4
' I I KHOA HQC - C O N G NGHENGHIEN CUnj UfNG SUAT - BIEN DANG MAT CAT NGANG DAM HOP CO XET ANH HirdNG DO XOAN
TS. LE BA KHANH KS. PHAM T H ^ HUNG Khoa Ky Thuat Xay Dung T r u d n g Dai Hpc Bach Khoa Dai Hpc Quoc Gia TP, HCM
Tdm tat: Ngi dung bai bao tgp tmng vio nghien cieu sy inh hwdng cOa mdmen xoin do dc logi tii trgng Idn hd sa do tinh cua ket du phan tren cau dim lien tuc. Tinh toan kit qua dya trdn hai logi sa do tinh chinh di xet trwdng ieng suit - biin dang trong dc mit dt dam chiu anh hwdng do xoin: sa dd tinh theo h^ dam phSng vi sa do hi kit ciu khdng gian. Trong tat d cic sa do tinh, v$t ligu cua h$ kit du xem nhw deu lam vigc dan hdi tuyen tinh.
Ly thuyet thanh thinh mdng mdt dt kin dwg^ s u dyng di xic djnh trwdng ung suit - biin dang trong mil mit cit dim hgp theo sa do phing. Phan mem ANSYS vdi phin tw khii dwac s u dyng de phSn tich sa do khdng gian.
Kit qua tinh toin cho thiy anh hudng nhat dinh cua mdmen xoin din wng suit tiip vi ung suit phip, d$c bidt tgi dc vi tri gin vung d$t lye.
Abstract: The content of thesis focuses on researching the influence of the torque on the calculated diagram of superstmcture of continuous girder bridge. The thesis periorm calculations based on two types of diagram for calculating and analyzing the stress - deformation diagrams in each section:
2D-beam diagram and 3D analysis diagram. In all diagrams, the scope of the thesis only research In the workspace of elasticity.
Thin-wall theory for close section is used to determine the stress - deformation in each box girder section in 2D analysis. ANSYS software with solid elements are used for 3D analysis.
Calculation results showed a certain influence of torque to tangential stress and direct stress, especially at positions near the set force.
1. GIOI THIEU
Trong ITnh v y c thiet ke va thJ cdng cau, cac so do tinh todn t h u d n g d u g c xac dinh d u d i dang dam phdng chiu uon, Tuy nhien tren t h u c t§, doi vdi cac cau kien be tong c6t thep trong khong gian t h u d n g la chiu tai Igch tam, chiu tac dung uon x o l n ddng thdi. Do do, ung s u i t - bien dang cua d i m se co s y thay doi.
Vigc tinh loan dam tren thuc te se khdng xet d u g c chinh xac gia tn va s y thay doi ung suat - b i l n dang lien tuc tren cac dam va cac thanh phan trong mat cat dam, Vi vay viec xac djnh chinh xac dng x u cua dam va ung suat - b i l n dang cua d i m d u d i tac dung day du cua tai trgng dam bao cho cong viec t h i l t ke dam chinh xac, dem lai tinh on dinh va kinh t l cho k i t d u d i m be tdng cot thep-
Cae tai trpng lech tam gay mdmen x o l n trong dam hpp, npi lye nay lam phat smh cac ung suat tiep do x o l n Viec xac dinh chi tiet s y phan bo ung suat -
bien dang trong dam hop do tac dung cua cac to hp'p tai trong {xet d i y du anh h u d n g do uon, cdt va xoSn) giup ta CO the xet d i n day du hieu ung luc, bo tri cit thep chinh xac,
Xuat phat t u nhung t h y c te neu tren, tac gia da t|p trung phan tich s y thay doi cua ung suat bien dgng trong mat cat ngang dam hop d u d i anh hudng cua mdmen xolin do tai lech t a m . Dong thdi xem xet sy chinh xac va an toan cua cac s a do tinh hg dim p h l n g . Trong pham vi bai bao nay chi nghien ci>u d u ddm be long lien tuc mpt hop.
2. CO S6 LY THUYET
2.1. Phan tich theo s a do dam phang
2.1.1. Ly thuyet
Toan bg k i t cau phan tren d u g c chuyen doi hoan toan ve md hinh he dam p h l n g theo phuong dpc
s a i l nam 2015 '
KHOA HOC - CONG NGHf ' d u . NOi lye trong kit d u dugc xdc djnh dau tien
dya tren ly thuylt ve sire ben, trong dd cd mflmen xoln do tai Igch ldm dgt trdn d u . Gid trj ndi lye do cdc tdi trgng gdy ra dugc dCing d l xdc djnh trudng dng suit - biln dgng trong mli mgt d t ngang eua kit d u phin trdn.
Trong qud trinh ttr lue bat d i u giai dogn thi edng eho din giai dogn khai thdc d u , tdi trpng gay ra mdmen xoan Idn nhil chinh Id hogt tdi xe dugc dgt Idch ldm hodn todn ve mOl phia trong giai dogn khai thac. VI vdy, ndi dung xem xet anh hudng cua mdmen xoan trong kit d u dim ehu y l u ddnh gid theo giai dogn khai thac eua d u (kll d u nhjp da hodn chinh v l kit elu vd tdi trgng).
D I xdc djnh cdc higu dng lye do xoan, ta sd dyng d c h quy d i i thdnh mdt d t dim ly tudng vd dp dyng iy thuyet thanh thdnh mdng kin nham xdc djnh gid tri vd sy phdn bo ung suit tilp do mflmen xoan vd lye d t tdc dyng xung quanh mgt d t dim d u . [1]
Biln dgng ty Ig vdi dng suit tudn theo djnh ludt Hook trong mdi trudng ddn hdi tuyIn tinh.
2.1.2. Md hinh tlnh toin
Kit d u nhjp ehinh se duge md hinh thdnh hg khung dim trong mgt phlng dpc d u .
• I r •
Hinh 1. Md hinh tfnh toin dim phing dgc du 2.1.3. Mitcit quy dii
Theo edng thue xdc djnh dng suit trong thanh thdnh mdng mdt d t kin:
^ t 2tn ' ' Trong dd:
-1 a be diy t^i mOt vi tri bk ky trin tiet di#n.
- q ia iM'C ti4p tuyen tac dgng trSn mpt do-n vj cliilu dii ttieo ciiu vi tilt dien tlnh theo du'dng trung binh.
q = T,t = hing so (2) - Q \k dien tfch gidi hsin bin du'dng tmng binh L„ ciia
tilt di$n (phSn di$n tich gidi h^n theo du'dng n^t dijt xung quanh tdm udn).
lul^t c i t d i m hOp se du'O'c quy doi thiinh m$t c i t dim hSp rSng thSnh m6ng iy tudng trong phSn tfch i n h hudng do x o l n . Q u i trinh tinh t o i n x i c dinh i>ng s u i t trong d i m c6 t h i x i c dinh dudi t i c d$ng ddng thdi cCia mdmen x o l n v i luc c i t , trong d6 c i c tfnh c h i t hinh hpc co b i n m$t c i t d i m hQp trong tfnh toan h i u nhu sg dmgc glO nguy§n. [2]
[
I S4l1 nam 2015
1 A
1
1 B
Hinh 2. Mit dt dim hgp ring thinh mdng ly twdng Nhu vdy theo d n g thdc (2), mdt d t dam h|p ly tudng cd khd nang khdng xoln luang l y nhu m§t d t dam h0p thyc t l thdng qua hai ddc trung b l ddy vdch t vd dign tich gidl hgn bdi dudng trung binh Q. Ti> do, ta ed the xde djnh dugc ung suit vd biln dgng do tdc ddng ddng thdi bdi lye d t vd mdmen xoan trong mli mgt d t dam.
2.2. Phan tich theo s a do k i t c l u khong gian 2.2.1. Ly thuyit phin tich
Toan bp kit d u nhjp phan trdn dugc mfl hinh hod bdng phin Id khdi. Phin mIm ANSYS dugc si>
dyng d l tinh loan giup ta xdc djnh duge ehinh xdc sy dnh hudng cOa d c tai trpng tdc dgng din dam, gid trj cdc npi lye phdt sinh trong h$ dim, dua ra bilu d l phdn b l dd Idn gid trj dng suit trong mgt d t vd phdn tieh mfl hinh ung suat - biln dgng eOa dim h|p dudl d c hidu dng ding thdi cOa keo uln, d t vd xoan trong khdng gian.
2.2.2. Md hinh tlnh toin
Md hinh tfnh toin: Kit clu nhip chinh se dugc mfl hinh bang phan Id khii (SOLID) trong khdng gian vd iidn kit tgi goi d u bang cac diiu kign bien. ANSYS dua ra phi ung suit vd biln dgng trong dim theo lung mdt d t ngang dam hgp. Dya vdo nhung ket qud ndy bdi bdo da ddnh gid d c vj tri ung suit Idn cyc bp, sy thay doi ung suit tiep trong dim khi dong thdi chju dnh hudng cQa lye d l vd mdmen xoan.
Khi phdn tieh, vige chia ludi phan tu phCi hgp giCip cho cflng tdc phdn tich bdi todn trdn phin mIm ddm bdo dugc t i c dg, higu qud vd dd chinh xdc phCi hgp vdi ydu d u .
Ill*'
Hinh 3. Md hinh kit du nhjp dim h^p lidn (yc
m i l KHOAHQC-CONGNGHe
3, P H A N T I C H A N H HirdNG X O A N T R E N M O T C O N G T R I N H e g T H £
3,1. Phin tich theo so dd dam phlng K i t d u nhjp d^ng dam hpp cua d u SAng LQy dugrc su dung d l phin tich [3], Mvc dich cfla vipc phan tfch niy chl d l dinh g i i i n h hudng xoln. Kit qua cua phin tfch chua the diJng d l phin x6t m$t each ting t h i v l giii phip thilt k l cOa d u Sing LOy, Tn«irc khi tfnh toin d n quy d l l mSt d t dim hOp thuc t l giO'a d u thinh m^t d t dim h$p ring thinh mdng iy tudng.
^ ^ 1
>iBaapo|¥i -^
. M l
" 2 0 " .32.32(lcN/m) (4)
\ = <^
(5)Bing 3.1. Gii tii Ong suit tiip do mdmen xoin
Vi tri khio s i t t r i n milt d h ngang eda h$p Bin nip (giira dim) Bin nip (m^p s i t vich hOp]
\/ich h$p Bin d i y hdp
II I
0,25 0,50 0,50 0,25
Glitr|i>ng s u i t tilp
(kN/m^
129,28
e*MM
80,80 1 129,28 •"
Gdc xoln tmng d i m hdp:
" - - ^ (6) Vdi; I l i mdmen khing xoln eda dim.
I.iS_.l°-_7.718(n,') (7)
•OS ^ s
Vdi: G - — = — Id mdmen d i n hdi tnrpl 2(l+v)
2(l+v) 2x0+0,2) Hinh 4. Kich thu<fc hinh hoc mit cit giira d^m
Ap dgng ly thuylt xoln thanh thinh mdng kin ddi vdi d u dim liln tgc mQt hdp, Xung quanh dudng trung binh chu vl cua dim hOp kin, dim chju mOt iuc tilp tuyIn khdng ddi bao quanh q theo cdng thi>c (1):
t 2tQ ^ '
Trong dd:
Mg = 588,17kNm l i momen xoln cue dpi tpi vj tri giOa dim.
Q l i di$n tich gldl hpn bdi dudng trung blnh, Q = 9,10m'.
M„L
" GI
588,17x13,53
14.896xl0'x7.718 -0.69xl0"^(nd) Bilu dd phin bd dng suit tilp do mdmen x d n trong m$t d t dim:
Luc tilp tuydn niy chinh l i lye don vj xung quanh dim (dan vj Lvro'Chilu dil). Luc tilp tuyIn niy khdng ddi xung quanh chu vi kfn eda dim v i ti Id nghjch vdi ung suit tilp do xoln trong dim tCiy vio chilu diy t.
HlnhS.BiiuStingsuittiipdoxointiongm^ckdlni Cie i>ng suit tilp phit sinh bdi luc d t thudng di/?c gii thilt (theo D,i, Zhuravshil) cd d c tinh chit sau ddy: [4]
- Cic ung suit tilp x hudng theo phuung cOa lv<:
d t F,.
- Slf phin bd cua ung suit tilp thi diu v i bing nhau theo b l rdng eua m^t d t (nghia l i mpi diitn nim d c h d i u dudng trung hda thi cd cdng mdl W sd O'ng suit Ulp).
sd 11 nam 201s i
KHOA HQC-CONG NGHE # # # # # Qua hai gid thilt trdn, ta nhgn thiy dng suit tiep phdt
sinh do lye d t khong dnh hudng theo b l rdng d u , cdc thdnh phin dng suit lilp theo phuung ngang giCra cdc Idp song song vdi tryc dim ed gia trj bang nhau. Hdm dng suit tiep Id mdl hdm phg Uiuflc vdo sy biln thien chilu cao tai vj tri xet ung suit den true tnjng hda cDa mgt d t .
Cdc ung suat tilp ndy bang khdng tgi mep trdn vd mep dudi cua mgt d l . Tgi eOng ede vj tri cd mdt d t khdng doi, hdm ung suit tilp la mpt hdm bde 2 ed gid trj Idn nhil lai vj tri g i n tmc tmng hda nhit.
Cdng thdc ting qudt xde djnh ung suit tilp phdt sinh trong m§t d t do lye d t F^ gay ra:
Bilu do dng suit tilp tong hgp do tac dung to hgp eua lye d t vd mdmen xoan:
''*" Hinh 6. Biiu di ieng suit tiip do lye cit trong mit W citdim
I S611 r
- | . 4 H P l ^ ^ =
mMiiifMBIiM
llil IBIIIIiillli
.«.11Wa
(8) Trong dd:
- s; Id mdmen trnh cua phin dign lich bj d t A' dii vdi tn,ie trung hda.
- A" Id dign lich bj d t gidi han bdi dudng di qua vi tri xdt dng suit song song vdi trgc tmng hda vd mep bidn cua mdt d l .
- y Id chieu eao tinh tu true tmng hda din vj tri xdt dng suit.
Cdng thdc tinh dng suit tilp cho dim chi dung khi vdt lidu d i m cdn dang Idm vide ddn h i i tuyen tfnh vdi biln dgng bd. Trong khflng gian thyc te doi vdi cdc lye tdp trung hay lyc phdn bo tren vung tilt dign bd, sy phan b l dng suit xung quanh dilm dgt lyc khd phde tgp vd chi anh hudng cgc bp md khdng lan rdng d cdc vOng d xa trdn todn mgt d t dim. Cac cflng thdc xae djnh dng suit tilp cho dam thudng ehi dugc xem id cflng thdc gan dCing vd an todn.
Cdng thdc xdc djnh biln dgng tn^gt do lyc d t :
V - ^ (9) Hdm ung suit tiep trong d u d i m hop lien tuc se d
sy thay doi khi di qua het bdn nap, vach hOp va ban ddy. Trong dd dng suit tilp dgt cyc dgi tai vj tri giua tryc tmng hda vd dgt cyc lieu (= 0) Igi ede vj tri thupc ., mdp bien eua d u dim hdp.
^, Bilu d l phan b l dng suit tilp do lye d t trong mat
^ : d t d i m :
0
Hinh 7. Biiu di Ong suit tiip ting hgp tlnh Uieo mit dt dim
Theo nhu bilu do tren, mdmen xoan ed dnh hudng ddng ke len gid trj ung suit tilp trong dim. Dudi dnh hudng eua lye d t , ung suit tilp phdt sinh trong thdnh dam hdp vd ed gid In Idn nhit tgi vj tri tn,ie tmng hda dim. Dudi tde dgng cOa mdmen xoln, dng suit tilp phdt sinh xung quanh dam hpp ring ed gid trj tucng dng t^ Id nghjch vdi b l ddy tai vj tri dd.
is hai ben vdch hop, ung suit tiep chju dnh hudng bdi to hgp lyc cCia mdmen xoln vd lyc d t . Dpc theo vdch hdp, gid tn dng suit cd sy thay doi mgnh ve dd Idn, mdt bdn dam gid trj dng suit tilp cd dfl ldn tang nhilu khi Id l l hgp cflng tdc dgng cCing chieu giua hai hidu ung lyc, ben cdn Igi la to hgp d n g tac dung ngugc ehilu. Vj tri ndy cd the cd sy thay doi ve ehilu cua ung suit tgi vj tri xung quanh trgc tmng hda khi gia tri dng suit cyc dgi do mflmen xoan trdn d u cd gid trj Idn hen.
3.2. Phdn tich theo so> do ket cau khflng gian
f b u Tld) Ket c*u nua t n Cau Souj Luy Txcn ve^ «;*u tromn -I-EEH u a u UDoq inuy
Hinh 8. Biin dgng ting thi ciu dim liin tuc (Tylg:103}
Doi vdi tnjdng hgp dat tai dOng tdm, tmdng biln dgng trdn dam chi ed chilu phdn bo thay ddi dgc theo ehilu dai d u , vd d i i xdng nhau (cung ddi mdu) theo phuang ngang d u .
O l i vdi trudng hgp dgt tai l$ch tam, tgi mgt d t dgt tdi, biln dgng thay doi rd rdng theo phuang ngang
mm
# # # # # KHOA HOC-CONG NGHf
d u (hinh 9). Vj tri biln dgng idn nhit la vj tri lai trpng Ieeh tdm duge b l tri, cdng xa tai Igch tam, biln dgng cang giam hay ung suat cang nho. Dpc theo chieu dai d u , sy thay ddi bien dang theo phuung ngang rd net tgi cac vi tri gan lai lech tam va giam ddn tgi cac vj tri xa lai Ideh tdm. Gia trj chuyen vi Idn nhdt Igi vj tri giua dam la DMX = 0.008145 (m).
Hinh 9. Trwdng biin dang theo phwang ngang tai mgt dt giiea dam (Ty 1$: 103) So sdnh vdi phdn tich biln dang mat d l ngang d u ung vdi md hinh phdng, mat d t ngang d u theo md hinh khdng gian cung ed bien dgng cua vdch hdp phia ddt tdi Igeh lam Id idn nhit, biln dgng trugt di xudng. Vdch hflp phia cdn Igi cd biln dgng trugt nhd so vdi mdt cat, it dich chuyin so vdi phia dgt lyc.
Ban ndp vd bdn day ed bien dgng tdng dan den vj tri dgt lyc.
Bien dgng theo phuang ngang d u cd sy thay doi dan tu dilm dau ednh ben nay din phia edn Igi, trong khi bien dgng Ihudng khflng doi theo phuang dung (dde bigt tgi hai vj tri vach hdp). Bien dgng Idn nhat tgi vj tri mdl d l giua dam: DMX = 0.008145 (m).
udn Idn nhat luc nay Igi giua mat d t dam, lam phat sinh trudng ung suit phap do uon. Nhdm ung suat phap nay ty Id thudn vdi mdmen uon trong dam vd chieu cao vj tri xet mdmen tinh tu tryc tmng hda. Xet trudng ung suit dugc tinh loan theo nhu hinh 11, ung suit nho nhdt tai vj tri mdp tren eua dam, ung suit Idn nhat tai vj In mep dudi eua dam. Sy thay ddi dp Idn tu ung suit nhd nhit d i n ung suit Idn nhat theo tinh chat luyen tinh phy thuflc vdo ehilu cao cua dam (bude chia cua lung dai mau gin nhu bdng nhau) tuang duang hd dam phang 2D.
Theo phuang ngang eua mdt cat ngang d u , ung suat phdp tai ban ndp vd ban ddy eo mau gin gidng nhau theo phuang ngang. Oing thdi, be ddy cua ede dai mau thay doi gii>a hai bdn vach h$p gin luang duang nhau. Dieu nay ehung Id trong mdt cit giua dam eua clu, sy phdn bd ung suat phdp theo chilu cao dim trong khoang vdch hop gan nhu Id tuyen tinh.
Tuy nhidn, trong khdng gian do anh hudng bai vige chju lyc xae dinh theo 3 phuang, nhdm hd so Poisson, vi tri va dien tieh nai dgt lai md se ed sy sai khdc. Theo Hinh 11, do anh hudng cua viec dat tai Igeh tdm ung suit trong mdt d t dam ed sy thay doi vd khdng edn ddi xung nhu linh loan trong bai loan phang. l^i'ng suit phap am nhd nhil tgi ngay phia dudi khoang vi tri dat lyc, ddy chinh la vj tri cd irng suit cyc bfl nhd nhat (SY = -0.33x1 O^Pa). l>ng suit duang Idn nhit nam d dudl cOa bdn ddy, ngay vj tri vach hflp. Day la vj tri ed biln dgng Idn nhil vd dng suit phdp Idn nhat trong k i t d u phan tren d u (SY
= 0.2x10'Pa).
Hinh 11. Trwdng phin bi Ong suit tiip tgi mgt cit giu-a dim
Trudng phdn bo ung suit tilp tgi mgt cat giOa Hinh 10. Trwdng phin bo ung suit phip tgi mgt cat dim phdn bo phuc tgp, dde bigt Id cac vj tri thuijc
giiea dim ban nap.
U'ng suit phdp tgi mat d t gii>a dim cd tinh chat l>ng suit tilp dat gia trj tuygt doi Idn nhit nam xung phdn bd gin luang duang tinh chat nhu mpt hg dam quanh vDng dgt hogi tai igch tam, hiu hit diu n^m phdng. Khi ddt nhdm tai tgp trung Idn hd, mdmen tren bdn ndp. Vj tri cd ung suit tilp dm Idn nhit nim
mm
KHOA HQC - C O N G N G H $ -
ngay ben dudi vj tri dgt hogt lai. Vi tri cd ung suit lilp duang Idn nhat nam tgi ede vj tri giao giua ban nap va vdch hop vd cae vj tri giua dam. Cdc vj tri nay d mflt vCing ung suit cyc bp Idn han rat nhieu so vdi ede vi tri edn Igi. Ddc biet la tai vi tri dgt hoal tai xe, vi tri nay ed ung suit tilp duang vd ung suit tiep dm gin nhau, each nhau mdl khoang dgt lye eua bdnh xe.
Quan sat sy phdn b l ung suit tilp trong vach hdp ben trdi, ta nhgn thay ung suat tilp cyc lilu ndm tgi vj tri giao giua vach hgp vd ban nap. Cfng suat tiep duang cd gia trj Idn luang duang nim trong vach hdp. CJ'ng suat cd gia trj dao ddng quanh vj tri giua vach hop khong Idn vd giam dot nggt khi di v l hai ben mep. Dieu nay chung td ham phan bo ung suit tren vdch hdp khdng tuyIn tinh vdi chieu cao vach hop. So sanh vdi phan tieh trong he dam phang, ung suat trong vach hpp Irudng hgp nay cd gia tri duang idn, la nhgn thdy eae tinh chat nay gan tuang duang vdi phdn b l dng suit trong vach hpp xet theo md hinh tinh loan trong khdng gian.
Lfng suit dm phat sinh tai hai vj tri d i u cuoi cua vach hOp khdng dugc xet den trong tinh todn k l l cau theo hg dam phang.
Ngodi hai vj tri khdp gida bdn day vdi vach hop, ung suit tilp cCia ban day gan nhu bang nhau Iheo suit chieu dai eua ban ddy. So sanh vdi phdn tich he dam phang, bdn day ehi chju ung suit tiep tac dung do mdmen xodn. Mdmen ndy lam phat sinh ung suit tilp chgy quanh tam quay cua mat d t dim cd gia tn t^ Id nghjch vdi b l ddy tgi eac vj tri dd.
Cfng suit tiep phan bo tren ban ndp khi duge md hinh linh loan trong khdng gian theo ANSYS dua ra kha phuc tgp. Cfng suit tilp duang vd dni cyc dgr dugc phan b l tren d dai cua ban nip, nam d hai bdn eua ede vj tri dgt lye vd cdc vi tri khdp noi curig;
vdi vdch hdp. Cdc vj tri ehu ylu xuat hidn ung suli tilp dm eye tilu la eae vj tri quanh khdp noi cung^Vgi vach hpp. Cdc vj tri chu y l u xull hien ung su^ttilp duang Idn nhat Id d e vj tri dudi khu vyc dat tai bdnh xe vd vj tri nam giua ban nap. ,-.:•
Tm^ng phdn bo ung suit tilp theo ANSYS nan nhu luang duang vdi cae bai loan phan tiphr&^n ndp theo phuang phap dai ban, trong dd k h i ^ x l ^ t Ieeh ldm, lyc d t dgt gia trj eye dgi va eye ti^u cd do Idn Idn nhit tai hai ben vj tri dat lyc cua ban nap."' Vigc phdt sinh nhilu ung suit tilp cyc b'd ldn tai cac vj tri khdp n l i thdng thudng do dp cdng tai cae vj tri ndy Idn, chju tdc dyng dong thdi ciJa nhieu hidu ung lye, dgc bigt id ban nap Id b l mgt dugc dgt tai nhieu nhit. LOe ndy to hgp eua eac tai theo fihilu phuang se ldm phdt sinh cdc dng suit tiep cyc bp.
I S6 11 nam 2015
dieu thudng khdng dugc xet den trong cdc bai loan ket d u tinh toan theo he dam phang. Cac vj tri ung suit l i l p cue bd ldn eung thudng la eae vj tri cd bien dgng tflng Idn trong he dim hdp, dudi anh hudng higu ung iye do mdmen keo uon trong dam.
Vi vgy d n thilt phai xem xet danh gid ky ludng anh hudng long t h i eija tai Igch lam khi linh todn theo md hinh dim phang. Quy ludt phan b l ung suit tilp tren ban nap r l l phuc tgp vd dgt gid trj Idn nhat quanh eae vj tri dat xe.
4. K^T LUAN
Xodn trong kit d u nhjp eau ddm hdp lien tyc la hieu ung lyc d n duge xet den trong linh loan phdn tich ket d u . Xodn lam thay ddi gid trj, chieu eua ung suit va bien dgng, anh hudng din bdi todn tinh kha ndng chju lyc cua k l l d u (ung suit lilp tgi cdc vi tri ehu vi mgt d t dim tang khoang 20%).
Theo phan tieh mo hinh dam phdng, gia trj cua dng suit tiep tren ban nap vd ban day, phy thudc vao chieu day cua ban. Tai vj tri vach hop, ung suit lilp phia vach hpp ed hoat tai dgt lech tdm gia lang dang k l ve dp Idn, ung suit tiep phia edn lai giam ylu do lye d l vd mdmen xodn trigt tidu ldn nhau.
Theo phan tieh md hinh kit d u trong khdng gian, ung suit phap d ben dat tdi Idch lam ed sy gia tdng v l dp ldn so vdi ben cdn Igi, sy thay ddi trong trudng ung suit phdp khdng chi theo chilu cao dim (mdi trudng ddn hdi). Doi vdi trudng ung suat tiep trong mat d t , tai Ideh tam se Idm phdt sinh ung suit tilp eye bp ldn d ban nap vd thay dii gia In ung suit tai cdc vj tri vach hop.
Khi bd tri d t thep d n phai xem xdt them anh hudng cua mdmen xodn nhdm dam bao kha nang chju lyc cua dim •
T A I L I ^ U THAM K H A O
II] BO Giao Thdng Vdn Tdi, TlEU C H U A N THltT KE C A U 22TCN 272-05, 2005.
[2] Gopal Mishra, "Behavior of box girder bridges", [Online]. Available: http://
theconstruclor.org/structures/behaviour-of- box-girder-bridges/2194/.
[3] Cdc ban ve thilt k l - thi cflng d u dim hgp Sdng Luy.
[4] e l Kiln QuIc (ChQ bidn), Gido trlnh SCFC B^N VAT LI$U, TP. H i Chi Minh: Nhd Xuit Bdn Dgi Hgc QuIc Gia.
