Jahon savdo markazining qulashi - Collapse of the World Trade Center

Koordinatalar: 40 ° 42′41.12 ″ N. 74 ° 00′44.00 ″ V / 40.7114222 ° N 74.0122222 ° Vt / 40.7114222; -74.0122222

Jahon Savdo Markazining Janubiy minorasining qulashi Uilyamsburg, Bruklin.

Asl nusxa Jahon savdo markazi yilda Quyi Manxetten, Nyu-York shahri davomida vayron qilingan 2001 yil 11 sentyabrdagi teraktlar, ikkitasi tomonidan urilganidan keyin o'g'irlab ketilgan tijorat samolyotlari. Bitta Jahon Savdo Markazi (WTC 1) (Shimoliy minora) ertalab soat 8:46 da urilgan. Sharq vaqti va qulab tushdi soat 10:28 da Ikki Jahon Savdo Markazi (WTC 2) (Janubiy minora) soat 9: 03da urilib, 9:59 da qulab tushdi. Natijada paydo bo'lgan qoldiqlar o'nga yaqin qo'shni va yaqin atrofdagi inshootlarga jiddiy zarar etkazdi yoki yo'q qildi. qulashiga olib keladi 7 Jahon savdo markazi soat 17:21 da

Jami 2763 kishi halok bo'ldi avariyalarda, yong'inlarda va keyingi qulashlarda, shu jumladan 2192 ta tinch aholi, 343 o't o'chiruvchilar va 71 huquqni muhofaza qilish organlari xodimlari samolyotlarda barcha yo'lovchilar va ekipaj bilan bir qatorda, tarkibida 147 nafar fuqaro va o'nta samolyotni olib qochgan samolyotlar bor edi.

2005 yil sentyabr oyida Milliy standartlar va texnologiyalar instituti (NIST) natijalarini e'lon qildi uning qulashi haqidagi tergovi. Tergovchilar hujumlarning zo'ravonligi o'tmishda binolarda bo'lgan barcha narsalardan yuqori ekanligini ta'kidlab, egizak minoralar dizaynida nostandart narsalarni topmadilar. Ular yong'inlarni qulashning asosiy sababi deb aniqladilar, shundoqqina pollar perimetr ustunlari ichkariga qarab tortilib, ularning egilib, keyin toklanishiga olib keldi. Binoning yuqori qismi pastga qarab siljiy boshlagandan so'ng, butunlay progressiv qulashni oldini olish mumkin emas edi.

Tozalash Jahon savdo markazi sayti kecha-kunduz operatsiyalarni amalga oshirdi va yuzlab million dollarga tushdi. Samolyotlar tomonidan urilmagan ba'zi atrofdagi inshootlar hali ham katta zarar ko'rgan va ularni buzib tashlashni talab qilgan. Yaqin atrofdagi buzilgan binolarni buzish, egizak minoralar o'rnida yangi qurilish boshlanganda ham davom etdi Bitta Jahon Savdo Markazi, 2014 yil noyabr oyida ochilgan.[1]

Fon

Qurilish tugagandan so'ng, egizak minoralar qisqa vaqt ichida dunyodagi eng baland binolar bo'lgan va teraktlar paytida ular hali ham birinchi beshlikka kirgan. Bitta Jahon Savdo Markazi (WTC 1) "Shimoliy Minora" ning balandligi 1368 fut (417 m), balandligi Ikki Jahon Savdo Markazidan (WTC 2) "Janubiy Minora" dan olti fut balandroq edi. . Hujumlar paytida faqat o'sha paytda yakunlangan Petronas minoralari yilda Kuala Lumpur, Malayziya va Uillis minorasi Chikagodagi (o'sha paytda Sears minorasi nomi bilan tanilgan) balandroq edi.[2] Ichki makonni maksimal darajada oshiradigan yangi dizayni bilan qurilgan minoralar yangi kuch ishlatganda og'irlik va kuch nisbati yuqori bo'lgan. "hoshiyali naycha" An'anaviy po'latdan yasalgan osmono'par binolardan 40 foiz kamroq po'lat talab qiladigan dizayn.[3] Bundan tashqari, WTC 1 tepasida 1978 yilda o'rnatilgan 362 fut (110 m) telekommunikatsiya antennasi mavjud bo'lib, u minoraning umumiy balandligini 1730 fut (530 m) ga etkazgan, ammo qo'shimcha ravishda antenna rasmiy ravishda hisoblanmagan.

Strukturaviy dizayn

Shuningdek qarang: Jahon savdo markazi qurilishi
Po'latdan yasalgan idishlar ustidagi truss truss tizimi va beton polni aks ettiruvchi diagramma

Minoralar ramkali trubka konstruktsiyalari sifatida ishlab chiqilgan bo'lib, ular ijarachilarga ustunlar yoki devorlar bilan uzluksiz ochiq pol rejalarini taqdim etishgan. Binolar to'rtburchak va har tomondan 63 m balandlikda bo'lgan, ammo 6 metr 11 dyuym (2,11 metr) burchaklar pog'onali bo'lib, har bir binoning tashqi qismi taxminan 210 fut (64 m) kenglikda joylashgan.[4] Ko'p sonli, bir-biridan uzoqda joylashgan perimetr ustunlari strukturaning katta kuchini ta'minladi, shuningdek, yadroning po'lat quti ustunlari bilan birgalikda tortishish yuki.[5] O'ninchi qavatning yuqorisida, binoning har bir yuzi bo'ylab markazda 3 fut 4 dyuym (1,02 metr) masofada 59 ta ustun ustunlar bor edi.[5] Minoralar to'rtburchak shaklda bo'lsa, ichki tomirlari to'rtburchaklar shaklida bo'lib, har bir minoraning to'liq balandligi bo'ylab 47 ustun bilan qo'llab-quvvatlangan.[4] Barcha liftlar va zinapoyalar yadroda joylashgan bo'lib, u bilan poldan yasalgan trusslar orqali o'tuvchi perimetr o'rtasida ustunsiz bo'sh joy qoldirilgan.[5] Yadro to'rtburchaklar shaklida bo'lgani uchun, bu perimetr ustunlariga uzoq va qisqa masofani yaratdi.

Qavatlar 4 dyuym qalinlikdagi (10 sm) yengil po'latdan yasalgan pastki ustiga yotqizilgan engil beton plitalardan iborat edi.[4] Engil ko'prikli trusslar va magistral trusslar panjarasi pollarni beton plita bilan kesishma bilan bog'lab turardi. kompozitsion harakat.[5] Uzun bo'yli joylarda trusslar 18 fut (18 m), qisqa masofada esa 11 fut (11 m) bo'lgan. Perimetrga muqobil ustunlar bilan bog'langan trusslar, shuning uchun 6,8 metrlik (2,1 m) markazlarda joylashgan. Trusslarning yuqori akkordlari perimetr tomondan spandrellarga payvandlangan o'rindiqlarga va yadro tomonidagi ichki quti ustunlariga payvandlangan kanalga mahkamlangan. Qavatlar perimetri spandrel plitalari bilan bog'langan viskoelastik damperlar, bu esa yo'lovchilarni qurish orqali sezgirlikni kamaytirishga yordam berdi.[5]

Minoralar 107-110-qavatlar orasida joylashgan "shlyapa trussi" yoki "outrigger truss" ni ham o'z ichiga olgan bo'lib, ular yadroning uzun o'qi bo'ylab oltita va qisqa o'qi bo'ylab to'rtta trussdan iborat edi.[4] Ushbu truss tizimi pol diafragmalarini perimetri va yadro o'rtasida optimallashtirilgan ravishda qayta taqsimlashga imkon berdi, shu bilan moslashuvchan po'lat va qattiq betonning turli xil materiallari o'rtasida ishlash ko'rsatkichlari yaxshilandi, bu moment ramkalari yadroga siqilishga o'tishga imkon berdi va bu asosan transmisyon minorasini qo'llab-quvvatladi. Ushbu trusslar kelajakdagi elektr uzatish minoralarini qo'llab-quvvatlash uchun har bir binoga o'rnatildi, ammo oxir-oqibat faqat shimoliy minoraga bitta o'rnatildi.[4]

Samolyotning ta'sirini baholash

WTC 2 ning shimoliy tomonidan zarba bergandan so'ng aviatsiya yoqib yuboradigan olovli shar paydo bo'ladi. Yong'inlardan tutun o'ng tomonda joylashgan WTC 1 ning shimoliy tomonidan kelayotganini ko'rish mumkin.

Garchi yong'inni o'rganish va hatto past tezlikda ishlaydigan reaktiv samolyotlarning ta'sirini tahlil qilish tugallangunga qadar amalga oshirilgan bo'lsa ham, ushbu tadqiqotlarning to'liq ko'lami endi mavjud emas. Shunga qaramay, yong'in hech qachon osmono'par bino qulab tushishiga olib kelmagani va samolyotning zarbalari ularning dizaynida ko'rib chiqilganligi sababli, ularning yo'q qilinishi dastlab muhandislar jamoatchiligi uchun kutilmagan hol bo'ldi.[6]

Jahon savdo markazida ishlaydigan muhandis-konstruktorlar samolyot binoga qulashi ehtimolini ko'rib chiqdilar. 1945 yil iyulda a B-25 bombardimonchi tuman ichida yo'qolgan edi 79-qavatga qulab tushdi ning Empire State Building.[7] Bir yil o'tgach, a C-45F ekspeditori 40-Uoll-stritga qulab tushdi bino. To'qnashuvda yana bir bor tuman sabab bo'lishi mumkinligiga ishonishdi.[8] Lesli Robertson, Jahon Savdo Markazi dizayni ustida ish olib borayotgan bosh muhandislardan biri, a ta'sirining stsenariysini ko'rib chiqqanligini aytdi Boeing 707 Tuman ichida yo'qolishi va nisbatan past tezlikda uchib ketishi mumkin JFK yoki Newark aeroportlari.[9] Bilan suhbatda BBC bino qulab tushganidan ikki oy o'tgach, Robertson, "707 bilan yonilg'i yuki loyihada hisobga olinmadi, men buni qanday ko'rib chiqish mumkinligini bilmayman" deb da'vo qildi. Suhbatda Robertson loyihalash ishlari va oxir-oqibat minoralarning qulashiga sabab bo'lgan voqea o'rtasidagi asosiy farq zarba tezligi bilan bog'liq bo'lib, u so'rilgan energiyani sezilarli darajada oshirganligini va qurilish jarayonida hech qachon hisobga olinmaganligini aytdi.[10]

Ularning qulashi haqidagi tergov davomida Milliy standartlar va texnologiyalar instituti (NIST) uchta sahifani oldi oq qog'oz binolar Boeing 707 yoki samolyot ta'sirida omon qoladi degan DC 8 soatiga 600 mil (970 km / soat) tezlikda uchish.[11] 1993 yilda, Jon Skilling, keyin o'tkazilgan intervyusida, WTC uchun etakchi muhandis-muhandis 1993 yil Jahon Savdo Markazining portlashi "Bizning tahlilimiz shuni ko'rsatdiki, eng katta muammo bu yoqilg'ining (samolyotdan tashqari) binoga to'kilishi bo'ladi. Dahshatli yong'in sodir bo'lishi mumkin. Ko'p odamlar halok bo'lar edi", dedi u. "Qurilish tuzilishi hali ham o'sha erda bo'ladi."[12] O'z hisobotida NIST samolyotlarning zarbasini va undan keyin sodir bo'ladigan yong'inlarni qat'iy simulyatsiya qilish texnik imkoniyatlarini yaqinda rivojlanganligini va bunday tahlil qilishning texnik imkoniyati 1960 yillarda ancha cheklangan bo'lar edi.[13][eslatma 1] Yiqilish bo'yicha yakuniy hisobotda NIST yuqori tezlikda uchadigan samolyotning ta'sirini yoki aviatsiya yoqilg'isi bilan ta'minlangan katta hajmdagi yong'inni tekshiradigan hujjatlarni topa olmaganligini aytdi.[14]

Yong'inga qarshi

1970-yillarning o'rtalariga qadar asbest uchun yong'inga qarshi qurilish sohasida keng tarqalgan edi. Biroq, 1970 yil aprel oyida Nyu-York shahridagi havo resurslari departamenti Jahon savdo markazini qurayotgan pudratchilarga izolyatsion material sifatida asbest sepishni to'xtatish to'g'risida buyruq berdi.[15]

Keyin 1993 yil bombardimon, tekshiruvlar yong'inga qarshi vositalarning etishmasligi aniqlandi.[16] Yiqilishidan oldin, minoralar egalari, Nyu-York va Nyu-Jersi port ma'muriyati, yong'inga qarshi qo'shilish jarayonida bo'lgan, ammo samolyotning zarbasi va yong'inlari ta'sir qilgan barcha qavatlarni o'z ichiga olgan holda, faqat 1 ta WTC ning 18 qavatida va 2 ta WTC ning 13 qavatida, hech kim samolyotning ta'siridan bevosita ta'sir qilmagan .[17]

NIST samolyot zarbasi binolarning qulashiga hissa qo'shib, o'tga chidamsizlikning muhim qismini olib tashladi degan xulosaga keldi. WTC 1-da zarba izolyatsiyani bir nechta qavatdagi 47 ta ustunli 43 ta ustunlardan va 60 000 kvadrat metr (5600 m) maydon ustidagi trusslarni olib tashladi.2). WTC 2-da zarba ko'p qavatli 47 ustunning 39 tasidan va 7400 m (8000 kvadrat metr) maydonni egallagan truss trusslaridan izolyatsiyani olib tashladi.2).[14]

Yiqilishdan keyin Lesli Robertson shunday dedi: "Bizning ma'lumotimizga ko'ra, bunday samolyotdan yong'in oqibatlari haqida juda kam narsa ma'lum bo'lgan va bu holat uchun hech qanday loyihalar tayyorlanmagan. Darhaqiqat, o'sha paytda yong'inga qarshi tizimlar mavjud emas edi bunday yong'inlarning oqibatlarini nazorat qilish. "[9]

2001 yil 11 sentyabr

1 va 2 WTC-da zarba joylari, ta'sirning taxminiy burchagi va yadrolarning har bir minora tashqi tomoniga to'g'ri kelishi.

Samolyotlarning ta'siri va natijada yong'inlar

Davomida 11 sentyabr hujumlari, to'rtta jamoa al-Qoida terrorchilar to'rt xil reaktiv samolyotni olib qochishdi. Ushbu samolyotlardan ikkitasi, American Airlines reysi 11 va United Airlines aviakompaniyasining 175-reysi, ikkalasi ham Boeing 767 samolyotlari, Bostondan uchib ketganidan keyin o'g'irlab ketilgan Logan xalqaro aeroporti. Oxirgi lahzalarda American Airlines aviakompaniyasining 11-reysi janub tomon uchib o'tdi Manxetten va soatiga taxminan 440 milya (710 km / soat) ning shimoliy jabhasiga qulab tushdi Shimoliy minora (WTC 1) soat 8:46 da, 93 va 99-qavatlar orasida ta'sir ko'rsatdi. O'n etti daqiqadan so'ng, United Airlines aviakompaniyasining 175-reysi janubi-g'arbiy tomondan, yaqinlashdi Nyu-York Makoni va janubiy jabhasiga qulab tushdi Janubiy minora (WTC 2) soat 9: 02da 77- va 85-qavatlar orasida soatiga 540 mil (870 km / soat).

Perimetrdagi ko'plab yuk ko'taruvchi ustunlarni kesishdan va boshqa konstruktiv shikastlanishlardan tashqari, zarbalar minglab galon samolyot yoqilg'isini yoqib yubordi va bu o'z navbatida ofis yonuvchan moddalarini yoqib yubordi. Yoqilg'ining taxminan uchdan bir qismi dastlabki zarba natijasida va o't pufagida sarflangan.[2-eslatma][18] Ta'sirdan olingan ba'zi yoqilg'i kamida bitta lift shaftasi bo'ylab pastga tushdi va Shimoliy minoraning 78-qavatida, shuningdek asosiy qabulxonada portladi.[19] Qurilishlarning yengil konstruktsiyasi va ichi bo'sh tabiati reaktiv yoqilg'ining minoralar ichkarisiga kirib borishiga imkon berib, ta'sirlangan pollarning keng maydonida bir vaqtning o'zida ko'plab yirik yong'inlarni yoqib yubordi. Samolyotlardan yoqilg'i ko'pi bilan bir necha daqiqa yondi, ammo binolar tarkibi keyingi soat yoki bir yarim soat ichida yondi.[20]

Favqulodda vaziyatlarni bartaraf etish va evakuatsiya qilish

Shuningdek qarang: 11 sentyabr xurujlarining talofatlari va 11 sentyabr xurujlarida halok bo'lgan favqulodda vaziyat xodimlari

Egizak minoralarda deyarli barcha o'limlar samolyot ta'sir qiladigan joylarning yuqorisidagi zonalarda sodir bo'lgan. Shimoliy minora to'g'ridan-to'g'ri inshootning o'rtasiga urilganligi sababli, minora yadrosidagi uchta zinapoyaning hammasi shikastlangan yoki quyi qavatlargacha qochishni oldini olgan axlat bilan to'silgan. Janubiy minorada zarba markazdan markazning markaziy qismigacha va markaziy yadroning shimoli-g'arbiy qismidagi A zinapoyasiga ozgina ta'sir qildi, faqat qisman to'sib qo'yildi va 14 dan 18 gacha fuqarolar samolyot zarbasi nuqtasidan qochishga muvaffaq bo'lishdi va undan yuqori qavatlar. Kim halok bo'lganligi va ba'zi hollarda qaerda bo'lganligi aniq raqamlar aniq ma'lum emas; ammo Milliy Standartlar va Texnologiyalar Instituti hisobotida shuni ko'rsatdiki, Shimoliy minoradagi zarba nuqtasida yoki undan yuqori qismida jami 1402 tinch aholi halok bo'lgan, ularning ta'sirida yuzlab odamlar o'lgan deb taxmin qilinmoqda. Janubiy minorada 614 tinch aholi zarb qilingan qavatlar va undan yuqori qavatlarda halok bo'ldi. Fuqarolarning o'limidan 200 nafardan kamrog'i zarba berish nuqtalari ostidagi qavatlarda sodir bo'lgan, ammo ikkita samolyotdagi barcha 147 fuqarolik yo'lovchilar va ekipaj a'zolari, shuningdek, 10 nafar terrorchi, shuningdek, erdagi va qo'shni inshootlarda kamida 18 kishi halok bo'lgan.[21]

Barchasi aytganda, qulashda halok bo'lgan favqulodda vaziyatlar xodimlari 343 kishini tashkil etdi Nyu-York shahar yong'in xizmati (FDNY); 71 nafar huquqni muhofaza qilish organlari xodimlari, shu jumladan 23 nafar a'zolari Nyu-York shahar politsiya boshqarmasi (NYPD), 37 a'zosi Port ma'muriyati politsiya boshqarmasi (PAPD), ning beshta a'zosi Nyu-York shtati soliq majburiyatlari idorasi (OTE), uch zobit Nyu-York shtati sud ma'muriyati idorasi (OCA), Nyu-York shahar yong'in xavfsizligi boshqarmasining (FDNY) bitta yong'in marshali, u huquqni muhofaza qilish organlariga qasamyod qilgan (shuningdek, o'ldirilgan 343 FDNY a'zosi orasida bo'lgan), bitta a'zosi Federal tergov byurosi (FBI) va .ning bir a'zosi Amerika Qo'shma Shtatlari maxfiy xizmati (USSS). Fuqaro va nodavlat fuqarolar uchun o'lganlarning umumiy soni 2606 kishini tashkil etadi.

Yiqilish

Egizak minoralarning vayron bo'lishi "eng shafqatsiz paradigma" deb nomlangan progressiv qulash.[6] Ular bir nechta tarkibiy qismlarning mahalliy ishlamay qolishidan boshladilar va butun tuzilmani qamrab oldilar.[22] Bunday qulashlar "konstruktiv tarkibiy qismlarni (shu jumladan, yuk ko'tarmaydigan elementlarni) ajratish, tortishish energiyasini chiqarish va ta'sir kuchlarining paydo bo'lishi" bilan tavsiflanadi. Vertikal ta'sir kuchi tarqalish harakatini ta'minlaydi, asosiy kuchlar parallel va asosiy yuk uzatish ketma-ket.[23] Tuzilishda muvaffaqiyatsizlikka uchragan asosiy element "bir qavatning vertikal yuk ko'taruvchi elementlari" tomonidan tashkil etilgan. Binoning yuqori qavatlarini hisobga olmaganda, umuman tortishish uchun etarli tortishish kuchini chiqarmagan bo'lar edi, qulashlar biron bir voqea muvaffaqiyatsiz tugashi bilan boshlanishi mumkin edi.[24]

Bunday sharoitda minoralar nosimmetrik tarzda yiqilib tushdi yoki ozroq to'g'ridan-to'g'ri pastga tushdi, garchi minoralar tepalarida biroz qiyshayish va yon tomonlarga katta miqdordagi qulash bo'lsa ham. Ikkala holatda ham, binoning samolyotlar tomonidan buzilgan qismi ishlamay qoldi, bu esa ta'sir zonasi ustidagi qavatlar pastdagi buzilmagan inshootga tushishiga imkon berdi. Yiqilish davom etar ekan, vayronalar ostidagi bir necha qavat ostidagi derazalardan chang va qoldiqlar otilib chiqayotganini ko'rish mumkin edi.

Har bir qulash paytida perimetr ustunlarining katta qismlari va ehtimol yadrolari hech qanday lateral qo'llab-quvvatlanmasdan qoldirilib, ularni tashqi tomonga yon tomonga qulab tushishiga olib keldi va ko'payib borayotgan moloz uyumi itarib yubordi. Natijada devorlar yirtilib, binolardan uzoq masofada (ba'zi hollarda taxminan 500 fut) ajralib, boshqa qo'shni binolarni urib, keyin 7-binoning qulashiga olib keladigan yong'inlarni keltirib chiqardi. murvatlar uzilib, ko'plab panellar tasodifiy tarqalib ketdi.[25] Yiqilgan Shimoliy minoraning tashqi devorlarining birinchi bo'laklari qulash boshlangandan 11 soniya o'tgach, Janubiy minoraning qismlari 9 soniyadan keyin erga urildi. Ikkala bino yadrolarining pastki qismlari (WTC 1 ning 60 ta hikoyalari va WTC 2 ning 40 ta hikoyalari) dastlabki qulash boshlangandan keyin ular qulab tushguncha 25 soniya davomida turdilar.[13]

Yiqilishni boshlash

Shimoliy minoraning qulashini oddiy tasvirlash

Samolyotlar binolarga urilganidan keyin, lekin binolar qulashidan oldin ikkala minoraning yadrolari uchta alohida uchastkadan iborat edi. Ta'sir etuvchi qavatlardan yuqorida va pastda tomirlar asosan ikkita qattiq quti bo'lgan; ushbu qismlardagi po'lat shikastlanmagan va sezilarli darajada qizib ketmagan. Biroq ular orasidagi qism sezilarli darajada zarar ko'rgan va ular uni eritish uchun etarli darajada issiq bo'lmasa-da, yong'inlar strukturaviy po'latni zaiflashtirgan.

Natijada, yadro ustunlari asta-sekin ezilib, qo'llab-quvvatlandi plastik va sudralmoq yuqoridagi qavatlarning og'irligidan deformatsiya. Yuqori qism pastga qarab harakatlanayotganda, shlyapa trussi yukni perimetr ustunlariga qayta taqsimladi. Ayni paytda, yong'inlarning issiqligidan perimetr ustunlari va pollari ham zaiflashayotgan edi va pollar osila boshlagach, tashqi devorlarni ichkariga tortdilar. "Keyinchalik vertikal yuk ko'tarish qobiliyatining yo'qolishi bir necha qavat bilan chegaralangan, ammo har bir minoraning butun kesimiga cho'zilgan."[26] Ikki WTC holatida, sharqiy yuz oxir-oqibat qisilib, yuklarini shlyapa trussi orqali ishlamay qolgan yadroga uzatdi va qulashni boshladi. Keyinchalik, 1 WTC ning janubiy devori xuddi shu tarzda qisilib qoldi va shunga o'xshash oqibatlarga olib keldi.[27]

Umumiy progressiv qulash

Strukturaviy tizimlar juda boshqacha javob beradi statik va dinamik yuklar va minoralar odatdagi sharoitda ulkan og'irlikni ko'tarish uchun mo'ljallangan bo'lsa-da, ular buzilgan pollar ustidagi uchastkaning harakatlanuvchi massasiga ozgina qarshilik ko'rsatgan. Ikkala holatda ham, qulashlar yuqori qismning kamida bitta qavat balandligidan (taxminan uch metr yoki o'n fut) tushishi bilan boshlangan, ammo yarim metrga (20 dyuymga yaqin) tushish zarur bo'lgan energiyani chiqargan bo'lar edi to'xtatib bo'lmaydigan qulashni boshlash uchun.[28]

U erdan qulash ikki bosqichda davom etdi. Davomida ezilgan Faz, yuqori blok bir vaqtning o'zida taxminan bitta hikoyani ketma-ket ustunlar qatorida quyidagi strukturani yo'q qildi. Har bir nosozlik yuqori qavatning pastki qism ustunlariga ta'siridan boshlandi, asosan poldan plitalardan betondan iborat moloz qatlami o'sib bordi. Har bir zarbadan olingan energiya "keyingi zarbada tuzilishga qayta kiritildi, ... ta'sirga to'g'ridan-to'g'ri ta'sir ko'rsatadigan yuk ko'taruvchi elementlarda konsentrat [d]."[23] Bu hikoyaning ustunlarini zudlik bilan vayronagarchilik ostida darhol lateral qo'llab-quvvatlashning keyingi nuqtasiga, odatda ushbu hikoyaning pol trusslariga bog'lab qo'ydi. Ustunlarni bog'lab qo'ygandan so'ng, blok yana bir marta qo'llab-quvvatlanmadi va shu hikoyaning masofasidan yiqilib tushdi va yana quyida joylashgan hikoya ustunlariga ta'sir qildi, so'ngra xuddi shu tarzda qisilib qoldi.

Bu yuqori blok erga yetguncha takrorlandi va maydalash bosqichi boshlandi. Bu erda ham ustunlar bir-bir hikoyani qisib qo'ydi, endi pastdan boshlab. Har bir voqea muvaffaqiyatsizlikka uchraganligi sababli, qolgan blok hikoyaning balandligidan keyingisiga qulab tushdi, u tom ham erga tekkancha.[6] Jarayon davomida tezlashdi va oxir-oqibat har bir hikoya soniyaning o'ndan bir qismiga qadar ezildi.[28]

Janubiy minoraning qulashi

Asosiy maqola: Jahon savdo markazi (1973–2001)
Yiqilgandan keyin saytning havodan ko'rinishi, qulab tushgan binolarning joylashuvi ko'rsatilgan

Yong'inlar davom etar ekan, Janubiy minoraning yuqori qavatlarida qamalib qolganlar sharoitlar to'g'risida ma'lumot berishdi 9-1-1 dispetcherlar. Soat 9:37 da, Janubiy minoraning 105-qavatida yashovchi, uning ostidagi qavatlar "90 qavatli qavatda" qulab tushganligini xabar qildi.[29] The Nyu-York shahar politsiya boshqarmasi aviatsiya bo'limi ham binolarning ahvoli yomonlashgani to'g'risida ma'lumotni politsiya qo'mondonlariga etkazdi.[30] Janubiy minoraning zarbasi urilganidan keyin uning ta'sir zonasidan faqat 14 kishi qochib qutulgan (shu jumladan) Stenli Praimnat, kim unga samolyot kelayotganini ko'rgan bo'lsa) va faqat yuqoridagi qavatlardan to'rttasi. Ular zarbadan keyin buzilmasdan qolgan yagona zinapoya - Stairwell A orqali qochib qutulishdi. Janubiy minora ichidagi shaxslardan qo'ng'iroqlarni qabul qilgan ko'plab politsiya ishonch telefonlari operatorlari vaziyat tez xabardor bo'lganligi sababli yaxshi xabardor emas edilar. Ko'pgina operatorlar qo'ng'iroq qiluvchilarga minoradan o'z-o'zidan tushmasliklarini aytdilar, garchi hozirda Stairwell A zarba berish nuqtasida va undan yuqori darajada o'tishi mumkin deb hisoblansa ham.[31] 9:52 da NYPD aviatsiya bo'limi radio orqali "WTC 2 tepasidan katta qismlar qulab tushishi mumkin" deb xabar berdi. U erda katta qismlar osilgan ".[29] Ogohlantirishlar bilan NYPD o'z zobitlariga evakuatsiya qilish to'g'risida buyruqlar chiqardi. Favqulodda vaziyatlarni bartaraf etish paytida NYPD va the o'rtasida minimal aloqa mavjud edi Nyu-York shahar yong'in xizmati (FDNY) va 9-1-1 gachasi dispetcherlar voqea joyida FDNY qo'mondonlariga ma'lumot etkazishmagan. Soat 9:59 da, Janubiy minora urilganidan 57 daqiqadan so'ng qulab tushdi.

Shimoliy minoraning qulashi

Janubiy minora qulagandan so'ng, NYPD vertolyotlari Shimoliy minoraning yomonlashib borayotgan sharoitlari to'g'risida ma'lumot tarqatdi. Soat 10: 20da NYPD aviatsiya bo'limi "minora tepasi egilgan bo'lishi mumkin", deb xabar berdi va bir daqiqadan so'ng Shimoliy minoraning "janubi-g'arbiy burchagida egilib, janubga egilib yotganligi" haqida xabar berdi. Ertalab soat 10: 28da aviatsiya bo'limi "tom juda qisqa vaqt ichida pastga tushishini" xabar qildi.[29] va haqiqatan ham Shimoliy minora 102 minut yonib ketganidan so'ng, darhol soat 10:28 da qulab tushdi.

Janubiy minora qulagandan so'ng, FDNY qo'mondonlari Shimoliy minoradagi o't o'chiruvchilarga evakuatsiya qilish to'g'risida buyruq berishdi. Sababli radioaloqa muammolari, minoralar ichidagi o't o'chiruvchilar voqea joyidagi rahbarlaridan evakuatsiya tartibini eshitmagan va ko'pchilik boshqa minoraning qulab tushganidan bexabar bo'lgan.[32] Binolarning qulashi natijasida egizak minoralarda uch yuz qirq uchta o't o'chiruvchi vafot etdi.[33][34][35] Hech kim Shimoliy minoradan zarba zonasidan yoki undan yuqorisiga qochib qutula olmadi, chunki bu qavatlardagi barcha zinapoyalar va lift shaftlari vayron qilingan yoki to'sib qo'yilgan.[36] Yiqilgandan so'ng, engil chang changgacha etib bordi Empire State Building, 2,93 milya (4,72 km) masofada joylashgan.

7-bino qulab tushdi

Asosiy maqola: 7 Jahon savdo markazi
Shimoliy minoraning tashqi qobig'ining qismlari Shimoliy minoraning qulashi paytida katta zarar ko'rgan 6 WTC qoldiqlariga suyanadi. 7 WTC qoldiqlari yuqori o'ng tomonda

Shimoliy minora qulashi bilan og'ir qoldiqlar 7 Jahon Savdo Markazini urib, binoning janubiy yuziga zarar etkazdi[37] va tushdan keyin davom etayotgan yong'inlarni boshlash.[38] 7 va 17 qavatlar orasidagi janubi-g'arbiy burchakda va 44-qavat bilan tom o'rtasidagi janubiy jabhada strukturaviy shikastlanish yuz berdi; boshqa mumkin bo'lgan strukturaviy shikastlanishlar, 24 va 41 qavatlar orasidagi janubiy jabhaning markaziga yaqin bo'lgan katta vertikal zarbani o'z ichiga oladi.[38] Bino a bilan jihozlangan sug'orish tizimi, ammo ishlamay qolishi uchun bir nechta nuqsonli zaifliklar mavjud edi: purkagich tizimi to'liq avtomatik tizim emas, balki elektr yong'in nasoslarini qo'lda ishga tushirishni talab qildi; pol darajasidagi boshqaruv elementlari purkagich suv ko'targichiga bitta ulanishga ega edi; va purkagich tizimi uchun bir oz kuch kerak edi yong'in nasosi suv etkazib berish. Shuningdek, suv bosimi past bo'lib, purkagichlarni oziqlantirish uchun suv kam yoki umuman yo'q edi.[39][40]

Yiqilishidan oldin yuqori markazda joylashgan WTC 7 da ko'rinadigan yong'inlardan tutun.

Ba'zi o't o'chiruvchilar binoni qidirish uchun 7 ta Jahon savdo markaziga kirishdi. Ular kichik yong'in cho'ntaklarini o'chirishga urinishdi, ammo suvning past bosimi ularning harakatlariga to'sqinlik qildi.[41] 7-Jahon Savdo Markazining 11 va 12-qavatlarida tushdan keyin yong'inlar yondi, binoning sharqiy qismida yong'in ko'rinib turdi.[42][43] Kunning ikkinchi yarmida, shuningdek, yong'in 6-10, 13-14, 19-22 va 29-30 qavatlarda kuzatilgan.[37] Xususan, 7-9 va 11-13-qavatlardagi yong'inlar tushdan keyin ham nazoratdan o'tmay davom etdi.[44] Taxminan soat 14:00 da o't o'chiruvchilar 10-chi va 13-qavatlar orasida 7-Jahon Savdo Markazining janubi-g'arbiy burchagida, bino beqaror ekanligi va bir tomonga g'orga tushishi yoki "qulab tushishi" mumkin bo'lgan belgini payqashdi.[45] Kunning ikkinchi yarmida o't o'chiruvchilar ham binodan g'ichirlagan tovushlarni eshitib, podvaldagi shikastlanishlar to'g'risida noaniq xabarlarni tarqatishdi.[46] 15:30 atrofida FDNY boshlig'i Daniel A. Nigro 7 Jahon Savdo Markazi yaqinidagi qutqaruv ishlarini, sirtni olib tashlashni va qoldiqlarni qidirishni to'xtatishga va xodimlarning xavfsizligi uchun xavotir tufayli hududni evakuatsiya qilishga qaror qildi.[47] 2001 yil 11 sentyabr kuni soat 17:20:33 da EDT, sharqiy mexanik pentxausning qulashi bilan 7 ta Jahon savdo markazi qulab tushishni boshladi, 17: 21: 10-da EDT butun bino butunlay qulab tushdi.[48][49] Yo'q edi qurbonlar qulashi bilan bog'liq.

7 Jahon Savdo Markazi qulab tushganda, chiqindilar katta zarar va ifloslanishni keltirib chiqardi Manxetten jamoat kollejining tumani "s Fiterman zali bino, G'arbiy Broadway 30-da, bino qutqarib bo'lmaydigan darajada qo'shni joyda joylashgan. 2007 yil avgust oyida Fiterman Hallni demontaj qilish rejalashtirilgan edi.[50] Qayta ko'rib chiqilgan reja 2009 yilda buzib tashlashni va 2012 yilda yangi Fiterman zalini 325 million dollarga sarflashni talab qildi.[51][52] Bino nihoyat 2009 yil noyabr oyida buzib tashlandi va uning o'rnini qurish 2009 yil 1 dekabrda boshlandi.[53] Qo'shni Verizon binosi, an Art Deco 1926 yilda qurilgan bino, Jahon Savdo Markazining qulashi oqibatida o'zining sharqiy jabhasiga katta zarar etkazgan, ammo u 1,4 milliard AQSh dollari evaziga qayta tiklangan.[54]

Boshqa binolar

Sfera hujumlardan 10 kun o'tgach ko'rilganidek

Minoralar qulashi sababli atrofdagi ko'plab binolar ham buzilgan yoki vayron bo'lgan. 5 WTC katta yong'in va uning temir konstruksiyasining qisman qulashiga bardosh berib, qulab tushdi. Vayron qilingan boshqa binolarga quyidagilar kiradi Aziz Nikolay yunon pravoslav cherkovi, Marriott Jahon savdo markazi (Marriott Hotel 3 WTC), Janubiy Plaza (4 WTC) va AQSh bojxonalari (6 WTC). Jahon moliya markazi binolari, G'arbiy ko'cha, 90 va Sidar ko'chasi, 130 yong'inlarni boshdan kechirgan. The Deutsche Bank binosi, Verizon binosi va Jahon moliya markazi 3 minoralar qulashi oqibatida zarar ko'rgan,[55] xuddi G'arbiy ko'chada 90 kabi.[56] Bitta Liberty Plaza derazalar singari tizimli ravishda buzilmagan, ammo doimiy sirt shikastlanishidan omon qoldi. 30 G'arbiy Brodvey 7 ta WTC qulashi natijasida zarar ko'rdi. 11 sentyabrdan keyin binoning zararini qoplash uchun katta qora "kafan" bilan yopilgan Deutsche Bank binosi, qo'shni minoralarning qulashi oqibatida suv, mog'or va boshqa jiddiy shikastlanishlar tufayli buzilgan.[57][58] Ko'pchilik san'at asarlari qulashda yo'q qilindi.

Tergov

Dastlabki fikrlar va tahlillar

1 WTC (o'ngda) va 2 WTC (chapda) ta'sir joylari

Hujumlardan so'ng darhol ko'plab muhandislar va mutaxassislar ommaviy axborot vositalari bilan suhbatlashib, minoralar qulab tushishiga nima sabab bo'lganini tasvirlab berishdi. Abolhasan Astaneh-Asl, qurilish muhandisligi professori Berkli shahridagi Kaliforniya universiteti, yong'inlarda yuqori harorat po'lat ustunlar va ustunlarni susaytirib, ularni "yumshoq va shilimshiq" bo'lishiga olib keldi va oxir-oqibat ular yuqoridagi tuzilmani qo'llab-quvvatlay olmadilar. Astaneh-Asl shuningdek, samolyotning dastlabki zarbalari paytida yong'inga qarshi himoya joyidan chiqib ketishini taklif qildi. U, shuningdek, dastlabki strukturaviy nosozlik yuz bergandan so'ng, progressiv qulash butun tuzilish muqarrar edi.[59] Sezar Pelli, kim tomonidan ishlab chiqilgan Petronas minoralari Malayziyada va Jahon moliya markazi Nyu-Yorkda "hech qanday bino bunday stressga tayyor emas" deb ta'kidladi.[60]

2001 yil 13 sentyabrda, Zdenek P. Bažant, qurilish muhandisligi va materialshunoslik professori Shimoli-g'arbiy universiteti, Jahon savdo markazining qulashini oddiy tahlil qilish natijalari bilan qoralama qog'ozni tarqatdi. Bažant yong'inlarning isishi asosiy omil bo'lib, yadro va perimetrdagi po'lat ustunlarning zaiflashishiga va yuk ko'tarish qobiliyatini yo'qotishdan oldin deformatsiyani boshdan kechirishiga sabab bo'lgan deb taxmin qildi. Muayyan qavatda joylashgan ustunlarning yarmidan ko'pi qisilib qolgandan so'ng, yuqoridagi konstruktsiyani qo'llab-quvvatlay olmadi va inshootlarning to'liq qulashi sodir bo'ldi. Keyinchalik Bažant ushbu tahlilning kengaytirilgan versiyasini nashr etdi.[61] Boshqa tahlillar MIT qurilish muhandislari Oral Buyukozturk va Frants-Yozef Ulm, shuningdek, 2001 yil 21 sentyabrda qulash mexanizmini tasvirlab berdi.[62] Keyinchalik ular tahrirlangan WTC qulashi haqidagi MIT hujjatlar to'plamiga hissa qo'shdilar Eduardo Kausel deb nomlangan Yo'qotilgan va undan tashqaridagi minoralar.[63]

Yiqilgandan so'ng darhol xizmat tekshiruvini o'tkazish vakolatiga ega bo'lganligi to'g'risida bir oz chalkashliklar paydo bo'ldi. Samolyotlarda sodir bo'lgan baxtsiz hodisalarni tergov qilishning aniq tartib-qoidalari mavjud bo'lsa-da, binolarning qulab tushishini tekshiradigan biron bir tashkilot oldindan tayinlanmagan[64] Tarkibiy muhandislar instituti tomonidan tezda bir guruh yig'ildi Amerika qurilish muhandislari jamiyati, boshchiligida V. Deni Korli, Katta vitse-prezidenti CTLGroup. Bu shuningdek o'z ichiga olgan Amerika po'lat qurilish instituti, Amerika beton instituti, Yong'indan himoya qilish milliy assotsiatsiyasi, va Yong'indan himoya qilish bo'yicha muhandislar jamiyati.[65] Oxir-oqibat, AAAA FEMA-ni tergovga qo'shilishga taklif qildi.[65]

Tekshiruv AQShdagi ba'zi muhandislar va qonunchilar tomonidan tanqid qilindi. Uning mablag'lari kam, dalillarni talab qilish huquqiga ega bo'lmagan va WTC saytiga kirish huquqi cheklangan. O'sha paytdagi eng katta tortishuvlardan biri shundaki, WTC uchastkasini tozalash binolarning temir qismlarining ko'p qismini yo'q qilishga olib keldi.[66] Darhaqiqat, NIST o'zining yakuniy hisobotini e'lon qilganda, qulashni tekshirish uchun qo'lida bo'lgan "ashyoviy dalillarning kamligini" qayd etdi. Tozalash tugagandan so'ng, binolarning faqat bir foizining bir qismi tahlil uchun qoldi: 236 dona temir po'latdir, garchi 95% konstruktsiya to'sinlari va plitalari va 50% mustahkamlash panjaralari tiklandi.[67]

FEMA o'z hisobotini 2002 yil may oyida e'lon qildi. NIST shu yilning avgustida qulashlarni tekshirish niyatida bo'lganligini e'lon qilgan bo'lsa-da, 2002 yil 11 sentyabrga qadar (falokatdan bir yil o'tgach), jamoatchilik tomonidan yanada chuqurroq tergov o'tkazish uchun bosim kuchaymoqda.[68] Kongress 2002 yil oktyabr oyida Qurilish xavfsizligi bo'yicha milliy guruh qonun loyihasini qabul qildi va NISTga Jahon Savdo Markazining qulashini tekshirish bo'yicha vakolat berdi.[69]

FEMA binosining ishlash ko'rsatkichlarini o'rganish

FEMA, yong'inlar samolyot ta'siridan kelib chiqadigan shikastlanish bilan birga minoralar qulashi uchun kalit ekanligini taxmin qildi. Tomas Eagar, Materiallar muhandisligi va muhandislik tizimlari professori MIT, yong'inlarni "WTC qulashining eng noto'g'ri tushunchasi" deb ta'rifladi. Buning sababi shundaki, dastlab yong'inlar pollar va ustunlarni "eritib yuborgan".[70] Reaktiv yoqilg'i asosan kerosin hisoblanadi va uglevodorodlarning juda katta, ammo g'ayrioddiy issiq bo'lmagan olovlarini yoqish uchun xizmat qilgan bo'lar edi.[71] Eagar aytganidek: "WTC-da olov harorati g'ayrioddiy bo'lmagan va u albatta po'latni eritishga qodir emas edi".[72] Bu Eagar, FEMA va boshqalarni konstruktsiyalarning eng zaif tomoni bo'lgan narsalarga, ya'ni pollar bino ramkasiga bog'langan nuqtalarga e'tibor qaratishlariga olib keldi.[73]

Har bir samolyot tomonidan olib o'tilgan ko'p miqdordagi aviatsiya yoqilg'isi har bir binoga zarba berganda yonib ketdi. Ushbu yoqilg'ining muhim qismi darhol o't o'chiruvchilarda iste'mol qilindi. Qolgan yoqilg'i binolar orqali oqib o'tgan yoki samolyot ta'siridan bir necha daqiqa o'tgach yonib ketgan deb taxmin qilinadi. Ushbu yonayotgan samolyot yoqilg'isi tomonidan ishlab chiqarilgan issiqlik o'z-o'zidan strukturaviy qulashni boshlash uchun etarli bo'lmagan ko'rinadi. Biroq, yonayotgan samolyot yoqilg'isi binolarning bir necha qavatiga tarqalganda, u binolarning ko'p qismini yoqib yubordi va ikkala binoning bir necha qavatida bir vaqtning o'zida yong'in chiqdi. Ushbu yong'inlardan chiqadigan issiqlik miqdori katta tijorat energiya ishlab chiqarish stantsiyasi tomonidan ishlab chiqarilgan quvvat bilan taqqoslangan deb taxmin qilinadi. Ko'p daqiqa davomida bu issiqlik buzilgan struktura ramkalariga qo'shimcha stresslarni keltirib chiqardi, shu bilan birga bu ramkalarni yumshatish va zaiflashtirish. Ushbu qo'shimcha yuk va natijada etkazilgan zarar ikkala strukturaning qulashi uchun etarli edi.[74]

NIST hisoboti

Asosiy maqola: NIST Jahon Savdo Markazining Tabiiy ofatlarni tekshirish
WTC ning Janubiy minorasi (2-minora) tashqi qobig'i hali ham o'ng tomonda. 22 qavatli Marriott mehmonxonasi oldingi minorada ikkala minora qulab tushganda ezilgan.

FEMA hisoboti nashr etilgandan so'ng va texnik mutaxassislar, sanoat rahbarlari va qurbonlar oilalarining tazyiqlaridan so'ng, Savdo departamenti Milliy standartlar va texnologiyalar instituti bo'yicha uch yillik 16 million dollarlik tergov o'tkazdi tizimli nosozlik va progressiv qulash bir nechta WTC kompleks tuzilmalari.[75] Tadqiqot ichki texnik ekspertizani, shuningdek, bir nechta tashqi xususiy muassasalarning, shu jumladan, Strukturaviy muhandislik institutining yordamini o'z ichiga olgan Amerika qurilish muhandislari jamiyati, Yong'indan himoya qilish bo'yicha muhandislar jamiyati, Yong'indan himoya qilish milliy assotsiatsiyasi, Amerika po'lat qurilish instituti, Simpson Gumpertz & Heger Inc., Baland binolar va shaharlarning yashash joylari bo'yicha kengash, va Nyu-Yorkning Strukturaviy muhandislar assotsiatsiyasi.

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 Yong'in dinamikasi simulyatori. 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. Ushbu modellar statik or quasi-static, including deformation but not the motion of structural elements after rupture as would dinamik modellar. 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 Jahon savdo markazi

Plan view of collapse progression, with structural failure initiating on lower floors, on the east side of the building and vertical progression up to the east mechanical penthouse

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. V. Deni Korli, 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.[iqtibos kerak ]

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 Yong'indan himoya qilish bo'yicha muhandislar jamiyati (SFPE), the Yong'indan himoya qilish milliy assotsiatsiyasi (NFPA), the American Institute of Steel Construction (AISC), the Baland binolar va shaharlarning yashash joylari bo'yicha kengash (CTBUH), and the Nyu-Yorkning Strukturaviy muhandislar assotsiatsiyasi (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]

7 World Trade Center on fire after the collapse of the Twin Towers on September 11, 2001

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]

Boshqa tekshiruvlar

In 2003, Asif Usmani, Professor of Structural Engineering at Edinburg universiteti, 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, ilgari 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]

Natijada

Tozalamoq

A New York City fireman calls for 10 more rescue workers to make their way into the rubble of the World Trade Center.

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 Boshqariladigan Demolition, Inc. (CDI) of Feniks, Merilend.[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 Jahon savdo markazi.

Sog'likka ta'siri

Asosiy maqolalar: 11 sentyabr xurujlaridan kelib chiqadigan sog'liqqa ta'sir va EPA 9/11 pollution controversy

The collapse of the World Trade Center produced enormous clouds of dust that covered Manhattan for days. On September 18, 2001, the Qo'shma Shtatlar atrof-muhitni muhofaza qilish agentligi (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. Asbestoz 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 Astma, sinusit, oshqozon-qizilo'ngach reflyuks kasalligi va travmadan keyingi stress buzilishi.[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]

Adabiyotlar

Tushuntirish yozuvlari

  1. ^ The three-page white paper titled Salient points with regard to the structural design of The World Trade Center towers described an analysis of a Boeing 707 weighing 336,000 pounds (152 t) and carrying 23,000 US gallons (87 m3) of fuel striking the 80th floor of the buildings at 600 miles per hour (970 km/h). It is unclear whether the effect of jet fuel and aircraft contents was a consideration in the original building design, but this study is in line with izohlar Arxivlandi 2008 yil 14 aprel, soat Orqaga qaytish mashinasi made by John Skilling following the 1993 WTC bombing. Without original documentation for either study, NIST said any further comments would amount to speculation. NIST 2005. pp. 305–307.
  2. ^ Ga binoan Milliy standartlar va texnologiyalar instituti (NIST) estimates, Flight 11 was carrying 10,000 US gallons (38,000 L) of jet fuel when it hit the North Tower. 1,500 US gallons (5,700 L) were consumed in the initial impact when the aircraft hit and a similar amount was consumed in the fireball outside the building. Approximately 7,000 US gallons (26,000 L) burnt inside the office spaces igniting combustibles. Similarly, Flight 175 was carrying around 9,100 US gallons (34,000 L) when it hit the South Tower. Up to 1,500 US gallons (5,700 L) was instantly consumed in the initial fireball and up to 2,275 US gallons (8,610 L) was consumed in the fireball outside the building. More than 5,325 US gallons (20,160 L) was burnt in the office spaces. NIST estimated that each floor of both buildings contained around four pounds per square foot (60 tons per floor) of combustibles.

Iqtiboslar

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