DdW Qia CadTNG D Q CHIU NEN H I £ N TRaCTNG Cdfl BE TONG THEO TIEU CHU^N EN 13791 : 2007
TS. HOANG MINH DCrC
Vien Khoa hoc Cdng nghe Xay dung
Tdm tat: Cudng do ehiu nen hien trudng eiia be tong dugc sir dting de danh gia su phii hgp ciia cae ket eau xay mdi, danh gia kha nang ehiu luc eiia eac ket cau hien cd,... Cudng do chiu nen hien trudng d Viet Nam cd the duge xac dmh theo TCXDVN 239:2006, edn a eie nude thudc edng ddng chau Au theo EN 13791:2007. Tuy nhien, cd mdt sd khac biet nhat dmh trong ky thuat sir dung de danh gia cudng do hien trudng trong hai tieu ehuan tren. Bai viet hudng dan cij the viec sir dung tieu ehuan EN 13791:2007 trong suso sanh vdi TCXDVN 239:2006.
1. Mddau
Cugng dp chju nen la mdt die tinh quan trpng cua be tPng dugc sd dung trong tinh toin thidt kd v i nghiem thu kdt cau be tdng v i be tdng cdt thep.
Cudng dd bd tdng khdng nhdng phu thudc vio chat lugng va ci'p phdi vit lieu sd dung ma cdn phu thudc vio qua trinh thi cdng be tdng v i cic ydu td khac. Do do, su chenh lech gida cudng dd miu diic tidu chua'n va cudng dp be tdng tren kdt cau l i khdng trinh khdi.
Trong nhieu trudng hgp, viee dinh gii cudng dp chju nen thuc td cua be tdng tren kdt ci'u va cau kien be tPng diic sin la ri't can thidt dd chdng nhin hoac giai quydt cic bai toin lien quan den ke't ci'u cdng trinh.
Tai chiu Au, viee dinh gia cudng dp chju nen hien trudng dugc thuc hien theo tieu chui'n EN 13791:2007
"Assessment of in-situ compressive strength in structures and precast concrete components". Tieu chua'n niy nam trong h6 thd'ng tieu ehuan chiu Au, dugc bien soan khi md, phii hgp v i duge sd dung ring rii tai nhidu qud'c gia khic nhau.
Nhim xiy dung he thd'ng tieu chui'n ddng bd, hien dai, hai hPa va tiam can vdi tieu chua'n qud'c td, Bd Xay dung da tidn hanh chuyen djch bd tieu chui'n chiu Au, trong dd cd tieu chui'n EN 13791:2007 sang tieu chua'n Viet Nam. Tiiu chui'n nay cd mdt sd khac biet nha't dinh so vdi tiiu chua'n Viet Nam hien hinh TCXDVN 239:2006 "B6 tdng ning. Chi dan dinh gia cudng dP be tdng trSn kdt cau cdng trinh".
Bii vidt niy de cap ddn mdt sd diem dac biet cua tieu "
chua'n EN 13791 va so sanh vdi tieu chua'n Viet Nam.
2. Gidi thieu chung ve tieu chua'n EN 13791:2007 Tieu chui'n EN 13791:2007 do Ban ky thuat CEN/TC 104 "Concrete and related products" bien soan. Tieu chuan nay trinh bay cac ky thuat va phuang phip danh gia cudng dp chju nen hien trudng cua kdt ci'u va ci'u kien be tdng diic sin. Thf nghiem cudng dp hien trudng cd tfnh ddn anh hudng cua ca vat lieu v i qui trinh thi cdng (dam, bao dudng,...). Tieu chua'n nay dugc vien dan trong EN 206-1 dd danh gia cugng dp be tdng cua kdt cau va cau kien be tong diic sin.
Tieu chui'n EN 13791:2007 dugc ap dung trong cic trugng hgp nhu:
- Oinh gii su phii hgp cCia cudng dp chju nen hien trudng theo yeu cau ky thuat cua du an hoac tieu chui'n ddi vdi san phi'm;
- Sda chUa hoac thidt kd lai cic kdt cau hien cd hoac can dinh gii cudng dp hien trudng trong qua trinh thi cong;
- Oinh gia su phii hgp ciia kdt cau trong trudng hgp mau tieu chui'n khong dat cuang dp chju nen yeu cau hoac danh gii su thich hgp khi nghi ngd v i cudng dp chiu nen ciia ke't ca'u do ldi thi cdng, hu hai do hoa hoan hoac cic nguyen nhan khac.
Hudng din sd dung cho cac trudng hgp tran dugc trinh bay tai hinh 1.
Phuang phap thi nghiem sd dung bao gdm phuong phap khoan li'y ldi va cic phuang phap giin tidp. Mdi phuang phip cd thd dugc thuc hien theo cac phuang an khic nhau. Can chii y rang, kdt qua danh gia theo cic phuang i n khac nhau cd su chenh lech dang kd.
Do dd, viec cin nhac lua chpn phuang an la can thidt v i nen dugc xem xet tren nhieu khia canh v i cho tUng trudng hgp cu the.
Mpt diem khac biet nda so vdi TCXDVN 239:2006 la EN 13791:2007 quy djnh cudng dp chiu nen die trung hien trudng nho nha't ung vdi cac cap cudng dd
Tap chi KHCN Xciy dung - sd 4/2010 55
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chju nen khie nhau thdng qua he sd 0,85. C i c gia trj G i i trj n i y dugc sd dung trong danh g i i c i e kdt qua cudng do dugc lay trdn tdi don vj (tinh theo N/mm^). thi nghidm.
Sii dung tieu chuan EN 13791:2007
Danh gia su phu hpp ciia cudng dp hien trudng, vf du ddi vdi cau kien be tong
SCr dung phuang phap gian tiep theo:
- phuong an 1 (muc 8.1.2)
- phuong an 2 (muc 8.1.3)
Danh gia su phu hop theo muc 8.3.5
Danh gia cac ket ca'u be tong hien CO
Sii dung Idi khoan
Phuang an B:
3 de'n 14 Idi khoan (muc 7.3.3)
Phuang an A:
15 Idi khoan trd len (muc 7.3.2)
Sddung phudng/phap
gian tiep
Sd dung phuang phap gian tiep theo:
- phuong an 1 (muc 8.1.2)
- phuang an 2 (mue 8.1.3)
Tiep tuc khao sat va danh gia theo muc 8.3.5
Danh gia khi nghi ngd ve chat lupng be tdng
Xac djnh ket cau co cudng dp phu hpp hay khdng
theo dieu 9
dat
Chap thuan be tdng ke't cau
khdng dat
Tfnh toan ke't cau de danh gia hoac phan dinh trach nhiem (khdng de cap trong tieu chuan nay)
Hinh ^.Sad6 hudng dan sir dung tieu chuan EN 13791:2007
Viec danh g i i cudng dp chju nen hien trudng dugc hudng dan thuc hien cho ba trudng hgp gdm: d i n h gia tren co sd Idi khoan, danh gia theo eac phuang phap g i i n tidp v i d i n h g i i khi nghi ngd su phii hgp cua be tdng theo thi nghiem tieu chui'n.
3. Danh gia ci/dng do chju nen hien trirdng tren cd sd loi khoan
O i n h gia cudng dp chju nen hien trudng tren co sd ldi khoan dugc thue hien theo hai phuang an: phuong i n A khi ed it nha't 15 Idi khoan hoac phuang i n B khi cd td 3 ddn 14 Idi khoan. Can chii y l i theo EN 13791:2007 sd lugng Idi khoan khdng dugc nhd hon 3.
C i c ldi khoan phai duge khoan, kidm tra v i chua'n bj tuan thu theo EN 12504-1 v i nen dugc dat trong phdng thi nghiem it nha't 3 n g i y trudc khi tidn h i n h thi nghiem.
Khi thuc hien theo phuong i n A, cudng dd chju nen d i e trung hien trudng cua vung thi nghiem l i gia trj nho hon:
fck.is = JmM.is -kjxs h o a c /^^ .J = fi,io„^„ + 4 Trong dd:
/ ^ i , , - cudng dd chju nen d i e trung hien trudng;
fm{n).is - gia trj trung binh cCia n ke't qua thi nghiim cudng dp chju nen hien trudng;
fis.lo^.esl - kdt qua thi nghiem cudng dd chju n i n hien trudng nho nhi't;
5 - gia trj Idn hon ciia dd lech ehuan cua kdt qua thi nghiem hoac 2,0 N/mm^;
/c^ - he sd, li'y theo quy djnh qudc gia hoac lay bang 1,48.
56 Tgp chi KHCN Xdy diptg - sd4/20lol
Khi thuc hien theo phuong i n B, cudng dd chju nen die trung hidn trudng cua viing thi nghiem l i g i i trj nhd hon:
/f*,-5 ~ fmlr,).is ~ ^ ^^^^ fck.is - fis.lowesi + ^
Trong dd:
k - bien dd phu thudc v i o sd lugng cac kdt qua thi nghiem.
Cugng dp chju nin die trung hien trudng xac djnh theo EN 13791:2007 phu thudc rat nhieu vio sd lugng Idi khoan. Bang 1 trinh bay tuong quan gida gia trj trung binh ciia cac ket qua thi nghiem cudng dp chju nen hiin trudng v i cudng dp chju nen die trung hien trudng (khi gia djnh cudng dp hien trudng dugc tinh theo gii trj trung binh cua cugng dp hien trudng).
Bang 1. Tuang quan giUa cuang do trung binh hien trudng va cuang do dac trung hien truang trong cic truang hgp khac nhau
Gia trj trung binh cudng dp chju nen
hien trudng, N/mm^
10 15 20 25 30
Cudng dp dae trung hien trudng, N/mm^
Dd leeh ehuan s (phUdng an A, k2=1,48)
han 15 Idi khoan 2,0
7,04 12,04 17,04 22,04 27,04
2,5 6,3 11,3 16,3 21,3 26,3
3,0 5,56 10,56 15,56 20,56 25,56
Bidn dp k, khi sd dung (phuong an B) 10-14 Idi khoan
5 5 10 15 20 25
7-9 Idi khoan 6 4 9 14 19 24
3-6 Idi khoan 7 3 8 13 18 23 Sd lieu tai bang 1 cho tha'y, vdi cung gii trj trung
binh cua cudng dd chju nen hiin trudng, khi cd cing it loi khoan cudng dd die trung hidn trudng cua viing thi nghiem cang nho. Hoac ndi cich khic, d l cd ciing gii trj cudng dd die trung hien trudng, khi cd cing nhieu miu khoan thi gii trj trung binh cudng dp cic miu khoan can dat dugc cang thap. Do dd, ndu cd didu kien thi khi dinh gii theo EN 13791 ndn sd dung cing nhidu Idi khoan cing tdt. Vi'n dd niy chua dugc dd cap tdi trong tieu chua'n Viet Nam. Tiiu chui'n TCXDVN 239:2006 khuydn cio sd dung td miu gdm 3 miu v i cho phep sd dung td mau gdm 2 miu.
4. Danh gia cU'dng do chju nen hien tri/dng theo phi/ong phap gian tiep
Cic phuang phap gian tidp sd dung trong danh gia cudng dp chju nen hien trudng bao gdm phuang phip xac djnh trj sd bit nay, luc keo nhd hoac van tdc xung sieu am.
Oanh gii cudng dp chju nen hien trudng theo phuong phip gian tiep cd thd tidn hanh bang cich xiy dung dudng tuong quan true tidp vdi Idi khoan (phuong i n 1) hoac hieu ehinh dudng tuong quan sin CO theo ldi khoan trong khoang gidi han cudng dp (phuang i n 2).
Trong hai phuang i n trin thi phuang i n 2 dugc hudng din khi cu t h i va cd the thuc hien dd dang.
Danh gii theo phuong i n 1 ddi hdi ngudi sd dung cd hieu bidt nha't djnh vd cic cdng cu toan hgc.
Viec xiy dung dudng tuong quan gida kdt qua thi nghiem theo phuong phip giin tidp v i cudng dd chju nen hien trudng (phuang i n 1) dugc hudng din thuc hien gdm cic budc sau:
- Xic djnh dudng thing hoac dudng cong phii hgp nha't bang cich phan tich hdi quy cac cap gia trj thu dugc trong thi nghiem. Kdt qua thi nghiem gian tidp dugc coi la bidn sd va cudng dp chju nen hien trudng la ham sd cua bidn sd dd;
- Tinh toan sai sd chua'n cua viSc xac djnh, gidi han tin cay cua dudng thing hoac dudng cong phii hgp nha't v i gidi han dung sai ciia cic kdt qua rieng l i ;
- Dudng tuong quan la phan vj mdc mudi phan tram cua cudng dp.
cac chi din cu thd hon dd thuc hien cic budc tren khdng dugc dd cap de'n trong tieu chua'n EN 13791:2007. Oidu niy gay liing tiing dang kd khi ap dung phuong i n niy trong thuc td. Tiau chua'n khdng quy djnh cu thi dang ciia dudng tuong quan la duong thing hay dudng cong, phuong phap phan tfch hdi quy, phuong phap danh gia sai sd cung nhu phuong phip xac dinh phan vj mdc mudi phan tram.
Md hinh dudng thing hoac dudng cong phii hgp cd the dugc xac djnh theo kinh nghiem thuc td. Tuy nhiin, cd the thi'y rang, trong mpt khoang nho vdi sai sd cho phep cac duong cong cd the dugc coi nhu dudng thing.
Hien nay cd mdt sd phuang phap phin tich hdi quy de xac djnh dudng thing hoac dudng cong phu hop
Tap chi KHCN Xdy diOig - sd 4/2010 57
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nha't. Trong sd dd phin tich theo binh phuong nho nhi't l i phd bidn hon ca. Theo dd, dudng phu hgp nhi't l i dudng cd tdng binh phuong cac sai lech gida g i i trj thue td v i g i i trj tinh toin l i nho nhi't. Tuy nhien, phuang phap niy cOng ed nhdng han chd nhi't djnh vi dugc xiy dung dua tren gia djnh rang sai sd theo gii trj X bang 0 va sai sd (dd lich chua'n) theo gia trj y l i cd djnh.
Khi xay dung dudng tuong quan gida cic thi nghiem gian tidp vdi cudng dp chju nen hien trudng, rd ring rang sai sd trong xic djnh cic tinh chat theo thi nghiem giin tidp l i kha ldn v i nhidu khi vugt qui ea sai sd trong xic dinh cudng dp chju nin. Ben canh dd, khi coi cudng dp chju nen cd he sd dao ddng chat lugng cd djnh (nhu da sd eie tai lieu ky thuat hien nay dang xit) thi gii trj dd lech chuan se ting khi cudng dp be tdng ting. Chinh vi vay, khi ddi hdi dp chit che cao thi phuang phip binh phuang nhd nhi't thdng thudng se khdng hoin toin phii hgp.
O l khac phuc, theo Ku H.H. [1] ndu nhu mdt tap hgp cd cung he sd dao ddng thi khi lay logarit co sd tu nhiin ciia chiing, dd lech ehuan cua cic gia trj logarit se ed gii trj cd djnh. Do dd, nen tidn hinh phan tich hdi quy vdi cac gia trj logarit cua cudng dp hien trudng va kdt qua thi nghiem giin tidp.
Dd khac phuc vi'n de sai sd ciia thi nghiem gian tidp, cd thd sd dung phuang phap Mandel J. [2] dugc phit tridn bdi Stone W.C. v i Reeve CP. Theo dd, trong tinh toin sd dung thdng sd X dugc tinh bang phuang sai ciia gii trj y chia eho phuang sai cua gii trj X. Ndu nhu cic thi nghiem cudng dd hien trudng v i thi nghiem giin tidp dugc thuc hien sao eho g i i trj trung binh ciia chiing ed do chinh xic gan nhu nhau thi gia trj X gan bang 1. Gii trj X duge sd dung trong tinh toan dudng tuong quan v i danh gia dp lech chua'n theo gia trjy[3].
Sau khi xic djnh dudng eong hoae dudng thing phij hgp nha't vdi cic cap kit qua thi nghiim, xac djnh dudng tuong quan bang phin vj mdc mudi phan tram ciia cudng do. Trong dd, phin vi mdc mudi phan tram CLia cudng dp duge hidu l i gia trj cugng dp m i 10%
nhdm cac g i i trj cudng dd dang x i t ed gia trj nho hon no.
Viec xic djnh dudng tuong quan theo phin vj mdc mudi phan tram cd the dugc thuc hien theo nhidu phuang phap khie nhau vdi eac gia djnh v i dd chat che khic nhau. Cung nhu dd'i vdi viec xic djnh dudng cong phii hgp nhi't, viie xac djnh dudng tuong quan eung cd thd thue hien dua trin gia djnh sai sd theo gia tri X bang 0 v i theo g i i trj y l i cd djnh. Khi dd, viec tinh toin cd the thue hien theo phuong phip ydu td sai sd Chung trinh bay trong [4]. Dudng tuong quan cung co the duge xiy dung theo de xui't eua De Gryze S. [5]
hoac Vardeman S.B. [6].
Vdi cic ddi hdi chat ehe hon, viec tinh toan cd thi dugc thue hien theo phuang phap ciia Stone W.C. v i Reeve CP. [3] cd kd den sai sd khi xac djnh dudng cong phii hgp nha't trong viee xiy dung dudng tuong quan cung nhu xac djnh dudng tuong quan vdi cac khoang tin cay khic nhau hay vdi cic mdc phin vj khac nhau. Tuy nhien phuang phap niy kha phdc tap.
De khac phuc didu niy, Carino N.J. [7] d i xuat phuong phip mdi, trong dd vin gid dugc tinh chat che cua phuong phip Stone W.C. v i Reeve CP. nhung cd the sd dung dd dang hon .
De hieu rd hon ve viec dinh g i i theo cac phuong an khic nhau cd the xet mdt vi du eu thd. Bang 2 trinh biy kdt qua thi nghiem cudng dp chju nin hien trudng v i chi sd bat nay eua ke't ca'u can danh gii.
Bang 2. Chi sd bit nay vi cudng do chiu nen cua ioi khoan tai cic vi tri TT
1 2 3 4 5 6 7 8 9 10 11
n (vach) Xi 22,0 21,5 25,5 25,0 24,0 24,0 26,5 25,0 25,0 26,0 29,5
R, MPa Yi 23,4 22,7 26,7 26,5 26,0 25,7 31,0 30,7 32,5 29,6 34,4
TT 12 13 14 15 16 17 18 19 20 21 22
n (vach) Xi 31,0 30,0 30,0 29,5 29,5 29,5 29,5 34,0 35,0 34,5 34,5
R, MPa Yi 34,9 34,2 36,9 33,6 34,0 35,1 36,1 39,2 39,9 40,8 40,2
58 Tgp chi KHCN Xdy dimg - sd4/2010
Viae xiy dung dudng tuong quan dugc thuc hian theo phuong phip eiia Vardeman S.B. [6] theo cdng thdc sau:
0"'(/7) + ^ x ( D - ' ( l - c c ) x 1 +
Y,,{X) = y{X)-dx- n-2 x(
i^-'ip))'
- ( c D - ' ( l - a ) ) ^ ) 1 - ( ^ " ( 1 - ^ ) ) ^2 X (« - 2) Trong dd:
y{X) =^ PQ+ P^y-X - dudng thang phii hgp nha't vdi sd lieu thi nghiem cd he sop^ va P xic djnh theo phuong phip binh phuong nho nhat thdng thudng;
Y^iyi-hY
^ 2
u —
' • \
' • = 1
n - 2
n S^
sai sd khi xay dung dudng phii hgp nha't hay phuang sai cua y;
theo dd <j X ^ la dd lach chui'n udc tinh ciia y\ ;
O"' (p) va O"' (1 - a ) - nghjch dao cua phan phdi chuan tich luy theo dp phu p va dp tin cay (1-a);
n - sd lugng cap kdt qua thi nghiem sd dung xay dung dudng tuong quan.
Kdt qua tinh toan dudng phu hgp nhi't, dudng tuong quan (phin vj mdc mudi phan trim ciia cudng dp) dugc trinh biy tai hinh 2.
Tai hinh 2 cung trinh biy dudng co sd v i dudng co sd sau khi d i chuyen djch thuc hien theo phuong i n 2.
• Ket qua thi nghiem
• — - ' Du'dng phu hgp nhat
—-—Dud'ng tu-cyng quan
— 'Du'dng CO sd
Du'dng co sd da djch chuyen
20 25 30
Chi s6 bat nay
35
Hinh 2. Xay dung cic quan he giira chi so bat nay vi cuang do hien truang
Dua tren dd thj hinh 2 cd t h i xic djnh cudng do chju nen hien trugng eua vung thi nghiam bat ky. Viec xac djnh cudng dd chju nen cua viing thi nghiem theo cae phuang an khac nhau dugc trinh biy tai bang 3.
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Bang 3. Xic dinh cudng do chiu nen hien trudng cua viing thi nghiem
TT 1 2 3 4 5 6 7 8
Chi sd bat nay 24,5 25,0 24,0 32,5 27,0 26,0 21,5 30,0
Cudng dp chju ndn hien trudng, MPa xac dinh theo phuong an 1
24,3 25,0 23,7 34,7 27,6 26,3 20,4 31,4
phuong an 2 22,5 23,4 . 21,7
36,4 26,8 25,1 18,5 32,0
TT 9 10 11 12 13 14 15
Chi sd bat nay 34,0 25,0 28,5 28,0 23,5 26,0 21,5 Gia tri nho nha't Gia tri trung binh
Dd lech chuan / . ( . ) , . - M 8 x 5
f -1-4
J is.lowest
Cudng dp ehiu nen hien trudng
Cudng dp chju nen hi6n trudng, MPa xac dinh theo
phuong an 1 36,6 25,0 29,5 28,8 23,0 26,3 20,4 20,4 26,86 4,699 18,2 24,4 18,2
phuong an 2 39,0 23,4 29,4 28,6 21,0 25,1 18,5 18,5 26,09 6,059 14,9 22,5 14,9
De so sanh, cung vdi cic gii trj chi sd bit nay trong bang 3, neu dinh gii theo TCVN 162:2004 v i TCXDVN 239:2006 se cd cac kdt qua sau:
Tinh toin gii trj cudng do chju nen hien trudng theo bidu dd quan he R-n:
- Cudng dp nho nhi't: 23,7 MPa;
- Cudng dd Idn nhi't: 40,0 MPa;
- Cudng dd trung binh: 30,2 MPa;
Xic djnh dp lich binh phuang trung binh: 5,7 MPa;
Xic djnh he sd bidn ddng: 15,8 %;
He sd ta dng vdi 15 vung: 1,75;
Cudng dp chju nen hien trudng: 21,8 MPa.
Kdt qua tren cho tha'y cd su khic biet ding k l khi xic djnh cudng dd chju nen hiin trudng theo cic phuang phip khac nhau. Ben canh dd, md hinh dudng tuong quan gida kdt qua thi nghiem giin tidp v i cudng dp chju nen (theo phuong an 1) cung anh hudng tdi kdt qua danh gii.
5. Danh gia khi nghi ngd sir phu hdp cua be tdng theo thi nghiem tieu chuan
Tiiu chua'n EN 13791:2007 dinh rieng mdt muc hudng din danh gii be tdng khi nghi ngd su phii hgp ciia be tdng theo thi nghiem tieu chuan.
Ol dinh gia chat lugng b i tdng trong trudng hgp niy ddi vdi vung thi nghiem gdm nhidu me be tdng can sd dung khdng it hon 15 Idi khoan. Dieu kiin can dat l i :
/„(,„,. ^ 0 ' 8 5 x ( ^ + 1 , 4 8 x 5 )
va fis. lowest >0,85 x ( ^ - 4 )
Ndu duge cic bin liin quan thd'ng nha't, cd thi khdng can tdi 15 Idi khoan. Khi dd can cd khdng it hon 15 kdt qua thi nghiem theo phuong phip gian tidp va it nhi't hai Idi khoan li'y tai vj tri cd cudng do thap. Ngoai ra, khi dinh gii mdt viing nhd ed chda mdt hoac vii mi be tdng, cd the sd dung kinh nghiem chuyin gia dd lua chpn hai vj tri dd khoan. Trong cac trudng hgp niy, didu kien can dat la:
A./o...^0,85x(^-4)
So vdi EN 13791:2007 thi cac quy dinh cua TCXDVN 239:2006 cd khac biet ddi chiit. Bd tdng cau kiin hoac kdt ci'u cdng trinh dugc coi l i dat yiu cau khi dap dng ddng thdi hai yeu cau:
R„ > 0,9R,. va i?„,„ > 0,75i?^, Trong dd:
Rf,, - cudng dd b i tdng hien trudng;
/?„,!„ - gia trj cudng dd be tdng hien trudng nho nha't trong td miu;
R^.^ - cudng dd yiu eau l i ei'p be tdng (ndu be tdng dugc ehl djnh theo cap cugng dd chju nen) hoac dugc quy ddi td mic be tdng.
Dinh gii su phu hgp gii trj trung binh ciia cudng dp hiin trudng Idi khoan theo EN 13791:2007 chi thuc hien khi ed gii trj dp lich chua'n, cdn TCXDVN 239:2006 khdng yiu cau dp lech chuan.
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Tgp clii KHCN Xdy dung - sd4/2010Cudng dd tdi t h i l u can dat cua Idi khoan dugc tinh theo c i c cdng thdc k h i c nhau. Khi cudng dd yeu cau nho hon 34 MPa thi cudng dd hi6n trudng tdi thidu cua loi khoan theo EN 13791:2007 nhd hon theo TCXDVN 239:2006 v i ngugc lai. D i i u n i y cd nghTa l i ySu cau ciia EN 13791:2007 chat che hon y i u cau ciia TCXDVN 239:2006 d mdc cudng dd cao.
6. Ket luan
Tieu chuan EN 13791:2007 dugc sd dung rdng rai tai nhidu nudc t r i n thd gidi, d i e bidt l i c i c nudc c h i u Au trong vide danh g i i cudng dd chju nen ciia b i tdng tren kdt cau b i tdng v i be tdng cdt t h i p . Tidu chuan niy cho phip d i n h g i i theo nhidu phuong i n , d i p dng c i c yeu cau k h i c nhau. Mdt sd d i l m k h i c biet cua EN 13791:2007 so vdi tidu chui'n h i f n h i n h cOa Viet Nam da dugc p h i n tich l i m rd.
Thuc td cho thay phuong p h i p v i phuong an sd dung anh hudng d i n g k l ddn kdt qua d i n h gia cudng do chju n i n hidn trudng. Do dd, c i c bdn lien quan can can nhac lua chpn va thdng nhat phuong i n trudc khi tidn hinh thi nghiam.
TAI LlgU THAM KHAO
1. KU H.H., Notes on the use of propagation of error formulars. Precision measurement and calibration
statistical concepts and procedures. National bureau of standards, SP300, 1969, vol. 1,pp. 331-341.
2. MANDEL J., Fitting straight lines when both variable are subjected to error. Journal of Quality Technology, 1984, vol. 16, No. 1, pp. 1-14.
3. STONE W.C, REEVE C.P., New statistical method for prediction of concrete strength from in-place tests.
Journal of Cement, concrete and aggregates. ASTM 1986, vol. 8, Wo. 1, pp. 3-12.
4. HINDO K.R., BERGSTROM W.R., Statistical evaluation of the in-place compressive strength of concrete.
Concrete international, 1985, vol. 7, No. 2, pp. 44-48.
5. DE GRYZE S., LANGHANS I., VANDERBROEK M., Using the correct intervals for prediction: A tutorial on tolerance intervals for ordinary least squared regression. Chemometncs and intelligent laboratory systems. 2007, vol. 87, No. 2, pp. 147-154.
6. VARDEMAN S.B., Statistics for engineering problem solving. Pws publishing company, boston, massachusetts, 1994.
7. CARINO N.J., Statistical methods to evaluate in-place test results. Wew concrete technology: Robert E. Philleo Symposium, SP-141. ACI, Farmington Hill, Mich, 1993, pp.39-64.
Ngiy nhin bil:4/11/2010