PHirONG NHIP HiTonvG

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KHAO SAT ANH HiTonvG CUA DQ CONG DEN NOI LITC TRONG KET CAu NHIP CAU D A M GIAN DON

(THEO PHirONG PHAP TINH G A N DUNG)

ThS. NGUYEN VAN V I N H PCS. TS. TRAN DUG NHIfiM Bp mdn Chu hdm

Khoa Cdng trinh

Tru&ng Bffi hpc Giao thdng Van tdi

Tom tat: Bdi bdo gidi thieu vi viec nghien cuu dnh huang cua do cong din su phdn bd ngi luc trong cdc ddm chu cua cdu dam thep liin hgp ndm tren duang cong bdng. Trong qud trinh nghien cuu ta cdn phdi tim mSi quan hi giiia bdn kinh cong cua cdu vd chiiu ddi nhip tire la khao sdt tim ra goc huang tdm cua kit cdu nhip md khi do dnh huong cua do cong din ngi luc trong ddm la rat nho vd co thi bo qua sic dnh huong do.

Tit khoa: Ddm thep, tdi trgng, img sudt, phuang phdp gdn diing, Vload-Method, duang cong bdng.

Summary: This article introduces into study the effects of bending on internal forces applying approximate method for simple girder bridges. We must find the relationship between by the curve radius of bridge and the length of span, in other words, we study to find centripetal angle of superstructure to the effects of bending on internal forces is too small, may be neglect.

Key words: Steel girder, load, stress, approximate method, Vload-Method, horizontal

I. DAT VAN DE

Theo cac phuang phap phan tich tinh toan ciu dim thep cong thi dp cong co anh huong kha Ion din npi lire trong kit ciu nhjp ciu, no lam cho gia trj npi lire trong dim tang len do anh huang ciia trpng lugng ban than kit ciu va cac tai trpng tac d\ing theo phuong ngang cau nhu luc lie ngang, lire ly tam va ap lire gio ngang ciu. Voi ban cong cang lan tiic la dp cong cang nh6 thi anh huong cua dp cong din npi lire ciia ciu cang nho khi do ta co thi b6 qua sir anh huong nay.

Nhu vay ta can phai tim moi quan hf gi&a ban kinh cong ciia ciu va chieu dai nhjp tiic la khao sat tim ra goc huong tam cua kit ciu nhjp ma khi do anh huong ciia dp cong din npi lye trong dim la rit nh6 va co thi b6 qua sir anh huong do. Viec khao sat anh huong cua dp cong can phai dugc tiln hanh doi voi ca kit ciu nhjp gian don va kit ciu nhjp lien tyc.

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n . TINH TOAN DOI V d l CAU CONG NTHP GIAN DON L = 33 M.

2.1. Can tao chung ket cau nhip a. So lieu chung.

- Quy mo thiet ke: Cau cong tren mat bang dugc thiet ke vTnh cuu bang dam thep lien hgp BTCT.

Tieu chuan thiet ke: 22TCN 272 - 05.

- Chieu dai nhjp: L = 33 (m).

Kho ciu: 0 8 + 2x1,5 + 2x0,5 (m).

Hoat tai thilt kl: HL93 + Nguoi b. Cau tao dam chii.

Kich thuoc cau tao dam chu:

3000

, 400 , a o i n

1600

n

20

1600

700 °

,

1910

Hinh 1. Mat cdt ngang ddm chu

1.2. Xac dinh ban Idnh cong ciia cau

Van t6c thiet ke ciia tuyen duong va ciia cau: V,k = 60km/h.

Ban kinh cong t6i thieu ciia tuyen duong (hay ciia cau):

R „ . „ = • V^ 60^

• = 134,98m 1 2 7 . ( i r + l i ) 127.(0,06 + 0,15).,.

Trong do:

+ V: la van toe thilt kl, V.^ = 60(km/h);

+ 137": la sieu cao Ion nhit: i'^" = 6% = 0,06;

+ p.: He s6 lire ngang, ling voi ban kinh nh6 nhat Rmin thi )LI=0, 15 (Ion nhat).

V ' 60'

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- Ban kinh cong kh6ng sieu cao: R^^^, =

127.(p-i„) 127.(0,08^-0,02) = 472,44m (2) Trong do: :,.

+ i„: d6 doc ngang thiet ke: i^ = 2% = 0,02; '•' + p: He s6 lire ngang, ling voi ban kinh Ion nhat Rn^x thi p=0,08 (nho nhat).

2.3. Triromg hop ban kinh cong cua cau R = 200m ';' a. Dgc trimg hinh hoc cua cdu

Van t6c thiet ke ciia tuyen (cua cau): V,k = 60km/h.

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Tap chi KHOA HOC GIAO THONG VAN TAI So 33 - 03/2011

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- Ban kinh cong cua cau R = 200m.

- Dp cong ciia cau: p = — = -1— = o 005 R 200 '

- Goc huong tam: a = — = — = 0,165(rad) = 9,45°

R 200 - Dp d6c sieu cao: isc = 4%.

- H? s6aplvrc ngang:^ = — - ± i = 0,04 = 0,1016 g.R 9,81.200

- Chilu dai nhjp: L^h = 33m (tinh theo duong tim ciu).

- Chieu dai duoi thing ciia cac dim chii dugc tinh theo c6ng thiic

L _"'dam R.a va L , = L,,„-2.a Trong do:

+ Ldam, Ltt: La chieu dai ruoi thing va chilu dai tinh toan ciia dim cong.

+ a: La khoang each tir diu dam din tim goi.

+ R: La ban kinh cong ciia dim (m).

+ a : La goc hu6ng tam ciia nhjp (rad).

Bdng 1. Chiiu ddi ruoi thdng ciia cdc ddm chii

SIT 1 2 3 4 5

T6n dSm D i m 1 Dim 2 Tim c i u

Dim 3 D i m 4

R (m) 204.5D 201.50 200.00 198.50 195.50

a (d6) 9.45 9.45 9.45 9.45 9.45

Lnn (m) 33.74 33.25 33.00 32.75 32.26

a (m) 0.30 0.30 0.30 0.30 0.30

L,, (m) 33.14 32.65 32.40 32.15 31.66

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b. Tinh noi luc trong ddm thdng

Npi lire tai mat cat giira nhjp ciia cac dam chu dugc tinh theo bai toan phing voi viec sii dung he s6 phan b6 ngang.

- Lin lugt tinh toan npi lire cho timg dam ta co:

Bdng 2. Ngi luc tai mat cat giiia nhip cua cdc ddm

Ten dam Dam 1 Dam 2 Dam 3 Dam 4

Momen (kN.m) 14076,8 10836,9 7735,8 4800.7

c. Tinh noi luc trong ddm do dnh hu&ng cua dq cong - So do tinh:

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M 4

"4 V

^Mp3

"4

Gi

H

^DQnngang

G2

H W

^Dpnrlgang

G3

H ((4

^DQnngang

H

G4

L::

^VJ = = = = = 1 : : : >

Hinh 3. Sa do tinh dnh hu&ng cua do. cong Xac djnh tai trpng V dat tai vj tri dam ngang tai mat cat giCia nhjp.

v = ^^^ V M

^pn

CK (7)

, Trong cau co 4 dam chii ta co c6ng thiic tinh tai trpng V nhu sau:

VfM

1,11K

^ V^ - Mp. +Mp, +Mp3 +M^, _ 14076,8 + 10836,9 + 7735,8 + 4800,7 _ ^^^ ^^^^^^

1,11.185,19 -.• •' • V' 182 19

+V4=-V,=-182,19; V = - ^ - ' V -182 19

3 = 60,73kN va V, = - ^ = J2±ll = .50,73kN

' 3 3 ' 3 3

Trong do:

+ Mpi, Mp2, Mp3, Mp4: La m6men ciia dam 1, dam 2, dam 3 va dam 4 khi tinh theo so do cau thang tai mat cat giira nhjp.

+ Vl, V2, V3, V4: La tai trpng V dat tai mat cat giira nhjp cua cac dam 1, 2, 3 va 4 do anh hu6ng cua dp cong gay ra.

+ C: La he s6 phu thupc vao ,s6 dam chu, doi voi truang hgp cau eo 4 dam ta lay C=l,l 1.

RD 200 3

+ K: La he s6 duoc xac dinh theo c6ng thiic: K = = '— = 185,19 d 3,24 + D: Khoang each giiia cac dim chii, D = 3m.

+ d: Khoang cachgiiia cac he lien ket ngang, d = 3,24m.

Xac djnh npi lire do tai trpng V gay ra: M ^ = V.y"^

Voi y"^: Tung dp DAH momen tai mat cat tinh toan.

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STT 1 2 3 4

Ten dam Dam 1 Dam 2 Dam 3 Dam 4

Bdng 3. Kit qud tinh My„

V kN 182.19

60.73 -60.73 -182.19

yM

8.29 8.16 8.04 7.91

do tdi trgng V gay ra

Mvn

kN.m 1509.6 495.7 -488.2 -1441.9 d. Tinh not luc trong ddm do luc ly tdm

- Diem dat cua lire ly tam each mat duong 1,8m.

48 Tap chi KHOA HOC GIAO THONG VAN TAI So 33 - 03/2011

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- C6ng thiic tinh be so luc ly tam:C = - . ^ ^ = 1 . J M L 3 g.R 3 9,81.200 Trong do:

= 0,01133 (10)

v: T6c dp thilt kl duong 6t6 (m/s): v = ^"^^„ =16,67m/s; g: Gia t6c trpng ttuong 3600

(m/s^), g = 9,807 (m/s^); R: Ban kinh cong cua ciu (m), R = 200m.

Tinh luc ly tam do xe tai thiet kl: H„ = J^ni-C-P^ = 7,362TkN Momen xoin do lire ly tam: T = Hi,.l,8 = 7,3621.1,8 = 13,252 kN.m

(11) (12) Tinh npi luc trong dam chii do luc ly tam gay ra:

Bdng 4. Npi luc trong ddm do luc ly tdm gdy ra STT

1 2 3 4

Ten dam Dim 1 Dim 2 Dim 3 Dim 4

V(kN) 1.325 0.442 -0.442 -1.325

yM

8.29 8.16 8.04 7.91

Mc (kN.m) 10.980

3.605 -3.551 -10.488 e. Tinh noi luc trong ddm do dp luc gio ngang.

- Dilm dat ciia ap lire gio len xe each mat duong 1,8m.

- Cong thiic tinh ap lire gio ngang tac dung len xe: H = WL.X = 1,5.32,4 = 48,6kN Trong do:

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WL: ap luc gio tac dung len xe, WL = 1,5 kN/m; 1: Chilu dai duong anh huong xIp tai trpng xe, 1 = 32,4m; M6men xoin do lire gi6 ngang tac dung len xe:

T = Hi,. 1,8 = 48,6.1,8 = 87,48 kN.m (14) - Bang tinh

STT 1 2 3 4

mo men u6n trong dam do ap lire gi6 tac dung len xe.

Bdng 5. Npi luc trong ddm do dp Ten dam

Dim 1 Dim 2 Dim 3 Dim 4

V(kN) 8.748 2.916 -2.916 -8.748

yM

8.29 8.16 8.04 7.91 ,

luc gio tdc dung len xe MwL (kN.m)

72.483 23.800 -23.439 -69.235 / Tdng hgp noi luc trong ddm cong.

M6men uon do anh huong ciia dp cong, ciia luc ly tam va ap lire gio tac dung len xe gay ra doi voi dim On tai mat cit bit ky phai dugc them vao momen so bp ban diu tai mat cat do de

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tao m6men u6n cuoi cimg Mn:

M„ = M „ + M ^ + M f , + M w ,

n pn vn C WL

Kiem tra dp chenh lech npi lire giiia dam cong voi dam thang:

M„-M„„

A M = ^ ^ ^.100%

M„

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(16) Bang t6ng hgp npi lire trong dam cong:

STT 1 2 3 4

Ten dam Dim 1 Dam 2 Dim 3 Dam 4

Mpn

kN.m 14076.8 10836.9 7735.8 4800.7

Mvn

kN.m 1509.6 495.7 -488.2 -1441.9

Mc kN.m

10.98 3.61 -3.55 -10.49

Bdng 6. Npi luc cuoi cimg MwL

kN.m 72.48 23.80 -23.44 -69.23

M„

kN.m 15669.8 11360.0 7220.7 3279.1

trong ddm cong Chenh

lech 11.32%

4.83%

6.66%

31.70%

Nhu vay theo nhu ket qua npi lire da tinh toan thi voi ban kinh cong R = 200m va goc huong tam a = 9,45° thi chenh lech npi lire giira cau cong va cau thang trong cac dam 1 va dam 4 Ion hon 10% so vai npi luc so bp khi tinh theo cau thang.

2.4. Phan tich va so sanh cac ket qua tinh toan khi thay doi ban Idnh cong R

Tinh toan tuong tu doi voi cac ban kinh cong khac cua cau ta riit ra bang chenh lech m6men giiia cau cong voi cau thang tuong ling voi tiing ban kinh cong ciia cau nhu sau:

STT 1 2 3 4 5 6 7 8 9

L (m)

33 33 33 33 33 33 33 33 33

R (m) 200 300 400 500 600 700 800 900 1000

a (do) 9.454 6.303 4.727 3.782 3.151 2.701 2.363 2.101 1.891

%)Chenh lech momen Dim 1

11.32%

7.73%

5.94%

4.86%

4.14%

3.62%

3.24%

2.93%

2.69%

Dam 2 4.83%

3.29%

2.52%

2.06%

1.75%

1.53%

1.37%

1.24%

1.14%

Dim 3 6.66%

4.52%

3.46%

2.82%

2.40%

2.10%

1.87%

1.70%

1.56%

Dim 4 31.70%

21.38%

16.31%

13.29%

11.29%

9.86%

8.80%

7.97%

7.31%

Bieu d6 quan he giiia goc huong tam va ti le chenh lech m6men giua cau cong va cau thang.

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Tap chi KHOA HOC GIAO THONG VAN TAI So 33 - 03/2011

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9 « 7 5 € e 3 0 540a71 J 203763^4 3 15 291270 2022.362.22210 1 « 1 8 f l

Hinh 4. Biiu do ciia ddm 1

9 45 7.56 6.30 5.40 4 73 4 20 3 76 3.44 315 2 01 2 70 ^52 2 36 Z22 2 10 1 » 1 8

400%

30CS 200S

!00S 000%

m '• f\

\-'\^

1

k~ ~ ~ ~

r H Fl fl jm ' ' •' f r Fl

m

9 45766630 540 4^3420 578 344 3 .5 231 270 2522M 223 213 I M 1ft

ffl.OOSf 25.00*

20 00%)' lEOOS 'OOOSf

5 00%

000% tiJllfk K ^{U p}

S45 7S6 630 640 473 420 378 344 315 291 2 70 252 236 222 Z"0 199 1 !9

Vay ta co the ket luan khi goc huong tam ciia nhjp nh6 hon gia trj cho trong bang sau thi chenh lech npi luc giira cau thang va cau cong la nho hon 10% va khi do trong tinh toan co thi bo qua anh huong cua dp cong cua dim.

Bdng 8. Bdng goc huang tdm co thi bo qua dnh huang cua dp cong S6 dam chu

2 3 hoac 4

> 5

Goc cho 1 nhjp 2°

30

4°

Goc cho 2 hoac nhieu nhjp

30

4°

5°

Ghi chii

IV. KET LUAN

Anh huang ciia dp cong din npi luc trong kit ciu nhjp ciu dim lien hgp nim tren dudng cong bing la rit dang k l . Anh huong do la do dp cong, do lire ly tam va lire gio ngang. No lam tang gia trj npi lire 6 cac dam ngoai va giam npi lire 6 cac dam trong.

Bai bao da gioi thieu vi?c su dung phuong phap gin dung (V-Load method) de phan tich tinh toan ciu dim thep chCr I nim tren duong cong bing. Tir kit qua phan tich va so sanh npi lire giira ciu cong va ciu thing da nit ra dugc kit luan v l goc huong tam ciia ciu de co the bo qua dugc anh huong cua dp cong.

T.ii lieu tham khao

[1]. Tieu chuin thilt kl dudmg oto 22TCN 273 - 01, Bp Giao thong Van tai. ^ ^ [2]. vn Song Kim vd cdc tdc gid khdc: Cong Nghe xay dung cong trinh ciu cao trong cac niit giao cat lap the.

[3]. V-Load Analysis, in USS Highway structures Design Handbook, Vol 1, AISC Marketing, Int., Chicago, IL, 1984, Chap 12, 1-56.

[4]. Guide Specification for Horizontally Curved Highway Bridges Amencan Association of stat Highway and Transporttation Officials 444 North Capitol Street, N.W.,Suite 249 Washington, D.C 20001.

[5]. DANG GIA NAI LE DUC CHINH: Beitrag Zum Enwurf Und Berechnung Von Im Grundril Gekrummten Spannbeton Bracken HFV 1976*