KHOA H O C - C d N G N G H l
P h a n tich a n h htf&ng cua cac tham so'
he lien k e t ngang d e n dn dinh cua d a m t h e p m a t cat I trong giai d o a n thi cong
bang phtftfng p h a p p h a n i& hffu h a n
• ThS. N G U Y E N T H A C H B,1CH
• T S . N G U Y E N H O U T H U A N Trddng Dgl hgc Giao thdng van tii
Tdm tat: Bai bao gidi thi$u mdt so kit qui nghidn edu inh hddng eua hg lien kit ngang den khi nang on dmh cua dam thep ddi (hai dam chu) dddi tdc dgng cua tii trgng thi cdng. Trong dd, inh hddng cua cdc tham so cua h$ lidn ket ngang nhdvi tri, ciu tgo, dg cdng, si Idtfng cda hg lidn kit ngang din dng xd cua dam ehu trpng gia dogn lap ghdp ddtfc phdn tich, ddnh gid bing phddng phdp phin td hdu hgn (PTHH).
Tii khoa: Dim thdp ddi, lidn kit ngang, phan td hdu hgn.
Abstract: This paper presents the results of a study on influence of beam cross-frame to the stability for l-gider system underr erection.
Which, the influence of the parameters of cross-frame systems: The location, structure, hardness, the number of cross-frame systems to behavior of l-GIRDER in stage of construction is analyzed, evaluated using of finite Element method.
Keywords: Double steel tjeams, cross- linked, finite element.
I . M d d i u
Kfl't cau nhjp cau thep dupc sis dgng tU l i u v i ngay cang rpng^ral d Viet Nam va tren the gidi. 6 Vlflt Narn, cd the k l den nhieu c i y c i u noi t i l n g silf dgng kfl't c i u nhip e i u thep nhU: C i u Long Bidn, cau Trang Tien, cau ChUdng DUOng, cau sflng H i n , cau Dudng... Trong tUdng lai, kfl't cau nhjp e i u thep se ngay c i n g duoe sd dung rdng r i i hdn nda do nhdng uu d i l m ndi b i t ciia nd [1,2]. Hifln nay, viee lua chgn kfl't cau nhjp dam thep n g i y c i n g dupe ehu trgng dgc biflt cho cac cau khu vgc do thi do nhung uu diem eua nd nhu thi eflng nhanh, ket cau thanh m i n h , d l t h i o dd... Trong dd, cau dam thep hai dam chu (cau d i m thep ddi) la mgt trong nhdng dgng kdt e i u duoc dng dung tuong ddi pho bien trong cau thep. Tuy nhifln, viec tfnh t o i n , thidt ke, thi cong cau d i m thep noi Chung va e i u d i m thep dfli ndi riflng eung edn ton tgi nhiflu v i n d l can dupe g i i i quydt. Ket c i u d i m thep thdng thudng dupe thi cdng theo trinh tU: C h d tgo c i c dogn dam trong nha m i y , v i n c h u y i n ra
cdng trudng Idp g h e p , cau lap c i c d i m chii gac Idn m d , trg c a u , lifln kdt, lap d i t c i c hfl lifln k^t gida e i e dam c h u , d l bd tdng mat cau [1,2],
Trong giai doan thi cflng e i u dam thep tl4i3i an nhieu rui ro vi ket eau trong giai doan naychiJa ed day du t i t e i e i e bg phan, chi tidt, k h i nang chju luc la chPa h o i n chtnh. Hon nda, trong giai doan thi cdng, so d d kfl't c i ' u , so dd t i i trpng (thi cdng) lufln luon thay ddi. Do vay, trang thai chju lgc cua kdt eau eung thay ddi theo tUng giai dogn thi cong. VI v i y , e i e dng x d c u a d i m thep trong giai dogn thi cdng can phai dac biflt chii y. Bai bao tap trung p h i n tieh k h i nang mat dn djnh t i n g th^
cua dam thep mat c i t I trong giai dogn nay diidi t i c d y n g c u a t i i trpng thi edng [3].
2. C i ' u t g o v i y d u c d u cCia he l i d n ket ngang He lien kd't ngang trong c i u d i m thep cd vai trd chu ydu la d l lien kd't cac d i m c h u , p h i n phfii' dieu hda tai trgng cho cac d a m . H d lifln kfl't ngang thudng dupe c a u tgo hai d a n g chinh la hfl thanh hoac dam d i e , tuy thupc vao k h o i n g cac dam ehii ma ed the cau tao khae nhau [1,2,3].
a, b)' Dang thanh; c) - D$ng dam dSc; d) - D^ng h5 hflp Hinh 2.1: Ciu tgo mdt si dang h$ lien kit ngang dam thdp
Cac bg p h i n eCia lidn kdt ngang p h i l dim bao dieu kifln d ^ m i n h de truyen dupc t i i trpng ngang [2], eg the la: Vdi cac bg p h i n chju keo: L/f
< 240; vdi cac bp p h i n chju n e n : K . L / r £ l 4 0 . Trong do: L - Chidu dai khung giang (mm); r - B i n kinh quan tinh nhd nhat (mm); K - He s d chieu d i i hieu dung (vdi lien kdt h i n 6 hai d i u thi K = 0 75- v^i lifln ket chdt d hai^diu thi K = 0,875).
3. K h i nang d n djnh cDa h$ thdng d a m ddi Hau hdt cac nghifln cdu ve dn djnh c u a cSu
64
KHOA HOC-CdNGNGHl
ddm thep ddu nhdn mgnh ddn khi ning lim vide v i khi nang chiu t i i trpng ciia tdng dam ddn bdn trong hfl thdng dam [4]. Hai nhi nghifln cUu Yura v i Widignto [5] da chi ra rang, khi ning dn djnh chju xoin ciia dam phy thuge chit che vio khoing each gida hai dam chii, vio ehilu nhjp, dd cdng cua hfl lifln kdt ngang v i v i t lidu thep sd dyng. Cdng thdc xac dinh khi ning chfu xoan eua dim trong hfl thdng dim ddi gian don nhu sau thudng dugc sd dyng [5]:
" . - ^ j w (1) Trong do:
- C[, - Hd sd didu chinh md-men xoin;
- S - Khoing each gida hai dim chii;
- E - Mfl-dun d i n hoi eCia vat lidu;
- L - Chieu dai cua dim thep;
-1^,1^ - Mo-men quin tinh ciia mit c i t vdi true Ox v i Oy.
Ben canh viflc xic djnh dUpc md-men chdng xoin eho dim, Yura cung ditim ra duoc chidu d i i ldn nhdt eda dim don d l dim bao dn dinh tong t h i cho dim [5]:
h.c.ji'-S£Ai, 1, (2) Trong dd:
- W - T i i trgng ban thin dam.
4. Phan tfch inh hddng cCia hp Jidn ket ngang den khi nang on dinh cda dam thep bang phddng phip PTHH
Trong mfl hinh niy thi he lien kdt ngang v i sUdn dam dugc md hinh hda l i phin td thanh, cdn hai bin einh dam duoe mo hinh hda l i phin td tdm [6,7]. Md hinh hda he lien kdt ngang: Tuy thudc vio eiu tgo he lifln kfl't ngang m i iga chpn md hinh phu hpp, vdi hfl lifln k^ ngang he thanh, mdt hinh nhu H?n/) 4.nhudng duoc silf dgng [6,7], Md hinh t i i trong v i lifln ket gdi cUng duoe sd dgng nhu trong Hinh 4.2.
Hinh 4.2: Md hinh hda gii vd tii trgng Lda chgn cdc thdng si md hinh phdn tich:
Bii bio iga chgn md hinh hda cho trudng hgp ciu dim thep hai dim ehii, nhjp giin dPn, hfl lien kdt ngang dUdi dgng hfl thanh. T i i trgng tie dyng l i trpng lUpng b i n thin va t i l trgng thi cdng r i i ddu (trgng lUpng b i n mit c i u , t i l trgng thi cdng).
D I x i t i n h hUdng ciia nhidu tham sd inh hudng, mflt sd md hinh PTHH d i ddpc phin tieh.
Cic he thdng ddm ddi eung vdi cic yeu
S6 12/2015 td kich thddc dupe khio sit, phin tich d nhieu trddng hpp kfl't edu de xuat. Bin eanh dim thay ddi td 305x25mm dfl'n 914x38mm v i bin sUdn td 1270x13 ddn 2400x17mm. Khoing each cCia dam td 1,83 den 4,27m. Nhjp dam L g i n bang Lmax (>90% d tat c i cic trudng hop. Ba logi he lidn kfl't ngang thep dupe sd dung (thep gdc): L26 X 26 X 5 (A = 767mm^), L152 x 152 x 13 (A = 2.jlx10''mm2), L203 x 203 x 22 (A = l.lxtO^mm^)]
de khio set anh hudng ciia do eUng khung giing ngang ddn kha ning oin xoan/ngang ciia cac hfl thdng dim ddi, bdi vi ndu nhu khoing each dim cd dinh thi do edng eda khung giing ngang phg thudc chinh vao hd lifln kdt ngang. Ngoii ra, hfl thdng dam ddi dude lap 2,3, 4 v i 9 hfl lifln kfl't ngang d l khio sit nhOng inh hudng ciia khoing each, so lugng hd lifln kfl't ngang den khi ning oan xoan ngang eiia cac hfl thdng.
V i t lidu thep l i M276, mfl-dun d i n hdi l i 2,1 GPa, va he sd Poisson (he sd bidn dgng ngang) la 0,30. T i i trgng thi cdng rii ddu dugc g i i thiet gii trj gip 1,5 lan trgng tai ciia dam (1,5Wsteel).
Nghidn edu sd dgng phan mem ABAQUS de md hinh hda cho hd thdng dim ddi v i tidn hanh phin tich v i Idy sd lieu vfl dp oan cua dam dddi t i c dyng eiia t i i trpng thi eflng. Trong m6i mfl hinh PTHH, md-men gidi hgn M^^^ ddpc xie djnh, qua dd so sinh tuong ddi vdi md-men gidi han theo cflng thUe cOa Yura (edng thdc (1)).
5. Ket qui phan ti'ch
Phin tich oan xoin da duoc tidn hanh trfln cac nhdm cic mfl hinh hai dam vdi mpt t i i ben ngoii 1,5 lan trgng lugng bin than. So lugng lien ket ngang quyflt djnh ddn khoing each gida Chung. NOi chuyen ngang Idn nhat xiy ra tgi gida nhjp, nhd the hien trong hinh dUdi (Hinh 5.1):
Hinh 5.1: Do oan xoan cua h$ thing dim ddi trong md hinh PTHH
Anh hddng cOa kfch thddc bin canh dam chu:
Tat c i cic kdt qui PEA (trong md hinh PTHH) la nho hon so vdi giii phip ly thuyet ciia Yura (M^^y Mg<100%).
Hill
Hinh 5.2: Anh hudng cua idch thadc bin canh dam th6p dSn i<ha nang dn djnh cda dam
65
KHOA HOC - C O N G N G H E
Anh hddng cda khoing each he lien ket ngang.
Theo kdt q u i ciia nhi nghifln edu Yura kd't hpp vdi cac ket qua thu ddpc td viec tinh toin hd lifln kdt ngang bang phdOng phap PTHH thi khoing each gida cic lien ket ngang dupc khuyen cao phii cd ft nhat 2 hd lifln kdt ngang hoac khoang cich giC^a eie hfl lifln kdt ngang < 25% L de dim bio khi ning on djnh cua ddi dam. Ket qua dd dugc the hifln bang bieu dd sau:
i:-
Hinh 5.3: Anh hddng eua khoang cdeh hd lidn kit ngang Idn hg thong dam
Anh hddng cua dien tich he lien ket ngang:Tis kdt qua mo hinh tinh toin he lifln kdt ngang, inh hudng cua tidt didn hd lien ket ngang dupe the hien qua bilu do dUdi diy: Bilu d6 trfln chl tinh cho he 2 giang ngang. Vdi hfl 3, 4, 9 giang ngang iam tUPng tg.
Theo kit q u i phin tfeh 6 tren ta thd'y tiet difln ciia hfl lidn kdt ngang cd inh hudng khflng ding k l ddn khi nang khi nang dn djnh ciia hfl thdng ddi dim.
mil
Hinh 5.4: Anh hddng eua di$n tfch mgt cat ngang hd Udn kit den klii ndng in dinh cua hg dam
Anh hudng cua dp cdng hd lidn kit ngang:
Dd cdng ciia hfl lifln ket ngang dugc xac djnh bing cong thdc:
Trong do:
- \ - Tiet difln he lifln kdt ngang;
-i_ =4fi+S' - Chidu d i i cOa he lifln kdt ngang;
- S - Khoing cich gida cic dam chu;
- \ - Khoing cich gida 2 tim bin canh dam;
- E - Md-dun dan hoi cua v i t liflu.
Anh hudng cua do cdng ciia hfl lifln kdt nggng dupc thd hifln qua bieu do sau:
]..
, S r . , , f - • • • 1
IX ^ •
Hinh 5.5: Anh hudng cua dg citng h$ ii§n Itet ngang den kha nSng dn dfnh cua d&m
6. K A luan va l<len ngiii
Viec tinh toan anti hudng cOa he li§n l<St ngang dSn kha nang on dmh cija he thdng dam doi duoc tign hanh trSn sif thay dSi cua cac tham so. Qua V.i\. qua thong ke, ta co cac ket luan sau:
- Kfch thudc dam ngang inh huflng kh6ng dang ke so vdi do ciJng den kha nang chdng xoan va chdng udn cua ddi dam.
- HS thdng dSm ddi se cd kha nang chdng udn It nhat bing 91% theo cdng thurc cDa Yura vdi 3 hoSc nhidu hon 3 dam ngang, nhung ch? cdn til 70 - 83% theo cdng thdc cda Yura ndu ch? cd 2 d£m ngang.
- Vdi he thdng i&m ddi, chidu dii nh|p phil nhd hdn L^^, neu khdng hd thdng se mit dn djnh ngay c i vdHcac khoing each tdt nhat va dd cdnj tdt nhat cda dam ngang.
- Ddi vdi hd thdng dim ddi trong qua trinh ttii cdng, ft nhat phii cd 2 dam ngang d l dn djnh, kill chidu dai nhjp gan L,„^.
- L > 95% l-,„„thi can it nhi't phii 3 dim trd len.
- Khoing cich tdi da giOa cac dim ngang la 25% L „ „ Q
Tii li^u tham l<hio
[1]. PGS. TS. Tran Bde Nhiem, BAI giing Ch thep phin 1, phan 2.
[2]. Tieu chuin thlSt ki ciu, 22 TCN 272-05.
[3]. Steel Bridge Design Handbooi( - Bracing System Design, 2012.
[4]. Coffelt, Sean Justin (2010), Stability Analysis of Single and Double Steel Girders during Construction.
[5]. Yura, J. A., and J. A. Widianto (2006), Lateral Buckling and Bracing of Beams: A He- evaluation After the Marcy Bridge Collapse, Proc.
Structural Stability Research Council, Montreal, pp. 277-294.
[6]. Trudng Bai hoc GTVT (2009), Luan vin Thac sy - Nguyen Van VTnh, Ldp Cao hpc Xiy difng ciu hdm, khda 13.
[7]. Trudng Bai hoc GTVT (2010), Luin vin Thac sy - Nguyen HiJu Thuin, Ldp Cao hpc Xiy diJng ciu ham, khda 14.
[8]. V-Load Analysis (1984), In USS Highway structures Design hiandbook. Vol 1, AISC Marketing, Int., Chicago, IL, Chap 12, 1-56.
[9]. Guide Specification for Horizontally Curved Highway Bridges - American Association of state Highway and Transporttatlon Officials 444 North Capitol Street, N.W., Suite 249 Washington, D.C 2001.
Ngay nhan bai: 26/10/2015 Ngay cha'p nh|n dang: 15/11/2015 Ngudi ptiin bi^n: TS. Bui Tidn Thanh
TS. Hoang Vi#t Mil
66
