Theo quy hoaeh tdng the phat trien giao thdng do thi tai thinh phd Ho Chi Minh, rit nhieu du an dudng sat do thi (metro) dUOC diu tu xiy dung, diln hinh la tuyen Metro sd 1 dang duoe[r]
Trang 1Anh hu'ang cua mat mat tilt dien cap CILF ipng ILPC cang ngoai trong giai doan khai thac den kha nang chju tai cua cau dam hop be tdng cot thep
Effect of loss of cross-sectional area of externally prestressed tendons on loading ca-pacity of reinforced concrete box girder bridge in service stage
Ngay nhan bai: 15/9/2014
NgaysCra bai: 5/11/2014
Ngay chap nhSn dang: 10/12/2014
TOMTAT
Trong qua trinh khai thac, van de thudng gap cua cau be t6ng cdt thep du dng lUc sii
dyng cap cing ngoai la an mon cap do tac dpng tii mol trUdng SU an mon xay ra cr cap
dli dng li^c cang ngoai se dan den diit mot vai tao cap hay ca bo cap, dan den viec giam
hieu ling liic di^ dng Idc, giam kha nang chiu tai ciia cau va co the dan den sU sup d6 cua
cfing trinh Bai bao nay di sau vao viec phan tich anh hi(6ng cua mat mat tiet dien cip
dil ling Ittc cing ngoii dfn kha nang chiu tai ciia cau dam hop be tong cdt thep
Tif khda: c3u dSm h^p bf tdng cot thep dU ting ItJc, cap du ifng liic cang ngoai, mat mat
tiet difn cap
ABSTRACT
In the service stage, the most common problem of external tendon reinforced concrete
bridge is that they are corroded by environmental effects The corrosion of externally
prestressed tendons causes the breaking of some strands or a whole tendon; thus, the
effects of post-tensioning force and the load capacity of the bridge is reduced, which
leads to the collapse ofthe whole structure This paper was carried out to the influence
ofthe loss in cross-sectional area of external tendons on loading capacity of reinforced
concrete box girder bridge
Key words: prestressed box beam bridge, external post-tensioning, loss in
cross-sectional area of tendons
Ths Pham Ngpc HUng
Cdng ty Co phan Ti( van dia tU va xiy dtfng GTVT
Email:hungphamngoc7189@gmail.com Dien thoai: 08.3849 3594
TS Nguyin Danh ThSng
Giing vien, Khoa Ky Thuat Xay Diing, Tnicmg Dai Hoc Bach Khoa - Dai Hpc Qudc
Gia Tp.HCM
Email; ndthang@hcmut.edu.vn Dien tho^i 08.3864 3955
TS Hd Thu Hien
Giang vifn, Khoa Ky Thu^t Xay Difng, TrUtfng Dai Hoc Bach Khoa - Dai Hoc Quoc
Gia Tp.HCM
Email: hothuhien@hcmut.edu.vn Dien thoai: 08.3864 5856
Pham Ngoc Hu'ng, Nguyen Danh Thang, Hio Thu Hien
1 Gidi thieu
Du ulng lUc ngoii la phuong phip dU ulng lue eang sau vdi eie bo cap duac dat ngoai tiet dien cua eie phin tif trong ket eau TrUde day, eip du u'ng lUc eang ngoii thUcmg duoe eho eau hay cong trinh bi huhong, xuong cap Nhu'ng nam gin day, dVlet Nam, viee siidung eip du u'ng lUe cang trong ket hop ciJng vdi eip cing ngoai cho cau be tong cot th^p l i cau Oieu niy duoc minh chimg bing nh&ng Gianh (Quing Binh), ciu Yen Lenh (HUng Y^n), eauThi Nai (Binh Oinh)
So vdi cap eang trong, viec sH dung cip dU
u'ng lUe cang ngoai ngay cang duae ap dung rong rai nhdvao mot so Uu diem nhu glim ton thit ling suit do ma sat, giim tiet difn giim yeu, duy tu bio dUdng don giin Mae dii
duoc bio vi bing vijra cudng do cao, nhUng do
nim ngoai tiet dien, khdng duoc ldp bi tdng
du ling lUc eang ngoai de bi hu h6ng vi inh hudng den sU lam viee cua cap
Theo quy hoaeh tdng the phat trien giao thdng do thi tai thinh phd Ho Chi Minh, rit nhieu du an dudng sat do thi (metro) dUOC diu tu xiy dung, diln hinh la tuyen Metro sd
1 dang duoe tap trung xay dUng de giii quyft mdt phan nhu eau giao thdng cdng cong cOa ngUdidan.Tuyen Metro sol, vdi han 17 kmdi tren cao, se sil dung ciu be tdng du iJng luc, eang ngoii, va thi edng theo phuang phap due hang can bing [1] Do tuyen Metro s61 l i edng trinh quan trong doi vdi he thdng ha ting giao thic can phii duac quan tam ngay tirgiai doan ban diu eiia qua trinh xiy dung
Trudc day, da cd mot sd nghien cinj vf mit mit ii'ng suat ciJa cip du ifng iUe trong ciu diic hang nhuti*bien,co ngdt, hay inh hudng cCia
Trang 2m i t Ong s u i t trong c i p d u utig l u t eang ngoai
cdt t h ^ p [2] Trong q u i trinh khai t h i c sU h u
hdng cOa c i p eung lam g i i m h i f u utig lUc d u
l i n g luc CLia e i p t i c dung vao be tdng [3]
Tif nhCIng ly do tren, nghien cilu nay duoc
tien h i n h d l danh g i i su i n h hudng ciia m i t
m i t t i f t dien c i p d i / i l n g liie cang n g o i i den k h i
n i n g ehju t i i cCia cau dam hop b ^ d n g eot thep
2 M^t s6 h u h6ng thudng gSp ciia cap d u
l i n g lUc c i n g n g o i i
Trong q u i trinh thi cdng Idp vCfa bao v f c i p
c i n g ngoai, v i n t d n tai mgt sd nguyen nhan lam
Tif d d t^o d i f u kifen eho mdi trudng x i m thUe,
cing n g o i i thudng bj gl khi sif dung trong mdi
ncao{Hinh 1 va Hinh2i
d u ling lUc se gay gia tang dtig s u i t t r o n ^ t a p
nhung hieu ilng d i i ttng l i i t cOa cap d d i vdi bi
tdng lai giam di, dan den i l n g s u ^ n^n t K j h g | P tdng cung giam theo
duy t u , b i o d u d n g thiic
I bj t i c ddng b d i m ^ ' l
iri[ih4 AnmongsycliltcBpodau i (6/1999)[8]
t.^: nguyen n h i n cd t h 4 c d d
c n j „ 3 < B l • ^ • • > * - :
^ ^ ^ ^ ^ b u ciia m f t mM t i e t dien cap
du 9P'^Hlv|>^^'<g^B' *^i ^"^ ""
Do t i c dong tif mdi trUdng c i p dU ilng l i ^ eang n g o i i cd k h i n i n g bj dn m d n d i n d f n dut cap Khi tiet di§n c i p cang n g o i i ban dau (A^^)
Hlnh 2 Oih bd cip dil ihig I ^c cing ngoii [4|
Theo [5] v i [6], m i t mat t i f t d i f n c i p d u ung
lyc do 5n mdn l i v i n d f nghiem trong bdi hai li
do chinh sau:
-I- Trong q u i trinh sil dung, b i n t h i n c i p
du img lyc da t d n tai ilng suat keo k h o i n g tif 55
mdn, ling s u i t k t o trong c i p tang len den gidi
ke ban d i u
+ Cudng d d chiu k^o cOa thep d y utig lUc
cao hon 4 d f n 5 lan so vdi thep thudng, do d d
mdc d p nguy hiem do an mdn thep d u utig lUc
cung cao han tuong ilng - ^ K a s ' i S i a C
Kinh 3 An mAn 25% tiet d l i ^ ^ d t f ibg[J^j;^< Hinh 6 MatcSt ngang flai di^nlaivitn'giOanhipvJIyhieuticlKScipdif iing luc
Trang 3Hinh 7 Mat cic ngang flai di^n t^i vitri dinh tru va ky hieu cac bo cap dudng luc
I "
I.-"-l""l
160 KN 160KN
1
13am 1 B
2Dm
21m
11
1
2 1m
11
!
1 >
20m
2-1 m
11
1
m 1 13-8m 20m
^ ^ 1
Hinh 12 OiianhegiQailTigsuatphiplAnnhSttrongbetdng
va t^ le mat m^t ti^t dien tiong cap dif litig lUC c9ng ngo^i
Ty 1^ m^ mM ti^ di^ cip dv ihig l|>c cing ngoii
Hlnh8.M6h1nhhoattiliflo^ntau,
31.41mm
Hlnh 9 Chuyen vi fliing idn nhat ciia can di/m tac dung ciia
hoattji,
1657 ^ 1 Un i 5 St cho phep 1
1
'•
Hinh 13 Quan h§ giDa chuyen vi Ifln nhat cua d^m tai vi
tri giiia nhip bien vh ty 1^ mat mat tiet diSn trong cip d^ ilng
luc cang ngoai,
Ty le out nut Det dicn cap dv ung Ivc clog Dgoli 0% 5% 10% 15% 20% 25%
' " • — • ' * III i - ^
Hinh n Quan he giifa ling suat tiep lon nhat trang be tong
ra ty le mit mat tiet flien trong cap dU Aig luc cang ngoai
0% 5% 10% 15*4 20% 2SH
I ^ l« mit mtt b ^ dite cip du ling luc
Hlnh 10 Quan hi giOa Utig suat va ty le mat mat tiet dien
tnng cip d^ Ong lire cang ngoai
=1 B N ^ : iN=3 " N ^ * N = i a l W
nh 14 Quan he gifla chuyen vi lon nhit ciia dim tai vi tn
Trang 4tang len A^, d d n g t h d i ifng s u i t nen trong be
AOj t u o n g Ung vdi sy g i i m tiet dien AA nay
N h u vay, sU gia tang i l n g suat trong c i p cang
ngoai dUoc xac dinh theo cdng thile sau:
Lfng s u i t nen trong be tdng sau khi cd si
m i t mat tiet dien cap duae xae dinh nhU sau:
Aa.,AA„, ffcz = - T d + Affc = -an + (—^^-—^ 4
Trong
do-A^ h Moment q u i n tinh eiia tiet d i f n dang
xet
e^^: D d lech tam cua bd cap so vdi true trung
hda cua tiet dien
y,: K h o i n g c i e h t i f true trung hoa ciia tiet
dien den t h d be tdng dang xet
Trong nghien eilu n i y , dieu kien d i t ra la
ifng s u i t trong cap dU ilng lUe nhd hOn gidi han
cap d u Lfng lUc eang ngoai l i m viec trong giai
doan dan hdi n h u t h i e t ke ban dau
Theo tieu chuan thiet ke TCN 272-05, ddi
vdi t h e p tUchCing thap, ilng s u i t k^o trong cap
0.8f N^u thiet ke tdi Uu thi ilng s u i t keo ban
cdn lai ciia cap la 20% f Ben canh dd, theo chi
[9] cd 6i cap gia trj ifng s u i t keo trong cap d
trang t h i i gidi han sit dung la 0.75f d d d u
trCf cdn lai cOa cap se la 25% f^^ Do dd, trong
n g h i i n cilu n i y , t i c g i i se xem xet g i i tri m i t
cang ngoai la 25%
3.2 Md hlnh phdn tUhOu hgn {FEM) cda cdu
due hdng cdn bdng
Md hinh sif dung trong nghien cifu nay dua
tren hd so thiet ke kythuat cau Sal Gdn [10], l i c i u
bien dai 82.50m mol nh[p; phan ti'ch dUa vao p h i n
m e i r MIDAS/Civil Trong d d cap cang ngoii sif
dung la loai cipT15,31 tao/bd, v i dien ti'ch chiem
t y 24.60% a^n 27.68% (ke e i cap dU phdng) ciia
tdng dien tich c i p dU ilng lUc ciia mat c i t ngang
tai V! tri dinh t n j (Hinh 5 Hinh 6, Hinh 7) Ben canh
dd, m d hinh h o a t t i i duacsif dung la hoat t i i Soan
tau (Hinh 8) Chuyen vi Idn n h i t ciia cau do hoat
t i i g a y r a l i 3 1 4 1 m m ( H i n h l O )
Anh hudng ciia mat mat tiet dien c i p d u
ifng luc c i n g n g o i i den cau due hang
Tfong nghien cifu nay, dUa tren nhiing hu
hdng t h u d n g xay ra vdi c i p dU uTig lUc cang
n g o i i , mat mat tiet dien ciJa c i p d u ilng luc
E l , E2 v i E3 se dUOc xem xet n h i f u t r u d n g hop
5%, 10%, 15%, 20%, 25% tiet dien trong cap
m a t t i e t diin cua cap dU ilng lUc eang ngoai, ket
q u i cho thay:
+ Cfng s u i t trong cap c i n g n g o i i dat gidi han chay khi mat m i t - 2 4 6 % tiet dien (Hinh 10)
+ Mac d i l ifng suat tiep tang nhUng khdng
d i n g ke (Hinh 11) Vdi cau tao ciia cdt thep dai, dam van dam b i o k h i nang ehiu c a t + Khi mat mat khoang 25% tiet dien, be tdng c h u y i n tif trang t h i i chju nen sang trang thai ehiu keo (Hinli 12)
+ Chuyen vi ciia dam dat gia trj f££ P^fp^y^^ ldn n h i t tai vi tri giCfa nhjp bien la 'c 45.41 m m nhUng van nhd han gia tri cho phep la L/1000=82500/1000=82.5mm (Hinh 13) Trong khi do, chuyen vi dam tai giCfa nhipchinh t i n g r i t it, khoang 5 m m (Hinh 14)
4 Ket luan Sau khi p h i n tich anh hUdng ciia viec mat mat tiet dien ciia cap dU u'ng luc cang ngoai den
phan tich m d hlnh phan tif hu'u han cua cau
Dua vao cac kit q u i trong nghien cifu nay, ta cd the rut ra cac ket \uhn chinh sau
+ Trong trUdng hop c i p d u yng luc cang ngoai bi mat mat tiet d i f n , vi tri chuyen sang tru.Tai vj trf nay, khi mat mat - 2 5 % tiet dien cap
t d trang thai chiu nen sang trang thai chju keo
Trong khi do, be tdng tai cae vi tri k h i c v l n chiu
+ Cfng suat tiep trong b^ tdng tang khdng dang ke khi ed mat mat tiet dien trong cap dU Lfng lUc ngoai
+ Mac dil do vdng Idn nhat ciia d i m do hoat tai tang len d i n g ke [khoang 1.5 l i n ) nhUng van nam trong do vdng cho phep (171000)
Tuy nhign, ket q u i nghien eifu trong b i i
b i o nay chi gidi han trong pham vi c i p c i n g ngoai D f ket qua mang tinh tong q u i t han,
ta can tien hanh nghien cilu m i t m i t tiet d i f n trong cap dU ifng luc cang trong va nghien cifu nhieu cdng trin cau cu the hon
TAI LIEU THAM KHAO [1] Ho so Bao cao tham flnh thiet ke ky thuat chinh thflc cau Sai Gon tuyen metro so 1, thang 7 nam 201 J
[2] KS Pham Ngoc Hung, TS Nguyen Danh Thang, TS Ho Thu Hien, "Anh Huflng Ciia Mat Mat Ijng Sua't Cap Du tfng Luc Ngoai flen Kha Nang Chiu Tai Ciia Cau Dam Hop Be Tong Cot Thep Ouc Hlngp'Tap chi xay dung - Bo Xay DUng, pp 32-J5,2015
[ i ] S Sumitro, K Hida, T Le Diouron, "Stnictural health monitoring paradigm for concrete structures," 2 8 ^ Conference
on Our World In Conuete & Structures, voi Conference Documentation Volume XXII, pp 525-532,27-29 August 2003
14] Randall Poston, Michael Ahem, Keith Kesner, Sharon Wood and Jinying Zhu, "Current Practice of Assessing Strength and Durability of Grouted Tendons and Cable Stays," in PTl Convention, Nashville TN, 2012
[5] ACl 222 2R-01, Corrosion of Prestressing Steels,
[6J ACl 423.4R-9e, Corrosion and Repair of Unbonded Single Strand, Amencan Concrete Institute, 1998, [7] Keith Kesner and Randall WPoston, "Evaiuai.on
of Corrosion Damage in Unbonded Post-Tensioned Concrete Stmctures: Misundeistandings and Moving Fonvard," Whitiock Daliymple Poston & Associates, Int, Consulting Engineer [8] Rodney G.Powers, Alberto ASagues and 'ftsh Paul Viimani, "Corrosion of post-tension ed tendons in Florida bridge," Reseaich Report No, FiyDOT/SM 0/04-475
[9] 'Specifications for Highway Bridge," Japan Road Association, 2002, p 26
[10] "Ho so thiet ke' ky thuat chinh thifc cau Shi 66n;2013
[11] N D Thang, "Fundamental Study On Structural Damage Detection Vibration Response Of Long Span Suspension Bndge", Dr.E Thesis, vol 2,2 Damage detection for long span bridge, Yokohama: Yokohama National University, 2010, pp
21-25, [12] G J W e b b ; PJ Vardanega.Ph D,MASCE, PRAFidler, and CR Middleton, PhD., C.Eng, "Analysis of Structural Health Monitonng Data from Hammersith Flyover," Journal of Bridge Engineenng, ASCE, vol 19, no 6,28 February 2014 [13] Jelf Pouliotte, "PT Grouting and Corrosion Issues m Florida," FOOT State Structures Maintenance Engineer, State of Rorida
[14] Nguyen DanhThang, Hitoshi Yamada, Hiroshi Katsuchi and Eiichi Sasaki, "Damage detection of a long-span bridge by wmd-induced resporse,"]ABSE-lASS Symposium London 2011,
2011