli asbesti kasutamine tulekindlaks ehituses laialt levinud. Kuid 1970. aasta aprillis käskis New Yorgi õhuvarude osakond Maailma Kaubanduskeskust ehitavatel töövõtjatel lõpetada asbesti kui isoleermaterjali pritsimine. [15]

Pärast 1993. aasta pommitamist leiti kontrollimisel tulekindlus puudulik. [16] Enne varinguid olid tornide omanikud, New Yorgi ja New Jersey sadamaamet, lisamas tulekindlust, kuid need olid valminud ainult 18 korrusel 1 WTC -s, kaasa arvatud kõik põrandad, mida mõjutas õhusõiduki kokkupõrge ja tulekahjud ning 13 korrusel 2 WTC, kuigi õhusõiduki kokkupõrge ei mõjutanud otseselt ühtegi. [17]

NIST jõudis järeldusele, et lennuki kokkupõrge eemaldas märkimisväärse osa tulekindlusest, aidates kaasa hoonete kokkuvarisemisele. WTC 1 -s eemaldati löögi tõttu isolatsioon 43 -lt 47 -st südamikusammast enam kui ühel korrusel, samuti põrandasõrestikud üle 60 000 ruutjalga (5600 m 2). WTC 2 -s eemaldas löök isolatsiooni 39 -lt 47 -st sambast mitmel korrusel ja põrandasõrestikelt, mille pindala oli 80 000 ruutjalga (7400 m 2). [14]

Pärast kokkuvarisemist väitis Leslie Robertson: "Meie teadmiste kohaselt oli sellise õhusõiduki tulekahju tagajärgedest vähe teada ja selle olukorra jaoks ei koostatud projekte. Tõepoolest, tol ajal polnud tulekindlaid süsteeme saadaval selliste tulekahjude tagajärgede ohjamiseks. " [9]

Õhusõidukite löögid ja neist tulekahjud

11. septembri rünnakute käigus kaaperdas neli al-Qaeda terroristide meeskonda neli erinevat reaktiivlennukit. Kaks neist reaktiivlennukitest, American Airlines Flight 11 ja United Airlines Flight 175, mõlemad Boeing 767, kaaperdati pärast õhkutõusmist Bostoni Logani rahvusvahelisest lennujaamast. Viimastel hetkedel lendas American Airlinesi lend 11 Manhattani kohal lõunasse ja kukkus kell 8:46 alla kiirusel 710 km/h kiirusega umbes 440 miili tunnis (WTC 1) põhjafassaadi, mis tabas 93. ja 99. korrus. Seitseteist minutit hiljem lähenes United Airlinesi lend 175 edelast New Yorgi sadama kohale ja kukkus kell 9:02 lõunatornis (WTC 2) lõunafassaadile 77. ja 85. korruse vahel kiirusega 540 miili tunnis (870 km/h).

Lisaks arvukate kandekolonnide lõhkumisele perimeetril ja muude konstruktsioonikahjustuste tekitamisele süütas löök tuhandeid galloneid reaktiivkütust, mis omakorda süütas kontoripõlengu. Ligikaudu kolmandik kütusest kulus esialgse löögi ja sellest tulekahju ajal. [märkus 2] [18] Mõningane kokkupõrke tagajärjel tekkinud kütus rändas alla vähemalt ühe liftišahti ja plahvatas nii Põhjatorni 78. korrusel kui ka põhifuajees. [19] Konstruktsioonide kerge konstruktsioon ja õõnes olemus võimaldas reaktiivkütusel tungida tornide kaugele, süütades samal ajal palju suuri tulekahjusid laiale mõjutatud põrandate alale. Lennukite kütus põles kõige rohkem mõni minut, kuid hoonete sisu põles järgmise tunni või pooleteise tunni jooksul. [20]

Hädaabi ja evakueerimine

Peaaegu kõik kaksiktornide surmajuhtumid leidsid aset õhusõiduki löögipunktidest kõrgemal asuvates tsoonides. Kuna Põhjatorn oli löödud otse konstruktsiooni keskele, olid tornisüdamiku kolm treppi kahjustatud või blokeeritud prahi tõttu, mis takistas põgenemist alumistele korrustele. Lõunapoolses tornis oli löök torni keskosast keskelt veidi eemal ja keskosa südamiku loodeosas asuv trepp A oli vaid osaliselt blokeeritud ning 14–18 tsiviilisikul õnnestus põgeneda õhusõiduki löögipunktist ja põrandad sellest kõrgemal. Hukkunute täpsed arvud ja kohati pole täpselt teada, kuid riikliku standardite ja tehnoloogia instituudi aruanne näitas, et Põhjatorni löögipunktis või selle kohal hukkus kokku 1402 tsiviilisikut, sadu hukkus hinnanguliselt löögi hetk. Lõunatornis hukkus 614 tsiviilisikut löögipõrandate ja nende kohal asuvate põrandate juures. Vähem kui 200 tsiviilisikutest hukkunutest leidis aset löögipunktidest allpool olevatel korrustel, kuid hukkusid kõik 147 tsiviilreisijat ja kahe lennuki meeskond ning kõik 10 terroristi koos vähemalt 18 inimesega maapinnal ja kõrvalasuvates ehitistes. [21]

Kokkuvõtteks ütlesid, et varingus hukkus kiirabitöötajate hulka 343 New Yorgi tuletõrjeosakonda (FDNY) ja 71 korrakaitsjat, sealhulgas 23 New Yorgi politseijaoskonna (NYPD) liiget, 37 sadamaameti politseijaoskonna (PAPD) liiget, viis New Yorgi osariigi maksujärelevalveameti (OTE) liiget, kolm New Yorgi osariigi kohtuameti (OCA) ametnikku, üks New Yorgi tuletõrjeosakonna (FDNY) tuletõrjuja, kellel olid õiguskaitsevolitused ( ja oli ka 343 tapetud FDNY liikme hulgas), üks Föderaalse Juurdlusbüroo (FBI) liige ja üks Ameerika Ühendriikide salateenistuse (USSS) liige. Tsiviilisikute ja mitte-tsiviilisikute hukkunute koguarv on hinnanguliselt 2 606 inimest.

Kaksiktornide hävitamist on nimetatud progressiivse kokkuvarisemise "kõige kurikuulsamaks paradigmaks". [6] Need algasid mõne konstruktsioonikomponendi lokaalse rikkega ja hõlmasid kogu struktuuri. [22] Selliseid kokkuvarisemisi iseloomustab "konstruktsioonielementide (sealhulgas mittekandvate elementide) eraldumine, gravitatsioonienergia vabanemine ja löögijõudude tekkimine". Vertikaalne löögijõud tagab paljundamise, põhijõud on paralleelsed ja esmane koormuse ülekanne on jada. [23] Ebaõnnestunud konstruktsiooni põhielemendi moodustasid "ühe terve korruse vertikaalsed kandvad elemendid". Kui hoone ülemised korrused välja arvata, mis ei oleks vabastanud piisavalt gravitatsioonienergiat totaalse kokkuvarisemise saavutamiseks, oleks varingud võinud alata mis tahes loo ebaõnnestumisega. [24]

Nendes tingimustes varisesid tornid sümmeetriliselt ja enam -vähem otse alla, kuigi tornide tipud olid veidi kallutatud ja külgedel oli palju sademeid. Mõlemal juhul ebaõnnestus lennukite poolt kahjustada saanud hooneosa, mis võimaldas löögipiirkonna kohal asuvatel põrandatel allapoole kahjustamata konstruktsioonile kukkuda. Kokkuvarisemise edenedes võis näha, et akendest paiskub tolmu ja prahti mitu korrust allapoole hävingut, mis on põhjustatud laskuvate ülemiste tasandite alla surutud õhu järsust kiirustamisest.

Iga kokkuvarisemise ajal jäid suured osad ümbermõõdulised veerud ja võib -olla südamikud ilma külgtoeta, mistõttu need kukkusid üha suureneva killustikuhunniku tõttu külgsuunas väljapoole. Tulemuseks oli see, et seinad koorusid maha ja eraldusid hoonetest suure vahemaa tagant (mõnel juhul umbes 500 jalga), tabades teisi naaberhooneid ja alustades tulekahju, mis hiljem viis hoone 7 kokkuvarisemiseni. poldid klõpsatasid, jättes paljud paneelid juhuslikult laiali. [25] Kokkuvarisenud Põhjatorni välisseinte esimesed killud tabasid maad 11 sekundit pärast varingu algust ja lõunatorni osad 9 sekundi pärast. Mõlema hoone tuumade alumised osad (60 lugu WTC 1 ja 40 lugu WTC 2) jäid seisma kuni 25 sekundiks pärast esialgset kokkuvarisemist, enne kui ka need kokku varisesid. [13]

Ahenda initsiatsioon

Pärast lennukite löömist hoonetesse, kuid enne hoonete kokkuvarisemist koosnesid mõlema torni südamikud kolmest erinevast osast. Löögipõrandate kohal ja all koosnesid südamikud sisuliselt kahest jäigast kastist, mille teras nendes sektsioonides oli kahjustamata ja ei olnud oluliselt kuumutatud. Nendevaheline lõik oli aga saanud olulisi kahjustusi ja kuigi need ei olnud selle sulatamiseks piisavalt kuumad, nõrgendasid tulekahjud konstruktsiooniterast.

Selle tulemusel purustati südamikukolonnid aeglaselt, säilitades ülaltoodud põrandate kaalust plastilise ja roomava deformatsiooni. Kui ülemine osa üritas allapoole liikuda, jagas mütsisõrestik aga koormuse ümbermõõdulistele veergudele ümber. Vahepeal nõrgendasid tulekahjude kuumus ka ümbermõõtu veerge ja põrandaid ning kui põrandad hakkasid vajuma, tõmbasid nad välisseinad sissepoole. "Sellest tulenev vertikaalse kandevõime kaotus piirdus mõne korrusega, kuid ulatus kogu torni kogu ristlõikega." [26] Kahe WTC puhul pani idapool lõpuks kinni, kandes oma koormused mütsifermi kaudu tagasi ebaõnnestunud südamikku ja alustades kokkuvarisemist. Hiljem kaldus 1 WTC lõunasein samamoodi ja sarnaste tagajärgedega. [27]

Täielik progresseeruv kokkuvarisemine

Konstruktsioonisüsteemid reageerivad staatilistele ja dünaamilistele koormustele väga erinevalt ning kuigi tornid olid konstrueeritud kandma normaaltingimustes tohutut kaalu, ei pidanud need kahjustatud põrandate kohal oleva sektsiooni liikuva massi suhtes vastu. Mõlemal juhul algasid varingud ülemise sektsiooni kukkumisega vähemalt ühe korruse kõrgusele (umbes kolm meetrit või kümme jalga), kuid vaid poole meetri (umbes 20 tolli) kukkumine oleks vabastanud vajaliku energia peatamatu kokkuvarisemise alustamiseks. [28]

Sealt edasi toimus kokkuvarisemine kahes faasis. Jooksul purustada faasis hävitas ülemine plokk allpool oleva struktuuri järk -järgult veergude ebaõnnestumiste seerias ligikaudu üks lugu korraga. Iga rike sai alguse ülemise ploki löögist alumise sektsiooni veergudele, mida vahendas kasvav killustikukiht, mis koosnes peamiselt põrandaplaatidest betoonist. Iga löögi energia "sisestati uuesti konstruktsiooni [järgnevas löögis".. Kontsentreeruda [d] kandevõime elementidesse, mida löök otseselt mõjutab. " [23] See pani loo veerud vahetult edeneva hävingu alla järgmise külgtoe punktini, tavaliselt antud loo põrandasõrestikesse. Pärast seda, kui veerud olid kinni pandud, ei toetatud plokki ja see kukkus selle loo vahelt läbi, mõjutades jällegi alloleva loo veerge, mis seejärel samamoodi nurgasid.

Seda korrati seni, kuni ülemine plokk jõudis maapinnale ja purustamine faas algas. Ka siin tõmbasid veerud ühe loo korraga kinni, alustades nüüd alt. Kuna iga lugu ebaõnnestus, kukkus allesjäänud plokk läbi loo kõrguse järgmisele, mille ta ka purustas, kuni katus lõpuks vastu maad põrkas. [6] Protsess kiirenes kogu aeg ja lõpuks purustati iga lugu vähem kui kümnendiku sekundiga. [28]

Lõunatorni varing

Kuna tulekahjud jätkasid põlemist, andsid Lõunatorni ülemistele korrustele lõksu jäänud sõitjad 9-1-1 dispetšerile teavet olude kohta. Kell 9.37 teatas Lõunatorni 105. korrusel viibija, et tema all olevad põrandad "90-aastasel korrusel" on kokku varisenud. [29] New Yorgi politseijaoskonna lennuüksus edastas politseiülematele ka teavet hoonete halveneva olukorra kohta. [30] Lõunatorni löögipiirkonnast põgenes pärast lööki ainult 14 inimest (sealhulgas Stanley Praimnath, kes nägi lennukit tema poole tulemas) ja ainult neli inimest selle kohal olevatelt korrustelt. Nad pääsesid trepikoja A kaudu, mis oli ainus trepikoda, mis oli pärast lööki terveks jäänud. Paljud politsei vihjeliinide operaatorid, kes said lõunatorni sees olevate isikute kõnesid, ei olnud olukorrast kiiresti informeeritud. Paljud operaatorid ütlesid helistajatele, et nad ei laskuks ise tornist alla, kuigi praegu arvatakse, et trepikoda A oli löögipunktis ja sellest kõrgemal tõenäoliselt läbitav. [31] Kell 9.52 teatas NYPD lennundusüksus raadio kaudu, et "WTC 2 pealt võib langeda suuri tükke. Suured tükid ripuvad seal üles". [29] Hoiatustega andis NYPD oma ohvitseridele korralduse evakueerida. Hädaolukorras reageerimise ajal oli NYPD ja New Yorgi tuletõrje (FDNY) vahel minimaalne side ning ülekoormatud 9-1-1 dispetšerid ei edastanud teavet kohapealsetele FDNY komandöridele. Kell 9.59 varises Lõunatorn kokku 57 minutit pärast lööki.

Põhja torni kokkuvarisemine

Pärast lõunatorni varisemist edastasid NYPD helikopterid teavet Põhjatorni halveneva olukorra kohta. Kell 10.20 teatas NYPD lennundusüksus, et "torni tipp võib kalduda", ja minut hiljem teatas, et Põhjatorn "kaldus edelanurka ja kaldus lõunasse". At 10:28 a.m., the aviation unit reported that "the roof is going to come down very shortly" [29] and indeed, the North Tower collapsed immediately thereafter, at 10:28 a.m., after burning for 102 minutes.

After the South Tower collapsed, FDNY commanders issued orders for firefighters in the North Tower to evacuate. Due to radio communications problems, firefighters inside the towers did not hear the evacuation order from their supervisors on the scene, and most were unaware that the other tower had collapsed. [32] Three-hundred forty three firefighters died in the Twin Towers, as a result of the collapse of the buildings. [33] [34] [35] No one was able to escape the North Tower from the impact zone or above, as all stairwells and elevator shafts on those floors were destroyed or blocked. [36] After the collapse, light dust reached as far as the Empire State Building, located 2.93 miles (4.72 km) away.

Building 7 collapse

As the North Tower collapsed, heavy debris hit 7 World Trade Center, causing damage to the south face of the building [37] and starting fires that continued to burn throughout the afternoon. [38] Structural damage occurred to the southwest corner between Floors 7 and 17 and on the south facade between Floor 44 and the roof other possible structural damage includes a large vertical gash near the center of the south facade between Floors 24 and 41. [38] The building was equipped with a sprinkler system, but had many single-point vulnerabilities for failure: the sprinkler system required manual initiation of the electrical fire pumps, rather than being a fully automatic system the floor-level controls had a single connection to the sprinkler water riser and the sprinkler system required some power for the fire pump to deliver water. Also, water pressure was low, with little or no water to feed sprinklers. [39] [40]

Some firefighters entered 7 World Trade Center to search the building. They attempted to extinguish small pockets of fire, but low water pressure hindered their efforts. [41] Fires burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, the flames visible on the east side of the building. [42] [43] During the afternoon, fire was also seen on floors 6–10, 13–14, 19–22, and 29–30. [37] In particular, the fires on floors 7 through 9 and 11 through 13 continued to burn out of control during the afternoon. [44] At approximately 2:00 pm, firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors, a sign that the building was unstable and might cave to one side or "collapse". [45] During the afternoon, firefighters also heard creaking sounds coming from the building and issued uncertain reports about damage in the basement. [46] Around 3:30 pm FDNY Chief Daniel A. Nigro decided to halt rescue operations, surface removal, and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel. [47] At 5:20:33 pm EDT on September 11, 2001, 7 World Trade Center started to collapse, with the crumble of the east mechanical penthouse, while at 5:21:10 pm EDT the entire building collapsed completely. [48] [49] There were no casualties associated with the collapse.

When 7 World Trade Center collapsed, debris caused substantial damage and contamination to the Borough of Manhattan Community College's Fiterman Hall building, located adjacent at 30 West Broadway, to the extent that the building was not salvageable. In August 2007, Fiterman Hall was scheduled for dismantling. [50] A revised plan called for demolition in 2009 and completion of the new Fiterman Hall in 2012, at a cost of $325 million. [51] [52] The building was finally demolished in November 2009 and construction of its replacement began on December 1, 2009. [53] The adjacent Verizon Building, an Art Deco building constructed in 1926, had extensive damage to its east facade from the collapse of 7 World Trade Center, though it was successfully restored at a cost of US$1.4 billion. [54]

Other buildings

Many of the surrounding buildings were also either damaged or destroyed as the towers fell. 5 WTC endured a large fire and a partial collapse of its steel structure and was torn down. Other buildings destroyed include St. Nicholas Greek Orthodox Church, Marriott World Trade Center (Marriott Hotel 3 WTC), South Plaza (4 WTC), and U.S. Customs (6 WTC). The World Financial Center buildings, 90 West Street, and 130 Cedar Street suffered fires. The Deutsche Bank Building, the Verizon Building, and World Financial Center 3 had impact damage from the towers' collapse, [55] as did 90 West Street. [56] One Liberty Plaza survived structurally intact but sustained surface damage including shattered windows. 30 West Broadway was damaged by the collapse of 7 WTC. The Deutsche Bank Building, which was covered in a large black "shroud" after September 11 to cover the building's damage, was deconstructed because of water, mold, and other severe damage caused by the neighboring towers' collapse. [57] [58] Many works of art were destroyed in the collapse.

Initial opinions and analysis

In the immediate aftermath of the attacks, numerous structural engineers and experts spoke to the media, describing what they thought caused the towers to collapse. Abolhassan Astaneh-Asl, a structural engineering professor at the University of California at Berkeley, explained that the high temperatures in the fires weakened the steel beams and columns, causing them to become "soft and mushy", and eventually they were unable to support the structure above. Astaneh-Asl also suggested that the fireproofing became dislodged during the initial aircraft impacts. He also explained that, once the initial structural failure occurred, progressive collapse of the entire structure was inevitable. [59] César Pelli, who designed the Petronas Towers in Malaysia and the World Financial Center in New York, remarked, "no building is prepared for this kind of stress." [60]

On September 13, 2001, Zdeněk P. Bažant, professor of civil engineering and materials science at Northwestern University, circulated a draft paper with results of a simple analysis of the World Trade Center collapse. Bažant suggested that heat from the fires was a key factor, causing steel columns in both the core and the perimeter to weaken and experience deformation before losing their carrying capacity and buckling. Once more than half of the columns on a particular floor buckled, the overhead structure could no longer be supported and complete collapse of the structures occurred. Bažant later published an expanded version of this analysis. [61] Other analyses were conducted by MIT civil engineers Oral Buyukozturk and Franz-Josef Ulm, who also described a collapse mechanism on September 21, 2001. [62] They later contributed to an MIT collection of papers on the WTC collapses edited by Eduardo Kausel called The Towers Lost and Beyond. [63]

Immediately following the collapses, there was some confusion about who had the authority to carry out an official investigation. While there are clear procedures for the investigation of aircraft accidents, no agency had been appointed in advance to investigate building collapses. [64] A team was quickly assembled by the Structural Engineers Institute of the American Society of Civil Engineers, led by W. Gene Corley, Senior Vice President of CTLGroup. It also involved the American Institute of Steel Construction, the American Concrete Institute, the National Fire Protection Association, and the Society of Fire Protection Engineers. [65] ASCE ultimately invited FEMA to join the investigation, which was completed under the auspices of the latter. [65]

The investigation was criticized by some engineers and lawmakers in the U.S. It had little funding, no authority to demand evidence, and limited access to the WTC site. One major point of contention at the time was that the cleanup of the WTC site was resulting in the destruction of the majority of the buildings' steel components. [66] Indeed, when NIST published its final report, it noted "the scarcity of physical evidence" that it had had at its disposal to investigate the collapses. Only a fraction of a percent of the buildings remained for analysis after the cleanup was completed: some 236 individual pieces of steel, although 95% of structural beams and plates and 50% of the reinforcement bars were recovered. [67]

FEMA published its report in May 2002. While NIST had already announced its intention to investigate the collapses in August of the same year, by September 11, 2002 (a year after the disaster), there was growing public pressure for a more thorough investigation. [68] Congress passed the National Construction Safety Team bill in October 2002, giving NIST the authority to conduct an investigation of the World Trade Center collapses. [69]

FEMA building performance study

FEMA suggested that fires in conjunction with damage resulting from the aircraft impacts were the key to the collapse of the towers. Thomas Eagar, Professor of Materials Engineering and Engineering Systems at MIT, described the fires as "the most misunderstood part of the WTC collapse". This is because the fires were originally said to have "melted" the floors and columns. [70] Jet fuel is essentially kerosene and would have served mainly to ignite very large, but not unusually hot, hydrocarbon fires. [71] As Eagar said, "The temperature of the fire at the WTC was not unusual, and it was most definitely not capable of melting steel." [72] This led Eagar, FEMA and others to focus on what appeared to be the weakest point of the structures, namely, the points at which the floors were attached to the building frame. [73]

The large quantity of jet fuel carried by each aircraft ignited upon impact into each building. A significant portion of this fuel was consumed immediately in the ensuing fireballs. The remaining fuel is believed either to have flowed down through the buildings or to have burned off within a few minutes of the aircraft impact. The heat produced by this burning jet fuel does not by itself appear to have been sufficient to initiate the structural collapses. However, as the burning jet fuel spread across several floors of the buildings, it ignited much of the buildings’ contents, causing simultaneous fires across several floors of both buildings. The heat output from these fires is estimated to have been comparable to the power produced by a large commercial power generating station. Over a period of many minutes, this heat induced additional stresses into the damaged structural frames while simultaneously softening and weakening these frames. This additional loading and the resulting damage were sufficient to induce the collapse of both structures. [74]

NIST report

After the FEMA report had been published, and following pressure from technical experts, industry leaders and families of victims, the Commerce Department's National Institute of Standards and Technology conducted a three-year, $16 million investigation into the structural failure and progressive collapse of several WTC complex structures. [75] The study included in-house technical expertise, along with assistance from several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers, Society of Fire Protection Engineers, National Fire Protection Association, American Institute of Steel Construction, Simpson Gumpertz & Heger Inc., Council on Tall Buildings and Urban Habitat, and the Structural Engineers Association of New York.

The scope of the NIST investigation was focused on identifying "the sequence of events" that triggered the collapse, and did not include detailed analysis of the collapse mechanism itself (after the point at which events made the collapse inevitable). [76] [77] [78] In line with the concerns of most engineers, NIST focused on the airplane impacts and the spread and effects of the fires, modeling these using the software program Fire Dynamics Simulator. NIST developed several highly detailed structural models for specific sub-systems such as the floor trusses as well as a global model of the towers as a whole which is less detailed. These models are static or quasi-static, including deformation but not the motion of structural elements after rupture as would dynamic models. So, the NIST models are useful for determining how the collapse was triggered, but do not shed light on events after that point.

James Quintiere, professor of fire protection engineering at the University of Maryland, called the spoliation of the steel "a gross error" that NIST should have openly criticized. [79] He also noted that the report lacked a timeline and physical evidence to support its conclusions. [80] Some engineers have suggested that understanding of the collapse mechanism could be improved by developing an animated sequence of the collapses based on a global dynamic model, and comparing it with the video evidence of the actual collapses. [81] The NIST report for WTC 7 concluded that no blast sounds were heard on audio and video footage, or were reported by witnesses. [82]

7 World Trade Center

In May 2002, FEMA issued a report on the collapse based on a preliminary investigation conducted jointly with the Structural Engineering Institute of the American Society of Civil Engineers under leadership of Dr. W. Gene Corley, P.E. FEMA made preliminary findings that the collapse was not primarily caused by actual impact damage from the collapse of 1 WTC and 2 WTC but by fires on multiple stories ignited by debris from the other two towers that continued unabated due to lack of water for sprinklers or manual firefighting. The report did not reach conclusions about the cause of the collapse and called for further investigation. [ tsiteerimine vajalik ]

In response to FEMA's concerns, the National Institute of Standards and Technology (NIST) was authorized to lead an investigation into the structural failure and collapse of the World Trade Center twin towers and 7 World Trade Center. [83] The investigation, led by Dr S. Shyam Sunder, drew not only upon in-house technical expertise, but also upon the knowledge of several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), the Society of Fire Protection Engineers (SFPE), the National Fire Protection Association (NFPA), the American Institute of Steel Construction (AISC), the Council on Tall Buildings and Urban Habitat (CTBUH), and the Structural Engineers Association of New York (SEAoNY). [84]

The bulk of the investigation of 7 World Trade Center was delayed until after reports were completed on the collapse of the World Trade Center twin towers. [44] In the meantime, NIST provided a preliminary report about 7 World Trade Center in June 2004, and thereafter released occasional updates on the investigation. [37] According to NIST, the investigation of 7 World Trade Center was delayed for a number of reasons, including that NIST staff who had been working on 7 World Trade Center were assigned full-time from June 2004 to September 2005 to work on the investigation of the collapse of the twin towers. [13] In June 2007, Shyam Sunder explained, "We are proceeding as quickly as possible while rigorously testing and evaluating a wide range of scenarios to reach the most definitive conclusion possible. The 7 WTC investigation is in some respects just as challenging, if not more so, than the study of the towers. However, the current study does benefit greatly from the significant technological advances achieved and lessons learned from our work on the towers." [85]

In November 2008, NIST released its final report on the causes of the collapse of 7 World Trade Center. [38] This followed their August 21, 2008 draft report which included a period for public comments. [44] In its investigation, NIST utilized ANSYS to model events leading up to collapse initiation and LS-DYNA models to simulate the global response to the initiating events. [86] NIST determined that diesel fuel did not play an important role, nor did the structural damage from the collapse of the twin towers, nor did the transfer elements (trusses, girders, and cantilever overhangs), but the lack of water to fight the fire was an important factor. The fires burned out of control during the afternoon, causing floor beams near Column 79 to expand and push a key girder off its seat, triggering the floors to fail around column 79 on Floors 8 to 14. With a loss of lateral support across nine floors, Column 79 soon buckled – pulling the East penthouse and nearby columns down with it. With the buckling of these critical columns, the collapse then progressed east-to-west across the core, ultimately overloading the perimeter support, which buckled between Floors 7 and 17, causing the entire building above to fall downward as a single unit. From collapse timing measurements taken from a video of the north face of the building, NIST observed that the building's exterior facade fell at free fall acceleration through a distance of approximately 8 stories (32 meters, or 105 feet), noting "the collapse time was approximately 40 percent longer than that of free fall for the first 18 stories of descent." [87] The fires, fueled by office contents, along with the lack of water, were the key reasons for the collapse. [38]

The collapse of the old 7 World Trade Center is remarkable because it was the first known instance of a tall building collapsing primarily as a result of uncontrolled fires. [44] Based on its investigation, NIST reiterated several recommendations it had made in its earlier report on the collapse of the twin towers, and urged immediate action on a further recommendation: that fire resistance should be evaluated under the assumption that sprinklers are unavailable and that the effects of thermal expansion on floor support systems be considered. Recognizing that current building codes are drawn to prevent loss of life rather than building collapse, the main point of NIST's recommendations is that buildings should not collapse from fire even if sprinklers are unavailable. [38]

Other investigations

In 2003, Asif Usmani, Professor of Structural Engineering at University of Edinburgh, published a paper with two colleagues. They provisionally concluded the fires alone, without any damage from the airplanes, could have been enough to bring down the buildings. In their view, the towers were uniquely vulnerable to the effects of large fires on several floors at the same time. [88] When the NIST report was published, Barbara Lane, with the UK engineering firm Arup, criticized its conclusion that the loss of fire proofing was a necessary factor in causing the collapses "We have carried out computer simulations which show that the towers would have collapsed after a major fire on three floors at once, even with fireproofing in place and without any damage from plane impact." [89] Jose L. Torero, formerly of the BRE Centre for Fire Safety Engineering at the University of Edinburgh, pursued further research into the potentially catastrophic effects of fire on real-scale buildings. [90] [91] [92]

Cleanup

The cleanup was a massive operation coordinated by the City of New York Department of Design and Construction. On September 22, a preliminary cleanup plan was delivered by Controlled Demolition, Inc. (CDI) of Phoenix, Maryland. [93] Costing hundreds of millions of dollars, it involved round-the-clock operations with many contractors and subcontractors. [94] By early November, with a third of the debris removed, officials began to reduce the number of firefighters and police officers assigned to recovering the remains of victims, in order to prioritize the removal of debris. This caused confrontations with firefighters. [95] Despite efforts to extinguish the blaze, the large pile of debris burned for three months, until the majority of the rubble was finally removed from the site. [96] [97] In 2007, the demolition of the surrounding damaged buildings was still ongoing as new construction proceeded on the World Trade Center's replacement, 1 World Trade Center.

Mõju tervisele

The collapse of the World Trade Center produced enormous clouds of dust that covered Manhattan for days. On September 18, 2001, the United States Environmental Protection Agency (EPA) assured the public that the air in Manhattan was "safe to breathe". [98] In 2003 the EPA's inspector general found that the agency did not at that time have sufficient data to make such a statement. Dust from the collapse seriously reduced air quality and is likely the cause of many respiratory illnesses in lower Manhattan. Asbestosis is such an illness, and asbestos would have been present in the dust. [99] Significant long term medical and psychological effects have been found among first responders including elevated levels of asthma, sinusitis, gastroesophageal reflux disease and posttraumatic stress disorder. [100]

Health effects also extended to residents, students, and office workers of Lower Manhattan and nearby Chinatown. [101] Several deaths have been linked to the toxic dust, and the victims' names will be included in the World Trade Center memorial. [102] More than 18,000 people have suffered from illnesses from the dust. [103]


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From numerous camera angles, what we see here is the collapse of the North Tower of the World Trade Center on 9/11. You will notice a remnant spire from the structural steel, which remains standing for a few moments after the bulk of the Tower’s collapse.

Then, as if Tinker Bell were hovering over there waving her magic wand, the spire literally turns into Fairy Dust before your eyes. You don’t have to believe me. Just watch it. From several angles.

The term “Dustification” was coined by Dr Judy Wood among others, like “Toasted Cars” to describe the anomalous evidence at the 9/11 crime scene, for which she felt normal descriptors were inadequate. The evidence was hauled off to the Fresh Kills dump in Staten Island without a proper crime scene investigation and the burnt steel was sold on the Chinese market at breakneck speed, all of this possibly to deter discovery of the “molecular dissociation” Dr Wood conjectured had been caused by Directed Energy Weapons that dustified the towers and toasted the cars. Wood’s exotic hypothesis might make more sense than the even kookier official explanations but we don’t really know what happened.

Ikka, I want you to see the image of this dustifying spire in your mind’s eye the next time someone speaks to you with authority about something they read in The New York Times või Washington Post or about what they saw on CNN, NBC, ABC, CBS, BBC, etc.

I want you to see the image of this dustifying spire when you recall that this is the same Mainstream Media that told you that airliners caused the collapse of the World Trade Center Towers, when expert pilots say they could not have maneuvered Jumbo Jets to nail their targets so perfectly, let alone to fly at full speed at such low altitudes due to higher-density air, let alone with delicate aluminum airframes that could not penetrate the structural steel of the World Trade Center Towers, let alone that the kerosene jet fuel could not burn hot enough to melt that structural steel, let alone that NORAD stood down on the very day that the very thing they were created for and had been training daily since 1960 to defend against – happened.

I want you to see the image of this dustifying spire when you recall that this is the same Mainstream Media that lied us into war with Iraq and Afghanistan, killing an estimated 1 million innocent people. The Shadow Government people who presided over all of the above and who covered it up not only walk free and are multi-millionaires but many still have jobs in the Government – and guess what? Donald Trump is not one of them.

I want you to see the image of this dustifying spire when you recall that this is the same Mainstream Media that is shrieking to you every day that Donald Trump is worse than George W Bush and that Trump needs to be impeached.


New Tapes Reveal 9/11 Drama

In gripping, vivid accounts of individual heroism and organizational chaos, firefighters describe their response to - and escape from - the World Trade Center in 12,000 pages of oral histories made public today.

The histories, recorded in the weeks after the September 11th attack, offer some of the most detailed and intimate descriptions of the day's horror as seen through the eyes of the firefighters who made the iconic rush into the twin towers, and lost three hundred and forty-three of their brethren.

Compelled by a lawsuit filed by The New York Times when the FDNY did not comply with a freedom of information request and ruling by New York's highest court, the department made public 15 hours of radio transmissions and more than 500 oral histories describing the rush to the World Trade Center, which saved an unknown number of civilians.

Some families and other critics of the city's response have been hoping the new documents would help them challenge the conclusion that many firefighters in the north tower heard, but chose to ignore, an evacuation message issued after the south tower collapsed at 9:59 a.m.

CBS News Correspondent Trish Regan reports that Michael Burke's brother, William, was the only firefighter in his company who didn't make it out of the north tower. Michael told Regan that he will listen to the tapes when he feels ready.

"I will probably listen to them in bits and pieces. I think they'll be very difficult. It will be interesting to hear if we could hear Billy's voice," he said.

Populaarsed uudised

The New York court ruling allowed the FDNY to remove painful or embarrassing portions of the tapes before releasing them, CBS' Bianca Solorzano aruanded. Regardless knowing the statements could have been edited, at least 450 relatives of firefighters killed in the tower collapses have requested copies of the oral histories so to gain any previously shrouded information about their loved ones' last moments.

Independent investigations with access to the documents, including that of the New York Times, have already described major flaws in the city's response to the attack: Emergency radios did not function properly. Police and firefighters did not work together. Discipline broke down. Vital messages went unheard.

Listening to the tapes yields an array of emotions. Some voices are sad some are terse. Some of the audio is garbled or difficult to understand. Hear more audio.

The 945 minutes of dispatches and recorded histories fill 23 cds, WCBS' Marcia Kramer aruanded. A reading of just a few of the 12,000 pages of transcripts from the oral histories made clear they were packed with dramatic descriptions of the day.

"When the south tower collapsed, what we did was we either ran, got blown or fell down. . I realized . we have people up there," said Fire Chief Salvatore Cassano. "The building is loaded with our guys."

Cassano was manning the department's command post with Department Chief Peter Ganci, who was later killed after the two were separated. Ganci was the highest-ranking firefighter who died that day.

"I'd like to hear his voice again," one father of a fallen firefighter

Firefighter Kirk Long, whose Engine 1 was sent to the World Trade Center's north tower &mdash the first to be struck by a plane and the second to collapse &mdash described rushing up a stairway as evacuees were coming down.

"I was watching every person coming down, looked at their face, just to make them happy that they were getting out and we were going in, and everything was OK," Long said in his oral history.

Long said he heard the north tower shake and thought something in the basement had exploded.

"At that time I never knew that the south tower had gone down," he said.

Firefighter Long described leaving the north tower and being helped by another firefighter to another building nearby that had some clean air.

"There was a lot of mothers and babies there," he said. "I was ready to leave. They were a little shook up because I was covered up with all this dust. I was leaving and they started to cry. They didn't want me to go without them. So I stayed for maybe 10 or 15 minutes until it cleared up a little bit. Then I walked them over to the west side, where there were boats and fresh air."

At least 450 relatives of firefighters killed in the trade center collapse requested copies of the oral histories and radio recordings, and they received them by express mail Friday, the fire department said.

Another firefighter, Patrick Martin of Engine 229, said that after the south tower had collapsed and before the north tower came down, his lieutenant instructed him to go on a boat that was taking people to hospitals across the Hudson River.

"I told him I wasn't leaving," Martin said. "We were still missing one guy."

Fire Lt. Gregg Hansson, whose Engine 24 was called at 8:47 a.m. - one minute after the first plane crash &mdash described hearing the call to evacuate while he was on the 35th floor of the north tower.

"I was in the vicinity of the battalion chief, who was on the command channel, when I heard a mayday given over the command channel to evacuate the building," Hansson said in his oral history. "He started to tell everyone to evacuate, and I did also. I saw all the units get up, everybody got their gear, everybody started for the staircases to evacuate."

Firefighter Maureen McArdle Schulman recalled how somebody yelled something was falling. They thought it may have been desks coming out of the windows but realized it was people. They were jumping out of the windows of the top floors and hitting the ground.

She said she was sickened because she felt like she was intruding on a religious sacrament.

She turned around to look at a wall so not to witness their deaths but could still hear the sound of people crashing into the ground.

The New York Times, joined by families of Sept. 11 victims, sued the city in 2002 to release the records, which were collected by the Fire Department in the days after the collapse of the twin towers.

The city withheld them, claiming the release would violate firefighters' privacy and jeopardize the prosecution of Zacarias Moussaoui, who ultimately pleaded guilty to conspiring with the Sept. 11 hijackers.

In March, the state's highest court ordered the city to release the oral histories and radio transmissions but said the city could edit out potentially painful and embarrassing portions.

In another oral history, fire Lt. Howard Hahn described using his cell phone that day but said his fire department radio was barely functioning.

"I was able to get through, but the transmissions was very hard," Hahn said. It was very hard to control. You're basically doing your own show."

First published on August 12, 2005 / 9:07 PM

© 2005 CBS Interactive Inc. All Rights Reserved. Seda materjali ei tohi avaldada, edastada, ümber kirjutada ega ümber levitada. The Associated Press contributed to this report.


Their 9/11 Heroism Saved Them

Only 20 people who were still inside the Twin Towers when they collapsed made it out alive, including six New York City firefighters from Ladder Company 6 in the city's Chinatown section.

Three of them remembered the events of the day on The Early Show Monday for co-anchor Harry Smith, who was reporting from ground zero.

They explained how assisting an elderly woman who worked in the north tower of the World Trade Center happened to put them in the right place at a very wrong time: a section a stairway that survived as the tower crumbled.

Capt. Jay Jonas, who has since been promoted to battalion chief, and five other firefighters from Ladder 6 responded to the attacks at the trade center immediately, arriving minutes after the first plane hit.

As they entered the lobby of the north tower, the south tower was hit.

Carrying 100 pounds of gear, the group started climbing the stairs in the north tower to help.

Populaarsed uudised

When they reached the 28th floor, the building shook, and Jonas ordered his men to evacuate.

On the 19th floor, they came across an older woman, Josephine Harris, who had walked down from the 73rd floor. She was exhausted, and not sure she could continue.

Bill Butler, now a lieutenant, the strongest man in the unit, put his arm around her and guided her.

But Harris was slow, and when they reached the fourth floor, she stopped, protesting she couldn't go on.

Capt. Jonas feared for his men, but they would never leave Harris behind.

Then the rumbling started, and the north tower collapsed all around them. Miraculously, the area of the stairway they were in, Stairway B, remained intact.

Hours later, with Mayday calls and major efforts from their fellow firefighters, the group was found and rescued.

Jonas told Smith on Monday that his men were in the stairs to begin with because the elevators were broken, and, "That's where people needed help, so that's where we hadda be."

Butler said carrying all that gear up all those steps was "a tough trek. We were running into a lot of people, some that were severely injured and burned, but they were being cared for so, while we wouldn't normally pass people who were injured, we had to that day for the people above that we had to get to."

When did they know it was time to get out?

"For us," firefighter Sal D'Agostino told Smith, "it was when the south tower had collapsed and the captain went over to the window and saw that the south tower was no longer there, and then he came over to us and told us it was time for us to evacuate."

When they came upon Harris, she was worn out and moving very slowly the men agreed.

"We made it to the fourth floor (with her) and she was so tired, she couldn't support her own weight anymore, and she fell to the ground and she was telling us to leave her," Jonas said. "We weren't gonna leave her."

"As (the building) came down," Butler added, "there was this tremendous roar, like the same shaking as when the south tower collapsed, but at the same time the roar &mdash I liken it to two trains coming in different directions &mdash and you're standing in between them."

But, said D'Agostino, the fact that Harris had to stop, and the firefighters stopped with them, saved all their lives: "That's the key to the whole thing, when she can't go anymore and she's telling us to stop (helping her), we stayed together, and we stuck with her and then a couple of seconds later, you could hear the floors pancaking one on top of the other."

What does the fifth anniversary of that day mean to Jonas?

"(Sept. 11 was) a very solemn day," he said, "but it was also a day that we saw the worst in people and also saw the best in people. We had a tremendous amount of courage and compassion and heroism shown that day. And sometimes that gets overshadowed by the grief. But these people were incredible heroes (even before) these buildings came down."


CBS to Broadcast Videotape Shot Inside Towers During Trade Center Attack

CBS announced yesterday that it would broadcast a two-hour documentary special on March 10 culled from the videotape footage shot inside the World Trade Center by two young French filmmakers during the terrorist attack on Sept. 11.

The network said that it had acquired the rights to the video shot by the two brothers, Jules and Gedeon Naudet, and would transform it, with the help of producers and editors at CBS News, into a broadcast dedicated to commemorating the six-month anniversary of the attack. The tape has never been seen on television.

Leslie Moonves, the president of CBS Television, who made the deal for the network, called the footage ''just phenomenal material.'' The Naudets, who had been making a film about a firefighter recruit's early days on the job, were in a unique position to capture the events of that day from inside the trade center towers as firefighters struggled to contain the disaster. Jules Naudet was inside the north tower when the south tower collapsed.

Only a 10-second clip showing the first plane crashing into the north tower has previously been shown on television news broadcasts. A 90-minute version of the videotape was obtained by The New York Times, and a Jan. 12 front-page article detailed the gritty and horrifying scenes of firefighters and their commanders struggling to respond to the fires and the eventual collapse of the two buildings.

Some of the footage has also been shown to Fire Department officials and at some firehouses. About 90 firefighters who died that day have been identified on the tape, and the Naudets have made clips of those scenes available to their families.

Frank Gribbon, the spokesman for the Fire Department, praised the Naudets for ''the respectful way they have handled this.''

The Naudets, who are working closely with a firefighter friend, James Hanlon, insisted that the broadcast also serve a fund-raising purpose, and the CBS special will help promote the Uniformed Firefighters Association Scholarship Fund.

The Naudets will also direct part of the money that they are receiving for the film to the fund.

CBS acquired the tape through some unusual connections to Vanity Fair magazine, which is publishing an article about their experiences in the issue that comes out this week.

David Friend, a Vanity Fair editor who wrote the article, has been a friend of the Naudet family. He said yesterday that he contacted the brothers soon after the attack to interview them for an article after learning that they had been on the scene with videocameras.

Graydon Carter, the editor of Vanity Fair, then contacted Jim Wiatt of the William Morris talent agency as well as Mr. Moonves, both of whom are personal friends of his, to work out the arrangements for bringing the tape to television.

Mr. Wiatt called in another William Morris agent, Ben Silverman, to represent the Naudets and Mr. Hanlon directly. Mr. Wiatt said that all the William Morris fees on the CBS project would be donated to a fund designated by the Naudets.

Mr. Moonves did not disclose how much CBS had paid for the rights to the footage, but Mr. Silverman called it 'ɺ minimal fee.'' CBS did, however, commit resources to complete the film, including the services of Susan Zirinsky, the executive producer of the CBS news magazine program '❈ Hours.'' She is leading the creative team on the project, though she said the Naudets remained in control of the film. Mr. Carter and Mr. Friend are also executive producers.

Despite Ms. Zirinsky's participation, CBS emphasized that the special was not a product of CBS News. '�use of the fund-raising aspect, it does not fit under a news heading,'' Ms. Zirinsky said. Mr. Moonves said that it would not be an entertainment special either. ''We're not going to label it anything,'' he said.

The network will sell commercial time in the special, Mr. Moonves said, but ''we are looking for just two or three special sponsors.'' Mr. Carter said the deal mandated that commercials would run only at the beginning and end of the film, with one break in the middle.

Mr. Silverman predicted that the special would be one of the biggest events of the television season. ''I think 50 million will watch this,'' he said. He said that CBS had acquired two runs of the film, but that it would still be owned by the Naudets. He said that they might expand it later, and that it would be sold internationally next. Proceeds from that sale will also go to the scholarship fund.


Vaata videot: 11-S: Derrumbe de la torre norte del World Trade Center - Las Noticias


Kommentaarid:

  1. Pol

    I have removed this message

  2. Lud

    Suurepärane idee

  3. Mur

    See on lihtsalt suurepärane idee

  4. Kaziramar

    Ma ei saa praegu arutelus osaleda - olen väga hõivatud. Ma tulen tagasi - avaldan kindlasti oma arvamust.

  5. Treven

    Ma saan sellest küsimusest aru. Saate arutada.

  6. Rolando

    Well done guy. Got out.

  7. Thuc

    Sõnumi arusaadavus

  8. Tyndareus

    liitun. Tänan informatsiooni eest.



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