cong trinh VietinbankTower
Calculation of the cooling pipe systein In mass concrete construction applied to Vietinbank Tower Nguyin Van DiircTrUorng Ky Khoi
Tom tat Bien phap giam i^g suat nhiet trong thi cong ket cau be tong khoi ldn co y nghia het
sdc quan trong. Mot trong cac bien phap thudng imc ap dung ktii thi cong nhutig ket cau CO khoi tich ldn nhu ttai mong nha sieu
cao tang do la suldung he thong dan ong giai nhiet cho khoi be tong. Bai bao nay gidi thieu ve each tinh toan he thong ong giai nhiet, vi du ap dung cho mot dai mong cong trinh duac thi cong trong dieu Men Viet Nam.
Tif khoa: Cong nghe xay difng, be tong khoi I ffn, he thong dan ong giai nhiet
Abstract The method of reducing the thermal stress in construction of mass concrete is significantly important One of commonly used methods in construction ofmassive foundations of sifyscrapers is tfie use of cooling pipe systems for concrete blocks. Thi5 paper introduces how to calculate the cooling pipe system and give an example for a foundation constructed under Vietnamese
conditions.
Hey words: Construction technology mass concrete, cooling pipe system
TS. Nguyen Vdn Dm:, ThS. Tnrang Ky Khai Khaa Xdy dung
Email: [email protected] IruongkhoL
Ngay nhan bai: 3/12/2018 Ngay sua bai: 20/302019 Ngay duyet dang: 8/01/2020
1. Dat van de
Hien nay, khi quy md cdng trinh ngay cang Idn han, cac cdng trinh xay dung ndi chung va dan dyng ndi rieng thi cdng be ldng khdi idn nhu dai mdng cda nha sieu cao ting rlt p h i biin, dac bidt la lai eae thanh p h i Idn nhu Ha Ndi, TP. Hd Chi Minh,...
Thuc le khao sat, cac kit elu be ldng va be tdng cdt thep kieh thudc ldn thudng bi ndt maeh, tham chi nirt sau, nirt xuyen trong thdi gian dlu be tdng ddng cung Nhilu vet nut dugc phat hien sau khi thao dd clp pha Cac ket elu nay thudng dugc thilt k l vdi be ldng cudng do cao, va duac thi cdng trong dieu kien mua he nang ndng lai Ha Ndi hoae mua kho tai TP. H i Chi Minh Vide kilm soat va hgn ehi cac v l t nut do dng suit nhiet phat sinh trong qua trinh ddng kit cda be ldng la phuc lap, ddi hdi cac ky su tham gia phai co kinh nghiem, dua ra cac giai phap ngay td khau thilt k l , lua ehgn vat lieu va thi cdng.
Vi vgy, vide nghien cuu tinh toan he thing dan Ing giai nhiet cho khoi do be tdng khai Idn la c l n thilt va cd y nghTa thye tiln.
2. Khai niem be tong khoi Idn, dieu kien gay nirt trong dieu kien khi hau Viet Nam
a) Kh^i niem
Theo TCVN 9341:2012, Kit c l u be tdng hoae be tdng cot thep duge eoi la khoi idn khi ed kieh thude du d i gay ra irng suit keo, phat sinh do hi#u dng nhiet thuy hoa cda xi mang. vugt qua gidi hgn keo eda be ldng, lam nut be tdng, va do dd c l n phai ed bien phap d l phdng ngua v l t nui.
Trong diiu kien khi hgu ndng am Viet Nam kit elu cd canh nhd nhlt (a) va ehilu eao (h) Idn han 2m cd t h i duge xem la khdi Idn
Ddi vdi cae kit eau cd dang ngam hoae kit c l u cd hinh khoi phdc tgp thi kieh thudc khoi Idn se do ngudi thilt k l xem xet quylt djnh.
b) Diiu ki$n gay nut be tdng khli Idn trong dilu kien khi hau Viet Nam Theo [5], dllu kien d l gay ndt be tdng khoi Idn la:
AT a 20''C - Dilu kien c l n ; MT > 50°C/m - Diiu kien dd;
Trong do: AT: Dp chenh nhiet dp giua 2 diem trong khdi be tdng, (°C);
MT: Md dun chenh nhiet dp (Gradient nhiet dd), la do chenh nhiet dp giira 2 diem eda khoi be tdng each nhau Im, (°C/m),
3. Tinh toan he thong dan ong giai nhiet trong thi cong be tong khoi Idn cong trinh Viettinbank Tower
3 1. Tieu chuan ap dung
- CIRIA C660: Early- age thermal crack control in concrete;
- ACI 207.2R-07: Effect of Restraint, Volume Change, and Reinforcement on Cracking of Mass Concrete;
- ACI 207.4R-05: Cooling and Insulating Systems for Mass Concrete;
- Computer & Structures (Jin Keun Kim, Kook Han Ki, Joo Kyoung Yang), Thermal analysis of hydration heat in concrete structures with pipe -cooling system;
3.2. Cac bimc tlnh toan, ap dung cho dai mong cong trinh Vietinbank Tower Du an Vietinbank Tower (Ha Ngi) ed hai khli mdng ldn nam dudi tda nha Van phdng va tda nha Khach san Khli mdng nlm dudi Ida nha Van phdng eao 7m
SO 37 - 2020
33
KHOA HOC & CONG NGHE
Hinh 1. Mat cat dai mong nha Van phong va dudi tda nha Khaeh sgn eao 5.5m. Khdi lugng be tdng dai mdng khu nha Van phdng khoang gan 20 000 m^. Do be tdng dai mdng khdi ldn nha Van phdng blng phugng an ehia thanh nhiiu dgt do theo phuang ngang ed sd dyng he thing dng giai nhiet. Dgt 1: 1150mm, Dgt 2: 3350mm, Dgt 3: 2500mm. Dudi day trinh bay tinh loan va kilm soat nhiet dd cho be ldng mdng nha Van phdng cho 2 khli do 3350mm va 2500mm.
3.2.1. Thdng s l dung trong tinh loan kilm tra dan dng giai nhiet cda edng trinh
a. Cac dac trung vat lieu cda be tdng
• Khoi lugng the tieh: yt, = 2500 Kg/m^
• Ham luang xi mang bao gom tro bay va xi Id cao: 560 Kg/m^
• Nhiet dung rieng cda be ldng: 1 KJ/Kg^C
• Hd s l din nhiet cda be tdng: 2,52 W/m^C b. Cac dac Irung khoi do
• Chilu day khoi do: Tinh loan cho 2 irudng hgp la 3350mm va 2500mm.
• Be mgt thoat nhiet: 5 2W/m^K c Dieu kien mdi Irudng
• Tdc dd gid: =4 m/s
• Nhidt dd be tdng d l u vao. Tinh toan eho 3 trudng hap la 28°C - 30°C - 32°C
• Nhiet dg mdi trudng, dua vao du bao thdi tiit d khu vuc Ha Ndi Irong thang 8: Nhiet dd dao ddng td SO^C -35°C, l l y trung binh la 32.5°C
d. He thing Ing giai nhiet
6ng giai nhiet dung Ing s i t ed dudng kinh ngoai Dp,pe
= 33.5mm, chieu day 2mm, khoang each ong Iheo phuang ngang va dung lan luat la: Sh = I m va S^ = Im.
Nude chay qua he Ihdng dng giai nhiet da dugc lam lanh bang Chiller, luu luang bam khoang tu 4-10 gal/min. Trong tinh loan, l l y gia tri trung binh la 8 gal/min = 2.19 m%. Khoi luang t h i tich cua nudc la p^ = 1000 (kg/m^), nhiet dung rieng eua nudc la c^ = 1 (kCal/kg°C). Nhiet dd nudc dlu vao la 8°C.
3.2.2. Xac dmh nhiet do ben trong khli do khi khdng cd he thing i n g giai nhiet
Viec tinh loan du doan nhiet dd tang va ehenh lech nhiet do trong khli do duge dya tren phuang phap dudng doan nhidt eda be tdng, ddng thdi ed xet d i n anh hudng cua cac thanh phln khac nhu phu gia tro bay, xi Id eao, toe dd gid, nhiel dd mdi trudng, nhiet dp ide do. Chi tiit tinh loan the hien trong CIRIA C660-Phu luc A2, [1]
Tinh loan trudng nhiet trong khdi do be tdng dugc thyc hien theo phuang phap sd, chia khli do thanh n phan blng nhau doc theo tilt dien, tren mdi phln, tinh toan nhidt dd phat Inin theo thdi gian dua vao du lieu dudng doan nhidt.
Sau dd, xac dinh nhiet dp Idn nhat tai tam va nhidt dd d hai b l mat khdi do, ehenh lech giua nhiet dd tgi tdm va hai b l mat chinh la ehenh lech nhiet dd Idn nhlt. Ddng thdi, dua vao nhiet dd lgi cac dilm doe theo lilt dien, ve dugc trudng nhiet do dng vdl thdi dilm ed T^ax va trudng nhiet ung vdi thdi diem ed AT^ax
Kit qua Bilu dd nhiet dp T^ax va AT^g^ eiJng nhu Bilu dd trudng nhiel dd dgc theo tilt didn eda khgi d i be long mong ed chilu cao 3.35m dugc t h i hign dudi day.
3 2.3. Tinh loan nhiet dg ben trong khoi do khi co h$
thong dng giai nhiet
a. Xac djnh viing anh hudng cda he thing i n g glai nhiel Dien tich vung anh hudng cda dng giai nhiet dugc xdt ia 1 hinh vudng cd dien tieh S^ x S^, (m^). Quy thanh dudng trdn cd dien tich tuang duung vdi ban kinh R:
TTR ^ -. S,S
(3,1) b Tinh loan anh hudng eda he thong dng giai nhiet din nhiet dd khli d l .
Goi AT (°C) la lugng nhiet dp giam duae trong I h do co hd thong dng gidi nhidt.
Ting luang nhiet cln h i p thu d l giam a n - ^ ii^ono nhidt AT(''C)trong1hla: * ^
Q = AT*C^*r,{kCallm') Trong dd:
Cc: nhiel dung ridng cda be tdng (kCal/kg''-;
V^: khoi lugng I h l tich ciia be tdng (kg/m-' Tinh trong irudng hap nguy hilm nhlt i.
(3.2)
'I dudng
34
TAP CHi KHOA HOC K I E N T R U C - X A Y D I T N G1 ... 1
Hinh 2. Du'dng doan nhiet tang theo thdi gian
Hinh 3. Nhiet do tai t a m , be mat va chenh lech nhiet dp duf doan
100 80 60 40 20 0
y^^ ^S.
r ^
0 1000 2000 3000 4000 0$ diy (mm) Hinh 4. Tru'dng nhiet dp dpc theo tiet dien
• u i chenh l»ch ldn nhat - t ^ nhif [ dp d (Im
ong dai nhlt (tru di 2 doan Ing theo phuang dung vi lai vi tri nay cd din 5 dudng Ing din nhiet):
L = 9 2 - 2 * 6 = 80(m)
Vdi ban kinh anh hudng cua 1 ong giai nhiet Ref, linh dugc t h i tich be ldng nlm trong viing anh hudng'
V^^=L*S\^=L*7r*iRl^-Rl^) ("i^) (^ 3) Nhiet luang eln giam trong suit chiiu dai ong la:
'?..p,i,='C/*e(kCal) (3.4) Theo [4], anh hudng cua ong giai nhiet d i n viec lam lanh
be tdng duge tinh theo cdng thuc sau:
^..ppiy ^ ?™, -<!,., ^ Qu- * ^ . *<=., *(L.,.,., -K.„.) (kCal) (3,5) Trong dd.
Qsjppiy- la lugng nhiet can hap thu tren suot chieu dai ong (kCal);
Q„' luu lugng nudc chay qua Ing giai nhiet trong 1 h (lay trung binh theo thiit kl) (m^/h);
p^: khoi lugng t h i Uch cda nudc (kg /m^);
Cvv' nhiet dung rieng cua nudc (kCal/kg °C);
Twout- la nhiel do cua nudc d dlu ra cda dng giai nhiet (°C); •
T„,n: la nhiel dd eda nudc d d l u vao cda dng giai nhiet (°C); '
T -T = — 2 a S ! — = — i
Q.'p.'c. Q.'p.'c.
Q.'P.''. (3.6) Nhi^ vay, nhiet tJo ni^o-c bum & (5Su vao he th6ng 6ng giai
SO 37 • 2020
35
KHOA HOC & CONG NGHE
giai nhiet
T* -'—'- •—'--'--•:":.
I l-. ---:
: • - + • - : - - • - - - - - ^
§j l - -;.
HHHH
Hinh 5. VCing anh hu'dng he thong ong giai nhiet trong khoi do 335Qmm
6ng gia nhiet </jifvh
Hinh 6. ViJng anh hu'dng he thong ong giai nhiet trong khd'i do 2500mm
'w.lMt
Hinh 7. M6 hinh tinh toan anh hu'dng ciia ong giai nhiet nhiet phai duge tinh loan iru them mdt lugng la {T^^, om - T^v,in) d l dam bao nhiet dd nudc dd Ignh sudt loan bg chiiu dai ong,
Theo Djnh luat Fourier v l din nhiet, thi luang nhiet trao doi giii'a hai be mat tilp xuc trong Ih ed I h l tinh theo cdng ihdc:
Q ^—(T,~T^)A (kCai)
a (3,7)
36
- K*A
"""^ eC) (3.8) Vay d l dam bao Ing giai nhiel lam viee hidu qua, nhiet dp nudc dlu vao eln dgt'
Trong dd,
d = Rat- Dp,pe/2: khoang each t u v| tri xa nhat cda vung anh hudng d i n mat ngoai eiia Ing giai nhiet (m);
K: he so din nhiet cua be tdng (kCal/h.m.''C);
A=7i*Dpipe *l= TT *Dpjpg*}: dien tieh mat ngoai cua ong giai nhiet dugc tinh trong 1 m dai, (m^);
Ti: nhiet dp lgi vj tri bien edg vung anh hudng bdi dng giai nhiet ("C);
T2: nhiet dp nude trong ong giai nhi$l (°C);
Tacd.
la nhiet lugng cln lam mat trong 1 m dai cda Ing Khi do, nhiet dp trong khli do giam duac do he thing dng gidi nhiel la'
j : „ . = 7 ; . - ( j ; - 7 ; ) - ( r „ - r j = 8 ° C (3.9) ,-0.5D,„)
iRl,-R;J'C.'r.-
Trong iJ6:1^ (°C): ia nhiet (36 ion nhlt -.
tri vOng anh hudng tai mpt thoi diem (h) Wk t;
Nhi^ vay, voi nhiet do ni^oc dau vao ia C diem (h), be tong dat mot nhipt dg la T,i, thi ta
(3,10) he tong tai vj
^•au khi do.
-., lai mat then
•'" Owe nh*l TAP CHl KHOA HOC K I E N T H U C - X A Y DUTIG
G
? t
ThM glsn (h)
Hinh 9. Tru'dng nhiet dp khd'i do' khi c6 va khdng cd he thdng dng giai n h i ^ t
Thcri gian (h)
Hinh 10. Sti chenh lech nhiet do khi cd va khong cd he thdng giai nhiet
dg giam dugc do anh hudng cda he thing Ing giai nhiet (trong Ih) Iheo cdng thue tren.
Vide tinh loan dugc ihuc hien ung vdi tung vdng anh hudng (tai mat tren, mat dudi va trung tam khoi do) 6e xac dinh lugng nhiet giam di do he thong ong giai nhiet.
3,2,4. K l l qua tinh loan
- Tinh tgan vdi 2 khdi do ed chieu cao lan lugt la 3350mm va 2500mm.
- Tinh loan vdi 3 Irudng hgp nhiet dp be ldng d l u vao lan lugt la 28°, 30°, 32°C
a. K i t qua iinh loan nhiet do vdi trudng hgp khdng ed he thong ing giai nhiet
Nhiet do cue dai trong be tdng: Tniax= 93°C sau 50 gid Dp ehenh lech nhiet do cue dgi: AT^ax^ 33°C sau 70 gid b. Kit qua tinh toan nhiet dp vdi trudng hgp cd hg thong dng giai nhiet.
Nhiet dp eye dai trong be tdng: T^^= 71°C sau 39 gid Dp ehenh lech nhiet dp cue dgi: AT^ax^ 15°C sau 67 gid - O bang kit qua dudi trinh bay nhiet dp T^^ va ATmaxOho ca trudng hgp khi khdng cd Ing giai nhiet ( d i tham khao) va khi cd dng giai nhiet.
Bang 3 . 1 . Ket qua T^ax va iTma^ u'ng vdi khdi do co chfeu cao 3350 mm
Nhiel do be tdng d l u vao (°C)
28 30 32
Chu'a CO 6ng giai nhiet (°C)
95 96 98
AT^ax (°C)
38 39 40
Co 6ng giai nhiet (°C)
73 74 75
CO
19 19 23
Kgt luan
Bat Dat Khong dat
(xem tiep trang 44)
