Nghien CLFU mo hinh phan tiF hCpu han dam cau dng thep nhoi be tong (CFT)
A finite element modelling study of concrete filled steel tube bridge girder (CFT)
Ngay nhan bai: 12/9/2014 Ngay su^ bai: 17/11/2014 Ngay chap nhan dang: 28/01/2015
Oang Dang Tung, Nguyen Qudc Tien
T O M TAT:
tTng xil u6n cCia cdc cau kien CFT da ddac dieu tra thUc nghiem va nhflng ket qua nay cung cap mgt cd sd de hilu bilt vl cac phan dng cua CFT va thiet lap cac dac tinh ky thugt ciia chung. Tuy nhien, mot minh ket qua thiic nghiem kh6ng dii dl ho tr^ ky thuat cho cac cau kifn n^y. Cac mo hinh so tien tien bo sung li can thiet de mo ph6ng cac iJng xil uon cua CFT de md rong nghien ciiu thiic nghi?m va phat trien cac cong cu du doan can thiet cho thiet ke va danh gia cac he thong ket cau. Trong nghidn ciiu nay, m6 hinh phan tii hiiu han cho CFT chiu uon diioc phat trien. Cac hieu iing kiem che, tiep xuc, Xic dfing lien hi?p va ilng xd u6n cda cac mo hinh phan td hflu hgn ddijc de xu&t cho CFT da ddijc xac minh bang each so sanh vdi ket qua thdc nghiem. Mpt sd hop 1^ duoc quan sat thay gifla cic ket qua tinh toan so va thdc nghiem. Mo hinh nay dflac sd dung de tien hanh so sdnh vdi cac mo hinh dam thep I truyin thong va cho thSy mot do deo tUOng d5i kha quan cua dam CFT.
Td khoa: dam ong thep nhoi be tong, phan mlm Abacus, giao thong do thi.
ABSTRACT
The bending behavior of CFT members has been investigated experimentally and these results provide a basis for understanding the response of these elements and establish their engineering properties. However, only experimental results are not sufficient to understand these structural behaviors. Complementary advanced numerical models are needed to simulate the flexural behavior of CFT to expand the experimental research and develop predictive tools required for design and evaluation of structural systems.
In this paper, a finite element model for CFT subjected to bending was developed. The confinement effects, composite action, and flexural behavior predicted by the proposed finite element model for CFT were verified by comparing with experimental results. A rationality is observed between the results of numerical calculations and experiments.
This model is used to make comparisons with conventinal I steel girder model and showed a relatively good ductility of CFT girder.
Keywords: CFT girders. Abacus, urban area TS. Ding Dang Tung
Khoa Ky Thugt Xay Ddng, Trfldng D^i Hoc Bach Khoa - Dgi Hoc Quoc Gia Tp.HCM Email: [email protected] Dien thoai: 0979 134 725
Th-S. Nguyin Quoc Tien
Hpc vien cao hpc, Khoa ky thuat Xay ddng, Trddng Dai Hoc Bach Khoa - Dgi Hoc Quoc Gia Tp.HCM
Email: Dien thoai:....
1. Giori thieu
M6theth6ngcau lifin hoptfiep-betdng mdi da dUOc phat trien sd dung ong th^p nhU cac dam chinh, the hi^n trong Hinh 1 a, B6 t6rg duac nhoi ben trong cac dam 6ng 3i tang cudng do cdng u6n being each ngan chan mJt on dinh cue bp cua thep tam chiu nen. Cdc dam ong thep nhdl be tong cung duoc dii kiln se gi3m mdc do tieng fin vi 36 rung gSy ra b^'
hoattii [11^ ' ~
(lb) Cfng dung trong thuc te.
Ifinhl.HMhdngcludlmCFT
l3ng thep duoc sin xuit tai nha miy ^ giSm so lu'png cac qui trinh han va chi phlchf tao. Mpt luong hlin nhd 1^ dCi de lam cho chung thanh cac dam cau. Do d d , no kinh te so vi^ cic
96IBDDIE193 9-2015
BSng 1. M l u thCr (Thfip ong SS400, D/t = 56.4)
Bang 1. M§u t h d (Thep dng SS400, D/t = 56.4)
" i t lieu nhdl Khda lifin k i t co hpc BOO-N-N
BCF-N-N
O n g t h e p Be t 6 n g t h u d n g
( f . = 27 MPa)
V d a k h d n g k h i {f= = 8MPa)
dSm t h ^ p tam thong thu'dng ma can sd lu'png han cUc Idn vl bin canh va bin bung dUoc han todn bd vi nhieu sudn tang cu'dng cung dupc hdn vdi b i n bung. Cac dam dng dUpc nhdi vdi dc vat lieu be t d n g khac nhau tdy thudc vao vj tri tren nhip. Dam dng gan cac gdi trung gian (chiu m d men udn am) dupc nhdi vdi b e t d n g sd dung cdt lieu nhe vdi khdi lu'png rieng khoang 1.5 T/m^ hoac bfi tdng thu'dng (2.4 T/m'), trong khi dd n d duoc nhdl bang vUa khdng khi (vCa nhe trdn vdi bpt khi cd khdi lUpng rieng thap khodng 1.0 T/m^) tai v i i n g giCfa nhip (chju mfi men udn duong) de gidm trpng lupng b^n than.
Ddm se lam viec nhU mfit dam lifin hop trong vung mfi men ufin duang d gida nhip. Cac tdm bfi tdng duac tya tren cac dam ong va k4t nfii vdi lifin ket chju cdt dupc han phia trfin cCia ddm dng. Trong vung mo men udn im quanh gdi trung glan, bdn bfi t 6 n g t r d nfin chiu kfio vi chl cd cdt thfip chdng lai lUc keo. Luong cdt t h i p d u duoc s d d u n g de han che cac vet ndt be tdng cua bdn, va cac lien ket chiu cdt du'oc han tren ddm fing. Han nO'a, cac spi thep dUpc trfin trong bfi tfing bdn di giSm t h i l u c^c v l t ndt bfi tdng, mh do d d cdi thifin dfi ben cua bSn.
He t h d n g cdu mdi nay da dUPc de xuat va I p dicing cho cdu cda Shinkansen (tuyen dudng sdt cao tdc cda Nhdt Bin) va dupc hoan thanh vho nSm 2000 (Hinh 1 b). Cdu bao gdm ba nhip ddm lien tuc vdi mol chieu dai nhip khodng 34~36m. Be ngoai cd v^ khac vdi cac dam thep tdm t h d n g thudng nhutig dep ve mat tham my.
C h l tao va xiy dung mdt 15 thang. Tong trong lupng chi bdng mdt nda cau bfi tfing thdng thudng vd chi p h i xay dung thap hPn dang ke so vdi cdu d u d n g sdt thfing thudng[1].
2 . Mdt s6 kit qui nghifin cdu t h d c nghifim 2,7 Thinghiim cuaJae-Yoon Kang vd cong sU (2007) xem xit dnh hudng cOa cudng do chiu nen cua v^t liiu nhoi den Ctng xCl udn cCia dSm CFT
Trong trUdng hpp cau kien CFT chiu tdi udn, Ifii bi tdng khdng d trong trang thai dng sudt ba true, va tiet dien ldi be tdng duac chia thdnh cdc v i i n g nfin vd keo bdi true trung hoa.
Tuy nhlen, t^c ddng lien hop gida dng t h e p va bfi t d n g vdn kiem sodt viec tang cudng d d cua cdu ki?n CFT t r o n g c i c thudc tinh cdu true bdi sg chdm trS mdt dn djnh ben trong cua vd thep.
Trong nghifin cdu nay, cac dng x d udn cua CFT
vdi cudng d d chiu nen khac nhau ciia vat lifiu nhdl ben trong dupc nghien cdu bdi mot t h i nghiem uon bdn diem n h u Hlnh 2.
Hlnh 2 Thiet lap thiJ' nghiem uiin ban diem.
Thdng sfi t h i l t k l cho mau thi nghiem dUcc trinh bdy trong B i n g 1. Dudng cong tai trpng - dd vdng thu duoc t d cac t h i nghiem duoc the hien trong Hinh 3. Trong mdu BOO-N-N, sau khi thep chSy dfio, du'dng cong da t r d thanh phi t u y i n bdi sU lan rfing cOa vCing dfio. Khi tai i p dung dat den cue dai, tam thep chiu nen d phia trfin bi mdt dn dinh va tdi ap dung giam dot ngdt. Tuy nhien, cd mdt sU gia tang dang k l trong cUdng do chiu udn va dp deo cCia BCF- N-N so vdi dng thep rong. Cu'dng dp chjU udn cCia BCF-N-N cao hon 1.5 Idn so vdi BOO-N-N.
Su mat on dinh cue bfi Idn tai phfa chiu nfin khfing x l y ra cho mdu nay. Mo hlnh BMF-N-N nhfii vCfa khdng khi dng xii tUPng t u n h u ong rdng, BOO-N-N, trong sudt giai doan dau cua tai trpng. Trong trUdng hcjp cua BMF-N-N, tai trpng ap dung van cdn tiep tuc tang len den 1 2 Idn so vdi dinh t i i eua dng rdng, va trang thai mat on dinh thap hem cda cac dng rong Oieu dd cd nghia la bfi tdng nhdi ddng mdt vai trd quan trong trong viec han che hoae tri hoan sU mat dn djnh cue b d cda cac dng thep va tang do dfio va eUdng d p chju uon cCia dng. Dieu nay dupc biet bdi cdc ket qud t h d nghiem cua BMF-N-N rdng hifiu dng kiem che nay cd the dat dUoc khi vat lieu nhdi cd eUdng dd thap [2].
2 2 Thi nghiem cOa Nazanin Mossahebi vd cgng su (2004)
N h u t h e hien trong Hlnh 4, mdu t h d n g h i e m la mdt dam nhip don gidn. Mdu bao g d m mdt dng thfip ASTM A714-99 Class 4 Grade VII dai 8.929 m. De g i l m trpng luong, mfit doan dng nhua PVC 152.4 m m SCHED 40 duoc dat bfin trong dng. Di t3ng khd nang chiu keo cua dam, ba thanh cdt thep # 6 Grade 60 duoe dat d phia dudi cua dng, nhu the hien trong Hinh 4. Hai hang dinh tan ehiu cdt tren ddu eua dng thfip dpc theo cdu kien de cung cap tdc dung lien hop gida dng va bdn bfi tfing. Cudng d d nfin 28 ngay eua be tdng bfin trong fing la 43.8 MPa;
eua b i n mat cau la 37.1 MPa.
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Hlnh 3. Mai quan he tai trong-do vong trong cac thd nghiem uon.
Hlnh 4. Mat dtmiu va tii trong (mm).
Hlnh 5 cho thdy bieu dfi tdi trpng - do vong quan s i t d u p c Mdu cho thdy mdt mdc d d dfio tfit trudc khi phd hdy. Quan hfi t l i trong - dd vong CLia hfi thdng 11 gdn n h u tuyen tinh eho 3in khi mdt dd vdng l i 47 m m dat dUpc, tuang dng vdi t l i i p dung l i 621.38 kN. Phdn tich da chi ra rang phia dudi ciing cda fing thep s e c h l y d mdc t i i nay, dieu nay dUpc xdc nhan bdi ket q u i thu dupe t d c i c t h i ^ t bj do bien dang. Khi t i l dat 711.68 kN mdt sd vet ndt do udn da dupc quan s i t d dUdi cung eua b i n bfi t d n g , chi ra rang true trung hda la thUe sU ndm trong b i n . Tai trong ap dung toi da dat dUpc lue do vong thang ddng k h o i n g 95.5 m m , tUong dng vdi tai trpng 783.4 kN. Sau khi mau dat tdi khd nang uon cudi cung cua nd ( t i l trong 783.4 kN tai do vong 95.5 mm) da cd sU sut g i l m tdi i p dung triing hap vdi su fip vd cue bd eua ban be t d n g . Su g l i m k h i nang udn nay l i cd the do sU ep vd ciia bin mat eau. Tuy nhifin, sau sU kifin nay, mdu cd the hap t h u them dd vong d mdc t i l da giam. Dd vdng tdl da la 123 7 mm, xdy ra sau khi ep vd thfim bdn be tdng va lan gldm t h d hai eua t i l i p dung, xufing cdn 579.6 kN. Mdc t i i g i i m tuang dng vdi k h i nang chiu ufin cCia bfi tdng nhdl trong dng thfip trong khi khdng ed bdn mat cau. Hfi thdng duoc d d t l i v i o t h d i diem nay. Nghien cdu trude day chi ra rdng c i c cdu kifin dng nhdi be tdng cd dp deo tuyfit vdi va cd t h i duy tri khd nang chju udn cua chung d mdc d p dfio rat cao. D i ^ u n i y cd the cung cap mdt Idi gidi thfch cho c i c mdu t h d nghiem efi khd n i n g duy tri mdt mdc tdi sau khi ep v d bdn mat cau [3].
9.2015 nnnfciHBBi tk-.
H'inh 5 K^t qui til trong -do vong tiiM nghidm tai tdi han.
3. Co s d ph&n tfch k ^ t c£u dSm d n g t h ^ p n h d i h& t d n g b ^ n g m d l i i n h p h a n t d h u t i h a n Trong ITnh vuc ky thuat ket cdu, ket q u i phdn tfch phdn t d hOu han efi the cung cap thfing tin ehi tiet ve dng sudt va su phdn bd bi^n dang trong k i t cdu Nhu'ng t h d n g t i n nay khdng de d i n g efi sdn Xil c i c thUc nghiem, va do dd, nghien cdu sd cd t h e duoc sd d u n g nham eung cdp dQ lifiu bd sung de edi thien sU hieu biet Han nda, dc nghien cdu t h a m sd ve m d hinh phdn t d hdu han cd the dupe thuc hien de nang eao hieu qud t h i l t k l ket edu.
3.1 Md hinh s6 vdt liiu
Mfii quan h^ dng suat - bien dang cho thep dupc minh hpa trong Hinh 6a. M d d u n dan hdi Es xdp xi bdng 200000 MPa; he sd Poisson us da dupc t h i l t Idp bdng 0.3. Cfng x d deo cua thep ban ddu tai fy. \Jng sudt ciia thep vdn d fy sang m d t b i l n dang bdng 10 Idn bien dang c h i y eda thfip (Esy), sau dd dng sudt tang Ifin den f u . B i l n dang tUOng dng vdi fu dUpc xdp xi bdng 0.1, n h u t h i hi§n trong Hinh 6 D l m d hlnh thfip, tifiu chudn chdy dfio Von-Mlses vd quy ludt t i l b i n ddng hudng duoc sd dung. Khdi luong rifing cua thfip duoc lay bdng 7.85E-9 T / m m \
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Hlnh 6. MOI quan h^ ilng suat bien dang M d hinh bfi tdng pha hoai deo dupc lUa
{7b) Dam CFT co ban be tong
ih7 Mo hlnh phan tuihuli han
(8a) BOO-N-N
(Be) BMF-N-N sosanhvfii ket qua thuc nghiem Hlnh 8. Moi quan he tailrong-do vong cua mfi hlnh
ehon cho p h i n tich sd trong nghien edu ndy.
Mdi quan hfi dng suat - bien dang dan true v i eae d i e tinh khac cua be tdng da duac lua ehon dua trfin e i e nghien cdu trudc va dudng eong duac the hien trong Hinh 6b. Bien dang tuang dng vdi eUdng dd nen cua be t d n g E'C da dupe Idy la 0.003 Gia tri eua dng sudt gidi han tUPng dng da dupe lay bdng O.Sf'c va mo d u n d i n hdi ban ddu cua be tdng Ec duoc tinh bang:
Ec = 4 7 0 0 ^ (MPa) (1) Mdi quan he uhg suat b i l n dang cda bfi
tdng chju nen duac x i c djnh:
i+(n+«E-2X=c/8'£)-pn-iX£, ,.;f
ig dd R v i F i:
R E ( R ^ - I ) 1
Trong dd R v i R^ dUOc tinh bdng c i c phuang trinh sau:
(8b) BCF-N-N
Trong phUOng trinh (3) va (4), Re v i Ro l i bdng 4, theo Idiuyen e i o cila Hu v i Schnobrich [41. Cudng d p keo cda bfi tdng f t la xdp xl 9%
cua cudng d d nen bfi tdng f e . Cic dng xd sau ^ pha huy cua be t d n g chiu keo bao g d m su t i n g ciitig keo, eho phep dng x d hda m l m b i l n dang eua be t d n g . G i i djnh idng cac iUng sudt kfio g i i m x u f i n g bang khdng, vdi tdng bien dang 0.001, theo khuyen c i o cua Abaqus vd the hien trong Hinh 6b. He sd Poisson cda bfi tdng uc ^ dupe lay bdng 0.2. Khfii lupng rifing cCia bfi tdng ^^
dupe lay bdng 2.4E-9 T / m m ' .
Ngoai ra, vdi vat lieu be tfing thdng sfi goc truang nd (delition angle] ip rdt quan trpng trong vific m d phdng iJYig x d cua bfi tdng d tr^ng thi^t tang d p edng sau deo. G i i tri gdc trUong n d d i i i p ^ lay bdng 20° dUa tren c i e nghifin cdu da cd [4]. " •
3.1 Mo hinh phdn tiyhduhan Su t u a n g tac giCte t h e p va be tdng duoc m d hinh vdi m o hinh t i e p xuc dua tren ma sit Coulomb theo hu'dng t i e p t u y i n [5) Md hinh t i l p xue nay dUa trfin m d t mdi quan hfi master- slave; Mat bfin trong dng thep la b l mat master, mat bfin n g o i i Idi bfi t d n g la be m i t slave. Bi mat master dupe phfip x i m ^ - ^ (2) nhap b l mat slave, nhung ••
f R ( e c / e ' t J khdng p h l i ngupc lai. Ma sit Coulomb xac djnh trupt khi
(«.-'/
edt tucmg d u o n g vUcrt qud cdc dng sudt cdt tdl J i han. Trong nghien cdu nay, he so ma s i t 0.47 da duoc lua chpn difa tren nghifin cdu trudc [4! vd
98Q0niEDBQ3l^-2<*l^
so sdnh vdi ket q u i t h d nghiem.
Phdn tCr ran 8 nut (C3D8R) da dupe sd dung d l mfi hinh dng thfip v i be t d n g nhdi. Phdn ldi cda bfi t d n g duac m d hlnh vdi phdn t d rdn 6 nut hinh nfim C3D6. Sd dung p h u o n g p h i p Dynamic/Explicit de t i l n hdnh phan tfch m d hinh. Thdng sd hlnh hpc phi tuyen NLGEOM da duoc kich hoat d l g i l i q u y l t cac p h i n tich c h u y i n vj Idn.
4. Ket q u d p h d n t i c h v ^ d a n h gia 4.1 Mo phong thi nghiem cua Jae-Yoon Kang vd cdng su (2007)
khdng cd ddu hifiu t l i trpng g i i m xuong {khfing xet d i n mat dn djnh cCia dng thep).
4.2 Md phdng thi nghiim cOa Nazanin Mossahebi vd cong sU (2004)
Hlnh 9. So sinh ducmg cong moi quan he tii trong dfi vong giQa cac mo hlnh
Oudng cong t l i trpng - d d vdng cua m d hlnh so vdi ket qud thuc nghiem nhusau:
(1) Md hinh dng thfip rdng BOO-N-N (Hlnh 8a):
d giai doan ddu ci^a m i l n dan hdi, t i i trpng nhd (dudl 300kN) ket qud khdng cd sU chfinh Ifich ddng ke; d g i a i doan cudi eua mien d i n hdi, tdi trpng gdn dat tdi han (td 300kN den 700kN) md hlnh cd do cdng Idn hOn, ddu hieu phi t u y i n xudt h i | n tre han. CS giai doan phi t u y i n , t l i trpng dat tdi han (idn hon 700kN), md hlnh cho k i t q u i dinh t i l thdp hon so vdi thuc nghifim khodng 3%.
(2) Md hinh dng thfip nhfii bfi t d n g BCF-N-N (Hinh 8b]:
d giai doan ddu cua m i l n dan hdi, t i i trong nhfi (dudl 700kN] k i t qud khdng cd su chfinh l?ch d i n g ke; d giai do^n eudi cua mien ddn hdi, t l i trong gan dat tdi han (td 700kN den 11 OOkN) mfi hinh cd dd cdng nhd hon, dau hifiu phi t u y i n xuat hi^n sdm hOn. Cl gial doan phi t u y i n , tdi t r p n g dat tdi han (khoang 11 OOkN], md hinh eho ket qud dinh t i i thdp han so vdi thyc nghifim khodng 10%, khdng cd ddu hieu tdi trpng giam xudng (khdng xet den m i t fin dinh cda dng thep).
(3) M6 hlnh fing thfip nhfii vQa BMF-N-N (Hinh 8e):
d giai doan ddu eua m i l n dan hdi, t l i trpng nhd (dudi 700kN) k i t qud khdng cd su chfinh leeh d i n g ke; d giai doan eudi cCia mien d i n hdi, t i i trpng gdn dat tdi han (td 700kN den 900kN) md hlnh c d d d cdng nhd han, ddu hieu phi tuyen xuat hifin sdm han. (3 giai doan phi t u y i n , t i i trong d?t tdi han (Idn hon 900kN), md hinh cho k i t qud dinh tdl thap han so vdi thuc nghifim khodng 7%,
Hlnh 10. MOI quan he tai trgng-do vong cua m6 hlnh dam cau CFT so sanh vdt ket qui thuc nghiem.
Dudng cong tdi trong - d d vdng eua m d hlnh so vdi ket qua thUc nghiem nhU sau: Cf giai doan dau eda mien dan hoi, t i i trpng nhd (dudi 700kN) ket q u i khdng cd sU chenh Ifich d i n g ke; d giai doan sau CLia m i l n d i n hfii, t i i trong gdn dat tdi hzin (Idn han 700kN) mo hlnh cd d p cdng nhd hpn, dau hieu phi tuyen xuat hifin sdm hon, k i t qua dinh tai thap hon so vdi thUc nghiem k h o i n g 8%, khdng ed ddu hieu t i i trong g i l m xuong (khdng xet d i n mdt dn dinh cua dng thep).
4.3 So sdnh ddm cau ong thip nhdi bi tdng vd ddm I truyin thong
Sd dung md hlnh dam cau dng thfip nhdi be tdng da dUpc thiet lap khi md phdng t h i nghiem eua Nazanin Mossahebi va cdng sU (2004), d l l u ehinh tiet dien ldi be tdng (khdng l i m rong).Tinh t o l n dd cdng hCTu hieu Eleff cCia m a t c d t d d m e d u o n g thfip nhfii bfi tdng. Sau do tien h i n h chpn mat cdt dam I cd d d cdng hQu hieu tUOng dUOng de phan tich. Cdc thdng sd cua ban be tdng phfa tren dupe g i d nguyen.
(ilnh 11 MOI quan he lai irong-do vdng cua roo hlnh dam cauCFivadaml.
DUcmg cong tai trong - d d vdng eua mfi hinh dam CFT so vdi dam I truyen thdng nhusau:
0 giai doan dau cua mien d i n hdi, tdi trong nhfi (dudl SOOkN) k i t q u i khdng ed sU chenh Ifich dang k l ; d giai doan sau cua m i l n d i n hdi, t i i trong gan dat tdl han (Idn hOn SOOkN) md hlnh dam CFT cd dd cdng nhfi hen, ddu hieu phi
tuyen xuat hifin sdm hon, tuy nhifin khi tdi trong dat tdl k h o i n g lOOOkN thi dam CFT cho thdy mdt dp dfio cao va van duy tri cudng d d (dieu nay phd htjp vdi eac nghifin cuU trUdc [4]), khi d d d p vdng ddm CFT thap hon so vdi dam I k h o i n g 10.5%, ddm I xuat hifin ddu hieu mat dn ^ n h tdng the. Mat khic, cd mdt diem luu y nifa la mdc du CO ciing hai mat cat ngang cd ciing d p edng nhung dam CFT cd trong luong b i n than Idn han so vdi ddm I. Dieu n i y dU k i l n sfi Idm cho dam thep nhdl be tdng cd the g i l m mdc d p tieng dn va dfi rung cua cdu gay ra bdi glao thdng.
5. K i t l u | n
Trong nghien edu nay, cde dng x d chiu udn ciia dam dng thep nhdi betdng bSng phdn m l m phdn t d hdu han Abaqus da dUOc thUc hien. Cic md hlnh sd bao gdm fing thep rdng, dng thfip nhfii vda cudng do thap, dng thfip nhdi be tdng cudng do binh thudng va dng thfip nhdl bfi tfing vdi bdn be tfing phia tren nhU mdt dam cau da dupe thiet l i p va x i c minh vdi c i c ket q u i thUC nghldm dupe cfing bd trUdc do.
Qng xdcp hoc ciia fing thfip nhfii bfi tdng chiu dnh hudng bdi cudng dd bfi tdng. SU hifin difin eiia be tdng nhdi lam keo dai pham vi dfio cua dng thep rdng. Cudng dd chiu udn ciia dng thep nhdi be tdng cao han 56% so vdi eUdng d p chju udn ciia fing thep rdng, edn eUdng do chju udn ciia fing thep nhfii vii'a cudng dp thap eao han 32%
so vdi cudng dd chiu ufin cCia fing thfip rong. D i l u ndy cho thdy be tong nhdi ddng vai trd quan trong trong viec tang dd deo va cUdng do chju udn ciia dng thep rong. Mat k h i c viee sd dung vda cUdng dfithdpcdthe lam giimtrong lupng b i n thanddm ma van d i m b i o k h i tot k h i nang chju udn.
Vific sd dung ddm dng thep nhdi be tdng nhu mdt ddm cau thay the cho dam I t r u y i n thdng cung da dupe xem xfit. Tren ea sd hai t i l t difin ddm cd cung do edng El, k i t q u i cho thay dam dng thep nhdi bfi tdng cd mdt do deo k h i quan so vdi dam I.
Ngoai ra dng x d cua dam cdu CFT khi Idp dat cap d u dng lUc v i o ben trong Idi be t d n g sfi duoc tiep tuc nghifin cdu.
TAILIEUTHAMKHAO
[1] Shun-ichi Nakamura et al - New technologies of steel/
concrete composite bndges. Joumal of Constiucdonal Steel Research 58 (2002) 9 9 - 1 3 0 .
[2] Jae-Yoon Kang et al - Flexural Behavior of Concrete- Filled Steel Tube Members and Its Application Steel StruPures 7(2007)319-324,
13] Nazanin Mossahebi, Aaron Yakel. Atorod Azizinamini, Experimental investigation of a b n d g e g l r d e r m a d e o f steel tube filled with concrete, Joumal of Constnictional Steel Research 61 (2005)371-386.
[4] Jiho Mool et al - Analytical modeling of bending of drcular concrete-filled steel tubes. Engineering Structures 42 (2012)349-361,
[5] 5aren Hansen, "Numerical and Expenmental Study of PaitialiyConcrete-Fiiled Circular Steel Sections^ Master's Thesis, FacuityofEngineenng and Science Aalborg University, 2011.
