NGHIEN Cl/U AP DUNG CAU DAM LIEN TUC THEP BE TONG UEN HOP SLT DUNG CONG NGHE f)IEU C H I N H U N G
SUAT TREN TRU CHfNH TRONG QUA TRINH THI CONG
Nguyin Binh Ha
ABSTRACT
Contents of this paper presents stress regulating teclinology from piers for continuous span steel- conaete composite girder bridge, interactive calculating effect of creep with moment of inertia of concrete desk, determine flexural resistance in positive and negative regions according to 22TCN 272-05 Specification.
TS Nguyen Binh Ha
Tnrdng khoa Dao tao Sau dai hoc Tn/dng Dai hoc Xay dung Di dong: 0904014868, Email:[email protected].
O
di vdi cau dam thep lien hop vdi be tdng cdt thep, thdng thQdng ban be tdng cdt thep dQpc dat d bien tren vQa lam dQdng xe ehay vQa tham gia lam viec chju nen eung dam thep, tuy nhien ddi vdi nhjp lien tue thi tai vung chju md m e a u d n am ban be tdng se bj keo do tinh tai II va hoat tai..., do do d vung nay trong tieu ehuan 22TCN 272- 05 khdng xet sQ tham gia eua be tdng vao tiet dien. De tan dung kha nang lam vlec eua vat lieu can tien hanh thQc hien cae bien phap nen tam be tdng d vung se bj keo trong qua trinh thi edng, nham dam bao trong sudt thdi gian lam viee Qng suat trong b e t d n g ludn nen hoac phai nhd hon Qng s u i t keo cho phep eua b e t d n g .De dat dQpc muc tieu tren cd the cd nhieu bien phap, trong bai bao nay ehung tdi se trinh bay edng nghe dieu chinh Qng suat bang each kich tren tru chinh, kiem toan tiet dien theo tieu chuan 22TCN 272-05 va anh hudng tQ bie'n trong dam lien tuc dQpc xae djnh theo edng thQc ed xet den dp cQng udn cua ban BTCT
Cac budc thi edng ehinh
Cac bQde thi edng eau dam thep lien hop vdl ban be tdng cdt thep nhjp lien tuc nhQ sau (hinh 1 - vi du ddi vdi cau 3 nhjp):
1. Thi edng dam thep theo eae phQOng phap nhQ: lao keo dpc, cau lap...
2. Sau khi da thi cdng xong phan dam thep, tai vj tri cae tru ehinh tien hanh kich vdng cac dam mdt ehuyen vj A. Ke ed djnh vj tri dam.
3. D d be tdng ban mat cau trong pham vi chju md men udn am (do b e t d n g dot 1).
4. Sau khi be tdng dcrt 1 dat cQdng dp, tien hanh ha dam xudng vdi ehuyen vj A l . Ke glQ cd djnh vj tri nay, do be tdng phan edn lai (dd b e t d n g dcrt 2).
5. Ha dam xudng vdi ehuyen vi A2.
6. Thi cdng Idp phu mat cau, lan can va dat hoat tai.
Vdi trinh tQ thi cdng nhQ tren, chung ta thay rang sau khi kich dam vdng len vdi chuyen vj A, dam chju m d men udn am, do do toan bd bien tren eua dam thep chju keo, tiet dien lam viec ehi cd dam thep. Ha dam vdi ehuyen vj Al sau khi be tdng do dcrt 1 dat cQdng dp da tao ra mdt bieu do md men udn dQPng, md men nay se nen ban be tdng dQpc do trong dcrt 1, tie't dien lam viec cua dam bao gdm tiet dien dam thep va tiet dien lien hpp vdl thep va BTCT. Tie'n hanh do be tdng dpt 2 va sau khi be tdng dat cQdng dp se ha dam vdi ehuyen vj A2, tae dung cua budc nay se tie'p tuc nen ban be tdng trong phan do dcrt 1 va nen ban be tdng dd dpt 2, tiet dien lam viec la tiet dien lien hop. Chia lam hai dcrt ha dam nham dQa ban be tdng trong vung se chju md men duong tham gia lam viee eung vdi dam thep, do dd cd the giam dien tieh dam thep trong vung dd va dam bao ban be tdng khdng bj nen qua kha nang ehju iQe.
NhQ vay sau khi ket thue bude 5 biin be tdng trong vung ehju md men udn am da bj nen trQdc, Qng sua't trong ban be tdng bang tdng Qng suat sau hai dpt ha kich, Qng suat nay se dam bam ban be tdng se khdng bj keo qua kha nang ehju keo khi bj tac ddng eua tinh tai II va hoattai... Gia trj ehuyen vj eua A, A1,A2 phu thude vao tQng trQdng hpp eu the, tdng eua Al va A2 ed the bSng hoac khdng bang A.
Xac dinh anh hQdng eua tQ bien gay ra trong dam lien hpp lien tue
Trong ket cau lien hop giQa thep va be tdng cdt thep he sieu tinh, bien dang eua tQ bien khdng nhQng lam phan phdi lai Qng suat giQa thep va be tdng ma cdn phat sinh ra ndi iQc phu, do anh hQdng cua tQ bie'n phu thude vao thdi gian, nen npi luc nay cung thay ddi theo thdi gian. Bie'n dang cua tQ bien phu thudc vao tai trpng tae dung lau dai, trong khi tai trpng nay cQng lai phu thudc vao bie'n dang cua t d bien, do vay bai toan nay thudng phai giai theo phQong phap dung dan.
05.2011 ^Einimgii 6 3
^C[j<Hi XAY DUNG
1. Thi cong dam thep
2. Kich dat chuyen vi A
I Kfch dat c h u y e n vi A
3. Do' ban BTCT trong vijng chiu mo men uon am
T
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4. Ha kich vdi chuyen vi A l do BT phan con lai
u
i l
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u,
Plastic 1
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/nelostic Eiasric
^\^,^
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Hinh 2.Ba vung thie't ke eho cau kien ehiu uon
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5. Ha kich vdi chuyen vi A 2
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i
6. Thi cong tTnh tai 2 va dat hoat tai
r
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Hinh 1. Qua trinh thi cong dam lien tuc dieu chinh npi lUc bang kich tt(tru chinh
TrQdc tien chung ta xae dinh ndi iQc trong he vdl gla thie't he hoan toan dan hdi va bd qua anh hQdng eua tQ bien xae djnh duac Mj^jj, H^^.^, tQ do xae djnh dQpc Qng suat nen ban dau tai trpng tam ban be tdng \c^^^.
Can cQ Qng sua't nay xac dinh dupe Qng sua't bj mat mat do tQ bie'n f^
fc(o)
CR.
Vdi
0.5(t)K+S|,n+1
Skn ^
nc
•"ST"c
(1)
(2)
(3)
Trong do: cp^- He sd tQ bien; F^, 1^- Dien tich
va md men quan tinh eua phan be tdng tham gia lam viee cung dam thep; n^ = E^^E^; E^^ 1^.^- md dun dan hdi va md men quan tinh cua dam thep; E|.-mddun dan hdi be tdng; Z^^.^-Khoang each tQ trpng tam dam thep den trpng tam ban betdng. ^
Xae dinh bieu dd M — trong dam thep do
sQ phan phd[ laj_Qng sua't M j j =fc ^cj-c,s^ va cac bleu do M^, M2 (vi du vdi trQdng hpp 3 nhjp) doan iQedan vjX = 1,X = 1, tinh cac ehuyen vj:
A„c„^II«^d>c.
" - S ' ST
A.c„=Ij-rV^dx;
-dx;
M ' -dx;
(4)
(5)
(6)
(7)
(8)
• ^ S ' ST.C
Lap he phQong trinh ehinh tac:
: 0
8 „ X , " + 5 , , X f + A , „ = 0 (9) Giai he phQong trinh ehinh tae, xae djnh
dQOc eae an sd xj-'^.Xj'^TQdd xae djnh bieu do mdmen M"^" theo edng thQc:
M'^''=M,X5^'^+M2X^'^ (10)
Lfng suat tai tiet dien i do tai trpng va tQ bien:
— ^/lCR rTTCR .
' i ( O ) •
i.STC
(11)
Trong do tj^ ,i^^ Qng sua't do tai trpng, do tii
bie'n gay ra tai tiet dien i; '^Xstc - md men khang udn eua tiet dien lien hop khi tinh vdi md dun dan hdi ed hieu tai thd xem xet.
So sanh gia trj Qng sua't toan phan tinh dQpc vdi gia trj tinh lan trQdc, neu sai sd thoa man dieu kien eua yeu eau thi se dQng qua trinh tinh lap.
Kiem toan tiet dien dam theo md men Ddi vdi tieu ehuan 22TCN 272-05 sQc khang udn eua dam thep dupe kiem tra bang 4 dang pha hoai: Chay deo, dn djnh cue bd cua canh, dn djnh cue bd eua sQdn, dn djnh xoan ngang (dn djnh tdng the). Can cQ vao gia trj dp manh X so vdi Xp va \ (Xp < \ va la cae dp manh gidi han), khi thie't ke eae thanh phan eua ket ca'u thep dQpc phan lam ba vung: dan deo, phi dan hdi va dan hdi, eu the khi ty sd dp manh A < Xp tie't dien la dac ehae, sQdung md men kha nang ehju iQe la md men deo (Mp); khi ty sd dp manh Ap < A < A^ tie't dien la khdng dac chac sQ dung md men kha nang ehju iQe nhd hpn Mp nhQng Idn hon md men dan hdi (M ); khi ty sd dp manh tiet dien la manh A > A^ tinh toan theo dang hU hdng dan hdi.
Op manh A dQpc bleu dien dQdi dang cac ty sd: ddi vdi dn djnh cue bd eua canh la ty so giQa chieu rdng va chieu day cua eanh (b,/t,), ddi vdi dn djnh cue bp cua sQdn la ty sd giQa chieu cao sQdn trong vung ehju nen va chieu day SQdn (D^ / 1 J , ddi vdi dn dinh tong the la ty sd giQa khoang each eae lien ket ngang va ban kinh quan tinh eua tie't dien ban bien ehju nen va mdt phan ba chieu cao sQdn trong vung ehju nen(L^/rp.
Tiet dien dac ehae la tie't dien ed the sQdung toan bd md men deo M trQdc khi xay ra mat on djnh tdng the hoae cue bd.Tiet dien khdng dac ehae la tie't dien cd the sQ dung md men bang hoae Idn hon M^ nhQng nhd M hon trQdc khi
6 4 B^l^niUP^H 05.2011
xay ra mat dn djnh cue bd eua nhQng phan tQ ehiu nen. Tiet dien manh la tiet dien ma mdt trong cae phan tQ chju nen la cd dp manh Idn ma chung bj mat dn djnh cue bd trQdc khi m d men dat tdi M^.
Md men deo M se dQpc xac dinh thdng qua true trung hoa deo, d do iQc trong nhQng phan eua dam thep nhQ ban bien, SQdn dam se sQdung cQdng dp ehay deo (F ), edn trong phan be tdng la Qng sua't phan bd deu tren toan tie't dien vdi cQdng dp bang 0,85f'_..
Md men M la md men dan hdi nhd nha't cua tie't dien khi dupctinh trong giai doan dan hdi, M lay gia trj nhd hOn trong hai gia trj la md men dan hdi Idn nhat ddi vdi t h d ehju nen (M ^) hoae t h d ehju keo (M ) khi Qng suat tai eae t h d nay dat gia trj F, dQpc tinh nhQ sau:
M„ = Mm + Mnp + Mro + M
CONG NGHE IVICfl
"AD (12)
"y - " " D T
Trong dd: M^, - Md men do tinh tai tae dung len dam thep (phan tinh tai I); M^^- Md men do tTnh tai tae dung len dam lien hop (phan tTnh tai II); M^^, - Md men do hoat tai tae dung va gay ra ehay d bien dam thep, nhu vay:
f
M i n = Sr M, toi M D 2 Sn
M CR CR ST.C
(4-19)
Trong do: S^, S^, S'^^^^ la md men chdng udn eua bien dam (thQdng tinh eho e^ hai thd bien dam va ehpn gia tri nhd hpn) cua tiet dien dam thep dOn thuan, eua tiet dien lien hpp Qng vdi khi tiet dien chju phan tai trpng tae dung ngan han, tae dung lau dai; F - Gidi han ehay cua vat lieu.
Viec kiem toan phai thda man bat dang thQc:
2^riiYi'Vl i^ <I'Mn = Mf trong dd M, la gia trj eua md men phat sinh trong tiet dien nhQ: do tai trpng tTnh tai 1, tinh tai 2, do kich vdng ngQpc, ha kich, m d m e n thQ cap; y . - h e sdtai trpng tuong Qng; p. - he sd dieu chinh tai trpng; (j) He sd sQc khang;
M^, M^ - sQe khang udn danh djnh va sQe khang udn. Trong trudng hop tiet dien la khdng dae chac hoae manh, sQc khang dQpc tinh toan theo cac edng thQc trong tieu ehuan 22TCN 272-05.
Vdi ke't qua nghien eQu tren, ehung tdi da tien hanh vie't chQOng trinh bang ngdn ngQ VISUAL BASIC de tinh toan thiet ke dam thep be tdng cdt thep lien hpp nhjp lien tuc sQ dung cong nghe dieu ehinh npi iQe bang kich tren tru tam. •
TAI UEU THAM KHAO
1. Nguyen Binh Ha, "Anh hifdng t i l bien co xet do ciJng uon cua ban BTCT trong ket cau dam thep lien hop voi BTQ", Tap chi Xay dang, thang 3 nam 2011, Ha Noi, 2011.
2. Nguyen Binh Ha,"Ket qua nghien cilu cau dam thep lien hdp vdl BTCT ket hop dieu chinh ling suat'; Tuyen tap bao cao Hoi nghj ket cau va cong nghe xay dimg-2000, tr 498-500,2000.
3. Nguyen Nhu Khai, Nguyen Binh Ha, Pham Duy Hoa, Cau thep BTQ lien hop, Nha xua't ban Xay difng, Ha Noi, 2005.
4. Bo Giao thong Van tSi, Tieu chuan ky thuat cong trinh giao thong -22TCN-272-05, Ha Npi, 2005.
5. Barker R. M, Design of Highway Bridges: based on AASHTO LRFD Bridge design specification - John Wiley & son. Inc 1997.
6. Wai-Fan Chen and Lian Duan..., Bridge Engineering Handbook, CRC Press, Boca Raton London New York Washington, OC, 2000
7. Va nhieu tai lieu tham khao khae.
T(:)A N H A CHOCTR(3l HINH CAY D O C DAO
Tda nha ehpc trdi ed hinh dang nhQ mdt eai cay trong nhQng bd phim vien tQdng nhQ Star Wars cd the se trd thanh hien thQc vao nam 2012.
Thanh phdTaichung (Dai Loan) da to chQe eupe thi thiet ke nhQng toa nha tQOng lal cho thanh phd thanh. Md hinh thiet ke tda nha choc trdi ed ten Floating Observatoryies, cd hinh dang cua mdt eai eay vdi nhQng ehiee la dung dQa, da gianh dQpc giai nhat va cd the dQOe bat dau xay dQng vao nam 2012.
Tda nha nay dQpc thiet eao han 300m va ed kieu dang gidng nhQ mdt cai cay vdi 8 dai quan sat ndi gidng nhQ nhQng ehiee la eay. NhQng dai quan sat nay vQa cd chQc nang nhQ mdt dai quan sat toan eanh thanh phd vQa ed ehde nang nhQ cae thang may ed the di ehuyen len xudng rat linh hoat.
Nhdm thiet ke ngQdi Romania eho biet, eae dai quan sat se Suae xay dQng bang nhQng vat lieu sieu nhe va dQpc ket ndi vdi phan chinh eua tda nha bang mdt iQe nam eham dien cQe manh. Sau khi hoan thanh, tda nha nay se sQ dung lam van phdng, bao tang, nha hang va khu giai tri.
Ngoai ra. Floating Observatoryies eung dQpe thiet ke vdi nhQng edng nghe xanh mdi nhat giup tiet kiem nang iQpng tdi da. Dien nang eung cap cho tda nha se dQpc cung cap bdi cae turbin gid va he thdng dien nang iQpng mat trdi. Trong khi dd, va he thdng sQdi va nQde ndng dQpc eung cap tQ mdt nha may dja nhiet.
Kien true sQ Stefan Dorin, tae gla thiet ke eua toa nha, cho biet:
"Chung tdi lay cam hQng tQ hinh anh Dai Loan nhin tQ tren cao - gidng nhQ mpt ehiee la cay. Tda nha gidng nhQ mdt eai eay vdi 8 ehiee
"la" ed ehQc nang nhQ nhQng thang may cd the di ehuyen len xudng va la nhQng dja diem ly tQdng de mpl ngQdi ngam nhin toan eanh thanh pho".
