HIEU QUA SCr DUNG BE TONG CUONG DO CAO TRONG THIET KE KET CAU NHA NHIEU TANG
PGS.TS Phan Quang Minh
Khoa XSy dt/ng Dan dung vS Cdng nghipp Trudng Dai hgc XSy dt/ng
Tdm tit: BSi bSo dSnh giS hidu qua sd dung cda bd tdng cudng dp eao trong kit ciu nhS nhiiu ting. NgoSi vide ISm giam dSng ki dipn tich cot thdp ehju It/e trong ciu kipn chju nen vS khdi lugng be ting, giam chi phi cop pha mS khdng ISm anh hudng din dp cimg cdng trinh, tinh hipu qua cdn tSng ten khi ISm tSng dipn tieh sCt dung cda cing trinh.
Summary: This paper discusses the economy of using HSC In taH buildings. In addition to reduce column sizes and producing a more durable material, the use of HSC has been shown to be advantageous with regard to lateral stiffness. Another advantage cited in the use of HSC columns is reduction in cost of forms and increase of rentable floor area.
I . D A T V A N O E
Be long cUdng dp eao dupc dng dung khd rpng rai trong k i t cdu nhd nhieu tang d cdc nudc tren I h l gidi, nhdt Id dd'i vdi cdc c l u kidn chju nen nhU cpt, vdch... 6 Viet Nam, be tdng cudng dp eao tuy budc dau dupc nghidn cdu, nhifng vide iJng dung trong thue te cdn rat han ehd. Ben eanh khd khdn trong thi cdng vd han ehe cda lidu chuin thie't k l TCXDVN 356-2005, vipe ddnh gid tinh hieu qua cua vipc sd dung cda be tdng cudng dp cao trong dieu kien thilt kd vd thi cPng cda Vidt Nam v i n chua dupc Idm ro.
2. SLf DUNG BE TONG C U 6 N G DO CAO TRONG KET CA'u NHA NHIEU TANG
Ode dilm cua hp k i t ed'u nhd nhieu tang Id ehju tai trpng ddng vd tai trpng ngang rat Idn.
He kit cdu cpt - vdch, d l chju dupe tai trpng ddng Idn thudng ddi hdi kieh thudc tilt dipn cpt Idn, dieu ndy anh hudng d i n yeu eau ve kiln true vd khdng gian sd dung. K i t cdu be tdng e l t thep dupe sd dung rpng rai trong cdc cdng trinh cd chieu eao vda phai vi chi phi thdp, dp b i n eao vd de bao dudng. Tuy nhien vdi cap cdng trinh sieu cao tang hay vdi edng trinh nhjp Idn thi dng dung vdt lieu bd long eo cudng dp ehju nen truyen thdng la khdng kha thi.
Vdi su phdt triln cda edng nghe vdl lipu be long, tao nen be tdng eudng dp eao (be tdng COC) vd sidu eao, ngudi la da nhdn thdy ring n l u mpt cdng trinh dupe xdy dung vdi hp cpt bing bP tPng cdt thep sd dung bd tdng COC hode cpt composite se mang lai hieu qua kinh t l Idn hon edng trinh vdi he edt hodn lodn bing thep. Thdm vdo dd su phat triln trong cdng tdc vdn khudn, edng nghp bom be IPng da gop phan Idm cho edng lac bP tdng dupe de ddng hPn trong thi cdng nhd nhieu tang. Vdi cdc ddc tinh dUpc cai tien cda be tdng COC so vdi bd tdng
14 TAP CHf KHOA HOC C O N G N G H $ XAY DUNG sd05- 6/2009
thudng, vide sd dung be tdng COC dan d i n ket c l u cd t h i chju life nen Idn hon rat nhilu, Idm giam dupe kich thudc tiet dipn cdu kipn.Cudng dp chiu nen cda be IPng COC hien nay theo quy djnh eua ACI td 42MPa den 138MPa. 0 Viet Nam vd Chdu Au, cUdng dp chju nen thudng vdo khoang 50MPa d i n 90MPa.
Be tPng COC ngdy cdng dupc dng dung rpng rdi khong chi vi nhdng ddc tinh vupt trdi cda vdt lidu md cdn vi uu diem sd mpt eda nd Id gid thdnh hpp ly. Ly do cda vide giam ehi phi ndy Id mde du ban thdn bd fdng COC cd gid thdnh cao hon be fdng thudng nhifng vide khae nhau v l gia ndy dupe bd d i p dang k l bdi vipc giim tilt didn c l u kien. Chinh kha ndng nay da khiln cho bP tPng COC dupe sd dung nhieu trong cpt. Ham lupng cd't thep sd dyng trong cpt cung giim mpt each dang k l .
NhOmg Uu diem khi sd dung bd tdng COC trong Ihiet ke ke't cau nha nhieu tang dupe t h i hipn trPn hinh 1 [2].
Lpi ich kinh t l dau tiPn do vide giam kieh thude tilt dien cdc c l u kien thing ddng (cpt, vdch) Id didn tich sd dung dupc ndng IPn. Trpng lupng ePng trinh eung dugc giam ddng k l neu ede cdu kidn dam, sdn eung sd dung bP tPng COC. Ngodi Ipi ich kinh te do sd dung it vdt lieu vd giam tai trpng xuIng mdng cdn cd Ipi ieh quan trpng v l k i t elu do trpng lupng cong trinh giam.
Oieu ndy liPn quan d i n phan tieh cdc fai trpng dpng nhu gio, dpng ddt vi mpt ke't eau edng nhe thi edng it nhay cam ve dao dpng.
Mdt khdc, sd dung bd tdng COC Idm tdng dp cdng cda k i t ed'u do md dun ddn hdi cda bd tdng COC Idn hon. Khi dd, k h i ndng chju t l i trpng dpng theo phuong ngang eda kdt c l u cQng tdng Idn. Nhdng y l u td ndy Idm tdng dp an todn vd b i n vdng cda edng trinh. Mpt Ipi ich kinh t l khde khi sd dung bd tdng COC frong nhd nhilu ting Id giim dupc hdm lupng cd't thep sd dung.
SO" DUNG BE T 6 N G COC TRONG NHA NHI^U T A N G
Tdng dp cd'ng
cua hp kdt c l u Giim kich thudc c l u kipn
Giim trpng lupng cdng trinh
Tdng k h i ndng chju tai trpng dPng cua k i t c l u
Giam hdm lucng edt IhPp
Tdng dipn tieh su" dung
Giam tai trpng xudng mdng
Tdng dp an todn
vd k h i ndng sd' dyng cua k i t c l u HIEU QUA KINH it
Hinh 1. Hipu qui sd dt/ng bd tdng CDC tmng kit ciu nhS nhiiu ting
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3. KHAO SAT VE HIEU QUA s U DUNG COT BE TONG CDC TRONG KET CAU NHA NHIEU TANG
3.1 So' lieu khao sat
Cdng trinh M5 TOWER tai sd 5 dudng Nguyen Chi Thanh, Hd Npi gdm 35 tang vd 2 tang ham (hinh 2; 3).Chieu cao tang ham Id 3,6m; tang 1 cao 5,4m; tdtang 2 de'n tang 7 eao 4,0m;
tang diln hinh eao 3,3m; chilu cao loan bp cong trinh tinh td mpt san tang ham 2 d i n mdi la 132,6m.
Cong trinh dugc thie't k l thue t l vdi cdc thdng sd sau:
- Vat lieu: be long B25 (R,, = 14,5 MPa ; E^ = 30000 Mpa). Cd't thep nhdm All cd R3 = 280 MPa cho cdc dUdng kinh td 10 s 0 < 018, nhdm AIM (R; = 365 Mpa) eho cdc dUdng kinh Id 018 trd len.
- Kieh thudc t i l l dipn cpt; eae cpt gida td tang ham de'n tang 7 la 1400x1400 mm. Id tang 7 de'n tang mdi la 1300x1300mm. Cdc cpt bien tdtang ham d i n tang 7 Id 1400x1400 mm. Id lang 7 d i n tang 29 Id 1300x1300, I d l i n g 29 d i n tang mdi Id 900x1300mm.
- Chieu ddy Idi, vach: 600mm, 400mm, 250mm.
- He sdn dam vdi ban sdn ddy 150
O l ddnh gid hieu qua sd dung be IPng COC, da lien hanh khio sat theo ede phuong dn sau:
+ Phuong dn 1: Theo cdc sd lipu thuc td cua edng trinh.
+ Phuong an 2; Thay doi vdt lipu be long sd dung. Cpt, Idi vd vach dung be long cdp dp ben BOO (R^ 33MPa, E^ - 30000 Mpa). Be tPng dam, sdn dupe gid nguyen theo thiet k l . Kich thude lilt dien edt gid nguyen.
+ Phuong dn 3: Thay doi vdt lieu bd tdng sd dung. Cpt, loi vd vach dung bd tPng cd'p dp b i n BOO. Bd tdng dam, sdn dupc gid nguydn theo thilt k l . Thu nhd kich Ihudc tidt dipn cpt thdnh 900x900 mm Id mdng d i n tang mdi edng trinh.
+ Phuong an 4: Be tdng cpt dung be tdng cdp dp b i n BOO. Be tPng Idi vach, dam, sdn dupe giu nguydn theo thilt k l . Thu nhd kich thudc l i l t dien cpt thdnh 900x900 mm td mdng d i n tang mdi edng
trinh. Hinh 2. Phii canh cdng trinh
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TAP CHf KHOA HOC C O N G N G H $ XAY DUNG Sd05- 6/2009Hinh 3. MSt bing kit eiu ting diin binh
3.2 Ket q u i tinh todn
Mdt s l k i t qua tinh toan dupe trinh bdy frong bang 1.
Nhan xdt:
- Chuyin vi tai dinh cda edng trinh phupng dn 3 vd 4 ed tdng len so vdi phuong an 1 (phupng dn thid't k l ) nhung van dam bao nhd hon ehuyin vj gidi han.
- Phuong dn 2 giim dupc 43% didn tich cdt thep edt (ddt theo yeu cau c l u tao) so vdi phuong I n 1.
- Phuong dn 3 giam dupc 67,3 % dien tich edt thep cpt so vdi phUOng an 1.
- Phuong dn 4 giam dupc 52,9 % didn tich cdt thep cpt so vdi phuong an Iva khoi lupng bd tdng cPt giam 52,2%.
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Nhu vay khi sd dung be tong CDC trong ket qua nhieu tang, cd the lam giam dang k l dien lieh edt thep chju life trong ca'u kien chiu nen va khdi lupng be long, giam chi phi cdp pha ma khPng lam anh hudng de'n dp cdng cong trinh (khi chpn kich thude tiet dien hpp ly). Tinh hieu qua cdn dupc tdng len khi giam kich thudc tiet dien cpt con lam tdng dien tich sd dung eda cdng trinh.
Bang 1. Kit qua tinh toan theo cae phuang an thiit ki
Phuong an 1 Phuong an 2 Phuong an 3
Kieh thude tiit didn cpt
1400x1400 mm 1400x1400 mm 900x900 mm
Chu ki dao dpng lu = 3,01 s ;
T „ = 2,767 s
T,. = 2,80 s ; T „ = 2,588 s
Tu = 2,99 s ; T „ = 2,70 s Chuyin vj tai dinh cdng trinh UX = 7,12cm UX = 6,22 cm UX = 7,70 em
Npi It/c cpt true B-3 - Tai chdn cpt:
N = 3279,34 T;
M, = 7,98 Tm;
M, = 56,25 Tm.
Tai ehan cpt:
N = 3365,57 T;
M. = 8,06 Tm;
M, = 57,71 Tm.
Tai chan cpt;
N = 2393,54 T;
M, = 5,19Tm;
M, = 5,73 Tm.
Didn tieh edt thep cpt
Theo tinh loan A, = 34it>36 (346,09 em')
- Theo tinh todn:
A,= 16(ti25 (78,54 cm') - Theo ca'u tao 1%,
\ = 196 em'
Theo tinh loan A^= 16it)30 (113,104 em')
Phuong an 4
900x900 mm
T „ = 3,138 s ; T,, = 2,837 s
UX = 8,29 cm
Tai chan cpt;
N = 2518,22 T;
M, = 5,51 Tm;
M, = 10,13 Tm.
Theo tinh loan A,= 16(|)36 (162,86 cm')
4. KET LUAN
Sd dung be long eudng dp eao trong k i t ca'u nhd nhieu tang la mpt xu hudng lien lien trong cdng nghe xay dung. Trong dieu kien Viet Nam, viee nghien edu can dugc lien hdnh theo hudng ddng bp ve ea cdng nghp che lao, Ihi cpng va quy trinh linh loan phu hpp vdi vat lidu sd dung de cd the dpi de'n tinh hieu qua kinh te vd hipu qua sd dung eda ePng trinh.
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TAP CHI KHOA HOC C O N G N G H ^ X A Y DUNG SO 05-6/2009Tai lieu tham khao
1. Priyan Mendis Design of High-strength Concrete Members, The University of Melbourne, 2007.
2. Shah, S. and Ahmad, S. - High pertonmanee concrete applications, Edward Arnold, London, 1994.
3. Phan Quang Minh, Ngo The Phong, Nguyen Oinh Cong - Kef cau be tdng cdt thep - Phan eau kidn ea ban. Nxb Khoa hpc va Ky thuat, 2006.
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