K^T CAU - CONG NGHE CONG NGHE
NGHIEN CO'U THyC NGHIEM VE GIA Cl/QNG KHANG CAT CHO DAWI BE TONG C 6 T THEP BANG TAM SOI THUY TINH
TS. N G U V e N H G N G P H O N G Dai hpc Xay d y n g
Tom tat: Bai bio trinh biy ve m0t nghien cim thu-c nghidm gia cu-dmg chju cit cho cic dim bi tdng cot thep. Bin dim giong nhau dirg/c chi t?o. trong do, ba dam du-g-c gia cu-d-ng bing tam sg-i thOy tinh vai cac hinh thO-c gia cu-dng khac nhau. Kit qua thi nghiem cho thiy, tim spj thuy tinh lim gia ting ding ki khi ning chju cit va lim ting dO cdng, d^ dio cua dim.
Cic yiu td vi ciu tao nhw d^ dinh kit giira be tong vi tim gia cu-ang, doan neo cOa tim, ban kinh cong goe gia cuvng, chit lu-ang l&p be tong bao v$ inh hu-ang l&n din hi$u qui gia cuung.
1. Tong quan ve p h y a n g phdp gia c y d n g Tinh trgng cdng trinh be tdng cot thep (BTCT) bj xuong d p theo thdi gian, c h i t lyg-ng thi cong cdng trinh khdng dam bao vd vide gia tdng tdi trpng s d dung len cong trinh ddi hoi cdng trinh can du'gc gia eo/gia cu'dng de tranh h y hdng, syp d l . Trong cdc hinh thde phd hogi k i t eau BTCT, phd hogi cat d i l n ra r i t d$t ng^t vd nguy h i l m , do dd, vide gia eudng, gia c6 chiu c l t cho cdng trinh cdn ddm bdo d$ an toan eao. Trong cdc phyang phdp dype s d dung, giai phdp gia c6 chju eat eho dam BTCT b i n g tam sg'i lien tuc cydng dg cao FRP (fiber reinforced polymer) la mpt gidi phdp t y a n g dor dan gidn, cho phep thi cdng nhanh vd it gdy anh hu'dng tdi k i l n trile cdng trinh.
Ngodi vide gia c6 khdng eat, gidi phdp ddn t i m FRP cdn giup bdo vg ket eau BTCT khdi tdc dung xdm thye cua mdi trydng va ddng vai trd neo cho gia eo khdng u l n b i n g each dan tam FRP d ddy dam. Cd nhilu hinh thde gia cudng khdng cat d i m BTCT bang tam FRP nhy gia cudng dgng tam lien tyc tren s u i t chieu ddi d i m hogc gia cydng theo tdng bang, gia cydng theo phyang t h i n g ddng hay phyang xien, gia cydng ddn ba mat d i m hodc hai mgt ben cOa ddm.
Hinh 1. Gia e6 khang dt cho dim BTCT bing lim FRP Trong s6 cdc Ioai tam FRP thdng dyng, tam sg-i thOy tinh (glass fiber reinforced polymer - v i l t t i t Id GFRP) dyp'c s d dung kha p h i b i l n do cd gid thdnh tyang d l i thap. Trong nghien edu thye nghigm ndy, tae gid da tien hanh thi nghidm gia tai cho b i n d i m BTCT du'pc gia cadng bang t i m GFRP theo cdc hinh thde khdc nhau. Qua k i t qud thf nghigm, tae gia da tien hdnh phdn ttch, ddnh gid v l hipu qua gia cu'dng cua tdm GFRP, hinh thde ndt vd phd hoai d i m cijng nha eae chi t i l t cau tgo trong gia cu'dng, t d do du'a ra ede khuyen cdo cho vide thilt k l , thi eong gia cudng khdng eat cho k i t c l u BTCT bdng t i m spi thCiy tinh.
2. Mau t h i nghigm 2.1. Chi tiit mau thi nghidm
Bon mau dam dyg'c ehe tgo hoan todn giong nhau trydc khi gia cudng t i m GFRP (hinh 2). Cac d i m nay d a y c bo tr\ cot thdp dpc vdi hdm lyp'ng Idn sao eho khd nang chju u l n cOa d i m Idn han kha nang chju c l t d nhjp phai (xem bang 3) de khi thi nghidm d i m khdng bj pha hogi do uon. Nhip cat ben trdi cua cdc dam (a = 550mm) dog-c b l tri cot dai thep tyang d l i Idn (4P 8 khoang cdeh 50 mm) d l sy phd hogi eSt se khdng xay ra d nhip ndy ma xdy ra d nhip ben phdi la nhjp ma cdc dam se d y p e gia cydng bdng t i m GFRP theo cdc hinh thde khde nhau (hinh 3). Cdc t i m (bang) GFRP gia cydng dyp'c dan d hai mgt bdn eOa d i m bdng keo epoxy vd dyp'c neo vdo mdt trdn vd mgt d y d i cua dam m^t dogn 50mm.
T^p chi KHCN Xay d{mg - so 3/2014 23
K^T CAU - CONG NGHE XAY DLfNG
Hinh 2. Chi tdt miu dSm trwyc khi gia cu^g tam GFRP
A pa
L
tfmGFRP \nji
1 T 1 »^^
- " ^ T -
ian
1 mm
ffij m 1 " 1 = u
I -. I
a. Dam D l : khong gia cuang
b. Dam D2' gia cuang tim GFRP:
- Be rgng tam «'/= 30mm - Khoang cdeh si= 100mm - Gdc nghieng o = 90°
c. Dim 03: gia cudng tam GFRP:
- Be r6ng tam Wf = 30mm - Khoang cdeh Si = 100mm - Goe nghi§ng a = 60°
d. Dim D4: gia cu'o'ng tam GFRP:
- Be rgng tam Wf= 50mm - Khoang each st = 100mm - Goe nghieng a = 90°
Hinh 3. Chi tiet gia cuang cac miu dam bing tim GFRP theo cie hinh thOx: khie nhau C y d n g do cua vat ligu thep va be tong du'gc
xdc dinh bang thi nghiem tgi thdi diem cung ngay vdi thi nghiem gia tai cae mdu dam va d u g c tdm lat trong bang 1. Cac dge trang ea hgc cua tam GFRP do nha phan p h l i cung cap, du'pc tdm tat trong bang 2. Cac thong so ve k i t cau cua cae dam tinh toan theo tieu c h u i n ACI
bang GFRP gia c y d n g pf d y g c dinh nghTa theo cdng thde (1).
2t,w„,
Pf-- • ' / ""P'
bs (1)
trong dd: f, - ehieu ddy cila bang GFRP; Wfn - be rpng cua bang GFRP theo phu'ang nam ngang; Sf - khoang cdeh gida cac bdng GFRP tinh t d tim; b - b l [4] d y p e tom tat trong bang 3 v d i ham l y p n g rdng cua dam.
24 Tap chi KHCN Xay dung - s6 3/2014
K£T CAU - CONG NGHg C 6 N G NGHE
Bang 1. Cudng t?$ thi nghi$m cua vit li$u thip vi be tong cDa cic mau dim Gidi h ^ chay cCia thdp dgc ^^4 fy
Gidi hgn chay ci^a thdp da\ ^ fyt
Cudng do chju ndn cCia be tong (mau tru 150x300mm} fc'
351 MPa 362 MPa 20,07 MPa Bang 2. Cic die trung co hgc cOa tim sgj thuy tinh GFRP Cdc a§c trung ca hgc (gia tri thi nghi|m)
Cudng dg chju kdo cyc hgn theo phuang cOa sgi ff DO dan dai cyc hgn ey
M6-dun keo Ef Chieu ddy tim tf
Tim sgi IhOy tinh 575 MPa
2,2 % 26,1 GPa 0,635 mm Bang 3. Cic thdng s6 vi kit du cOa cic mau dim tinh theo ly thuyit eOa tiiu chuin ACI [4]
Ten dSm D1 D2 D3 D4
D^c dilm gia cu'cyng ntljp piiai Khdnq qia cif^nq Banq tiianq 30mm Banq xign 30mm Bang thanq 50mm
HSm lu'p'ng bang GFRP pf
(%) -
0,254 0,293 0,423
Kh3 nang chju cSt nhip IrSi {V, * V,)
203,8
Kh5 nang chju uon (P/2 = M/a)
(kN) 103,7
KtiS nang cliiu cSt niiipphai(l'c+ Vf)
(i<N) 66,8 (Vt)
75,9 79,2 81,9 (P; tong tai trong kich thOy Iyc tdc dgng len dam
2.2 Quy trinh gia cu-dng miu
Trydc tidn cdc mau dam dygc ddnh sach bang mdy mdi cam tay va giay rap de logi bo Idp vya xi mang ben ngoai m l u , tang dp dinh bam gida tam GFRP vd bd tdng (BT). Cde gdc ddm d y g c mai tron vdi bdn kfnh cong 10mm d l ddm bdo k i t dfnh tot vd trdnh tdp tnjng dng suat trong qud trinh chju Iyc. Sau dd, dung choi lan san lan epoxy len be mgt eua mdu cho kin todn be mgt, de eho epoxy tham vdo trong BT.
Tiep theo, dung choi lan epoxy Idn b l mgt tam GFRP da dugc c l t theo dOng kfch thydc can thtet. Lan ca hai mdt sao cho epoxy tham dam vdo trong sgi vai thuy tinh. Trong khi lan can chu )f lan choi theo
chia Idm hai Iyc tgp tmng hai ben, moi luc = P/2) phyang dgc vdi phyang cOa sgi, khdng dygc lan theo phyang vuong gdc vdi phyang eua sgi se Idm hy hdng cdu true eua vdi. Cu6i eijng, ddn tam GFRP da t i m epoxy len be mat m i u . Khi dan lu'u y dung tay vuot nhg Idn be mat tam de tam dugc phang, khong ed bgt khi ben trong, ddm bdo tiep xiic tot giya be mgt BT vd t i m GFRP.
C6 the nhgn thay quy trinh gia cydng Id tyang d l i dan gidn vd nhanh chdng. Qud trinh gia cudng ba d i m thf nghigm kdo ddi trong khoang 3 t i l n g . Thi nghigm gia tat cdc dam d y g c tien hdnh sau thdi gian gia cydng mau it n h l t Id 72 tilng d l ddm bao epoxy khd cdng, dat cydng do va Iyc dfnh toi da.
c. Tim epoxy vio hai mat tam d. Din tim_ len bi mat dim Hinh 4. Quy trinh gia cu-dng miu
Tap chi KHCN Xiy dung - s6 3/2014
K^T CAU - CONG NGHE XAY DLfNG
3. Thi ngtiiem m l u
Sa do till nghiem la dam dtm gian ke len goi c6 dinh va g6i dl dpng. Thiet bi gia tai la kich thuy iiPC lo?l 20 tan, k i t hi?p v4l he khung phan lu'c va dam phan tai t j o n§n hai a i tnjng tap tnjng vm khoang each 500 mm. Tai trong thi nghiem duvc do bang dau do tai trpng (load cell) ky hiSu la P. CSc gia tq chuyin vi (86 vong) cua d i m du'gc do t^i vi tri giii'a nhip va hai goi b^a bang cac dau do chuyen vi ky hlju 11,12,13 (hinh 5).
A
P ( 2 | | P I 2
L
1
soo1
A1 ' ' a o o
Hinh 5. Sa d6 thi nghidm miu
Sau khi Idp dat vd cdn chlnh cdc thiet bj do, cdc m l u d i m dygc thi nghidm theo quy trinh sau ddy.
Dya vdo Iyc phd hogi d y dodn eCia dam chpn ra thang Iyc thi nghigm phCi hgp. Tien hanh gia tdi theo
tdng e l p cOa thang lye. Can quan sdt k? BT vung kdo d l phdt hien vet ndt t h i n g gdc v d v l t ndt xien. Tgi m l i cap gia tdi, ddng tai de quan sdt, chyp dnh, theo ddi so dpc tren cdc t h i l t bj do vd tien hdnh ve s y phdt trien cua vet ndt trdn d i m . Tang tai trpng theo tdng cap cho den khi ddm pha hogi - quan sdt ky d l xdc djnh nguyen nhdn v d hinh thde phd hogi cua dam.
4. K i t qua thi nghigm va n h d " xet 4.1. Bleu do quan he tii trong - do vong
Hinh 6 t h i hign dadng cong quan hd tdi trgng - dd vdng cua ede d i m trong qua trinh thi nghidm. Gid trj cCia tai trpng the hien khd nang ehju edt cua dim.
Cdc dam d y g c gia c y d n g (D2, D3, D4) cd kha nang chju cat tang ddng k l so vdi dam D 1 . Kha nang chju cat cOa cdc dam d y g c tdm tat trong bang 4. Ta thay mdc ddu hai dam D3 v d D4 ed hdm lygng tdm GFRP Idn han so vdi d i m D2 nhyng kha nang chju cat cua hai dam nay Igi nhd han so vdi dam D2 vl chiing bj phd hogi sdm do cdc chi t i l t cau tgo trong qud trinh gia tai. Nguydn nhan phd hogi se dage thao lugn ky han d phan sau.
So sanh khd ndng chju eSt cQa cdc d i m theo thye nghidm (bang 4) vd thep ly thuylt (bang 3) ta thiy kit qud thye nghigm khd gan so vdi tfnh todn ly* thuylt - dam D2 co khd ndng chju cat thye te Idn han ly thuyet, trong khi tihm D3 v d D4 do bj phd hoai sdm ndn CO kha ndng ehju cat thye t l nhd han so vdi l|?
thuylt.
Lye P/2 (kN)
• 1
r
— / J'
^ X
:.„.-
* M ~ . • « • ; •—'- "I""
Dam D2 Dim D1 1
1
1 8 10 12 14 16 18 20 22 24
B$v6ng (mm) Hinh 6. Quan h$ til trgng - di? vdng cOa cic dim
T?p chi KHCN Xiy dimg - s6 3/2014
KtT CAU - CdNG NGHE CONG NGHE
Bdng 4. Khi nSng chju dt ciia eic dim theo kit qua thi/c nghi$m T«n
dam 01 D2 D3 D4
D^c dilm gia caitng tam GFRP Khdnq qia ctfonq Banq thSng 30mm Banq xien 30mm Banq thanq 50mm
Ham luong tam GFRPpf
(%)
0,254 0,293 0,423
Kha nang chju cat cua dam(V„=H2)
(kN) 53,53 80,29 77,08 77,33
Kha nang chiu cat cua tam GFRP (W= v.- V,) (kN)
-
26,76 23.55
23.80 1 Cde d i m D1 d i n D4 xuat hien vet ndt thang gdc d
tdi trgng xap xl nhau, khodng 15kN. Sau do, cd t h i thay rang vdi cung mot gia trj tai trpng thi dam D1 cd dp vdng Idn han so vdi ba d i m kia. D i l u ndy cdng trd nen rd rgt han sau khi cde d i m x u l t hign vet ndt xien d tai trgng khodng 30-35kN, Nhu- vay. vigc gia cydng tdm GFRP cdn lam tang do cdng (chfnh Id dp doe cua bieu do tdi trgng - dp vdng) so vdi dam khdng dygc gia cydng. Nguyen nhan Id do cdc tam GFRP dupe ddn trdn mat ben cCia d i m cdn trd s y phdt t r i l n cua vet ndt nghieng Idm cho dg cdng ciJa dam du'pc gia c y d n g khdng bj suy gidm nhieu sau khi v l t ndt nghidng xuat hign.
Ngoai ra, cung trdn bieu do tai trpng - dp vong cd the t h i y rdng cdc ddm d y p e gia cudng tam GFRP eo khd nang chju b i l n dang tot han nhieu so vdi dam D l . D i m ndy bi phd hogi dpt ngpt d dO vdng khoang 5,8mm trong khi ba dam kia sau khi dgt tdi trpng cye_
dgi thi khdng bj phd hoai dgt ngpt ma t i l p tue eo kha nang chiu tai gan bang gia trj c y c dgi cho tdi dO vong len den khodng han 20mm. Oieu dd cho thay cdc dam d y g c gia cudng tam GFRP co dO dec cao hgn han so vdi d i m D1, tdc Id c6 the Idm vide an todn han, khd bj syp do hgn dydi tdc dyng cua tdi trpng dgng dat.
4.2. Sir phat trien ci/a vet nuiva hinh thu^pha ho?i
Sy phat t r i l n cua v l t ndt d d i m D1 va cdc dam dugc gia cydng Id toang doi khae nhau. 6" ddm D l , dau tien, khi tai trpng (P/2) dgt 15kN thi dam x u l t hien vet ndt thang gdc. Sau dd, khi tilp tyc tdng tdi trpng tdi 30kN, thi dam bat d i u xuat hidn v l t ndt nghidng - dp cdng cua dam gidm mgnh (hinh 6). Vet ndi nghidng ndy lien tyc phat t r i l n khi tdi trpng tang dan vd d i n tdi dam bj pha hogi edt (tension shear failure) theo t i l t dign nghidng ndy. Gdc cua v l t ndt nghidng so vdi trye dam Id khoang 40" (hinh 7).
Hinh 7. Syp/ia ho$idim D1 Doi vdi cdc dam gia cudng t i m GFRP, vet ndt nghieng x u l t hign mupn han (P/2 «= 35kN). Tuy nhien, sau dd do cdng cua dam khong bi suy giam, the hien qua dp doc cua bieu d l tai trpng - dp vong gan nhy khong thay doi (hinh 6). Vet ndt nghieng phdt then ggp phdi sy can trd cOa cac bang GFRP ndn khong md rpng d y g c nhanh vd do dd mpt so v l t ndt nghieng idn cgn hinh thdnh. Cae vet ndt nghieng nay glLip truyin deu tai trpng ra cho cdc bang GFRP cung tham gia chiu Iyc (hinh 8).
Hinh 8. Sij-phit trien cua cic vit nCet nghieng & dim D3 (cie vit nift dugc td den)
Khi tai trpng tiep tyc tang thi dng s u i t trong ede bang GFRP tgi vj tri v l t ndt nghieng tang rat nhanh.
Do sgi thuy tinh cd md-dun dan h i i thdp nen b i l n dgng eua cdc bang kha Idn, Igi Idm cho vet ndt nghieng phdt trien rpng han. lli'ng suat trong bang GFRP truyen t d vi fa-i v l t ndt d i n vj tri neo thong qua dng s u i t dinh gida bang GFRP va b l mgt BT c6 d y g c nhd keo epoxy. Do do, khi dng suat trong bang tdng nhanh thi ddn d i n hign tygng bong ( m i t dinh k i t ) gida cde bang vd be mat BT. Hign tygng bong dau tien xdy ra xung quanh v l t ndt nghidng. Chinh nhd hien tygng bong nay ma cdc bang GFRP khdng bj tgp tnjng dng sudt qua Idn tgi vj tri vet ndt ma dng s u i t d y g c phan deu tren ehieu ddi doan bong, lam
T^p chi KHCN Xiy dung - so 3/2014 27
K^T CAU - C6NG NGHE XAY DUNG
cho bang khdng bj ddt tai vj tri vet ndt nghieng. Khi tiep tyc tang tdi, chieu ddi doan bong tang d i n va lan rgng ra vj tri dau neo eua bang d mat tren va mgt dudi eua dam. VI be rdng v l t ndt nghieng Idn han d phfa dudi chilu eao dam ndn cdc bang GFRP thu'dng bj bong d dau neo phia day dam. Khi cdc ddi neo b]
bong thi bang GFRP mat hoan todn tde dyng va ddn d i n dam bj phd hogi.
Ta thiy, do t i m sgi thuy tinh eo eudng dp cao han cua epoxy khd nhieu nen sy phd hogi eua cdc dam du'pc gia eudng bang GFRP phy thupc vao hign lu'png bong tam GFRP tren b l mgt BT. Do dd, khi hdm lugng
Phd hoai BT vung nen
tam (bdng) GFRP taang doi Idn thi khd nang ehju clt eua eae ddm khdng phy thudc nhilu vao ham lypng tam ma phy thupe chfnh vao thdi diem bdng bi bong vd tupt dau neo. Vi vdy, tren thye t l khd nang ehju c l t cua dam D3 vd D4 khdng Idn han eCia d i m D2 mdc dCi gia eudng nhieu tam GFRP han.
Quan sdt thi nghigm cho t h i y d i m D2 bj pha ho?i do BT vCing nen d dau vet ndt nghieng bj dp vo (compression shear failure), sau do dam vdn tiep tyc duy tri kha nang chju tai khoang 90% gid tn cue dgi roi bj phd hogi hodn toan khi d i u neo eua t i m GFRP bj bong khdi be mgt BT d day dam (hinh 9).
Tudt neo cac bdng GFRP
Hinh 9. Sy-phi hosiidam D2 0 d i m D3, khi bj phd hoai, doan bang GFRP
theo phyang xidn d gdc dam bj ddt s d m . Tgi vj tri gdc ndy, do bdn kinh cong khdng du tdn dan d i n t i m GFRP bj tdp trung dng s u i t ; thdm vdo dd, dogn gdc Igi nam theo phyang xien (khong phdi phygng vudng goe) vdi phyang cCia spi nen tam GFRP CO cydng dO chju keo thdp han vd bj ddt
dpc theo gdc sdm h a n . VI vay, kha nang chju tSI cua dam D3 nhd hon cua d i m D2 (bang 4). Qua dd, ta CO the thay rang vide dam bdo cdc chi tiet c l u tgo khi gia c y d n g n h y mdi trdn cdc goe dam cd anh h y d n g dang ke d i n higu qua gia eudng khdng c l t , n h l t Id vdi t r y d n g hgp gia cydng cSc bang theo p h a a n g xien.
Ddt tdm GFRP d gdc dam
Hinh 10. Su-phi hoai dam D3 D i m D4 dygc gia cudng vdi bdng GFRP b l rpng
50 mm. Do bang r^ng nen be mat tiep xuc vdi BT Idn vd d i u neo cua bang khdng bi bong ra. Tuy nhidn, khi vet ndt md r0ng, lye dinh gida bang GFRP vd BT Idn da tgo thanh mpt Iyc kdo tung Idp BT bao vg cot thep dpc, Idm mat hipu qud gia cydng ciia bang vd ddn 28
d i n phd hogi dam (hinh 11). Nhy vdy, c h i t lygng cua Idp BT bdo vd cot thdp doe vd Iyc dfnh gida BT vd c l t thdp dpc cQng dnh hydng tdi hidu qud gia cudng.
Trong trydng hgp ndy, eung cd the thay rdng vigc gia c y d n g vdi mgt hdm lygng tam GFRP qud Idn Id khdng hidu qud vd gdy Idng phf vdt lidu FRP.
T^p chi KHCN Xay d^mg - so 3/2014
K^T CAU - CdNG NGHE CdNG NGHE
Mdng BT bdo vd cot thep dgc bj kdo bung ra
Hinh 11. Su-phi hoai dam D4
d trgng thdi phd hoai, cdc d i m du'gc gia cydng ludn thu nghiem ngat cdc dieu kien edu tao d l trdnh tam GFRP deu ed be rpng vet ndt nghieng r l i Idn do xay ra tiudng hgp phd hogi sdm.
mo-dun ddn h i i ciJa tam GFRP khd nhd. Do dd, Irong cong lac thiet ke gia cudng chju edt cho dam BTCT bang lam GFRP can hgn ehe dng suat (biln dgng) trong lam de trdnh be rgng vet ndt nghieng qua Idn, khdng dam bao dieu kign sd dyng ve be rgng khe ndt va Idm mat higu dng chdn cot ligu d BT. Ngodi ra, sgi thCiy tinh rat dd bj phd hogi dgt ngpt do tac dyng cCia ldi trgng dai hgn (creep rupture) ndn khi gia cydng can hgn c h i dng s u i t dai hgn trong tam spi thuy tinh nam trong gidi hgn cho phep.
5. K i t luan va kien nghj
Nghien cdu thye nghigm gia cydng dam BTCT bang l i m GFRP cho t h i y day Id mgt phaang phdp gia cydng dan gidn, cd the thye hign nhanh chdng vdi chi phi taang doi thap va khdng Idm tdng kich thydc cau kign. K i t qua thf nghigm cho t h i y phyang phdp gia c y d n g ndy Idm tang ddng ke kha ndng chju cat cua dam BTCT, dong thdi ldm tang dp cdng vd dp ddo cOa dam.
Khd nang chju cat cua dam d y g c gia cydng khdng nhdng phy thu^e vdo hdm lygng vd hinh thde b l trf tam GFRP, md cdn phy thupc rat nhieu vao s y dfnh ket gida tam GFRP va be m i l BT, hay ndi cdeh khac Id phy thuoc vdo hien tagng bong tam GFRP trong qua trinh chju tai. Ngoai ra, hidu qua gia cydng vd hinh thde pha hogi cua dam bi dnh hydng Idn bdi cac chi tilt c l u tgo trong qud trinh gia cydng nhy dogn neo lam GFRP, bdn kfnh mai cong cua goe gia cygng hay cadng dO va dp dinh bam eua Idp BT bdo vg cot thep dgc. Do dd, trong qud b^inh gia cydng e i n
Do lam GFRP cd md-dun ddn h i i keo thap ndn b l rpng cOa vet ndt nghieng taang doi Idn, anh hydng den ydu c l u s d dyng va kha nang chiu edt cua BT. Vi vdy, trong qua trinh thiet ke gia euo'ng chju cat cho dam BTCT can hgn ehe dng s u i t trong tam GFRP ndm trong gidi hgn eho phep de tranh be rpng vet ndt nghieng Idn vd trdnh hign tu-gng pha hogi dgt nggt do t d bien (creep rupture) cOa l i m GFRP.
Hu'dng phdt trien tilp theo cOa nghien edu Id gia cydng lam GFRP cho ede cau kign BT cudng dO cao vd di sau vdo tim hieu v l dnh hydng cua keo epoxy va s y dfnh k i t giya BT va tam GFRP d i n higu qud gia cudng cho ket cau.
T A I u g u THAia K H A O
1. N G U Y E N T I E N D O N G , Gia CLcdng ch[u clt dim bg tong cot thep bang tim sgi cudng dg cao FRP, Lu$n vin thac s^, D$i hgc Xay di/ng (2014).
2. N G U Y E N H O N G PHONG, Nghien cdu thye nghi$m ve gia cu'dng cgt be tdng bdng tam sgi lien tyc cu'dng dg cao, T^p chi Xiy dung. 6-2014, trang 89-93 (2014).
.3. ACI 440.1R-06, Guide for the design and constiuction of structural concrete reinforced witii FRP bars, American Concrete Institute (2006).
4 ACI 440.2R-08. Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures, American Concrete Institute (2008).
NgAy nh$n baisu-a: 5/9/2014.
T^p Chi KHCN Xiy dung - so 3/2014 29
