Trao ddi hqc thudt & Thdng tin Khoa hqc Cdng nghe
Str DUNG CHirONG TRINH EVERFE 2.25 PHAN TICH KET CAU AO DlTOfNG CUNG
TS. NGUYEN QUANG PHUC Tnrdng Dgi hgc Giao thdng Van tai ThS. NGUYEN HONG PHONG Viin Khoa hgc Cong nghe Xay dtfng Tdm lit: Bai bdo trinh hdy viec nghiin cuu sir dung chuang Irinh EverFE2 25 - My trong viic phdn tich kit cdu do dirdng cung.
Summary: This paper present reseach using program EverFE2.25 - America for analysis rigid pavements.
Keyword: FEA, rigid pavement, concrete pavement. Ever FE. elastic soilds.
I. DAT VAN DE
Ao dudng Cling la ket cau do dudng phiic tap vdi nhilu ldp ehju tdc dgng ctia tai trgng xe, tdc dgng ciia sy thay ddi nhiet do va ca che truyen tai tai cdc khe noi... Phdn tich sir tuang tac, cac ca che ho^t dgng ciia chiing ddng mgt vai trd quan trgng quyet dinh den kha nang ehju lyc va tudi thg cua mdt dudng ciing. Westergaard (1948) da dua ra Idi giai cho bai toan tdm tren nen dan hdi. Bdi todn Westergaard cd nhieu han che trong viec the hi?n diing ban chat ldm viec ciia ket cau do dudng cting nhu han che ve lien ket gitra tdm va nen, tai trgng tac dung cung nhu lien ket truyen tai trpng tai mdi ndi, viec ti'nh todn vdi tdi trgng nhi^t dg,... Do dd can cd phuang phdp mdi de md phdng dung hon sir lam viec ctia kit cau dudng BTXM. Phuang phdp phdn tich phdn tu hiiu han ra ddi da dap ung dugc cac yeu cdu dd. Phuong phap phdn tu hdu han cd thi gidi quyet cdc bai toan nhieu ldp, nhieu md hinh nen khdc nhau, vdi cac dieu kien bien khac nhau, md rdng vdi cac kich thudc hinh hgc phiw; tap,...
Bdi bdo trinh bay kit qud budc ddu nghien cuu su dung Ever FE 2.25 de phdn tich, tinh loan ket cdu do dudng cung.
II. CAC KHA NANG CUA EVER FE 2.25 Ever FE2.25 Id phdn mim mien phi dugc phdt trien bdi cdc trudng Dai hgc Maine vd Dai hgc Washington vdi su tdi trg ctia Sd Giao thdng vdn tai Washington vd California. Ever FE2.25 dugc tai miln phi tai http://www.civiI.umaine.edu/EverFE/.
Ever FE2.25 Id phan mem su dung phuang phap 3D phdn tir hiru han de phdn tich, md phdng ung xu ciia ket cau mat dudng be tdng xi mdng thdng thudng cd khe n6i (JPCP) dudi tdc dyng ctia tdi trpng xe va tai trgng mdi trudng. Ever FE2,25 cd thi phdn
FT
-h-h
Hlnh I. Su dung FE trong tinh toan Icel call phuc tgp
266
Tap chi KHOA HOC GIAO THONG VAN TAI So 43 - 09/2013Trao doi hoc thual & Thdng tin Khoa hgc Cdng nghe tich tuyin tinh vd phi tuyin ddp ung dugc cac yeu cdu nghien cuu va thiet kl mat dudng.
Ever FE2.25 la phdn mem chuyen dung, than thien, dl tuang tdc, dd hga true quan duoc nhieu tdc gid su dung trong nghien ctiu, phdn tich kit cau.
Ever FE2,25 co khd ndng md phdng cbinh xdc su hoat ddng cua ket cdu do dudng cung nhu: mo hinh hda din 9 tam BTXM lien kit vdi nhau; 3 ldp ndn dan hdi phia dudi (cac Idp lien kit hodc trugt tu do); md phong sy hoat dgng ciia thanh lien ket; cdc gradient nhiet do bdc 1, bac 2, bac 3 dugc xdc dinh; Ever FE2.25 cd thu vien tdi trgng day du de ddng tao ra he tdi trgng phiic tap...
Sau ddy la mdt vai tinh nang ddc trung ciia Ever FE2,25 trong viec mo phdng su hoat dgng ciia ket cdu do dudng cung.
2.1. Gradient nhiet do
Ever FE ly tudng hda cac gradient nhiet do la tuyen tinh bdc nhdt, bdc 2, bdc 3 vd trong I phdn tir FE thi gradient nhiet do la tuyin tinh.
SpecifiBd Temperature Va nation
Temperature Variations Used in F£ Analysis
Hinh 2. Md hinh hoa gradient nhiil do 2.2. Mo hinh tuong tac tam - nen
wheel load
-dowel
# 1
high stress on subgrade
W
-separation ofslab and subgrade \m\U.i tmiiiKLime icjaiioiivjuii
Hinh 3. Mo hinh hoa tdm - nin
Hinh 3 thi hien viec EverFE mo phong tuong tac gitta tam BTXIVI va n6n. Viec chia thanh cac niit cho phep xem xet 2 truong hop giita tim va nen co ti6p xiic hoac tach neng ra lihong.
Trong ca 2 truong hyp tam va nen Ichong chia sc cac mit va han chS cac nut <te dap tag dicu kien lien kk khio nhau. Cac gia tri eua k va S„ (sit dung khi tam va njn con tirong tac) (tucrc Rasinussen va Rozuck (2001) lap thanh bang.
Tap chi KHOA HOC GIAO THONG VAN TAI SS 4 3 - 0 9 / 2 0 1 3 267
Trao doi hqc thudt & Thdng tin Khoa hqc Cdng nghe 2.3. Md hinh hda thanh lien ket tai
cac moi noi
Ever FE 2,25 md hinh hda vd tinh todn khi cac thanh truyen lyc tai cac khe noi nhu hinh 4. Cd thi md hinh thep truyen Iuc nam ngang, lech hudng, vd md hinh lien ket giua thanh truyen luc va tdm BTXM.
III. MOT SO KET QUA CUA VIEC SC DUNG EVER FE 2.25 TRONG VIEC PHAN TICH, TINH TOAN KET CAU AO DUOTVG BTXM 3.1. Giai quyet bai toan Westergaard
Westergaard (1948) da dua ra Idi gidi cho bai todn I tam BTXM dat Ien nen ddn hdi.
Tdc gid da dua ra 3 vi tri tinh todn cho tdm BTXM, Trong bdi bao nay xin dugc gidi quylt vdi bdi todn luc d%\ tai CEtnh tam la vj tri bat Igi nhat (hinh 5).
Xet 1 tdm BTXM dan gian cd kich thudc Id 5000mm X 5000mm X 254mm dat tren nin ddn hdi vdi k = 0.027 Mpa/mm, p = 0.20 vdi tai trgng dan 40 kN kich thudc 405mm X 405mm dat t^i canh tdm, Tdi trgng nay tuong duong tai trgng 40 kN kich thudc r = 457 mm (vdng trdn cd dien tich bdng hinh vudng).
Westergaard dua ra ldi giai vdi ung sudt Idn nhdt la 1.43 Mpa.
EverFE 2.25 xet vdi tam BTXM chia ludi 12x12 phdn tu x2 phdn tu theo chilu day dugc ung sudt Idn nhdt la 1.50 Mpa.
ittmitip
Hinh 4. Mo hinh hoa thanh truyen luc tgi cdc mot noi
Hinh 5. Md hinh bdi lodn Westergaard vdi vi tri ddt luc bdt lgi nhdt
268 Tiept
OnB&Iroeai Daerttman 8XS 10X10 12X12 lEXlE
mii
c chia cdc ludi {
kcn^Slat) TUckneu Slab Strri: (MPa)
149 153 1,53 149 145
han tu ciia tam (8, 10, 12,.
Diicrncaitoii SXS 10X10
3;xu
1SXI8
; j x : 4
Hinh 6. Chia ludi vd kit
labSuesifttPa) i . r 1-19 150 14B
qua cdc irng .24)
sudt ta dugc
...
ket qua.
1
1
'
11
___
trong ldm BTXM
Tap chi KHOA HOC GIAO THONG \^fi TAI So 43 - 09/2013
Trao ddi hqc thudt & Thdng tin Khoa hoc Cdng nghe Bang so sdnh gid tri tinh todn giua Westergaard vd Ever FE2.25
Bieu do so sdnh gid tri tinh todn giUa Ever FE vd Westergaard
3000 SOOO 7 0 0 0 91 Slab Size imm) Gid tri tinh lodn vdi cdc kich thudc khdc nhau bdng Ever FE.
Hinh 7. Kit qud so sdnh giUa Ever FE vd Westergaard 3.2 Phan tich anh hirdng cua nfaiiet do
lop of slab heals relative ta Ihe bottom dull ng a vamiday
k f i ;\ T
1 1 I
Hinli 8. Mo hinh hoa tdc dung cua gradient nhiet do.
EverFE 2.25 phdn tich ung sudt, bien dang trong tdm be tdng dudi tdc dung cua nhiet do vd tac dung ddng thdi cua tai trgng va nhiet dg. Cdc ket qud kiem chung phii hgp vdi gid tri do dac thirc te hien trudng [6].
3.3. Sir dung Ever FE de phan tich truyln lire d moi noi cua tam BTXM
Hinh 9 mo td gidi phap cua Ever FE trong viec mo phdng su ldm viec cua thanh lien ket tai moi ndi. Anh hudng cua thanh lien ket tdi sy hoat ddng ciia ket cdu do dudng cung Id rdt Idn.
Kha ndng tuong lac vdi tdm BTXM, do chimg cung nhu sir lech hudng ctia thanh lien ket dugc xij ly nhu thi ndo?
• Rigorous treatment
• Either bonded ot unbonded
• Can be severe nonlineanly
Dowel-Slab Support Modulus
\ K^ = modulus of
l\.
• Less rigorous treatment
• Model remains linear
• Ailo^rs intemiediate bond le
Hinh 9. Ever FE mo hinh thanh Hen kef
Tren day la mijt so vi du ve viec sii dung EverFE trong viec phan ticli su hoat dong ciia liet cSu ao dirimg ciing. Ngoai ra, EverFE co IhS xii ly, tinh toan kit cju ao duong ciing duoi tai trong ciia nhiet dp, mo hinh hoa cac khe CO tren dirong... rat phii hop de phan tich, tinh toan ket
Tap chi KHOA HOC GIAO THONG VAN TAI S6 43 - 09/2013 269
Trao ddi hqc thudt & Thdng tin Khoa hqc Cdng nghe
cdu do dudng cdng. Cdn cd nhirng nghien cdu them, sdu hon nua de thay dugc kha ndng cua EverFE.
3.4. So sanh gia tri bien dang tinli toan ciia Ever FE vdi bi^n dang do tai hien trudng Thdng 3 ndm 2001, A.Qaium Fekrat trudng dai hgc Ohio da chimg thuc khd nang cua Ever FE trong viec sir dung phan tich, tinh todn ket cau do dudng cung. Nghien ciru thuc hien cdc thi nghiem hien trudng vd so sanh vdi ket qud ma phdn mem tinh loan ra, tir dd dua ra cdc bieu dd so sdnh [6].
Cdc kit qud tinh toan ciia Ever FE phii hap vdi cdc ket qua do dac thuc te ngodi hien trudng. Hinh 10 the hien kit qua so sanh cac bien dang tinh toan va biln dang thuc te, cac gia trj bien dang sai khdc khdng nhieu.
nt iDir« I r o m f l r i t ]olBt (In) Oliiance of I r o n ante irom firit jolni (In)
Hinh 10. Vi du so sdnh kit qud biin dgng tinh bdng Ever FE vdi kit qud do thuc ti
— ~ gid trj tinh bdng Ever FE, ^ ~ ~ " gja tri thuc do IV. NHAN XET, KIEN NGHI
Qua khao sat mdt sd trudng hgp bang EverFE cd mdt sd nhan xet:
• Lyc cat giua tdm vd nen cd the anh hudng Idn den ung sudt ciia tam BTXM,
• Su tiep xuc giu'a thanh thep lien ket va tdm BTXM anh hudng den ting sudt cua da dudng vd su truyen Iuc tai mdi ndi.
• Sy !6ch vi tri cua thanh truySn luc anh hudng dang kl tdi su truyln luc tai mdi noi.
• Cdc kit qua tinh todn ctia EverFE phii hgp vdi cac ket qua do dugc tu hien trudng.
• Sir dyng EverFE phdn tich, tinh toan dugc ung xu ciia tdm BTXM vdi nhirng dilu kien phuc tap, tinh todn dugc he sd truyen tai trgng qua mdi ndi.
Tai li£u tham khao
[1]. B? giao thdng van lai (1995), Quy trinh thiet ke mat dudng ciing 22TCN223-95
[2]. Nguyin Hdng Phong (2013), Luan van "Nghien ciru tinh todn kit cdu mat dudng BTXM thong thudng CO xet din lien kit gi&a cac tdm", Trudng Dai hgc GTVT Hd Npi.
[3]. EverFE2.25, Help.
[4]. William G. Davids, Zongmu Wang George Turkiyyah. Joe P. Mahoney, and David Bush (2003), "3D Fine element analysis of jointed plan concrete pavement with Ever FE 2.2"
[5]. Bill Davids, PhD, PE,(2004), "Ever FE workshop", University of Maine .
[6]. A. Qaium Fekrat, Calibration and Validation of EverFE 2.24: A Finite Element Analysis Program for Jointed Plain Concrele Pavements, M.S., March 2010, Civil Engineering
[7], http://www.civiI umaincedu/EverFE*
Phan bi|n: TS. Vii Dtic Sy
270 Tap chi KHOA HOC GIAO THONG VAN TAI So 43 - 09/2013