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ANH HUdNG TAl TRONG DONG BAT DEN NOI LDI: VA BIEN DANG TRONG TRU T H A P CAU TREO DAY VONG
TS. PHUNG MANH TI^N Trudng Dgi hpc Xdy dyng mien Tmng
ThS. DAO T R O N G PHO Cdng ty Kilm djnh Sdi Gdn
KS. L O XUAN DAI
Khoa Cdng trinh Giao thdng, Trudng Dgi hpc Giao thOng Vfn tdi TP.HCM
rdm tit: Ciu treo ddy vdng thudc to^i ciu cd kiin tnic dgp vdi khi nang vucA nhjp Idn. Tmngc ddy vdng, trg thdp Id mdt tmng nhQng kit ciu chlnh. Dgng dit la trudng hgp tai trQng die bidt c xem xdt khi thiit ki ciu ldn. Chlnh vi vdy, nil dung bdi bdo tip tmng khio sdt inh hudng cCia ding dit din sgn0i Igc vd biin dgng cOa trg thdp ciu treo ddy vdng.
Abstract: The suspension bridge belongs to beautiful bridges which have very long span. The tower is one of the main stmctures of the suspension bridge. Earthquake is the special load which must considered in designing of such large bridges. So that, the main aims of this article will focus on sun/eying the effects of earthquake to the internal fomes and deformation of the suspension bridge's^
towers.
LDATVANOt
Dli vdi clu treo ddy vdng, vifc tinh todn nfi lyc vd biln dgng rit phdc tgp. Tai trpng dOng dat thuOc dgng tdi trpng dfc bift cdn dupc xem xet khi thilt k l nhung edu nhjp Idn nhu cau treo ddy vdng. Khi dfng dat xdy ra, try thdp cd kha ndng chuyen vj vd bj gdy Idm dnh hudng din todn kit eau edu. Nhdm mye dich hilu rd han anh hudng eiia tai trpng ddng dit din nOi lyc vd biln dgng ciia try thdp cau treo ddy vdng, nOi dung bdi bdo phdn tfch vd so sdnh kit qud tinh todn nOi lyc vd biln dgng cua tn,i thdp dydi tdc dyng ciia tTnh tai vd cdc tai trpng dOng dat khdc nhau v l dO idn cung nhu phuang tdc dyng.
2. D 6 | TU'Q^NG VA PHU-OTNG PHAP NGHIEN CU'U 2.1. Dfng dit vd cac thang do
2.1.1. Sg hlnh thdnh ddng dit
Trdi ddt 6ugc tgo ndn td Idp Idi trong vd ngodi, tiep din Id Idp phli vd ngodi cung Id vd trdi dat. Vd trdi ddt vd tdng trdn cung cua Idp phii tgo thdnh mOt Idp vd cung dupe gpi Id thgch quyln. Thgch quyen bj vd ra thdnh cdc mang kiln tgo. Lyc hiit xuong dudi ciia trpng lyc Ifn cde mdng kiln tgo, vd trong phgm
vi nhd han Id lyc day ciia Idp thgch quyln mdi td- cdc day niii dudi Idng biln, khiln cde mdng kiln tgo chuyin dOng. Hau hit ede trdn dfng dit xdy ra tgi ranh gidi giua cdc mang kiln tgo.
Nhung mdng kiln tgo khde djch ehuyin chf m song song nhau. Cdc vet nut xuat hifn tgi ria eua cdc mdng kiln tgo nai vd trdi dat djch chuyin theo cdc hudng khde nhau. & mft sd nai, cdc mdng kiln tgo bj dfnh vao nhau. Nang lup'ng tiem tdng thudng tich ty trong ede mdng kiln tgo bj dinh vdo nhau ndy. Khi cdc mdng kiln tgo tuang tdc nhau. ndng lupng tfch ty se dup'c giai phdng dudi dgng mOt trfn dfng dit 2.1.2. Cdc thang do:
O l danh gid dup'c mdc df thift hgi, nguy hilm ciia cac trgn dfng dat cde nhd khoa hpc su dyng cdc thang do dOng dat nhu thang Richter, thang dO ldn moment vd thang Medvedev-Sponheuer-Kamik.
Trong cdc thang dpng dit, elp dfng dit dLrgrc xdc djnh theo gid trj dinh gia tic nen tuang dng. Vifc chuyin doi dinh gia tic nin ciia d p dOng dit theo thang dO ldn MSK-64 vd thang MM dugre thi hifn trong bang 1 nhu sau:
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Bing 1. Bing chuyin dii gia tic nin T h a n g M S K - 6 4
afpflAngaJt
V VI VII VIII K X
U n h g l a t ^ nAi{a)g 0,012 - 0,03
> 0,03 - 0,06
> 0,06 - 0,12
> 0,12 -0,24
> 0,24 - 0,48
>0,48
T h a n g M M Qlpff&ngdft
V VI VII VIII IX X
Oinh gia t &
n ^ ( a ) g 0,03 - 0,04 0,06 - 0,07 0,10 - 0,15 0,25 - 030 0,50 - 045
>0,60 2.2. TrM thap c l u treo day v d n g
Cdc b f p h f n chfnh cua cau treo ddy vdng gdm: dam chu, cdp chO, h f ddy treo, try thdp, mo neo. Try thdp Id m f t trong nhdng bO phgn chinh tgo nen d f c d i l m n i l b f t vd d f c trung cho c l u . V f t lifu thiet ke try thdp thudng diing thdp hof c bd tdng edt thdp. Theo phuang ngang c l u , try thdp thudng dup'c t h i l t k l dgng ddn (Hlnh 1), dgng c i n g (Hinh 2) h o f c dgng p h l i hp'p gida hai logi tren. Try thdp dugc phdn logi thdnh thdp cdng, thdp m l m vd thdp chdn khdp khi xdt d i n d f cdng cua tn^ thdp. Thdp mem thudng dung eho c l u treo nhjp Idn. Thdp cdng thudng diing eho c l u treo n h i l u nhjp d l cung d p du d f cdng cho d u . Thdp chdn khdp thudng dung eho d u treo nhjp n g i n . Trong phdn tich tinh todn, tn,i thap dup'c xem nhu k i t d u chju ndn uon [1].
Hinh 1. Tn,! thdp d^ng dan
Hinh 2. Tn.j thdp d^ng cong 2.3. Cdc tru'dng hprp nghien c d u 2.3.1. Sa do nghien cim
Bdi bdo nghien cuu d u treo ddy vdng vdi sa dd ba nhjp. Hai nhjp bien cd chieu ddi bdng nhau L l = 100 m, chieu dai nhjp chinh L = 400 m. Kho ngang d u S
= 11m. C l u dup'c bd tri hai m f t phang ddy, cdc ddy treo t h i n g ddng song song. Neo cdp chii cd dgng neo vdo dat nen bdng khoi neo. Try thdp dgng khung cung, bd tri ba giang ngang tgi vj tri each dinh tn,j thdp 1,25m, giua dfnh tn,J thap vd ban mdt d u , tgi vj tri ban mgt d u . Chieu cao try thap 60 m (td dinh try thdp tdi ban m f t d u : 40m, t u ban mat d u tdi chdn try thdp: 20 m). Cap ehii dupc ngam vdo dinh try thap.
Hinh 3. Sa do ciu treo day vdng nghien cuu 2.3.2. Thdng so vdt liQU va ddc trung hinh hQc cua cdc bQ phan kit ciu
• Vgt l i f u
Cdc thdng sd ky thugt ve vat lifu ciia cae b f p h f n k i t d u ehinh trong d u treo ddy vdng nghien cdu dup-c chpn theo Bang 2 [2].
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Bing 2. Thdng so vdt liQu cua cac bg phdn kit ciu chinh ciia ciu
d p VII: gia tdc nen 0,12g
ThAngsj 0«nvj
Mft flun O n hA (Evl) xlOS kM/in2 Trpng liftfngrttag kN/m' He s j Poisson
Hang muc
ap diu
2,0 82,5 0,3
ap tree
1,4 78,5 0,3
Dam did
2,1 78,5 0,3
Tru thip, giSng ngang 2,1 78,5 0,3
Thing s<(
A l„
'«
'-
Cip diu 417,8
0 0 0
d p treo 20,9
0 0 0
Dim diii 5395 4399 1316 32667
Truthjp 1690,6
1540 1450 1143
Giing tni 1046 1540 1080 913
2.3.3. Cic trudng hgp tai trQng ddng dit nghien cim:
Nhdm nghien edu dnh hudng eiia d f n g dat d i n nOi lye vd b i l n dgng ciia thap d u trong d u treo day vdng, bai bdo xem xet trudng hpp dOng dat cd sdc tdn phd nghidm trpng vd vd eung ldn tren nhung d i f n tfch r i t rOng, dOng dat d p VII, VIII vd IX vdi hinh dgng vd gia tdc n i n nhu tren Hinh 4. DOng dat xay ra theo phuang dpc, phuang ngang d u vd phuang t h i n g dung.
Theo 22 TCN 272-03 tde dyng eiia tai trpng dOng d i t cd t h i tinh todn theo phuang phdp pho dgng dan phuang phdp tdi trpng rai deu tuang duang, phuang phdp p h i dgng phdc va phuang phdp ljch s u thdi gian. Trong phgm vi nghien c u u , tdc gia thyc hifn phdn tieh theo p h y a n g phdp ljch s u thdi gian [3].
• Dgc t r u n g hinh hpc
Thdng s l d f c trung hinh hpc nhu d i f n tieh mat d t ngang A dan vj cm^, moment qudn tinh 1^ quay quanh tryc X, moment qudn tinh 1^ quay quanh tryc Y, vd 1^ quay quanh tryc Z (x 10* cm*) ciia ede mgt d t dien hlnh ciia ede hgng myc k i t d u chinh ciia d u treo ddy vdng nghien cuu dup-c trinh bdy trong Bdng 3 [2].
Bing 3. Ddc trung hinh hQC cac bQ ph$n kit cau chinh cua ciu
Cap
J •M U | - |
VIII gia toe nen 0,24g
$-|i|IB
1 niiV 1"'
• • •
**"
9 ••Jim
IE
d p IX: 3 la
-^111
t i c nen 0,48g
Hlnh 4. Ddc trung dgng dit nghien cuv Cdc d p d f n g d i t nghien cdu cd d f c diem: gia tic nen d p VIII Idn gap 2 lan gia tde n i n d p VII; gia tic nen d p IX Idn g i p 4 lan gia tde n i n d p VII [4].
2.3.4. Cic ndi lgc, biin d?ng va vj tri nghidn cdu Khao sdt 6 thanh phan nOi lyc gom moment x d n Mx (kNm), moment uon My vd Mz (kNm), lyc dpe tn,ic Fx (kN), lye d t Fy vd Fz (kN) tgi cdc vj tri:
+ Vj tri 1: Tai ban mgt d u (VT1) + Vj tri 2: Tgi chan tn,j thdp (VT2)
Bai bao khao sat chuyen vj Dx theo phuang X, Dy theo phuang Y vd Dz theo phuang Z tgi cde vj tri:
+ Vj tri 1: Tgi vj tri giang ngang 1, cdch dinh trg thap 1,25m (ky h i f u VT1)
+ Vj trf 2: Tgi vj tri gilng ngang 2, cdch dinh try thdp 20m (VT2)
+ Vj tri 3: Tgi bdn m f t d u (VT3).
3. K^T QUA NOI LI/C, BI^N DANG TRONG TRg THAP
Phdn tfch tinh todn md hlnh d u treo ddy vdng dudi tdc dyng cua tdi trpng bdn thdn vd tai trpng dfng dit theo cdc phuang dpc d u , ngang d u , thing dung vdi cdc d p df dfng dit khdc nhau bdng phan mlm chuydn dyng Midas/civil cho thiy anh hudng eua dfng dit din nfl lyc vd biln dgng tgi nhung vj trf nghidn cuu ciia tn,i thdp nhu sau:
3.1 O^ng ddt theo phiForng dpc c l u : Gid trj moment xoan Mx (kNm), moment uln My vd Mz (kNm), lyc dpe tn,ic Fx (kN), lyc d t Fy vd Fz (kN) tgi cdc vj tri vj tri nghidn cuu dudi tdc dyng ciia tTnh tdi khi khdng xdt din dOng dit vd dudi tdc dyng ciia dOng dit xdy ra theo phuang X dup'c trinh bdy trong Bdng 3.1 nhu sau:
Bing 3.1: Nil Igc cd/khdng cd dQng dit a(pff^(tft
VTI
VT2 Mx-1 My-1 Mz-1 Fx-1 Fy-1 Fz-1 Mx-2 My-2 Mz-2 Fx-2 Fy-2 Fz-2
Khftng 3.0 3133 472 11287 36 33 2.9 4453 213 12065 28 41
VII 58 3235 59 1267 5 78 55 6610 61 1301 4 339
VIII 116 6470 118 2534 8 155 109 10989 122 2603 6 678
n 232 12940 237 5067 20 310 218 21978 244 5205 17 1356 Mdc df biln thidn cua md ment My-1 tgi vj tri 1 vd My-2 tgi vj tri 2 trong tn,i thdp dup'c thi hifn qua bilu d l trdn hlnh H.5, cua lyc dpc tn,i Fx (Hinh6) vd lye d t Fz (Hinh 6.7).
B MO
c SS
{ M O
1
I I^i—
^ j j ^ ^
^^^* ^^^'
- • * « k « lHinh 6. Quan hd Fx va cip dQng dit theo phuong X
« M »
' < :
^
^ ^ , , j ^ ^
* - » " * - • ^ • a
Hinh 7. Quan hg Fz va cip ddng dit theo phuong X
Kit qud tinh todn cho thay khi xdy ra dfng dit theo phuang dpe d u , ehuyin vj ciia try thdp tgi cdc vj trf nghifn cdu (tinh bdng m) cd nhung gid trj nhu tdng hgp trong Bang 3.2.
Bing 3.2: Chuyen vj trg thdp cd/khdng cd dQng dit dp adng ait
Dx
Dy
Dz V j t r i l V!trf2 V|tri3 V j t r f l V!tri2 VjtifS V j t r f l V|tri2 V!trf3
Khdng 0.184 0.097 0.032 0 0 0 0.019 0.013 0.007
VII 0.025 0.037 0.025 0 0 0 0,002 0,001 0,001
VIII 0.050 0.074 0.049 0 0 0 0,004 0,003 0,002
IX 0.101 0.149 0.098 0 0 0 0,008 0,006 0,003
Hinh 5. Quan hd My vi cip ddng dit theo phuong X
3.2. Dfng dat theo phucmg ngang cau:
Khi cd xdt din dOng dit xay ra theo phuang ngang d u (phuang Y), tgi cdc vj tri nghien cdu tren tn^ thdp ed gid trj nOi lye dup'c trinh bdy trong Bang 3.3 vd chuyin vj trong Bang 3.4 nhu sau:
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Bing 3.3: Ndi lgc tmng tnj thdp cd/khdng dQng dat
Trudng M p
VTI
vn
Mx-1 My-1 Mz-1 Fx-1 Fy-1 Fz-1 Mx-2 My-2 Mz-2 Fx-2
Fy-2 Fz-2
Bing 3.4: Chu^
cuffing tit
Dx
Dy
Dz V i t r i l V | t r ( 2 V | t r i 3 V i t r i l
V i t r f 2 V | t r i 3 V j t r f l V ; t i { 2 V i t r i 3
nnh t i i
3.0 3133 472 11287 36 33 2.9 4453 213 12065 28 41
rin vj tn.1
Khftng
0.184 0.097 0.032 0 0 0 0.019 0.013 0.007
O f p f l f t n g t i t
VII 118 935 3170 1219 306 66 425 1463 12838 2706 1036 116
thap cd/
VII
0.001 0.004 0.005 0.077 0.066
0.051 0,002
0,002 0,002
V I I I 236 1869 6340 2439 611 122 851 2926 25677 5411 2072 232
khdng dQ V I I I
0,003 0,008 0,009 0,154 0.133 0.102 0,005 0,004
0,003 IX 473 3738 12680 4877 1222 244 1702 5852 51353 10822 4144 464
ngdat IX
0.008 0.016 0.019 0,308 0,265 0,205 0,010 0,009 0,007
3.3. Dfng d i t theo phiporng thing dung Khi xdy ra dOng dat theo phuang thing ddng (phuang Z), tgi cde vj tri nghien edu trdn trg thdp cd gid trj nOi lye duvc trinh bdy trong Bdng 3.5 vd chuyin vj trong Bdng 3.6 nhu sau:
Bing 3.5: NQI lgc tmng trg thap cd/khdng ddng dit
Mdi tuang quan giua ehuyen vj theo phuang Y va d p dOng ddt xdy ra theo phuang ngang d u dupc thi hifn trdn Hinh 9.
VTI
vn
Mx-1 My-1 Mz-1 Fx-1 Fy-1 Fz-1 Mx-2 My-2 Mz-2 Fx-2 Fy-2 Fz-2
T u i h t i i
3.0 3133 472 11287 36 33 19 4453 213 12065 28 41
O f p t f t a g A l t VII
8 378 181 819 13 23 7 475 166 979 11 20
V I I I 16 698 363 1637 27 47 15 950 326 1958 23 40
IX 32 1510 726 3274 54 94 30 1899 664 3915 45 80 Bang 3.6: Chuyen vj trg thdp cd/khdng ddng dit
O f p f f f t n g t i t
Dx
Oy
Dz V i t r i l V l t r i 2 V i t r i 3 V i t r i l V i t r i 2 V i t r i 3 V i t r i l V i t r i 2 V i t n 3
Khftng 0.184 0.097 0.032 0 0 0 0.019 0.013 0.007
VII 0.019 0.007 0.003 0 0 0 0,001 0,001 0,001
V I I I 0.026 0.014 0.005 0 0 0 0,003 0,002 0,001
IX 0,053 0,029 0,011 0 0 0 0,006 0,004 0,002
Moi tuang quan giua chuyin vj theo phuang Y vS d p dfng dit xdy ra theo phuang ngang d u dupc thi hif n tren Hinh 10.
Hinh 9. Quan hd Dy va ddng dat theo phuong Y Hinh 10. Quan hg Dz vd ding dit theo phuang Z ,
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4. B A N L U A N K ^ T QUA
N f i lyc vd b i l n dgng trong try thdp do tai trpng dOng d i t gdy ra tdng theo h f sd gia tdng dfnh gia toe n i n cua cde d p d f n g ddt. Npi lyc vd b i l n dgng do d f n g d i t d p VIII cd gid trj g i p ddi, do dOng dat d p IX cd gid trj Idn gdp bdn Idn so vdi nOi lyc vd bien dgng do dOng d i t d p VII gdy ra.
- D f n g d i t d p VII xdy ra theo phuang dpc d u (phuang X) gdy ra trong try thap: moment xoan Mx cd gid trj khodng 20 l l n , moment u l n theo phuang dpc d u My cd gid trj bdng 1 l l n , moment udn theo phuang ngang d u Mz bang khoang 0,12 l l n , lyc dpc Fx ed gid trj khodng 0,1 l l n , lyc cat theo phyang ngang d u Fy cd gid trj khodng 0,13 lan vd lyc d t theo phuang dpc d u Fz cd gid trj khodng 2,36 ~ 8,26 l l n tuy theo vj tri mgt d t t u bdn m f t d u d i n chdn try thdp, so vdi gid trj nOi lyc tuang dng do tTnh tai gdy ra. Gid trj nOi lyc tang nhieu n h l t Id moment x o l n , moment u l n vd lyc d t theo phuang dpc d u . Chuyin vj theo phuang dpe d u Dx tdng nhieu nhlt, gid trj bdng khodng 0,13-0,78 l l n , c h u y i n vj theo phuang t h i n g dung Dz ed gid trj 0,07 ~ 0,14 lan so vdi ehuyin vj do tTnh tdi gay ra.
- D f n g d i t d p VII xdy ra theo phuang ngang d u (phuang Y) gdy ra trong tn,j thdp: moment xodn Mx ed gid trj khodng 40 - 1 4 6 lan, moment u l n theo phuang dpc d u My ed gid trj bdng 0,3 lan, moment uon theo phuang ngang d u Mz bdng khodng 6,7-60 l l n , lyc dpc Fx cd gid trj khoang 0,1-0,2 ian, lyc d t theo phuang ngang d u Fy ed gid tn khodng 8,5-60 Idn vd lyc d t theo phuang dpe d u Fz ed gid trj khodng 1,8-2,8 l l n tuy theo vj tri mgt d t t u bdn m f t d u d i n chdn tn,j thdp, so vdi gid trj n f i lyc t y a n g dng do tTnh tdi gdy ra. Gid trj nOi lyc tang n h i l u n h l t Id moment xoan, moment uon vd lyc d t theo phuang ngang d u . C h u y i n vj theo phuang dpc d u Dx cd gia trj bdng khodng 0,04-0,15 lan, chuyin vj theo phuang t h i n g dung Dz cd gid trj 0,10 - 0,28 tuy theo vj tri t u dinh d i n chdn tn,J thap, so vdi c h u y i n vj do tTnh tai gdy ra. Khi xay ra ddng dat theo phuang ngang d u , trong tn,i thdp se x u l t h i f n chuyin vj theo phuang ngang d u Dy.
- O f n g d i t d p VII xdy ra theo phuang t h i n g ddng (phuang Z) gdy ra trong try thdp: moment xoan Mx cd gid trj khodng 2,5 l l n , moment u l n theo phuang dpc d u My cd gid trj bdng 0,10-0,12 l l n , moment u l n theo phuang ngang d u Mz bdng khodng 0.38-0,77
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lan, lyc dpc Fx cd gid trj khoang 0,075 lan. lyc d t theo phuang ngang d u Fy ed gid trf khoang 0,38 lan vd lyc cat theo phuang dpe d u Fz cd gid tq khodng 0,69-0,48 lan tuy theo vj tri mat d t t u bdn mat d u d i n chdn try thdp, so vdi gia tri n f i lyc tuang ung do ttnh tai gdy ra. Gia trj nOi lyc tang nhieu n h l t Id moment xodn, moment udn vd lyc d t theo phuang ngang d u . C h u y i n vj theo phuang dpe d u Dx ed gid tri bang khoang 0,07-0,10 lan, chuyen vj theo phuang t h i n g ddng Dz cd gid trj 0,05 - 0,14 tuy theo vj tri t u dinh d i n chdn try thdp, so vdi chuyen vj do tTnh tai gdy ra.
5. K t T LUAN
Khi tinh todn sa bO try thdp d u treo ddy vdng ehju tac dyng ciia dOng dat, khong d n quan tdm den moment xodn, lyc cdt theo phuang dpe d u , mgc du tai trpng dOng dat gay gid trj Idn g i p nhieu lan so vdi gid tn nOi lyc tuang dng do tTnh tdi gdy ra tuy nhien nOi lyc do tTnh tdi gay ra cd gid trj rat nhd. Khi xem xdt dOng dat d p VII nen tang h f so an todn gap ddi cho moment udn theo phuang dpc d u , tdi thilu tdng gap 7 lan cho moment udn theo phuang ngang d u , tang 1,5 lan cho lyc dpc tn,ie. Khi d f n g d i t xdy ra theo phuang dpc d u d n quan tdm den sdc khdng moment udn theo phuang dpe d u . Khi dOng d i t theo phuang ngang d u d n quan tdm den sdc khdng udn vd lye d t theo phuang ngang d u . Odi vdi e l p dOng d i t d p VIII vd IX d n tang h f sd an todn Idn gap ddi hogc g i p bdn so vdi d p d f n g d i t d p VII. DOng dat theo phuang ngang d u (phuang Y) se gdy bat Ipi nhat cho nOi lye, dOng d i t theo phuang dpc d u se gay b i t ipi ve ehuyen vj tm thdp d u treo ddy vdng •
, Bridge f r A i LIEU THAM KHAO
fri. Ed. Wai-Fah Chen and Lian Duan, Engineering Handbook.
2. TS. PhOng Mgnh T i l n . Hudng d i n phdn tich.
tinh todn d u treo ddy vdng bang phdn mem Midas 6.71. Bdi gidng chuang trinh cao hpc.
3. Ngd Ddng Quang. Nguyin Ddc Thanh. Md hlnh hda vd phdn tich d u treo ddy vdng p h i n m l m MIDAS/CMI. Tgp chf d u dudng Vift Nam.
4. MIDAS IT, MIDAS/Civil - Analysis Reference.
\ 2005.
