cau tao va tinh toan
cho ket cau be tong cot tiiep chiu nong
ThS. Dao Van Cuxmg
Tom tat
Be tong cot thep chiu nong Avtqc dung trong cac 16 nha may, ong khoi, 16 dien giai va cac thiet bi khac lam viec trong dieu kien chiu nhiet do cao tac dung dai lau. Khi chiu nhiet do cao neu su* dung Be
tong cot thep (BTCT) thong thu'6Tig cSu kien BTCT se bi pha hoai. De dam bao
thoa man dieu kien ve chiu lure va dieu kien sir dung binh thwong cua ket cau trong dieu kien chiu nong can phai thay doi ve vat lieu, cau tao va each tinh toan.
Bai bao nay neu nguyen tac ehung ve vat lieu, cau tao va tinh toan ket eau be tong cot thep chiu nong
Abstract
Heatproof reinforced concretes are used for equipments working at high temperatures in a long time including furnaces of factories, chimmeys and so on. If mild / normal reinforced concrete is used at high temperature in a long
time, its components may be destructive. To meet the requirements, it's necessary to change its materials, structural detailings as well as the calculation method for heat-bearing reinforced concrete structures.
ThS. Bao Van Cucmg
Bo mon Be tong cSt thep - Gach da Khoa Xdy dung
DT 0913210900
1. Gio'i thieu ehung
K i t c l u be t6ng e l t thep chju nong thuo'ng duge SLP dung trong cac 16 nha may, I n g khoi, 16 dien giai... Be t6ng e l t thep chju nong la sy k i t hgp giCpa be t6ng chju nong va e l t thep dual dang thanh ro'i b l tri trong be t6ng hoac dual dang vo hay khung kim loai lien k i t toan khIi vai be t6ng. Thye c h i t cua viee e h l tao be t6ng chju nong la thay cac e l t lieu thuo-ng bang e l t lieu co d l y du kha nang chIng ndng.
2. Dac diem ve vat lieu cho ket cau BTCT chju nong:
2.1. Vat lieu be tong
Khi bj nong cac thanh p h l n trong c l u true cua be t6ng thuo'ng se bj pha hoai bo'i cac nguyen nhan sau:
- Sy n l cue bp do nuo'c thCpa bay hai nhanh Do da xi mang bj khu" m I t nuac
- Sy thay d l i t h i tich khae nhau cua thanh p h l n be t6ng - Sy giam sut euo'ng dp cua da xi mang
Sy b i l n dang vi nhiet dp kh6ng d i n g d I u cua da xi mang tai cac vj tri rieng biet
Sy b i l n d l i cua da thach anh trong e l t lieu se lam giam euo'ng dp cua e l t lieu
Do phan Cpng hoa voi cua da xi mang khi bj ngupi se hut I m tu" kh6ng khi...
Be t6ng chju nong la vat lieu da nhan tao kh6ng nung c6 the dung khi nhiet dp cao tac dung lau dai va v I n dam bao duge tinh c h i t ca ly trong gio'i han c I n thilt.
Thuc c h i t viee che tao be t6ng chju nong la thay t h i cac e l t lieu thong thuo'ng bIng cac cot lieu c6 du kha nang chju nong va co he s l gian na vi nhiet nho. Khi bj d I t nong va de ngupi BTCT chju nong vSn giO" nguyen duge cuo-ng dp yeu c l u va khong thay doi tinh c h i t ca ly cua ehung.
Can CLP vao c h i t k i t dinh nguai ta co 3 loai be t6ng chju nong.
- Be t6ng chju nong SLP dung xi mang PoocLang - Be t6ng chju nong SLP dung xi mang Aluminate
Be tong chju nong SLP dung thuy tinh long co fluorua silicat natri.
' C i t lieu g I m :
+ C i t lieu hat lan (da dam) eo d = 5^25mm + C i t lieu hat nho (eat hat trung) c6 <i = 0,15 -^ 5mm
SO 13-2013 A S
KHOA HOC & CONG NGHE
0|.i
"2
Hinh 1. Quan he li'ng suat -bien dang cua be tong d nhiet do cao
+ Chit phu gia nghiln nho ehl tCp erom, sa mIt, gach do dap vun, xi 16 cao, da ba dan, da di-a-ba va da an de- dit.
Vo'i be t6ng chju nong SLP dung xi mang aluminate kh6ng eIn chit phu gia vi ban than xi mang nay da eo tich chiu nong. Be t6ng SLP dung xi mang pooe lang hoac thuy tinh long co fluorua silicat natri thi cIn them phu gia d l tang tinh chju nhiet. Bang 1 ghi thanh phln ca ban va chi tieu cua mpt s l loai be t6ng chju nong.
Bang 1. Thanh phan cd ban va cac chi tieu cua be tong chju nong
Chit k i t dinh Xi- mang aluminat Xi- mang aluminat Xi- mang poc- lang Xi- mang poc- lang Xi- mang poc- lang Xi- mang poc- lang Xi- mang poc- lang Xi- mang poc- lang Xi- mang poc- lang
Thuy tinh long co Fluoruasilicat- Natri
Thuy tinh long co Fluoruasilicat- Natri
Thuy tinh long co Fluoruasilicat- Natri
Thuy tinh long co Fluoruasilicat- Natri
C h i t phu gia nghiln nho
Sa m I t CO dp chju ICpa kh6ngduai 1580°
Sa m I t CO dp chju ICpa kh6ng duo'i 1730°
Xe- mi- an- ka, tro nui ICpa, Xi vun eua 16 gang Xe- mi- an- ka, tro nui ICpa,
Xi vun cua 16 gang
Cr6- mit Sa- m I t Sa- mot
Sa m I t va xe- mi- an- ea
C i t lieu be va lo'n Cr6m
Sa m I t CO dp chju ICra kh6ng duo'i 1700°
Nhu tren - kh6ng dual 1580°
Nhu tren - khong duo'i 1730°
Badan, diaba, andedit Xi 16 gang Gach dat set thuang,
dap vun Xi 16 gang Gach d I t set thuang,
dap vun Cr6- mit Sa- mIt Badan, diaba, andedit
Gach dat set thuo-ng, dap vun
Nhiet dp SCP dung(d6) 1000-1400 1000-1300 400-1100 400-1200 250-700 200-700 200-700 100-350 100-350 200-1000
200-900 200- 600 200-600
Trpng lugng the tich(kg/m3)
2700 1800 1800 1800 2200 1700 1600 1700 1600 2700 1800 2200 1700
Cae dac trung ca hpc cua vat lieu be t6ng thay doi ro ret khi 6- nhiet dp cao. Cuo-ng dp va m6 duyn biln dang cua
O O TAP CHi KHOA HOC K I E N T R U C - XAY DITNG
0.04 0 06 Srrdin
IHinh 2. Quan he u'ng suat - b i e n dang cua thep can nong d nhiet dp cao
be tong giam khi tang nhiet dp. D l xac djnh quan he giO'a Cpng suit - b i l n dang cua vat lieu be t6ng a nhiet dp cao, nhilu thi nghiem da d^ygc t i l n hanh. Dang quan he Cpng suit - b i l n dang eua be tong duge xac djnh nhu 6' Hinh 1 trong do true tung "a/ Ouu chi ra ti s l cuang dp be t6ng 6- nhiet dp cao tren cu6-ng dp be t6ng a nhiet dp thu6'ng, true hoanh E la b i l n dang ti d l i eua be t6ng.
2.2. Vat lieu cot thep
Khi nung nong thep tinh c h i t eo li cua thep bi thay doi do CO sy pha hoai c l u true vu-ng chae ban d I u . Vo'i thep CI, CU khi nung nong 6- nhiet dp 250°C- 350°C euo'ng dp, dp eCpng va dp don cua thep tang. Khi lo-n han 350°C cuo-ng dp giam eon dp deo tang len. Vo-i thep lan han hoac bang CIII tra len do trong thep eo them c h i t hgp kim nen kha nang chju nong t i t han nhung tinh c h i t thay d l i vi nhiet gilng CI,CII nhung cuo-ng dp giam it han.
Khi nhiet dp tang mo duyn dan hoi cua thep giam xulng kh6ng dang k l . Khi nhiet dp tren 350°C tu- biln trpng thep tang len nhanh cheng ngay ca khi chju tai trpng thuo-ng xuyen tac dung nho.
Nhu vay chi nen dung thep CI, CII vai nhiet dp nho han 400°C, thep lo-n han hoac bang CIII vai nhiet dp nho han 450°C. Khi nhiet dp cao han thep tra nen gia va d l bj 6 xy hoa.
2.3. Li/c dinh giO'a cot thep va be tong chju nong Vo-i thep tron tran: Khi nung nong d i n 150-250°C lye dinh se tang va ngay ca khi lam ngupi do cu6'ng dp be tong chju nong tang. Khi nung nong qua 250°C luc dinh v i n tang nhung khi lam ngupi lye dinh se giam. D i l u do duge giai thich: Khi bj nung nong l l n d I u tien b i l n dang cua be t6ng chju nong co dp gian na vi nhiet dp nho han elt thep (do be t6ng chju nong d i n g th6'i na vi nhiet va eo ng6t vi nhiet). Luc nay thep no- vi nhiet nhieu han se ep vao be t6ng chiu nong lam tang luc ma sat d i n d i n luc dinh tang va gay Cpng s u i t nen cue bp tai vung be t6ng bao quanh c i t thep gay len b i l n dang du. Khi lam ngupi.
e l t thep se tach ro'i khoi be t6ng va lue dinh se giam.
Vo'i thep CO go-: Lye dinh phu thupc vao kha nang cat, nen cue bp cua be t6ng duo'i cac go- c i t thep nhu vay no se phu thupc vao loai be t6ng chiu nong va sy tang nhiet dp. Noi ehung khi tang nhiet dp 150°C lye dinh tang khi qua nhiet dp nay lye dinh giam. Khi dat duge nhiet dp 450°C lye dinh g i n bang a nhiet dp binh thuo'ng.
3. Dac diem tinh toan cho ket cau BTCT chju nong Viee tinh toan k i t e l u be t6ng e l t thep chju nong khae vo-i k i t e l u be t6ng c i t thep a nhiet dp th6ng thu6-ng 6- cac d i l m sau:
- Cu6'ng dp va m6 dun biln dang eua vat lieu suy giam theo nhiet dp tang cao;
- Ngoai cac biln dang tuang Cpng vo'i Cpng suit, phai ke them cac biln dang no- ra va co lai do thay d l i nhiet dp;
- Co t h i phai k l d i n hien tugng bong troe be t6ng khi nhiet dp cao lam thay doi t i l t dien tinh toan.
Do vay, viec phan tich k i t c l u be t6ng c i t thep chju nong phu-e tap, c I n dung cac p h l n m I m tinh toan chuyen sau. Cac tieu chuln thilt k l cung dua ra mpt s l each tinh toan nhung dya tren nhieu gia thilt dan gian hoa, dp chinh xac chua cao va thuo-ng phai lap bang tra.
4. Dac diem cau tao cua ket cau BTCT chju ndng K i t c l u BTCT chju nong eo t h i SCP dung phuang phap thi cong toan khoi hoac l i p ghep. Cac c l u kien duge c l u tao theo quy tac ehung nhu be t6ng e l t thep thuo-ng va tuan theo mpt s l yeu c l u sau:
Khi bj nung npng c l u kien se bi nung nong kh6ng deu.
Mat nong it se x u l t hien U'ng x u l t keo, d l chju duge Cpng s u i t keo nay eIn b l tri thep o- mep ngoai chju nong it.
C i t thep SLP dung CI,CII,CIII duge b l tri bIng luo'i han, khung han, khung bupe hpac cac thanh rieng biet tuy vao loai c l u kien.
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KHOA HOC & CONG NGHE
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Hinh 3. Cac kieu mai be tong cot thep diing cho ham 16 co tiet dien hinh chu' nhat a) Ban co chieu day thay doi lien ket toan khoi vdi lu'dng
b) Mai vom cong c) Ban ke txi do
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Hinh 4. Noi cac manh lu'dng Idn va mai cua ket cau chju ndng 1 / Khe vijra chju ndng 2/ Thep gdc 3/ Thep ban 5/ Vu'a chiu ndng 6/ Ban dem de noi 7/ Ooan ndi chap Clu tao mai trong kit clu BTCT chju nong (hinh 3) 5. Ket luan
CD
8-
4 / Moi han
8 / Be tong chju ndng
Clu tao cac tuo-ng trong kit elu BTCT chju nong lip
ghep (Hinh 4) Cac kiln thu-c v l vat lieu, tinh toan va elu tao kit cau be tong elt thep chju nong chua duge d l cap nhilu trong eae tai lieu thilt k l . Bai bao da tong hgp mpt s l kiln thCpc CO ich cho cac sinh vien, ky su, can bp ky thuat lam v l Clu tao tai vi tri giO'a mai va tuo'ng trong kit elu BTCT nganh xay dyng./.
chiu nong bang phuang phap thi c6ng toan khIi (hinh 6) c l u tao cac lap bao ve (Hinh 5)
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TAP CHi KHOA HOC KIEN TRUC XAY DUNG~i
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^Hinh 5. Tu'dng bang be t o n g cot t h e p a / Lam tang chieu day Idp bao ve c/ Lam idp phu mat bang t a m BTCT
1 / Cot thep 2 / Ldp t r a t each nhiet 4 / Vd thep 5 / Ldp khong k h i
b / Lam Idp each nhiet bang Idp t r a t d / Lam vd bang thep va Idp each nhiet
3 / Lu'di kim loai 6 / Ldp phu mat
(0.6-0.7)h
(0.6-0.7)h
Hinh 6. Ndi tiep
a / Ndi tu'dng vdi mai va giO'a tu'dng vdi nhau b/ Ndi tu'dng vdi vdm
Phan bien: TS. Chu Thj Binh
T a i lieu t h a m khao
;. Kit cdu be tong c6t thep- giao trinh dai cuang V.I- MI- RA- SOP *E.E.XI- GA- LOP; V.N. BAI-COP - Nha xudt bdn giao due 1964.
2. Quy trinh thiet ke kit cau be tong vd bi tong c6t thep chiu nong - Nha xudt bdn xdy dimg quoc gia 1962.
3. TCXDVN 332-2004: Vat lieu chiu lira- ky hieu vd cac dai luang, dan vi
4 Evariste Ouedraogo, Mohsen Roosefid, Nicolas Prompt, Cyrille Deteuf Refractory concretes uniaxial compression behaviour under high temperature testing conditions. Journal of the European Ceramic Society 31 (2011) 2763-2774
SO 1 3 - 2 0 1 3
