BANH GIA TAC ©pXG CUA KET CAU VA OAT NEN KHI XAY RA DONG OAT

BANH GIA TAC ©pXG

CUA KET CAU VA OAT NEN KHI XAY RA DONG OAT

TS. N G U Y I N VIET KHOA Vien chuyen nginh Cau Ham

Vien KH&CN GTVT

Tdm tat:

Kit eau eong trinh duac thiit ki an toin, ed the chiu dUde tie ddng eiJa ea hai loai tai trgng tTnh va ddng. Mdt trong cic dang tai trong ddng la sdng dia chan, lan truyen td tam ddng dat hay tdeic ngudn dao ddng nhin tao tie ddng din cdng trinh xiy dung vi ed the giy nen sup dd cdng trinh. Phin tich cic tinh chat eua sdng dia chan eho thay: Nguyen nhin ehinh tic dpng vi phi huy cdng trinh li do sdng ngang gay nen. De xae dinh phan ung eua kit eau va dat nen chiu tie ddng eua ddng dat, mot md hinh tinh toin kit ei'u vi dat nen duac phin tich.

Abstract: •

The structure is designed ta withstand safely all static loads and dynamic loads. One of the dynamic loads is seismic waves, that propagate away from the earthquake epicenter, or from other sources by man-caused vabrations effect on structures and could cause collapse of structures. Analyzing the prop- erty of seismic waves realizes that one main reason for collapse is the effects of horizontal wave. To determine the response af sail-structure interaction under the influence of earthquake, one soil-structure model is analyzed in this paper

I . D A T V A N D E

Trong subt hai thap ky qua, van de tac dbng qua lai gida k i t eau va dat nen dugc thda nhan rpng rai;

Dat nen ed t h i anh hadng den ket cau xay dyng tren nd khi dpng dat, dac biet trong tradng hgp ket cau cung dat tren dat nen taong dbi mem. Sy tuang tae nay c i n thilt phai dugc xem xet d i n khi thiet k l cac cdng trinh quan trpng [11],

Hien nay, trong eae tieu chuan thiet k l cdng trinh cua cac nudc phat trien deu ed hudng d i n xae dinh chuyin vj, van tbc va gia tbc chung va rieng cac bp phan ket c i u khi tinh toan k i t cau cdng trinh chiu tac dbng dja c h i n . Tieu chuan ASCE 4-98 cho bilt anh hudng cua ket cau va dat nen dagc xet den eho tat ea ket cau ma khbng d§t tren n l n da hoac vat lieu dat duOi mdng tuong ty da.

Cd nhieu mo hinh phan tich moi tradng dat nen khi xet taong tac cua k i t cau va d i t nen. Trong dd, ed hai

each tiep can co ban ti§u bleu cho mdi trudng dat trong tac dpng cua ket eau va dat nen; Md hinh Winkler va mdi tradng lien tyc [1],

Khi mpt k i t c i u ehbng lai tac dpng eua dat nen, no se tae ddng vdi mdng va dat cua nd, va vl vay lam thay dbi chuyen dpng cua dat nen. Dudi tae ddng eua dpng dat, tuong tac dpng eua k i t cau va d i t nen la mpt hien tugng cd lien quan den nang lugng vao va nang lugng ra, dugc truyen qua tuong tac ket c i u va dat nen. Sy khac biet gida nang lagng vao va ra tuong ung vdi nang lugng du tru trong k i t cau, ed lien quan chat che d i n mdc dp thiet hai dbi vdi ket eau.

Tac ddng eua k i t c i u va dat nen cd t h i anh hudng d i n thiet ke cdng trinh ve cac khia canh nhu an toan, dp ben va gia thanh cbng trinh. Gia thanh xay dung phu thupc vao hinh dang ket cau va mdng duoc lya chpn, ma chung cd the anh hadng trd lai tdi sy phan bb tai trpng trong cac bp phan do cd sa tae ddng eua k i t eau va dat nen.

TAP CHi CAU OL/ONG VIET NAM

KHOA HOC - CONG NGHE 2. SONG D!A CHAN

Dao dpng eua dat nen xuat hien do sbng dja chan, lan truyen td tam dbng dat hay td eae ngubn dao dpng nhan tao tae dgng den cong trinh xay dyng. Tbn tai hai dang sdng dia chin ca ban la sdng the tich (sdng khbi) va sdng be mat.

Cae dang tac dpng dpng phb bien den cbng trinh khi tinh toan ein dagc tinh den tac dbng eua kit cau va dat nen dugc chi ra d hinh 1 nha tac dung cua gid, chuyin dpng cua phuong tien tham gia giao thdng, tac dpng co hpc va tac dpng cua dpng dat.

C c h^c

a).

-' GI6 Chuyen dijng p h u c n g tl^n gtao thong *"

u

\ 1

r

Chuyen dpng

A

phu-ong t i f n - giao tliong

b).

/ - % Dpng a i

n

Hinh 1. Cic trudng hpp tai trong ddng thdng thudng (a) vi ddng dat (b)

2.1. Sdng the tich P vi S.

Khi cd sy lan truyen cua sdng P, eae hat dat djeh chuyin song song vdi hudng lan truyen cua sdng, vi vay cac sdng nay gpi la sdng doe. Van tbc lan truyen eua sdng dpe la Idn nhat khi so sanh vdi van tbc eua cac sdng khac, do vay sdng nay edn dugc gpi la sbng so cap [primary).

.».-^-?>.t

m^...

Song P

• ' ^

Ifc-S

Hinh 2. Chuyen ddng eua dat nen do sdng P

Cdn khi cd sy lan truyen cua sdng S, cac hat dat djch chuyen vudng gde vdi hadng lan truyen cua sdng, vi vay cac sdng nay gpi la sdng ngang, hay cdn gpi la sdng citva la sdng thu cap (secondary).

Obi vdi cac sbng ma trong dd cac hat dat chuyen dong trong mat phSng thing dang daac ky hieu la SV, edn dbi vdi sdng ma trong dd cac hat dat chuyen dgng trong mat ph§ng nim ngang dugc ky hieu la SH. Sy tac dpng va pha huy eong trinh chu yeu do sbng ngang gay ra [5].

So db chuyen dpng cua cac hat dat khi ed sy lan truyen eua sdng doe va sdng ngang dugc minh hpa d hinh 2 va 3.

Hinh 3. Chuyen ddng eua dat nen do sdng S

Van tbc lan truyen cua sdng dpc.a duacjcae dinh bang eong thdc:

a =

/l-i-2/y

P

\-v

p{l + v){\-2y) ⁽¹⁾

trong db, X va p - he sd Lame eua dat nen, E vi V- md dun dan hoi va he sd Poisson eCia dat nen, p - mat do eua dat nen.

Van tbc lan truyen cua sdng ngang p duae xic dinh bang bieu thdc:

(2)

Van tbc cua sbng ngang lubn nho han van tbc sdng dgc. Quan he eua chung phy thupc duy nhat vao he sb Poission v .•

^ = iz^<l (3)

a ' 2(1-V)

2.2. Sdng bi mat:

Sdng Love va sdng Rayleigh xuat hien do sy tae dbng cua sdng the tich vdi be mat ta do va chi tbn tai d gan be mat.

Hinh 4. Chuyen ddng cua dat do sdng Lave Sy chuyen dpng eua cac hat dat khi ed sy lan truyen cua sdng Love xay ra song song vdi be mat dat nen, vudng gde vdi hudng lan truyin (hinh 4). Khi ed su lan truyin eua sdng Rayleigh, cac hat dat chuyen dpng theo hinh elip trong mat p h i n g vudng gde vdi be mat dat nen (hlnh 5).

S6ng Rayleigh

Hinh 5. Chuyen ddng cua dat da sang Rayleigh Sdng b l mat lan truyin cham hon sdng t h i tich va trong sdng be m i t thi sdng Rayleigh chuyen ddng cham nhat. Chuyin dpng eua sdng be mat, cung nhu cua cac Idp dat vdi tinh chat khac nhau, chung phan xa, khde xa tdng phan va b i l n dbi td dang nay sang dang khac.

So sanh phan chia nang laong do tac dpng eua cac sdng khac nhau den t i i trpng tap trung n i m d be mSt ban khdng gian dan hbi chi ra ring: Sdng Rayleigh truyen 67% nang lagng, sdng ngang S chiem 26% va sdng dqc P chi cd 7% [9].

3. P H L T Q N G PHAP DANH GIA TAC DONG CUA K^T CAU VA DAT NEN

Phan tich tae dbng k i t cau va dat nen cd the dugc

thyc hien b i n g nhieu each tiep can khac nhau nhu phaong phap true tiep va phaong phap thbng sb ket cau [6, 15].

Guttierrez J.A. va Chopra A.K. daa ra ba phuong phap khac nhau khi phan tich tac dbng cua ket eau va nen dat chju tae dpng eua dbng dat [4]:

Hinh 6. Cie md hinh tinh toan

a). Ban khdng gian dan hdi, b). Ldp dat tren nen cdng; e). Pham vi gidi han eua dat nen Phuong phip thu nhi't trong db ket cau cdng trinh dugc md hinh hda b i n g he nhieu khbi lugng don g i i n , dagc nbi thdng qua tam cdng ban khdng gian dan hbi. Nhage diem eua phuong phap nay la khdng ed kha nang tinh toan anh hudng cua he cd hai cdng trinh trd len, tinh khbng dbng nhat eua dat nen va sy thay dbi tac dpng eua dpng dat theo chieu sau.

Phuong phip thd hai duac sd dyng rpng rai trong nghien cuu, trong dd k i t eau dugc xem xet dbng thdi vdi mpt phan eua dat n l n . Ldi giai dugc thae hien b i n g phaong phap phan td hdu han, co the tinh toan den sa khdng dbng nhat cua dat nen va c h i l u sau eua cong trinh. Tuy nhien, phuong phap nay cd mdt vai nhage diem, nha ddi hdi bd nhd may tinh Idn (vi vay, thadng ehi sd dung md hinh p h i n g d l phan tich); khbng t h i tinh toan i n h hadng cda sdng be mat Rayleigh; khdng tranh dugc sai sb.

Phuong phip thd ba dagc sd dung nhieu nhat, trong dd k i t cau dugc tinh toan b i n g phuong phap phin tu hdu han, cdn dbi vdi dat nen dugc md hlnh d dang ban khong gian dan hbi hoac d dang cac phan tu huu han cho phan dat dudi mdng. Phuong phap sau cung nay cd hieu q u i hon theo quan diem giam khbi lagng tinh toan.

Ngoai ra, trong mbt sb tradng hgp cb t h i sd dyng mpt sb phuong phap khac de danh gia tac dpng eua k i t cau va dat nen nhu md hlnh dde lap [12].

TAP CHi CAU DLTONG VIET NAM

KHOA HOC - CONG NGHE

Mong cua ket cau

^

Lcp ccr bin ky thuat

r Chuyin dong dat n«n do

I dong dat ir Icp dat t r i n b« mat i«.

Chuyin d9ng J dat n i n cua dong dat

Hinh 7. Tfnh toin kit ei'u va dat nen thea md hinh doe lap

4. v l DU OANH GIA TAC DONG CUA KET CAU VA DAT NEN KHI CO DONG DAT

Tac dpng eua k i t cau va dat nen ehju tae dpng eua sdng dja chan khdng ehi phu thupc vao dp cdng cua dat n l n , ma cdn phu thupc vao khbi lagng va dp cdng cua ket cau.

Hinh 8 chi ra md hinh vdi hai bac ty do md ta tac dbng gida k i t eau va dat nen khi chju tae dpng tran dpng dat. Gia thiet r i n g gia tbc nen (hinh 8) eua tran dbng d i t do dugc d tang da cung.

Ket cau tren

VsO

• J ^ k

- Dat n In Mong

Ket

'

M

' •

cau tren

-*

' k ' onq

•

'nr UR

^k

Um

^m

Dat nen u(x)

Tang da cijng

Hinh 8. Md hinh kit ei'u vi dat nen chiu tic ddng cua ddng dat

Phuong trinh chuyen dbng cua dat nen dagc viet d d a n g sau:

g d7^ ~dt~ ''d^~ g dt'

⁽⁴⁾

Daa tren phan tich dang dao dbng, chuyen vi cua dat nen cd t h i dagc tinh nhu sau:

u(x, 0 = X "' (^' 0 = Z f^. (-'^)'?. (^) *^'

1=1 1=1

trong dd, c?,-- tpa do tbng quat eua dang dao dpng thd /. Thay phaong trinh (5) vao phaang trinh (4):

^,+24^,'7,+^'9, =-r,>^.

⁽⁶⁾

vdi ^5/ - he sd can eua ldp dat, cogj - tan sd daa ddng rieng eua Idp dat vi r, - he sd tham gia dang daa ddng thd i: H

r =-5

|r,/g.Of(x)fl!x

⁽⁷⁾

va (j)j(x) - dang dao dbng thd i, cb the lay theo [16].

Tren hinh 10 trinh bay ket qua tinh toan gia tbc be mat cua dat nen va gia tbc nen khi xay ra dpng dat trong dd su dyng phuong phap bien dbi Fourier ham huu han [2] de giai phuong trinh vi phan cua chuyin dpng, tinh vdi cac khoang thdi gian At=0,005s.

a (ni/s^)

Gia toe be mgtdatn^n Giatdcn^ndOnga^t

1 2 3 4 5 6 7

Hinh 10. Gia tdc be mat dat nen vi gia tdc nen dong dat

Phuong trinh chuyen dbng cua he hai bac ty do gay ra bdi gia tbc be mat dat nen Xso ;

m ii + c II -i-li ll -CM, -li.u. =-m '\' (8)

/'( m mm mm k k k K m. s<l

Hinh 9. Gia tdc nen a lap da

^ * ("™ + " * ) + c,u, +k,u,= -m,y^ (9)

'1

-1-

1

'^l

0

1 1

0 "

CD _{c _}

'2iA 0

0 2^,^,

jl/ 1 | ( l + /^)>^.o

Ui ^{I >'.o}

trong dd, y ^ , y^^., va y g Q - chuyen vj tuyet dbi eua mdng, k i t cau tren va Idp dat dat ty do tren be mat taong dng, vdi u^=y^ - y^Q, va ui^yj^ - y^g la chuyin vj taong dbi cua mdng vdi be mat dat nen va k i t cau tren tuong dbi vdi mdng. Cae thdng sb mf^, kj^, Cj^va m^, k^, e^ - khbi lugng, dp cdng, lyc can dbi vol k i t eau tren va dbi vol mdng tadng ung.

Khi dd, eae phuong trinh (8) va (9), cd the viet d dang dang ma tran:

•-f

(10) vdi ^/f , ^ ^ -he sdean cua kit cau tren vi mdng; cuff, a)fj^ - tan sddaa ddng rieng cua kit eau tren vi mdng; p=

mj/m^ -tyle khdi iuong kit eau tren va khdi Idqng mdng.

Cae thdng sb ban dau cua mdng, k i t cau va d i t nen; Tan sb dao dpng rieng eua mdng cdng trinh (O^=2.7T0,7 rad/s; he sd can khdng thd nguyen eua mdng ^^=20%. Tan so daa ddng rieng cua kit ei'u tren (i}j^2.nO,5 rad/s; he sd can khdng thd nguyen eua kit eau tren ^i^5%. Ty sd khdi luang cua kit cau tren va khdi luang mang p=5. Be diy Idp dat td Idp da eung din be mit dat nen H=50m. He sd can khdng thu nguyen eua Idp dat nen t,g=10%; tan sd dao ddng rieng eua Idp dat nen (Og=2(orad/s. Van tdc chuyin ddng cua sdng cit V^ -200m/s.

Hinh 11 -h 13 trinh biy dd thi chuyen vi taong ddi, van tdc tuong ddi va gia tdc tuyet ddi cua mdng vi kit cau vdi bade thdi gian tinh tain ddoc lua chgn t=0,01s.

Ket cau Mong

Ket cau Mong

1 2 3 4 5 6

Hinh 12. Van tdc tuong ddi eua kit ei'u tren vi mdng

Ket cau Mong

t(s)

0 1 2 3 4 5 6 7 8 9 10

Hinh 11. Chuyen vi tuong ddi cua kit eau tren vi mdng

Hinh 13. Gia tdc tuyet ddi cua kit cau tren va mang

5. KET LUAN

Oe danh gia ehinh xae lyc thiet ke, anh hudng den tae dpng k i t c i u va dat nen, khdng ehi xem xet dudi tae ddng cua tai trpng tTnh ma cdn phai xet d i n eae loai tai trpng dpng do cae nguyen co hpe, dpng dat, do chuyen dpng eua phaong tien tham gia giao thbng,... gay nen.

Mpt md hinh danh gia k i t eau va dat nen ehju tac dpng cua sdng dja chan do dpng dat gay ra dugc phan tich d l xae djnh phan dng cua k i t eau tren va mdng cbng trinh ( c h u y i n vi, van tbc va gia tbc); trong dd, b i n ghi gia tbc nen dugc gia thiet d t i n g da cung.

Hien nay, vdi cac tien bp khoa hpc phat trien nhanh trong cbng nghe xay dyng (nha eao tang, cau treo, dap cao, thap nude,...), viec danh gia tac ddng k i t eau va dat nen ngay cang cd y nghTa thyc tien va ed t i m quan trpng, phan anh ehinh xae quan he taong tac cua ket c i u va dat nen •

TAP CHi CAU DLTONG VIET NAM

KHOA HOC - CONG NGHE

TAI L I | U THAM KHAO:

1. Nguyen Viet Khoa. Cac mo hlnh danh gia tac dpng chung cua ket cau va dat nen. Tap chi Cau Dudng Viet Nam, 363, 2009, tr. 24 - 28.

2. Kurbatsky E. N., Nguyen Viet Khoa. Phuong phap sb mdi xay dyng phb phan dng - Phuong phap bien doi Fourier ham hau han. Tap chi Cau Budng Viet Nam, Sb 5, 2008, tr.

28 - 32 .

3. Arnold Verruijt. Soil Dynamics. Delft University of Technology, 2005. - 363 p.

4. ASCE 4-98. Seismic analysis ot safety-related nuclear structures and commentary. American Society of Civil Engineers, 1998.

5. Eurocode 8: Design of structures for earthquake resistance. Part 5: Foundations, retaining structures and geotechnical aspects. Final Draft, 2003. - 44 p.

6. Fema 440. Improvement of nonlinear static Seismic analysis procedures. Applied Technology Council (ATC-55 Project) 201 Redwood Shores Parkway, Suite 240, Redwood City, California 94065, June, 2005. - 392p.

7. John P. Wolf, Chongmin Song. Some cornerstones of dynamic soil-structure interaction. Engineering Structures 24, 2002, p. 1 3 - 2 8 .

8. John S. Horvath. Basic SSI concepts and Applications overview. Manhattan College, School of Engineering, Bronx, New York USA, 2002. - 128 p.

9. Josia Inwan Rastandi. Modelization of Dynamic Soil- Structure Interaction Using Integral Transform-Finite Element Coupling. Lehrstuhl far Baumechanik der Technischen Univesitat Munchen, 2003. - 98 p.

10. Hikaru Nakamura. JSCE specification for seismic performance verification and damage of concrete structures due to recent earthquakes. Nagoya University.- p. 69 - 84.

11. Kazuo K.,Yuanbiao Y., Yoshitaka M. Single beam analogy for describing soil-pile group interaction. Soil Dynamics and Earthquake Engineering 23, 2003. - p.

213-221.

12. Keni Ishihara. Soil Behaviour In Earthquake Geotechnlcs. Oxford University Press, 1996. - 3 7 6 p.

13. Pala M., Caglar N., M Elmas. Soil-structure dynam- ic interaction using artificial neuraf networks. IJCI Proceedings of Intl. XII. Turkish Symposium on Artificial Intelligence and Neural Networks, Vol.1, No.1, July 2003. - p. 348 - 354.

14. Towhata, I. Development of Geotechnical Earthquake Engineering in Japan. Department of Civil Engineering, the University of Tokyo, 2006. - 42 p.

KHAN TRl/QNG THLTC HIEN CAC HANG MUC THUpC DLT-AN DAI LO DONG - TAY VA DLT AN CAU PHU MY

Nham giai quyet cac vudng mac phat sinh td sy cb not cac dbt h i m trong viec thye hien gbi thau sb 4

"Xay dang h i m vagt sdng Sai Gbn va daong mdi Thu Thiem" thupc dy an Dai lb Dong - Tay, thai gian vda qua, UBND TP. Hb Chi Minh vda chi dao Ban quan ly da an Oai lb Dbng - Tay va Mbi tradng nade thanh phb khan traang phbi hgp vdi cac don vj lien quan gbm: nha thau, ta van giam sat va ta van thiet ke kiem tra, danh gia tbng the ve chat lagng cua hien trang be tbng cac dbt h i m ; dbng thoi de nghi dan vj ta van dbc lap tham tra lai. Da kien cbng tac saa chiJa cac dbt ham se dagc thyc hien trong thang 6 nay.

Ve sy cb lun tai ham ha chd U (phia bd quan 2), UBND thanh phb yeu cau cbng ty ta van bao bao nguyen nhan va giai phap xy ly cu the. Don vi ta van ty chju trach nhiem bb sung sda chda khac phuc cho bao d i m theo yeu eau eua hb so thiet ke cbng trinh.

O i n nay khbi lugng thi cbng gbi thau sb 4 dat tren 70%. Ngoai cac sy cb tren, tien do thae hien gbi thau

nay cbn bi anh hacrng do cbn vadng 11 can hb tai nut giao thbng Cat Lai thubc dadng cbng vu sb 1. Cung thubc da an Oai lb Obng - Tay, gdi thau sb 6 "Xay dyng dadng phia TSy va ma rbng dadng ven kenh" do vabng cap ngam Oien lyc Chg Quan chaa di ddi nen anh hadng den tien do thi cbng,' hien mdi dat 73%.

Sa Giao thbng van tai TP. Ho Chi Minh va Cbng ty cb phan BOT cau Phu My cung vda cb thbng bao; k l td ngay 5/6 den 31/7, dadng Lien tinh lb 25B va dadng Nguyen Thi Dinh, thupc pham vi nut giao thbng Lien tinh lb 25B - Vanh dai 2 se dagc rao c h i n mat dadng hien hOu. Mat dacfng tam se dagc lau thbng thay the phan mSt daang hien hdu bi rao c h i n trong thdi gian tren. Viec rao c h i n nay la n h i m tao dieu kien thuan Igi cho viec thi cbng nut giao thbng Lien tinh lb 25B - Vanh dai 2, thubc cbng trinh xay dung dadng Vanh dai 2, doan nbi td cau Phu My d^n Raeh Chile. Hien, dadng Vanh dai 2 dang dagc d l y nhanh tien dp thae hien de khi c i u Phu My khanh thanh vao dip 2/9 n§m nay se phat huy hieu qua tbng hgp cua cbng trinh •

HM