Phan tich ung xu

KHOA HOC-CONG NGHE-

Phan tich ung xu cua ban mat cau dam I be tong cot thep duoi tac dung cua xe qua tai

I ThS. NGUYEN OtfC HIEU;TS. NGO C H A U P H U O N G Trudng Dai hoc Giao thdng van tdi - Phdn hiiu tqi TP. Hd ChiMinh

• PGS.TS. TRAN THETRUY^N Trudng Dqi hoc Giao thdng vdn tdi

TOM TAT: Bai bac thyc hi?n cac tfnh toan mo phdng ung xd ca hpc ngoai gioi han dan hoi cda ket cau b^n mgt cau be tong cot thep (BTCT) cda ket cau nhip dam I djnh hinh chiu tac dgng ciia xe qua tai, su dung mo hinh phi tuyen cua vat lieu be tong, mo hinh phan tich ndt, GiOa be tong va cot thep ton tai mot lye dinh bam, gia thiet luc nay la du ion de dam bao cho bien dgng giua be long va cot thep la bSng nhau Ket qua nghien cuu cung cap cac so lieu ve dp vong, ung suat va ca che xuat hien va lan truyen cac duang ndt trong be tong khi t i i trong banh xe 6 to tang dan

TL/ KHOA: Phi tuyen, ndt, be tong cot thep, ban m^t cau, xe qua tai.

ABSTRACT: This paper performs simulation calculations of mechanical behavior beyond the elastic limit of the reinforced concrete bridge deck of superstructures with I beams affected by overloaded vehicles. Using nonlinear model of concrete materials, crack analysis model Between concrete and reinforcementthere is a cohesive force, this assumption is sufficiently large to ensure equal deformation between concrete and reinforcement.

The research results provide data on deflection, stress of reinforcement and the mechanism of appearance and propagation of cracks in concrete when the load of truck wheels increases KEYWORDS: Nonlinear, crack, reinforced concrete, bridge desk, overloaded vehicles.

I.DATVANDE

Giai phap b i n mat eau bang BTCT do tai chd dUdesU dyng phd bien nhat trong cae cdng trinh cau dViet Nam.

Day la bd phan dong vai trd quan trong, tham gia ehju lUc tdng the, chiu lUc cue bd do t l i trgng true, ehe ehan bao ve ket cau ben dUdi v l gdp phan phin phdi hoat tai theo phaong ngang eau. Cle dang hU hdng chii yeu cua ban mat cau thudng gap nhu nUt, vd, bong trdc be tdng, m i l mdn. Mdt trong nhdng nhan td eo ban lam i n h hudng den dd ben ciia eau BTCT l i ndt ban mat eau. Mae du mdt 34

lugng d i n g ke nghien cdu cu the van de, nUt trong cic b i n mat eau BTCT van la mdt mdi quan tam rdng rai eho eleaucuvaeaumdi,

Nghien edu trudc day dUoc thUe hien bdi Ganapuram v l edng sU tap trung ehu yeu v i o hien tugng ndt eiia ban mat cau cho la do eo ngdt ciia san be tdng (Ganapuram va edng sU 2012, Patnaik v l Wehbe 2013).Tuy nhien, han ehe cua nghien cdu la cd sin trang t h i i nut eua ket cau bin mat eau. Cong ddng nghien edu van ehUa td ra sU ddng t h u l n ve each tiep can giai quyet van de. Cae vet ndt ed the phit tnen trong mat eau be tdng thudc nhieu nguyen nhin, nhUng ehii yeu chiing cd nguyen n h i n bdi be tdng ed eudng dd keo thap, khong dn djnh the tieh hoae phin dng hda hge. Dp md rdng v l khoang eieh vet ndt cung anh hudng bdi kich thudc eiia eae thanh cdt thep v i dien tieh be tdng hdu hieu boc xung quanh thanh (Soltani v l cdng sy 2013). Bat ke nguyen nhin, ndt l i mdt mdi quan t i m nghiem tuc ddi vdi ban mat cau, bdi vi eae vet ndt tao dieu kien xam nhap gay hai, eie ehat I n mdn hda hge nay lam hu hdng cdt thep d i t trong be tdng. Khi elorua va cae ehat I n mdn khie x l m nhap vao be tdng, cdt thep bin trong se b i t dau bi i n mdn, dan den g i i m tiet dien thep va ndt vd be tdng. SU suy g i l m nly cd the I n h hddng tdi khi nang chiu udn va k h i nang chju eat eua b i n mat cau be tdng, Ngoai ra, cae vet ndt b i n mat cau cho phep nude chly xuyen qua ban v l ed the pha buy ket eau ben dUdi (Krauss v l Rogalla,1996). Theo khio sit eiia 52 cO quan GTVT tren khap Bac My, hon 100000 eiy cau d l tim thay vet ndt sdm, thudng la khi be tdng duae mdt thing tudi (McDonald va cdng sU 1995). Nhdng quan sat tUong tUda dugc ghi lai bdi Patnaik va Wehbe (2013),

NUt ddi vdi be tdng l i khdng the t r i n h khdi do nd cd eudng dp keo thap, kha nang bien dang keo thap. Ket el'u BTCT ed Ung suat trong thep thap dUdi t i i trpng eho phep khai thac nen ndt rat han ehe, ngoai trd cic vet ndt xiy ra do su eo ngdt eiia be tdng va thay doi nhi^t do (Piyasena 2002). Tuy nhien, trong trUdng hop tai trpng khai thic ldn gay ra dng suat cao trong thep, dae biet 11 khi sd dyng thep eudng dp eao, elc vet nUt ed the quan sat nhin thay dugc cho l i dUdl tae dung tai trgng xe qui t i l . Cie vet ndt rdng v i ed the nhin thay I n h hddng den tinh tha'm my eua cdng trinh va cd the g i y ra eie t i c ddng b i t lpi. 0 Viet Nam, tinh trang xe q u i t l i eua elc phuong

KHOA HOC-CONG NGHe. So 03/2019

tien giao thdng tuong ddi phd bien. Nguyen n h i n ciia sU qua t i i do q u i trinh edng nghiep hda dien ra nhanh ehdng m i ha tang giao thdng chua d i p Ung kip, y thde ehap hanh luat le giao thdng ehua eao hole do nhu cau van ehuyen mgt sd loai m i y mde, thiet bj d i e biet. Do eae yeu td bat loi ve mdi trUdng va dieu kien khai thie nen hien tuong ndt ciia b i n mat eau be tdng dViet Nam do xe qua tai van xay ra. Cdng t i c sda ehda cau trong dd ed b i n mat eau dien ra k h i thudng xuyen v i trong nhieu trudng hop p h i i thay the bSng ban mat eau mdi.

2. M d HlNH P H A N TfCH PHI TUY^N NLTT BAN MAT CAU BTCT DO T A I TRQNG

2.1. Thdng sd cau tao va sd dd tinh

Ket cau nhip dam I cung vdi cac ket eau nhip dam super T, dam T dugc sU dung rat phd bien trong cac cdng trinh cau d Viet Nam. Trong eie edng trinh duge xiy dUng mdi trong thdi gian gan diy, ket eau nhjp dam 1 dugc sd dyng rat pho bien trong eae edng trinh eau nhd, cau trung hole trong cle nhjp dan trong cac cdng trinh eau ldn. Dam I BTCT DlJL thudng duge sd dung l l cle dam dinh hinh vdi cac chieu dli nhip 33m, 25.7m, 24.54m, 24.7m, 20.7m, 18.6m, 12,5m.

Trong khi gili phap b i n mat cau bang BTCT thudng va duge do tai ehd sau khi d l lao l i p xong eae dam, do dam ngang.

Ban m i t cau BTCT ciia ket cau nhip dam I BTCT DLfL dinh hinh vdi eae thdng sd eau tao nhutrong Sdng2.?:

Bing 2.1. BMC BTCT cda kdt eiu nhip dim i BTCT DUL nhip giin don

l1B,6m CT l12SmCT l3BmCS 130m CS

HL93 HL93 HL93 HL93 l25 7mCS HL93 l20 7mCS HL93 175m 175m 21m 21m 2 1 m

016m OMrn 0 2m 0 25m 0 2m 0 2m

„

018m OlSm 0175m 0175m 0 2m 0 2m 0 2m 0 2m

C6t t h i p ngang BMC 013,3 = 0 15m 013,3 = 0.15m 013,3 = 0 ISm 013,3 = 0.15m D12,a = 0,1m 012,3 = 0.1m D12,a = 0 1 m DI2.a = 0 l m

Cttc i h « p difc BMC D10,a = 0 2 m DIO, 3 = 0 2m 010,3 = 0 2m D10,3 = 0 2 m 010,3 = 0 2m DID, 3 = 0 2m D!0,3 = 0 2 m

Chi chu: S • Khoang each giDa tim cac dam dpc: ft,, - Chieu day suun dam; t^ - Chieu day ban mSt cau: f^ - Cidi h^n chay CUB cdt thep: f, - Cudng dp chiu nen cua be tong (mau hinh lang tru, tudi 28 ngiy); D - Duong kinh cot thep; a - Budc cdt thep: CT - Cang truoc, CS - Cang sau.

So dd tinh b i n m i t eau dugc tinh theo so do ban ke tren 2 eanh [1] nhUHinh2.f,trongdd:

- Khau dd tinh toan, S^ - Cu ly tU mat den mat vieh dam, Se = S-b^.

- Be rdng ciia b i n , B: Ldn hon be rdng d i i b i n hdu hieu, +M = 660 + 0.55S, -M - 1220 + 0.25S.

- Dieu kien bien: Hai dau ngam ke tren eie dam doc, hai canh tudo.

-Tii trgng ticdung:Trpng luong b i n than b i n , Idp phu mat eau, t i i trong binh xe vdi he sd xung kieh 1 + IM = 1.33.

Trong dd, t l i trgng banh xe p h i n bd deu tren dien tich hinh ehd nhat d tren dinh b i n m i t cau [1 ]. Vi tri vung t i e dung ciia b i n h xe n i m tai chinh gida b i n mat cau de gay ra hieu dng tai bat Igi cd kieh thude nhu sau:

- Phuong ngang eau: 510mm + 2*74mm - 658mm (cau tao Idp phu m i t c i u : 4mm Idp phdng nudc radcon/, 70mm be tdng nhua);

- Phuang dgc eau: 250mm + 2*74mm = 398mm.

Tien h i n h khio sit sU hinh thanh, lan truyen, p h i n

bd vet ndt theo cle eap t i i khic nhau. Tinh do vdng ldn nhat cua b i n , Ung suat trong cdt thep. Cap t l i Idn nhat tuang Ung vdi trye banh xe nang nhl't eua xe q u i t i i 21.45 tan [4].Tii trong phan bd tac dung trong vung dien tieh tiep xue vdi mat cau khi da xet tdi lUe xung kieh:

q - 1.33*214 5/2/(0,658*0.398) - 544.68 (kN/m')

Hinh 2.1: So do tinh ban mit cau

-\

Tinh toan ban mat eau eua cac ket eau nhip nhU Bdng 2.1, khi dieu kien ve t i i trgng t i e dung, tinh chat v i t lieu nhu nhau thl can tien hanh xem xet khau dd tinh toan, ehieu day eua ban mat cau v l cieh bd tri cdt thep.

Phin loai cac so do tinh ban mat cau dUa tren cle thdng sd eiia md hinh nhu khau dp tinh t o l n S^, ehieu day b i n t va cau tao edt thep. Gil thiet gida cic so dd tinh cd tinh ehat eo ly eCia vat lieu la nhU nhau. Cae so do tinh toan dugc phan loai nhutrong Sdng2.2.

Bang2.2. Cic sa do tinh bin mat cau cda cic ket cau nhip dam I BTCTDUL

=,^f

SDI S02 SD3

" s ^ S . .

.'^Lhi.

l24 54niCT 133 m a nssmCT ll2JmCT 13am C5 133 m C5 US 7m CS 120.7m CS

S.

(in) 1.572 1.59 1,59 1.61 215 2,2 22

(m)

..

018 0,18

B Im) 25 25

„^'^^am " ' B M C ' ' "

O13,s = 0!5m O13,d=01Sm 0175 . 2S ! D 1 3 , a = 0 l 5 m 0175

0 ! 03.

0.2 21 ; 0 2

25 1 D13.a=01im 3.5 25 2,5

D i : , 3 = 01m DI2.3 = 01m D I 2 . a - 0 1 m 25 1 D12.E, = 0lrr.

DIO, a ^ 0 2m

• 10.a^02m DIO a ^ 0 2 m

• l O ^ ^ O i m

• l O . a ^ O l m DIO, 3=^ 0,2m DI0,3 = a2m D10.3=02m

f, (MPa)

120 120 120 120 120 120 120 _«o_

f. (MPa)

2B 29 28 28 28 28 28 28

2.2. Mo hinh phi tuyen

Phan tieh phi tuyen nut cac so do ban mat cau nhU trong Bang 2 1 bang phan mem ehuyen dung Midas FEA.

35

KHOA HOC - CONG NGHE .

hinh tinh xet den sU l i m viec chung gida cdt thep, be tdng VOl gia thiet cot thep dmh bam hoan toan vOi be tdng

Hinh 2.2: Mo hinh phi tuyen tinh bin mit cau bang phan mem Midas FEA Tinh ehat eo ly eua v i t lieu:

Quan he gida dng suat v l bien dang eua be tdng khi ehiu keo, ehiu nen duoc the hien nhu Hinh 2.3 dudi day:

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d«gsua Uo

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Hinh 2.3: Dae trung ehiu keo, nen eua bi tdng Tinh chat co ly eua thep: Lfng xd cua edt thep trii qua 3 giai doan nhU H'inh 2.4. Qui trinh phan tieh eho thay md hinh nly ed do tin ely eao hon khi md t l day dii elc giai doan iam viee eua thep va dam b i o khdng i n h hudng den tdc dp hdi ty ciia bai toan phin tich [6],

Cdt thep ed cac chi tieu co ly: E = 200000Mpa, he sd poisson V = 0.3, y = 0.000785 N/mm', fy = 420MPa.

Hinh 2.4: Mo hinh thip din hoi - dio - hda edng Gil thiet be tdng chiu keo theo md hinh Hordijk nhu trong Bdng 2.3, chiu nen theo md hinh Thorenfeldt. Tinh chat coly eiia eie vat lieu nhutrong Bdng 2.3:

Bing 2.3. Tinh chat ea ly cua be tdng [5]

Chia ludi phan tU:

Phan t d be tdng: Chia khdi be tdng thanh elc phan t d khdi hinh hop, diing cho eae ket cau khdi chiu t l i trpng 3 ehieu, cie phan tdcd kich thudc trung binh bang 25x25x25(mm).

Phan tU cdt thep: Chia cdt thep ra thanh cie phin td thanh. Mdi phan tdthanh cd ehieu d i i 50mm. Ngoai ra, md 36

Hinh 2.5: Phan tdkhdibe tong, kich thude trung binh 25x25x25(mm}]

Hinh 2.6: Phan tu thanh eot thep, ehieu dai trung binh 25mm Gida be tdng va edt thep tdn tai mgt lUe dinh bam.

Trong cac p h i n tich thdng thudng, ea trong phin tieh ket el'u tdng the cung nhuphan tich cue bd, ngUdi ta thudng gia thiet luc nay la dii ldn de d i m b l o eho bien dang glOla be tdng v l edt thep l l b i n g nhau [8].

3. K^T QUA P H A N TfCH 3.1. Ket q u i ti'nh do vdng

Ket qua tinh dd vdng dUdi t i e dyng cua t l i trong b i n h xe cua xe qua t l i ldn nhat.

Bing 3.7. Kdt qui tinh dp vong bin mat eau

< ^ W 4 < ^ |

KHOA HOC-C6NG N G H E .

So 03/2019

Nhan xet:

- Dp vdng theo phan tich phi tuyen Idn hon khoing 1.5 lan theo phan tieh tuyen tinh;

- Dp vdng van nhd hon rat nhieu so vdi do vdng cho phep;

- Do vdng xap xi ty le thuan vdi ty sd S^Vt^^.

3.2. K^t qud tinh dng suat cdt thep

Ket qua tinh dng suat cdt thep dudi t i c dyng ciia trgng lugng b i n than, ldp phu v l t l i trgng binh xe ldn nhat.

Bing 3.2. Ket qui tinh dng suat trong cdt thep bin mat ciu

l^/ ^ .-^ ^{I i}

I _

I

I

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^

I Nhdn xet:

- l?ng suit keo Idn nhat trong edt thep theo p h i n tieh phi tuyen Idn hon khoing 5 tdi 6 lan so vdi p h i n tieh tuyen tinh trong khi Ung suat nen ldn hon chua tdi 1,5 lan.

- Cng suat keo phan tich phi tuyen Idn hon nhieu so vdi dng suat nen. LTng suat keo trong cdt thep nhd hon nhieu so vdi Ung suat keo cho phep.

- Cng suat p h i n tieh phi tuyen xap xi ty le t h u l n vdi ty sd S /t .Trong khi dd, dng suat phan tieh tuyen tinh xap xi ty- le t h u l n vdi ty sd S/t^^. Ngoli ra, gili phap sd dyng

edt thep ed dudng kinh nhd vdi khoing eleh nhd nhu trong SD 5, SD 6 eho dng suit ldn hon.

3.2. Ket qua phan tich ndt

Ket q u i p h i n tieh sU hinh thanh vet ndt v i dng xd ndt eda b i n mat cau dUdi t i c dung cua t l i trgng sd dyng Idn nhat.

Bing 3.3. Ket qua phan tieh nut vdi eie cap tii

SD2 ,0

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GW chd: P^^-TIi trpng b i t dau g l y ndt b i n mat cau.

Nhdn xet:

- Khi tai trong trye xe l i 10 tan b i n g gidi han eho phep thi tat el eae so dd b i n mat eau ehua bj ndt trd SD 4 da xuat hien vet ndt nhd.

- Khi tai trgng true xe 11 14.5 tan bang vdi t i i trgng true thiet ke thi t i t e l eie so do b i n m|t eau deu da bi ndt tai day ban dudi vi tri dat tai, bien n g l m . Chil yeu la cac vet ndt nhd theo phuong doc cau, cd vet nUt xien d SD 3, vet ndt ngang d SO 4, d l ed vet ndt ldn d SD 4 theo phuong dgc eau.

- Khi t l i trpng true xe la 21.45 tan bang t l i trong xe q u i t l i fdn thl tat ca cae so dd b i n mat eau deu da bi ndt nghiem trong tai day b i n . Vet ndt nhd tai day ban dudi v;

tri dat tai va lan rdng ra eae hudng. Vet ndt ldn sdluong it, ehu yeu theo phuong dpe cau.

- Anh hudng eiia eae thdng sd eau tao ban tdi dng xd ndt eua ban mat eau:

+ Ban cd chieu day nhd, bin cd khau do tinh toan ldn 37

KHOA HOC - CONG NGHE _

bat d i u ndtdeaptli nhd hon. Khi t i n g tai hinh thinh them nhieu vet nut phan bd, ed vet ndt ldn tram trong hon.

+ Ban cd kha'u dp tinh t o i n ldn va chieu day ldn it ndt han so vdi ban ed khau do tinh t o l n nhd v l ehieu day nhd. Chieu diy ciia ban i n h hudng den ndt nhieu hon so vdl khau dd tinh t o l n .

4.KeTLUANVAKieNNGH!

4.1. Ket luan

Cle ket qua phan tich cie so dd ban eau ciia ket eau nhip dam I BTCTtrong thue te vdi cle thdng sd eau tao khac nhau dudi tie dung eiia t l i trong xe q u i t l i eho thay:

Ve dp vdng:

- Dp vdng deu nam trong gidi han eho phep;

- Dd vong ldn nhl't eua ban xap xi ty le thuin vdi ty so gida binh phuang chieu dai nhjp hdu hieu ehia eho lap phuang chieu d i y b i n mat eau.

l^e dng sudt trong cot thip:

- Lfng suat keo trong edt thep nhd hon nhieu so vdi dng suat cho phep;

- (ir\g suit phin tieh phi tuyen xap xi ty le thuan vdi ty sd chieu d l i nhip tinh toan chia eho chieu diy ban. Trong khi dd, dng suat phan tich tuyen tinh xap xi ty le thuan vdl ty sd ehieu dai nhip tinh toan chia cho binh phuong chieu day ban. Ngoai ra, giai phap b i n mat cau sddyng cdt thep cd dudng kinh nhd eho dng suit ldn hon,

VeUngxdndt:

- Khi t i i khai thae xe q u i t i i ldn thi ban mat cau bi nut nghiem trpng tai day ban. Vet ndt nhd b i t dau tai diy b i n dadi vi tri binh xe va lan rdng ra cac hudng. Vet ndt ldn sd lugng it, chii yeu theo phuong doe eau dudi vi tri banh xe.

- Bin cd chieu day nhd, b i n cd khau do tfnh t o i n ldn bat dau ndt d cap tai nhd hon. Chieu day ciia b i n I n h hudng den ndt nhieu hon so vdi khau dp tinh toan,

4.2. Kien nghj

Mpt sd kien nghi tU ket q u i nghien cdu nhU sau:

- Cd the gilm ham lugng edt thep so vdi cac gili phip thiet ke b i n mat cau ciia ket ca'u nhip dam 1 hien nay;

- Nen chon ehieu diy ban mat eau BTCT day t d 0.2m trd len;

- Xe q u i tai Idn gay ra cac vet nUt ldn eho ban mat eau, can phaj han che de d i m bao tudi tho llu d l i cua ban m i t cau v l edng trinh,

Tai lieu tham khao

[1]. Bd GTVT (2017), Tieu chudn Viit Nam TCVN 11823:2017

[2], Tran The Truyen, Nguyen Xuan Huy (2015), P/7d huy vd rqn nUt bi tdng. NXB Xiy dUng, Ha Ndi.

[3].TraongTichThien,Tran Kim Bang (2010), Co/loc phd buy, NXB. Dai hoe Qude gia TP. Hd Chi Minh

[4]. Tran Ddc Thuan (2016), Nghien cdu dnh hudng so lupng vd tai trpng truexe cuaxe tdi thUc te'tren cdu den dng xdcua ddm cdu BTCT dudng luc nhip gidn dan. Luan van Thae si,Trudng Dai hoc GTVT,

[5], Tran The Truyen, Nguyen Xuan Huy (2011) I Damage and fracture of Concrete, Publishers construction I [6i.Vu Hong Nghiep (2011), Shear design of straight

38

and haunched concrete beams without stirrups. Shaker VerlagGmbH.

[7], Prince Baah (12/2014), Cracking Behavior of Structural Slab Bridge Decks. In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy, The Graduate Faculty ofThe University of Akron.

[8], MIDAS IT (2017), MIDAS FEA Training Series.

Ngay nhan bai: 10/01/2019 Ngay chap nhan dang: 28/01/2019 Ngudi phan bten: TS. Le Ba Anh

TS. Hoang Viet HSi