Phân tích ổn định khí động lực và hướng kiểm soát FLUTTER cho cầu dây văng

DAI HOC QUOC CIA HA
.NOI TRUNG
TAM
KHOA
HOC
Tl'
NHIEN
TRUNG
TA.M HOP TAC
DAO
TAO
VA
CO.NG
NGHE QLOC GIA
VA
BOI
DUONG CO HOC MEN CO HOC
LE THAI
HOA
•' ^
PHAN
TICH
ON
DINH KHI
DONG
Ll/C
VA
HUONG
KIEM
SOAT
FLUTTER

CHO CAU DAY
VANCi
CHUYEN N(;.ANH
: CO HOC
L'N(;
Dl NG
M.\
SO : 2 .
O:
. 02
LUAN VAN THAC SY
CO
HOC
NGirOl
HUONG DAN KHOA HOC
1.
GS.TSKH.
NGL VtN
DONG ANH
2
PGS.TS.
VI MANH
LANG
HA NOI -
2003 ;
MUC
LUC
MO
DAU
1.

Giai thieu chung
1
2.
Bai hoc tu
sir
c6 pha buy cau
Tacoma Narrow
2
3.
Mien tugng
mat on
dinh
khi
dong
lire
Flutter
3
4.
Tinh
hinh nehien
cuu bai
toan
6n
dinh
khf
done
luc aniroc
nsoai
7
5.

Tmh
hinh nghien
cuu bai
loan
on
dinh
khf
dgng
luc
a
trong
nuac
10
CHl/ON(;
1.
TAC DUNG
CUA
GIO
LEN
CONG TRINH
CAU
1.1. Giai thieu chung
1 1
1.2. Xae
dinh
van
toe
gio tu
nhien
12

1.3. Cac
thanh phan
luc khf
dgng
14
1.4. Cac dae
irimg
xac
dinh phan
limg
cua
dong
khf khi qua
eong trinh
15
1.4.1.
So
Reynold
va
sir
hinh thanh xoay
khf,
vising
trong
15
1.4.2.
So
Struohal
va tan so
xuat hien

cac
xoay
khf sau
eong trinh
16
1.5. Dao
done
tu
kfeh thfeh
iheo
huane vuone
eoc efo
loi
do
hien tugng Flutter
17
1.6. Cac
hien tuans done
luc
khac
ciia
eio
len
cone trinh
cau 18
1.6.1.
Dao
dgng cuang
bue
iheo hueVng

vuong
goc
gio tai do
hien
lUcTne
Vortex-sheddine
18
1.6.2.
Dao
dgng
tu
kfeh thfeh
iheo
huang
\
uong
goc gio tai do
hien tugng Galloping
19
1.6.3.
Dao
dgng
ngi\u
nhien
iheo hue^ng
gio tai do
hien
tuone Buffetine
-0
1.7.

Vai tro
eiia
cac
hicMi
tuone
khf
dowz lire
trone
ihiei
ke eau dav
vang
21
1
.S.
Kel
luan
euoi ehiro'ne
CHUONG 2. MO HINH HOA VA PHAN TICH DAO DONG CAU
DAY VANG THEO
PHUONG PH.AP
PHAN TL
HLX
HAN
2.1.
Gidi
thieu chung 23
2.2.
Cau tao so bg cac bg phan cau day vang 24
2.3.
Mo hinh kel cau

ciu
day vang
iheo
phuang phap PTHH 24
2.3.1.
Mo hinh dam cung 24
2.3.2. Mo hinh cot thap 27
2.3.3.
Mo hinh day vang 28
2.3.4. Mo hinh dieu kien bien 28
2.4. Phan bo khoi
luane
tren kel cau
'^9
o
*— -^
2.5.
Phan
ifeh
dao dgng cau day vang
iheo phucmg
phap PTHH 30
2.5.1.
Phuang trinh vi phan ehuyen dgng cua he nhieu bae
tudo
30
2.5.2. Dao dong rieng va cac dang dao dgng rieng 30
2.5.3.
Giai bai loan dgng
lire iheo

phan
tieli
dao dgng 31
2.5.4. Chuan hoa ma
Iran
dane riene
^^
2.6.
Vf du
linh
loan 33
2.6.1.
TTiong
so cau tao cau da\' vang
2.6.2. Phan
tieh
dao dgng rieng
ciia
eau 34
2.7.
Kel
Iuan
euoi
ehuitng
39
CHUONC;
3. CAC PHUONG TRINH CO BAN CLA HIEN
TLONG
FLLTTER
3.1.

Giai thieu chung 40
}.2.
Phuone irinh
\i
i^han
ehuNcn
done eua phan to dam trone done khf 41
3.3.
(Vie
thanh phan luc khf dong
lir
kfeh 4-
3.3.1.
Mo hinh
lire
khf dgng theo thue nghiem eua Scanlan 44
3.3.2. Mo hinh luc khf done
iheo
eiai
tieh eiia Tlieodorsen
46
3.4. Plurang
irinh
vi phan ehuyen
dong lluiter eho
he nhieu bae
tudo
4"^
?*.5.
Kel luan

euoi
elurone
49
CHUONG 4. PHUONG PHAP XAC DINH VAN TOC GIO
TC)I
HAN
6
TRANG THAI XAY RA MAT ON DINH FLLTTER
4.1.
Giai thieu chung 50
4.2.
Tfnh loan van
toe
gio tai han theo cone
ihiJc
thue nehiem Selbere 51
4.3.
Lai giai bai loan 6n dinh khf dgng luc Flutter vai he hai bae
tudo
52
4.4.
Phuang trinh vi phan
ehuyen
dgng Flutter cua he nhieu
bae tudo
55
4.4.1.
Phuang trinh vi phan
ehuyen
dgng Flutter 55

4.4.2.
Chuan hoa theo khoi
lugng
56
4.4.3.
Nghiem cua phuang trinh (4.4.2.2) 57
4.5
Ma
Iran
phan
tucua lire
khf dgng 59
4.6.
Phuang phap chong
limg
cap dang dao dgng 60
4.7.
Vf du tfnh loan 63
4.7.1.
Dal bai loan 63
4.7.2.
Tfnh loan van
toe
gio tai han
phuong
phap giai
Ifeh
cho he 2
bae tir
do 63

4.7.3.
Tfnh loan van
toe
gio tai han theo phuong phap chong dang dao dgng 66
4.8.
Kel luan euoi chuang 73
CHUONG 5. CAC
HUONG
KIEM SOAT FLUTTER CHO CAU DAY VANG
5.1.
Giai thieu chung
74
5.2. Kiem
soal
cau tao khf dgng
lire
75
5.3.
Kiem soat co hgc bi dgng 77
5.3.1.
Thiet bi eiam chan khoi krone
ludieu
ehinh (PTMD) 78
5.3.2.
Phiromg
trinh ea ban
eiia
kiem soal Flutter dung PTMD 78
5.4. Kiem soal co hgc
ehii

dgng
80
5.4.1.
Kiem soat
ehii
dgng kel cau cau day \ang
81
5.4.2.
Phutmg
trinh vi phan ehuye'n dgng eua kie'm soat kel eau
ehiidgng 81
5.5.
Vai tro
eiia
cac hien phap kiem soat Flutter eho eau day \ang 83
5.6. Ket luan euoi ehuang
84
KET
LI
AN
T.AI
LIEl
THAM KHAO
MO
DAU
1.
Gioi
thieu chung
Ket cau cau treo va cau day vane da khane dinh duac tfnh uu
viei

so vai cac
dang ket cau cau khac do kha nang vugt khau do
Ion
va kien true dep. Loai hinh ket
cau ciu treo va cau day vang dugc ap dung rat rgng rai tai nhieu nuac tren the giai,
cac
eong
trinh
cfiu
quy mo
Ian
va ky thuat lieu bieu tren the giai cung da phan ap
dung cac loai hinh ket cau cau nay. Tuy nhien dang ket cau cau treo va
ciu
day
vang nay la cac
eong
trinh co ky thuat dae biet, rat phuc
'ap
trong phan
ifch
va thiet
ke.
Han
nua,
ket cau nay co xu huang ngay
cang
thanh manh va nhe do vay bien
dane
Idn,

do
cixne neane
va
xodn giam
va nhav cam dao done vai kfeh done neoai.
Danh eia cac lac done
eiia hoal
lai.
eio va done dat
luon
co vai tro quan trone
irone
thiet ke vai cac loai hinh ket cau nay. Dae biet cac lac dgng khi done
lire eiia
gio
can phai dugc nghien
ei'ru
va danh
giii.
Cho tai thai diem
10/1940,
cau Tacoma Narrow
a
Hoa ky bi do hoan loan do gio thi
Uie
done khi done luc
ciia
eio
duoc
dat van di va quan tam nehien

CIJTJ
voi doi
tugng la kel can dan dung noi chung va cone trinh cau noi rieng. Cung ke tu
sir
co
nay va cac nghien
ciai
sau do
v^
cac hien
tucrng
khf dgng
lire dae
biet eua gio da lam
ihav
doi cac quan niem \e thiet
ke
eau khau do
Ian.
hie nay cac phan tieh
\'e
dong
lire
khf done
lire
va dia chan anh huane quvet dinh tai quan niem \e thiet
ke
eau
chir
khong phai la cac phan

ifeh iTnh
do tTnh tai va hoal tai nhu cac kel cau cau thong
thuane Cune nho \ao cae ket qua nehien
ciru \i
tac done eio noi ehune
(Iv thu\ei
va thue nghiem)
nia
nhieu eong trinh eau Mrgt bien
qu\
mo Ion da dugc
xa\
dimg
ihanh
eong lai nhieu
niroe
tren the gidi trong nhung nam gan day.
Trong cae lac dgng
eiia
gio len eong trinh eau thi nghien cuu \e mat 6n dinh
khf dong
lire
luon dirge uu
tien ehii irgng
\i mat
6n dinh
khf dgng
liJc thULvng
dien ra
nhanh dot nedt, khd

ludne
eav hu hai nehiem trone. Phan
ifeh
on dinh
khi
dgng
lire
elu)
cone trinh
ciiu
la
iiioi
bai loan khd va dugc nude ngoai nghien cuu nhieu lir
nhune nam 60.
Kho
khan d
ehd lae
dong
eiia
eio vao eong trinh vdi nhieu hien
_ 7
_
tugng,
dae
biet cac tac dgng dgng luc cua gio gay ra cac phan ung phuc lap
,
kho
ludng
cua
eong

trinh. han nua nghien cuu gio can phai co
sir
ket hgp giua
Iv thuyei
va thue nghiem, khong co mot phuang phap so hay giai tfch \an nang nao mo la
duac
ddy dii
cac hien tuone. Bai loan on dinh khf done nav van tiep tuc duac nehien
cuu va
phai
trie'n, gan day nhd vice ap dung ky thuat
16
hgp cac dang dao dgng va
bai loan tri rieng trong vice giai phuang trinh khf dgng
lire
da lam tang do chfnh xae
cua phan tfch
ly
thuyei,
ddng
thai
gan
doi
lugng
nghien cuu vdi ket eau cau day
vang va cau treo quy mo
Idn.
0 Viet Nam hien nay mot so
eong
trinh

ciu
day vang quy mo
Idn
dang va se
dugc xay dung. Cau day vang quy mo
Idn
dau lien dugc xay dung d trong nude la
cau My Thuan (Long An), cac
d\X
an can day viing
Idn
khac dang dugc xay dung
nhu cau Bai Chay (Quang Ninh), cau Kien (Hai
Phong),
eau Bfnh (Hai Phong), cau
Can
They
(Can
Th(t),
eau Raeh Mieu (Song Fie). Phan tfch on dinh khf dgng
lire
luon
dugc dat ra va la mot bg phan rat quan trong trong phan tfch, tfnh loan ket cau cac
eong trinh nay. Vdi cac eong trinh eau
Idn
dang dugc xay dung trong nude deu do
nude
ngoai phan
lieh
\a thiet ke kel

effu.
viec phan tfch on dinh khf dong hay danh
eia tac dons cua
cid
noi ehune khdne duoc eiai thfeh va ehuven
eiao.
Viec eiai
qu\et bai loan phan
tieh
on dinh khf dgng
lire
trong nude con mdi
chi
bude dau \a
rat han
che,
dae biet khi gan nghien
eiiii \di
doi tugng la
eong
trinh cau. Hien na\'
nhu eau \e nehien cuu on dinh khf done
lue
ndi riene
ha\
cae phan tfch done luc
duac dat ra de dap
irng
doi hoi
eiia

thue tien la trong nude
lu
kha nang phan tfch \'a
thiet ke cae cone trinh cau dav vane va cau treo
qu\'
mo
Idn.
2.
Bai hoc
tii sy
co pha huy cau
lacoma
Narrow
Can Taeoma
Narrou ihiige
bang Washington. Hoa Ky bi sup do hoan loan
nam
1940
do uie done khi dgng
lire
eua
gio.
Phan
tieh
nguyen nhan pha huy cau la
do lae
ilimg khi
ddng
lire
lam eau dao ddng vdi hai dang udn va xoan ddng thdi dudi

eune
n'\o\
tan so.
Sir tuong
lae dgng
lire
giua ddng
khi
\a eong trinh gay
phai
sinh
lue
khi
done bo \ung cung cap them nang
lirong
cho dao dgng eua ket eau lam bien
d(^
[>han
kv
ga\
mat on
dinli
kel eau. Hien tugng khf dgng
lire
ga\
mat
ow dinh
eau
-
J

-
Taeoma Narrow dugc biet den la hien tugng Flutter c6 dien (gidng phan
ting
dgng
luc
ciia
canh may bay trong ddng khf da dugc nghien cuu
irudc
do). Tai bien dot
nggl
cua
eong
trinh eau Tacoma Narrow da lam cac ky su thiet ke cau
ehii
trgng.
danh gia dung vai tro cua cac hieu ung dgng
lire
cua gio len
eong
trinh dan dung ndi
chung va eong trinh cau ndi rieng. Pha hoai do tac dung dgng
lire
cua gio thudng
di^n
bien nhanh, dot nggt va khd ludng.
't^K^^
:< — -^••;^.—
Hinh
1.
FTmh

anh dao dgng manh cua eau Taeoma Narrow
trirde
qua huy
3,
Hien
tirgng
mat on dinh khi dong luc Flutter
Khi
nghien
eiru
phan
ling eiia
ket eau phan bd theo chieu dai dat
n^m
ngang
trong ddng khi. ed
phai
sinh cae lue khf dgng tac dung len ket eau theo hudng gio
(phuirne
neang
ciia
ket
eairi.
lh-?o phuoiig
vuong gdc (phuong dung)
\a
lam xoan ket
cau. Cae lue khi dgng
na>
lam kel cau ed hai dang phan

I'mg
nhu sau :
-
l)afv.l
phiin
lOi;^
ihi'r
nln'il:
Do
lieh ehal
hdn loan eua dong khi va phan ung
ciia
done khi qua kel cau. cae
lire khi
dgng nay ed the la cac
liic
bien
ddi
theo
thdi eian hoae
bieti dien llieo
cac ham xae
sual.
Trong
irudne
hgp dau cae
lire
khf done eav kfeh ddng
lam
kel eau dao dgng eudng bue. eon d trudng hop

sau lam kel eau dao dgng
ng;Ui
nhien.
Da\
la eae
hien
tuong ma cae
kieh
4-
dgng dang nay chi don thuan lam kel cau dao dgng
phii
thuge vao eudng do,
tinh
chat
ciia
ban than dong khf ma khong cd
sir
tuong tac giua ddng khf va
kd't
cau.
Dae
diem chung
ciia
cac hien tugng dang nay
la
lam ket cau dao
done vdi bien do eidi han.
*
*— .
i—

- Dang phan Ung
thi(
hai: 0 trudng hgp
eij
the cac luc khf dgng khong nhung
chi phu thugc vao
dae
trung ban than
ciia
dong khf ma con phu thuge vao
ehuyen
dgng
ciia
kel
ciu
trong ddng khf. tuc la cd
sir
tuong tac giua ket cau
va ddng khf. Nhu vay cae
lire
khf dgng tu kfeh phu thuge vao ddng khf va
ehuye'n
dgng cua ket cau. Cae hien tugng nay ggi chung la hien tugng khf
dan hoi. Trong mot so dieu kien, cac
lire
khf dgng tu kfeh bd xung them
nang lugng eho ehuyen dgng lam
lire
can
ciia

he thong
chu>en
sang bi dgng,
bien do ehuyen dgng
ciia
ket eau pha n ky dan
t-di
ket cau mat
6n
dinh.
Cae hien tuong khf ddng lue lac dune len kel eau ndi ehune
ha\
cone trmh
can ndi rieng bao gdm hien tugng Flutter.
Buffeiing.
\'ortex-shedding
va Galloping.
Hien tugng mat on dinh do dao dgng udn-xoan ddng thdi con ggi la hien
tuctng
Flutter. Tac dgng gay dao dgng
ngaii
nhien theo hudng gid ggi la hien tugng
Buffeiine.
Hien
tuctne
Vortex-sheddine eav dao done
eirdne
bue theo
huc^e
\udng gid

\a\
hudng gid do cac xoay khf hinh thanh sau eong irinh. Cae uie ddng
dao dgng
lir
kfeh thfeh nhu hien tugng dgng lue
dae
trung
eiia
gid khi qua eae
\ai the
dang hinh
iru,
iron,
ehu nhat.
ha\
day cap ggi la hien tugng Galopping. Vdi mot ket
can ed the ddng thdi phai xem
xei
lae dgng
eiia
ca bdn hien
lucmg
tren.
tu>
nhien \ ai
tro quan trgng \a
mire
do
eiia
eae hien

tuctng
lac dgng len eong irinh la khac nhau.
Theo
[5J,
vdi eae eong trinh dang
egi
eao thi thudng phai ehu trgng xem
xei
uie
done
ciia
hien
luane
Galoppine
\a
hien tuone
\'onex-sheddine,
con \di
ciic
cone
trinh eau phan ho
itieo ehieii
dai can phai
ehii
trgng xem
xei
hien tugng Flutter
\a
hien tuong
Buffeing

do
\\\
ra d \an
ide
gid Idn
ga>
hu hai eong trinh. Cae tac dgng
khf done
lire
eua done khf ed the tae done len ket eau ed the
lom
tat trone so do
iinh
5-
Dao dong
ihco
phi/ong
cua dong
khi
Dao dong ngau nhien
Uj
5 -c
Cue
lac
done i
dong
lire ciia
gio
Dao dong
ihco

phuong
vuons
26c
done
khf
Dao dong
ci/cmg hue
1
^
*
Zij
X
c
ZJ
'3
u-
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>
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zo ^
£.
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r.
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iixki'ch
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Hinh
1.
So do phan nhanh cac hien tuone khf done luc cua eid
Cae hien tugng gay mat dn dinh ehuyen ddng ket cau thudng
ditoc
dae biet
ehii
trong, irong dd hien
tuetng
mat on dinh khf dan hoi Flutter ed the
ga\
ra eae hu
hai cho
diim
eau, tham
ehi

cd the dan tdi pha hoai eau. Nehien
ei'ru
hien tuone nav
se la ndi dune nehien
eiini ciia
luan van. Co nhieu
each
dinh
nehla
hien
lUtme
Flutter. Theo each dinh
nghia
ed dien thi hien
tugiig
Flutter la mot hien tugng mat
6n dinh khf dan hoi trong dd d trang thai tdi han dau lien ed su kel hgp ddng thdi
dao dgng udn \a dao dgng xoan
eiia
ket cau. Dinh nghia nay xuat phat tu nghien
eiru
thue nghiem canh
ma\
bay. tuy nhien khi nghien
cCru
vdi cdng trinh can co nhieu
Irucmg lio[t
do cau tao
eiia
eau d trang thai tdi han ed su ket hgp

eiia
dang dao dgng
bai
k\
h(K)e
nhieu dang dao dgng ddng thdi. Cae dinh nghTa gan
da\
xem hien lugng
I'lutier
la mot dang mai on dinh ehuye'n dgng \'a ap dung dinh ly
Liapuno\
noi
lieng
de dd
lim
trang
thai
tdi han, tu dae diem
eiia
he dao dgng do lue tu kfeh eae tri rieng
dugc bieu dien
duo\
dang eae cap sd phue lien hop nhau. trong trudng hop nao dd do
tuong uie giua kei
eaii
va ddng khf xuat hien eae gia tri phan thue eua cae cap tri
rieng bat kv duong
ihi hien
do dao dong se phan
k\

\a he thong mat on dinh ehu\en
done. Trang thai tdi han bat
liau
\a\ ra mat on dmh khi phan thue eua cap tri rieng
lien hgp bang khong. Hien lugng Flutter se lien quan tdi mat dn dinh khf dan hoi do
dao dgng
tir kfeh
dgng vdi bien do phan ky.
Muc tieu
ciia
viec giai bai loan mat on dinh khf dgng luc ky thuat ndi chung
cdn
phai xac dinh dugc van toe gid d trang thai tdi han dau tien he bit dau mat 6n
dinh, con goi la van tdc gid tdi han. Cd 2
hudne
xac dinh van
ide
eid tdi han trone
bai toan 6n dinh khf dgng luc :
-
Hi((/ng thi(
nhdt (phuang phap ly
thiiyet)
: Xac dinh
van
tdc gid tdi han thong
qua viec giai true tiep phuang trinh vi phan ehuyen ddng cua cdng trinh dudi
tac dune
ciia
cac lue khf ddng tu kfeh Flutter d trane thai xav ra mat on dinh

de tim ra van tdc gid tdi han.
-
Huc'/ng ihi'f
hai
(phiamg
phap
ihi/c
nghiem) : Xae dinh van tdc gid tdi han
thong qua
ihf
nghiem md hinh vat ly ket cau Ciiu trong thf nghiem ham gid.
HucVng
xac dinh van tdc tdi han theo phuang phap ly thuyei ggi la phan tfch dn
dinh khf done
lire.
Trone
tructne
hop van tdc eid tdi han xav ra mai dn dinh
nani
trong
vimg riii
ro eao thi
huge
phai tien hanh sua ddi cau tao ket cau hoae ap dung
cac bien phap kiem soat dn dinh khf dgng lue. So dd ung
xii
vdi bai loan dn dinh
khf dgng cho cau ndi chung va eau day vang ndi rieng md la tren hinh 2:
Bai loan
6n

dinh
khi
doni:
lire
Mo
hinh
loan hoc
C6ne
ihuc ihirc nshiCink
Mo
hinh vai
i Phiin
ii'ch
6n dinh
khi
done tuc
Thi
nghiem mo
hinh
irone
ham eio
BiCn
phap cau
lao
lans cuCme
On dinh I
b •-—~—^^——'
BiCn
phap co hoc
(FtC ihong

bi
dOng)
DitHi khic^n kOi
ciVu
(He
ihoiie ehu
done)
\'an loe
gio
tir
nhien
on
nhJl
tai cone
irmh
Hinh 2.
Svv diS
une
xueiia
bai loan on dmh khi done lue eho eau
-7
4.
Tmh hinh
nghien
ciiu
bai toan on dinh khi dgng
lire
cho cau d
nirdc
ngoai

Cac nghien cuu hien tugng Flutter eho cau dau lien phai
ke'
tdi cae nghien
cuu
CLia
tac gia Theodorsen, Roeard,
Bleich,
Scanlan
Bleieh[19]
gidi thieu cdng
thiJe thue
nghiem ndi lieng de" tfnh loan van tdc gid tdi han eho
liet
dien dam cau
dang ban mdng thoat khf, Cong thue nay dugc
Selberg[19]
sua doi va bd xung he sd
hinh dang mat
cdt
eho phep tfnh loan vdi dang mat cat cau bat ky, hien nay
eong
thiic
thue nghiem Selberg van dugc su dung rgng rai. Ldi giai giai tfch cung dugc
Roeard
[ 10]
gidi thieu nam
1950
ap dung cho phan tfch cau treo vdi md hinh hai
bae
lu do. Ve phan minh Theodorsen da phat trie'n cae nghien

eiai
trude dd cho canh
may bay de xay dung phuang trinh khf ddng
lire
Flutter ap dung cho cdng trinh cau
cd liet dien ban mdng, dua ra cae ham luan hoan Theodorsen
de'
thiet lap tfnh loan
cac
lire
khf dgng tu kfeh trong
phucmg
trinh \i phan
ehuyen
dgng, cac luc khf ddng
dugc tfnh loan theo giai tfch. Seanlan[5]. [7] da
x^y
dung cae
lire khi
dgng tu
kfeh
nhd dua vao eae he sd khf dgng Scanlan hay edn ggi he sd phat sinh Flutter ed
ngudn gdc thue nghiem.
Cach
xay
dimg ifnh
loan eae
lire
khf dgng theo thue nghiem
ciia

Scanlan
vin
edn dugc ap dung rgng rai hien nay do cd the ap dung eho eae mat
cat bai ky theo dae
trimg eiia
eau. Theo dd. eae he sd Scanlan dugc xae dinh thong
qua thf nghiem md hinh hoae su dung cae kei qua ed
sSn
theo dang mat
cdt.
Bai loan dn dinh khf dgng co dien
eiia
eau dugc
xei
tdi la phan ung
eiia
phan
to chieu dai dam eau trong ddng khf dn dinh, ehuyen ddng phan
id
dam theo 2 bae
tu do: ehuyen vi thang dung h \a ehuyen vi gdc xoay a (sau
na>
ed xet them thanh
phan
ehuye'n
vi ngang p) (hinh 3).
-^l_^->
J),
(jc lh.inh
ph.in

chuun \'\
ih;
lh.in^
{liriiL;.
p:
irj-iiiL;.
a
:''**<
\t).n
i
bi.
CJC
luc khi
doni;
Inn
inol
(JMTI
\i cliiiu
daj
djrn
[linh 3.
Dieh ehu\en
eua dam trong ddng khf \a eae
lire
khf ddng phat sinh
-8
Phuang trinh vi phan
ehuyen
dgng
ciia

phan
id
dam cau bieu
diln biine
phuang trinh dao dgng udn xoan ket hgp sau :
mh +
C;,/?
-
S^d
+ CJi
-
L,^
Trong dd :
m,
I^,
S,
kin
luat
la khdi
luane,
mo men quan
iTnh
khoi luane va md
men
iTnh
khdi lugng
ciia
phan
id
dam

Ch,
CV
C(^,
C„ Ian lugt
thong sd can va dan hoi ung vdi 2 thanh phan
ehuyen vi thang dung va gdc xoay
Lh,
Mu Ian lugi
la cac luc nang va md men xoan khf dgng tren phan
id
Can xac dinh cac
lire
khf dgng tu kieh Flutter
L^,
M^
trong phuang trinh tren.
Cach phd bien la xay dung
lire
khf dgng theo md hinh giai tfch eua Theodorsen va
md hinh thue nghiem
eiia
Scanlan.
TTieo
md hinh Tlieodorsen
[5],
[7] eae
lire
khf
dgng tfnh tren mot phan
id

chieu dai dam dugc tfnh theo cdng thue sau:
L,
= -;rph
M^
= -Kpb
lFUh-{bU{\^F)^~GU')d-2L'oGh~{2U'F~bU(uG)a
bUFIi + (h'U
U'G)d-bLcuGh
+
{ —
UcuG-hL:'F)a
2
cu
2
Trotm
do :
F(k).
G(k) la phan
ihue
va ao cua ham luan hoan Theodorsen
C(k)=F(k)+iG(k)
U,
b, p.
U3 Ian lugi
la van tdc gid, mot
nija
chieu rgng mat eau. mat
do khong khf \a tan sd goe
ciia
dao ddng

A'
=
—
hi
tan so
ehiei eiam
(thone so khone thu
neu\en)
L:
^
Theo mo hinh Scanlan |5|, [7| eae
lire
khf ddng dirge xae
dinh
nhu sau:
L=]-pU'2B
Kf!'{K
)~
+
Kff'AK
)—^K-f!'{
K )a
U
=-pi'2R
K.l'
(K)—
+
K.4l
(K)~
+

K i{K
)a
U
' U
-9
Trong dd :
//',/^\.>('(/-1,2,3) Ian
lugt la cac he sd phat sinh Flutter hay so'
Scanlan.
K
la tan sd chiet
giam,
B la chieu rone mat cau (
B=2b)
U
•
-
.
Scanlan[5],
[7J cung gidi thieu ldi giai giai tfch de giai phuang trinh \
i
phan
ehuyen ddng
eiia
bai loan on dinh khi dgng
lire
cd dien 2 bae tu do. Viec xae dinh
van tdc tdi han la qua trinh tfnh lap vdi van tdc tang dan cho tdi khi thoa man lieu
ehuan nhan biei mat dn dinh. Scanlan
[5].

[7]. [20] cung da phat
irien
xay dung
phuang trinh \
i
phan ehuyen ddng
ciia
hien tugng Flutter cua he nhieu bae tu do, tuc
la xet tdi su lam viec khong gian
eiia
ket cau cau. Vice giai bai loan dn dinh khf
done
lire
eho loan kei cau eau la bai loan khd eiai qu\ei do he nhieu bae tu do. luc
khf dgng phu
ihugc
vao van tdc gid,
utn
sd dao dgng kei cau \a
ehu>en \i
kei eau va
dao ham
eiia
ehiing,
xae lap lieu ehuan on dinh va do lim trang thai mat dn
dinh.
Phuong phap sd giai
phui^g
trinh khf dgng hre Flutter da phat trien kha
manh tu dau nhung nam 90 nhd ap dung

phuemg
phap phan tu huu han(PTHH) va to
hop dang dao ddng
ricMig
eho phep tiep can long quat ldi giai. md hinh kei can hat
ky va cd the to hgp nhieu dang dao dgng trong mot phan ung. lieu bieu la eae nghien
ei'ru eua
Seanlan[21
].
|22]. Agar
[24J.
Naminil24].
Chcn[24]
Thu tue lap va each
thue
Id
hgp eae dang dao dgng van tiep tue
d\iac
nghien
ei'ai
\a
phai
trien \i no anh
hudng tdi tdc do xu ly va su ehfnh xae
eiia
ldi giai. Gan day cd hudng xae dinh he sd
Scanlan
iheo
thuan tuy ly
ihuyet

nhd
phuong
phap
kich
dong ngau nhien tham sd.
Nhir
\'ay bai loan on dinh khf dgng
lire
eua ket eau eau ndi chung hay ket cau
eau
da\
\ang noi rieng la mot bai loan phue tap. thu tuc giai bai loan
na\
\an
edn
wcp
tue dirge nghien
eiru
va phat trien. Gan da\. trong
ihue
tien phan tfch
\a
thiei ke
ehdne eio eho eau dav vane da ehu
wonsi
tdi
huone kiem
soat khi done lue \ a
kiem soat co hoc kei eau bang each them \ao
liei

dien eae thiei hi thoat khf. hudng
ilone \a
thiei bi giam chan nham lam
giam
eae uie dung eua eid \a kiem
soat
phan
ixn^i eiia
eone irinh.
-10
5. Tmh hinh nghien
curu
bai toan dn dinh
khi
dong
lire d
trong nude
Nghien
ciru
trong
nude
ve tac dgng
ciia
cac hien tugng khi dgng
lire
gio ndi
chung hay hien tugng mat dn dinh Flutter ndi rieng gid len cdng trinh dan dung va
cdng trinh cau con rat ban che. Ve ket qua nghien cuu tac dgng cua gid len ket cau
xay
dung phai

ke
ldi cac nghien cuu cua Vien KHCN Xay dung tren ca sd tfnh loan
cac thanh phan
lue iTnh
va thanh phan
lire
dgng cua gid tu nhien eho cdng trinh dan
dung va da xay dung dugc lieu chuan nganh ve tai trgng gid. mot sd nghien cuu
ciia
irudne DH Xay dune
v6
lue tac dune len cone trinh
eiia
gid
Ide,
nehien cuu
ciia
trudng DH Quan
sir
ve hien tugng Flutter cho kel cau ban mdng. V.Q.Tru [13] da
nghien cuu mot sd phuong phap giai bai loan dn dinh khf dgng luc cho he dan hoi.
Nhdm nghien cuu do
GS.TSKFL Nguyen
Van Khang (Dai hgc Bach Khoa)
dimg
dau
(GS.TSKH.
NguytMi
Van Khang, TS. Dd Xuan Thg, TS. Hoang Ha, TS.
VQ

Van
Khiem) da nehien cuu
\'6
dao
done
uon
ciia
cau dav vane dudi tac dune
eiia
doan tai
trone di
don<i-
Mot so nehien cuu
ciia
mot sd Uie eia lien quan tdi eae uie dune
dgng
lire eiia
gid va dn dinh khf dgng dugc trinh bay trong [26], [27], [28], [29],
[30],|3IM321.[33J,[34].
Hien nay, cae nghien cuu trong nude ve cae hien tugng khf ddng
lire
edn bi
han che nhieu \e mat thue nehiem do
ihieu
phone thf nehiem md hinh ham eid.
Hgc vien Phdng khong- Khong quan (Bd Qude phdng) ed phdng thf nghiem ham gid
\an
ide
thap. quy md nhd phue vu cho nghien
eiru

\a giang day ve khf cu
bav.
\'ien
Khoa hgc Cdng nghe Xay
dimg
(Bg Xay
dimg)
dang dau tu xay
dimg niot
phong thf
nghiem ham gid
qu\
md nhd phue vu nghien cuu \ a phat trien danh gia uie dgng eua
gid len ket eau dan
dung,
lu kinh nghiem
ciia
nude ngoai vice
xa\
dimg \a
khai
ihae
phdng thf nghiem thdi gid deu phai dua tren mot ddi ngu can bg nghien cuu ed
hieu biei
sau rgng ve mat ly ihuyet v a
ihire
nghiem. Chae chan nghien cuu
\e
tac
ddng (long lue

eiia
gid se
lang
len nhanh trone thdi gian tdi khi irong nude
tir
thiet
ke
cae eong irinh dan dung \a eau khau do
Idn
cd de cap ldi phan
ifeh
khf dgng
lire
va \ iee
nlia nUiVe
dau
lu mgl
phdng
ihi
nghiem mo hinh
gid ijuoe
eia.
CHUONG 1. TAC
DONG
CUA GIO LEN CONG TRINH CAU
LL Gidi thieu chung
Tac dgng cua gid len cdng trinh cau ndi chung hay dang ket eau cau treo va
cdu
day vang ndi rieng chia lam 2 nhdm : tac
dijng iTnh

va tac
dijng
dgng
lire.
Tu
dae
diem cua dang ket cau cau treo va cau day vang cd ket cau dam manh, m6m
deo do su lam
\
iee ddng thai cua dam
,
cot thap va cae day vang, do cung udn va do
cung xodn kha yeu so vdi cac dang ket cau cau thong thudng nen rat nhay dao dgng
dudi tac dune cua cac kfeh
ddno
ddng luc cua eid. Vai
ird ciia
eae hien tuone khf
dgng luc
eiia
gid la rai quan trgng trong thiet ke cau day vang. trong nhieu trudng
hctp
anh hudng quyet dinh tdi
lira
chgn phuang an kei cau cau.
Dudi tac dune
ciia
done khf hdn loan eae lue khf done bien ddi la ham
ciia
thdi gian. Cae

lire
nay tae dung vao kei eau lam cho ket cau dao dgng eudng bue.
Day la nhiem \u nghien
eiai
cac hien tugng Buffeting va Vortex-Shedding. Cac dao
dgng eudng bue ed tfnh ehai tat dan do hao tan nang lugng eo hoe. Nhung Irong
nhieu
tructne
hop khi nehien cuu dao done ket cau d van tdc eid
Idn
thav rane ban
than dao done ket cau lai phat sinh ra
lire
khf done bd sune tao them nane krone
mdi
ehi^
dao ddng
lir
than dan tdi bien do dao dgng dot nggt tang nhanh
ga>
hu hai
va tham ehf
hu\
kel eau. Cac dao done tu kfeh thfeh do cae
lire
khf done duoc phat
sinh tu ban than dao ddng ban dau
eiia
cdng trinh
ha_\

do
tucfng
tae co hgc giua ket
cau va done khf ehu khdne phai ed neudn
ede
tu tae done ddne khf. Giai thfeh hien
luttne
nav d van tdc eid
Idn
tuone lac ddne khf \a kei eau dane dao ddne eav ra eae
lue khf ddng bd sung ket hgp vdi cac
lire
san cd lam cho dao dgng
eiia
ket cau eo lue
can khf ddng
lire
lien ldi bi ddng, lue
na_\
bien do dao dgng dot nggt phan ky gay
mat dn dinh ddng
lire
eho kei eau va pha
hu\
ket eau. mat dn dinh
na\
ggi chung la
mai dn dinh khf dan hoi ma nghien cuu nd d eae hien tugng Flutter \a Galloping.
Cac anh
hirdne

do tac dune ddne lue
ciia
eid vao kei eau ed the eav mdi ddne
.

\^ * •*-
lue.
ea>
hu hai eae bd
pluin
ehiu
lire
eua kei eau. hay
ga>
anh
huoiig
lam ly tdi ngudi
qua eau. tham ehf gay pha
hiiy
kel eau trong trudng hgp mat on dinh khf ddng neu
tren. Cae anh hudng
loi
lam ly
xual phai
ur
\iee kei
eau
hi
eong huong
nga>

vdi van
- 12-
ide
gid thong thudng lam dao ddng cua ket cau phue tap. Cac tac ddng va anh
hudng
ciia
gid tdi ket cau cau ndi chung va dang kel cau cau day vang ndi rieng cd
the'
tdm tat trone bane 1.1.
Bang 1.1. Tdm tat tac dgng cua gid len ket cau cau
Tac dong
Tinh
Tae dong
dong lue
Luc tinh
Mai
t">n
dinh
iTnh
- Do luc khf dong
Mai
on dinh dongluc
- Do luc
khi
dong
bo xung
- Tae dung vuong
goc
hu(jmg
gio

loi
HiCn luang
Buffeting
-
Theo
huong gio
u'ti
Ap luc gio va ciic
lire khi
dong
Hien tuong phan ky do xoan
Mai
on dinh ncn uon
Hien
tuong Flutter co dien
Hien tugng
Galloping
Hien tuong Vortex-Shedding
(Van
l6c
gio thap)
Buffeting
do su
h6n
loan
Buffeting do vat can
Dao dong b.d phan ky
- Dao dong tu
kfeh thfeh
- Van

toe
gio
eao
Dao dong b.d giai han
- Dao dong
cuong hue
-
\'an
toe gio
eao
Phan tfch
ciu
Mat on dinh
iTnh
Mat on dmh
dong luc
Hieu ung tam ly
Moi
Hu hai \a moi
Trong
ehmmg
nay se trinh bay long quat eae tae ddng eua gid len cdng trinh
cau ndi chung va kei eau cau day vang ndi rieng, xae dinh van tdc gid tu nhien, cac
thanh phan
lire
khf dgng linh, eae dae
irung
xac dinh phan ung
ciia
ddng khf vao

cdng trinh eau, so luge eae hien
tircmg
khi done
lire
\a \'ai
ird eiia
cac hien
tucTng
khf dgng luc trong thiet ke cau day vang.
1.2. Xac dinh van tdc
gid tu
nhien
Gid tu nhien ed
linh
chat hdn loan, bien ddi eudng do va hudng lien lue, tac
dong mang tfnh ngau nhien. Tai mot dia hinh va thdi gian nhai dinh. \an toe
eiia
gid
tang trong khoang \ai tram met chieu eao theo ly
ilui\et Idp
bien do tfnh chat hdn
loan \a
lire
can eua
mM irai
dat. Dia hinh anh hudng tdi bieu do bien thien
\an
toe
\a
ehieu eao \an tdc gan mat dat, dia hinh cang trdng trai van tdc cang tang nhanh

thei^
chieu eao va cang giam
ehani
khi gan mat dai nguge lai \di dia hinh thanh phd
\-;'m ide
lang eham
lio'n
khi len eao \a
giani
nhanh khi
gfin
dat. Theo
\\ thu>ei Idp
bien cone thue tfnh \an tdc eid bieu dien nhu sau (hinh
1.
h
:
t_
.
*—
u,,.,
(z,
t)
= u
(/)
+
u
iz,
I) (1.2-1)
Trone do : u,

„ I /.t»
la
\an
tdc eid
idne
cone (van
ioc
eio
eiai)
0
-
il
(z) la van tdc gid trung binh (phu thuge chieu
eao
z)
u
(z,
l)
la van tdc gid chenh lech do tfnh chat hdn loan
Tfnh loan van tdc gid trung binh
u iz)
theo cdng
thiic
Davenport nhu sau:
U/
u
z
(1-2.2)
Tron"
dd : a, z

Ian luot
la he sd dia hinh va chieu eao tfnh van tdc eid
Ug,
z^
la van tdc va eao do so sanh
Thong thudng van tdc trung binh ca sd lay tai eao do 10m tren mat dat thien
nhien nen van tdc trune binh tao
chi^u
eao z
vie
lai nhu sau :
u
,=
u
,0.
f"
- Y
0
(1.2.3)
Trong dd : Lay a
=
0.16
vdi dia hinh trdng trai; a - 0.28 vdi riing
ihua.
ddi
thap,
thi
Iran
nhd, a
=

0.4 \di thanh phd
Idn.
nha eao tang
Ap luc gid
iTnh
xae dinh
lu
van tdc gid trung binh theo cdng thue BecnuUi:
q= p.u
(1.2.4
Trong dd : p la mat do khdng khf (p
=
1.2
kg/m'
d dieu kien thong thudng).
Thanh phan \'an tdc gid chenh lech u(z.t) bieu
di^n
tfnh chat hdn loan cua gio tu
nhien. Tfnh loan van tdc gid giat
\\i
\an
ide
gid trung binh
iheo
he sd gid giat
Vf-
:
Uu>,(/.
I)
=

7G-
^"^(Z)
(1.2.5j
Z (m
I
A
10
utotcr.t
>
UCz>
TK^Ti
1 I
f
I,
r
171
i"
loII /.11 '"
Hinh
1.1.
l.r>p
bien khong khf
\"a
\'an toe
giiS
" I I en '^
- 14
L3.
Cac thanh phan
lire

khi dgng
tinh
Ddng khf khi vugt qua cdng trinh tac dung luc true tiep vao cdng trinh.
Lire
nay phu thugc kfeh
thude,
hinh dang vat can, van tdc va hudng tdi cua gid. Khi xet
tdng quat uic dung cua ddng khf hdn loan vao vat the khdng gian se phat sinh 6
thanh phan
lire:
3 thanh
phiin lire
dgc
true
va 3 thanh phan md men xodn. Tuy nhien
vdi ket cau eau thi lue khf dgng gdm 3 thanh phan
lire tinh
la
lire chdn
(F^),
lire
nane
-r
r^

-r
/
• —
T.im
xoAn

Turn uon
a.
V^t
the khong gian
b
Vat the 2 chieu (Dam cau)
Hinh 1.2. Cae thanh phan
lire
khf ddng
tinh
(hi)
va md men xoan (Mp). Day la eae thanh phan
lire
gid linh trung hinh dirge
ke
tdi trong phan tfch cau (hinh
1.2).
De dae trung cho do
Idn eiia
cae
lire
khf dgng
F^,
FL,
MR
dua vao cac he sd
hinh dang la he sd chan gid
(C^)-
he sd nang
(CL).

he sd mdmen
(Cv.,)
xae dinh nhd
thf nehiem md hinh hay
sir
dune lai lieu
siin
ed. Cae luc khf ddne tae dune len cone
trinh cd
the'
xac dinh theo cone thue :
F„
=
C„.c].H.L
(l.?.l)
FL = CL.q.H.L
M,
= C„.q
.
H.L
. B
Trofii!
<\6:
H. L. B
Ian lirol la chitju
eao.
chieu dai \a rone cua ket cau cau
t]
la ap
lire

gio
\ac
dinh
iheo
\oi
vdi
\an
toe
gio thiet
ke u^
Hay
Fo= /i.»:.Cy.//./.
:;
-)
(l ^.i)
F,
=
p.ir.C.H.l.
Mp= p.ii:.C„.U .L.B
- 15-
Cac he sd
C^, C^,
C\i
theo cac dang mat cat liet dien cau
sfin
cd trong cac tai
lieu tham khao hoae xae dinh trong thf nghiem ham gid vdi md hinh doan ket cau.
L4.
Dae trirng
xac dinh phan ung cua dong khi khi qua

eong
trinh
L4.L
Sd Reynold va
sir hinh
thanh xoay khi, vung trdng
De xac dinh phan
ijmg
cua dong khf khi qua vat can
sii
dung cae sd khdng thu
nguyen Reynold va Strouhal.
Sir
lien quan
giiia
lue nhdt (tfnh can) va luc quan tfnh
the hien ung xu
eiia
ddng
ihuy
khf qua vat can phu thugc vao hinh dang, kfeh thude
va tfnh nhdt,
sir
nham mat cua vat lieu mat eua vat the. Dinh
nghia
sd Reynold nhu
sau:
Re =
'""-'
(1.4.1.1)

Trong dd :
lner,j,,Vise,^,
Ian
lugt la lue quan tfnh va lue nhdt
eiia
vat the
Bienddi thanh: Re
=
— (1.4.1.2)
Y
Trons
dd :
U,L,7
Ian
luot la van tdc cua ddne khf,
kfeh
thude bao mat
tiep xue ddng khf \'a he sd
nhdl
ddng
S(>'
Reynold se cho biei dae diem
ciia
ddng khf va mdi trudng phfa sau \at the la
ddng dn dinh. done hon
kxm,
eo xoay khf, \ung trdng \a tfnh ehai
uieh ha}
dfnh
ird

lai
ciia
ddne khf. Khi sd Revnold be ean nhu khdne ed su uieh phfa sau
\'at
the cua
ddne khf va neu ddne phfa trude la dn dinh thi ra khdi
\ai the
cune
van
la ddne on
dinh. Vdi cae dang mat cat dae biet nhu canh may bay, hay mat cat mdng ed chieu
rgng Idn dang
ihoai
khf dgng
lire
thi ung xu
eiia
dong khf d (Jang
lien.
Vdi sd
Reynold
dii
nhd ddng khf qua vat the se bi taeh qua bien. dong thdi phfa sau tao
thanh eae
xoa\
khf xuai hien ed ehu ky goi la eae
xoa>
khf
Kamian.
Cae dang mat

cat cau
ihdne ihudne
cd cau lao thoat khf ddne luc nam d pham
w irne xii
nav. Khi
SO
Re\nold
Idn img xiiddng
khi phfa sau eong irinh kho doan trude \a can xae dinh
qua
lln'
nghiem mo hinh.
Tu\
nhien. hie
na\
ddng khf phfa sau hon
loan,
khdng ddi
xung, xuai hien
xoa\
khf dan
xeii.
kieh
thude \a tan sd xuat hien eae
xoa\
khf khae
nhau (hinh
1.3).
- 16-
Ntici (tunciiiniK Im (SaR^aidnJi

ihjf^
QL
viiy KiTTwaii f»^ihj)tiiik>
T
N
tl ail
&c> rhim(SS RjvaiJ
ri
ci>)
Hinh
1.3.
Pluin ung
eiia
ddng khf qua vat can theo sd Reynold
L4.2.
Sd Strouhal va tan sd xuat
hien
xoay khi sau cdng trinh
Hien
tucmg
tao ra eae
xexiy
gid va \iing trdng edn dirge md la bo\
mdi
sd
khdng thu ngu>en khae la sd Strouhal. Sd Strouhal lien quan tdi tan sd hinh thanh
cac xoay khf
ciia
vung trdng. Vdi viec hinh thanh cac xoay gid sau vat lam phan bd
lai van tdc va ap

lire
gid len \at the.
Sir
taeh \a dfnh
eiia
eae xoa\ khf quanh \at the
phu thude vao sd Reynold, kfeh thude vat va dae trung hdn loan eua ddng khf.
Trong trudng hgp ddng khf tao ra cac xoay khf \a viing trdng sau \at ean.
thi
tan sd
xiKii
hien
eiia
eae
xoa\
khf edn duoc xac dinh theo sd Stroutral nhu sau:
u
(1.4.3
Trone
i^o
:
f,
.
L.
ii hin hroi
la tan so cac
.\oa\-
khi.
kieh thiroe
ehan \a

\an
toe
S()
Strouhal phu thude
wit)
kfeh thude net
dien.
So Strouhal
diroc
tra irong
bane
1.2
ime
\di eae loai liei dien dae
irime.
-
17
STT
1
2
3
4
Dang
m^i
cat
Tici JiOn 171 ji cji iron
vj cjp
JJ^
vjng
TICI

diifn
n
iji cjr hinh ehu
nhat
"1 1
Ti^l di<n
mat
cii hinh thij
n.
rruni:
d.im
(
d
(
Tici Jiifn mJi cji hinh hl^p
d
s
<
kin
(4J)
1
-
.1
/
h
<
H)
1
r~
0 5

<d/h <
:
d/b<
5
d
\ '-^^' /
"1
d
/
h >
ID
So Strouhal
(St)
0.2
0.05
- 0.15
0.154
(4J)
(4b)
1
1,1.d/b
+ 1
0.083
Bang
1.
2.
Sd St
eiia
mot sd
dang mat

cat cau dae
tnmg
1.5. Dao dgng
tif
kich theo hudng vuong gdc gio
tdi do
hien
tuoTig
Flutter
Hien tugng Flutter
la mot
dang
tac
ddng
tu
kfeh
xay ra
dudi
\
an
tdc gid
Idn.
cae
luc khf
ddne
bd
sune phat sinh
tu
ban than dao ddne
ciia

cone trinh
do
tucfne
tae
giua ddng
gid va kei eau.
Trong
iruimg
hop,
sir
ket hgp
eiia lire
khf
dgng
ho
sung
na_\'
lam
lire
can am,
liie
nay
bien
do ket cau
tang nhanh khdng
ngimg
dan tdi pha
luiy
cdng trinh. Hien tugng dugc nghien
cuu dau

lien
eho
canh
ma\
ba\'
sau dd la
cac phat trien
eho
cdng trinh
eau nen edn ggi la
Flutter eho
eau
ha_\
Flutter
ed
dien.
0 day,
hien iue)*ng
Flutter
xay ra khi cd
sir
ket
hgp
dao
ddng
udn va dao
dgng xoan
eiia
kei eau
dudi

citing
mot tan sd
dao dgng (hinh
1.4).
Cone
dmmi;
.
Cons am
Cdnc
tli/tTiii:
""-
^
QNnc
JuiTTii:
Cvn-z Jm
a.
Do
Icch
pha
bariiz U - Jong coiiii
bang
0
Life
n^ng
HiivVru;
«.hu\cn
Joni:
b.
Do
loch

pha
bani:
90'
-
Toriii
com:
uuoiit:
Hinh
1.4.
Dang dao ddng udn
-
xofm
ddng thdi
[12].[I6]
1 1
-
18-
Hien tugng Flutter cd the xem la hien tugng dao dgng tur
kfeh
co bien do
phan ky. Van de dat ra la can xac dinh van tdc xay ra hien tugng mat dn dinh
Flutter, ggi la van tdc gid tdi han xay ra Flutter. Cae cdng thue thue nghiem
de'
xac
dinh van tdc
gid
cue ban dugc trinh bay trong [17], [20], [ 29], [39], [41]. Viec
xac dinh van tdc gid gidi han edn dugc tien hanh trong thf nghiem md hinh loan kei
cau [41]. Cach tiep can ly Ihuyet de xac dinh van tdc cue ban la giai phuang trinh
khi ddng lue

ciia
hien tuone Flutter d trang thai tdi han. Cach thue xav dune
phuerne
trinh vi phan ehuyen dgng
eiia
hien tugng Flutter va each giai se dugc nghien cuu
va trinh bay d cae chuang 3, 4.
1.6. Cac hien
tucrn^
khi dgng
lire
khac cua gid len
eong
trinh cau
1.6.1. Dao ddng
eudng hire
theo hudng vudng goc gid tdi do hien tugng \ ortex-
Shedding
Vdi phan
Idn
dang kei cau dam eau thoat khi cd sd Reynold kha be ddng
khf qua cdng irinh lao thanh eae xoay khf Ian toa sau eong trinh
\di
tan sd
Ian
toa
xae djnh
iheo
sd Strouhal:
L-^

(1.6.1.1)
Cac xoay khf nay lao thanh
lire
nang uic dung \ao ket eau theo hudng thang
dune lam kei eau dao done cudne bue theo cac dane dao ddne udn vdi tan sd
Ian ida
xexiy khf. Nhu
\'ay
neu tan sd
Ian
toa xoay khf bang
Ian
sd dao dgng rieng
ciia
eong
trinh thi kei eau xay ra cdng
huemg.
Van tdc tdi han
ga\
cdng hudng do
Ian
toa
xoa\
khi x;ie dmh theo:
//,,
=
(1.6.1.2)
S,
Trong dd:
U^^

,
1^
Ian luett
la van
ide
tdi han gay cdng hudng
\a
tan sd dao
dong rieng dau tien
eiia
eau
Thue nghiem
ihay
rang,
khi \an toe gio
iir
nhien {rong dai
\an ide
trirde \a
sau \an
Ide
ldi
hvUi
se xuat hien hien tuone dao ddng eua cdng irinh do
xoa>
khf ed
Ian
sd ddne nhai \di
lan
sd dao ddne riene

ciia
eo ne trinh (hinh
1
"^).
19-
Hien tugng nay con ggi la trang thai "khoa" tan sd. nhu vay trong vung "khda"
nay d tai dai van tdc nhat dinh da xay ra cdng hudng do xoay khf lam tang bien do
ciia
dao ddng cdng trinh. Nhung do ket cau cd luc can nen dao dgng la tat dan. nen
con ggi dao dgng do lan
Ida
xoay khf con ggi la dao ddng eudng bue vdi bien do
gidi han. Thudng hien tugng nay xay ra vdi van tdc gid thap, hien tugng eong hudng
lai xay ra tren mgl dai van toe quanh van tdc cue ban.
Vune
khoa
-
t^n
so
Lur khi
done xuat hien theo
ehu
kv
i
'
Hinh
1.5.
Vung
"khoa''
tan so va tae ddng

lire
do cae xoay khf
Tae done ddne
lire ciia
hien tuone nav ihudne khone eav pha hoai kei cau
nhung
gay
hu hai mdi va dae biet la gay hieu ung \i\xn ly vdi ngudi qua cau do dao
dgng manh
eiia
kei eau d mien cdng hudng. Cae cdng thue thue nghiem xae
dinh bien do dao dgng
Idn
nhat va eudng do luc nang
Idn
nhai d trang thai eong
hudng dugc neu trong [17].
[26],
[39]. [40].
Lire
kfeh dgng va phuang trinh dao
dgng
eiia
cdng trinh d trang thai
"khda"
duge trinh
ba\
trong [5].
[6].
1.6.2.

Dao ddng
tir
kich theo
hudiig
vuong gdc gid tdi do hien
tugng
Galloping
Khi ddne khf tac ddne xien ede len kei eau mat eat khdne phai hinh
iron,
se
phai
sinh
lire
nang khf ddng lam ket cau
elui\en
dieh quanh \\ trf can bang ban dau.
Tii\
nhien.
iir sir
dao dgng ban
ctfiii eiia
kei
eaii
lam
tha\
ddi gdc tdi
eiia
eio va se
dan \o\
iha\

ddi tuong
irng lire
nang khf ddng (hinh
1.6).
Neu lue nang
na\
tang len
Cling hudng \di dieh ehu\en eua kei e:Vu se lam lang dieh
ehu\en
len nua eho ldi
khi
dd
eirne eiia
kei eau khae phue duoc lue nane
na\
hoae hre nane bat dau eiam irone
-20-
khi gdc tdi cua gid
van
dang tang. Do tac ddng cua hien tugng nay phat sinh tu dao
ddng cua ket cau
ehu
khdng phai
tir
ban than ddng khf nen nd la hien tugng dao
dgng tu
kich.
Mat dn dinh khf dgng luc do hien tugng Galloping cung dugc xem la
mgl dang dao dgng tu kich cd bien do phan ky.
a

f
—
1
.
Vi tri.
can
hhne
Uone
khi
on
dinh
Vi
tri
c in
b ^ntr
linh
1.6.
Tae dung do Galloping
Vat ran
'-'one
khi hon
loan
a. Tac dong Buffeting
do dong hon loan
Uone
khi hnn
loan
b.
Tac dong Buffeting
khi qua vat

c.in
Cone
Hinh
1.7.
Tae dune do ButTetin:
Cdng thue thue nghiem tfnh van tdc cue han gay mat dn dinh Galloping dugc
trinh bay irong [39],
[40],
[41], xae lap phuang trinh ddng luc
ciia
hien
tuctiig
Galloping dugc neu trong [5]. [
6],
[7].
1.6.3. Dao dgng ngau nhien theo
hudng
gid tdi do hien tugng
BufTeting
Do tfnh chat hdn loan
ciia
ddng khf se phat sinh ra
lire
bien ddi ma bien do
eiia lire
nay la ham
eiia
mat do va eudng do eua hdn loan lam eong trinh bi dao dgng
neau nhien doc theo
huctne

eid dudi lac dune
eiia
cae
lire
bien ddi nav. Dav duoc
xem nhu la hien tugng Buffeting do su hdn loan eua ddng khf. Mgl hien tugng khae
Cling do
lire
gio phat sinh tu
sir
hdn loan
ciia
ddng khf
ga>*
dao dong eudng
hue ciia
cone irinh. nhune su hdn loan
na\
khdne phai tu than tu ddne khf ma do dong khf
khi
\Uol
qua cac vat can phfa
irude
lao ra
sir
hdn loan
khi
tdi eong trinh nam phfa
sau (hinh
1.7).

Day duac xem la hien
luong
Buffeiing trong
\ung
trdng (hien tugng
Buffeiing do
vai
can). Hien lugng sau ed
the
lam don
gian
hda hon hien tugng
irudc
khi eae lue
bien
ddi la ham
eiia ehi
tan sd lan toa xoa\ khi sau
\al
ean. Cong
ihue
llure
nghiem tfnh ehu\en \i
Idn
nhat do hien tuong Buffeiing trinh bay trong [39].
-21
[40]. [41],
xae lap phuong trinh vi phan ehuyen ddng
eiia
hien tugng Buffeting duge

neu trong [5], [6], [7].
1.7. Vai tro
ciia
cac hien tugng
khi
dgng luc trong phan
tieh
va thiet ke ket cau
cau day vang
Cae m uc tren da neu tdm tat ve tae d one
iTnh
va khi ddna luc
ciia
sid len
*—
•
*—
.
t^
cdng trinh cau. Tuy nhien. can thiei phai xae dinh \ai
ird eiia
eae hien tugng khf
dgng
lire
da trinh bay trong thiet ke va tfnh loan eau day vang. Nhu da irinh bay anh
hudng
eiia
cae hien tugng khf dgng luc
eiia
gid the hien d cae mat hu hai va pha hoai

mdi,
iinh hudng tam ly va pha buy ket cau. Vdi eae hien tugng Vortex-shedding va
Buffeiing can
ihiei
phai kiem tra
\'a
gidi han bien dd
h'rn
nhai
eiia
dao dgng. edn vdi
cac hien tugng khf dan hdi (lien quan ldi mat dn dinh kei eau nhu hien tugng Flutter
va Galloping) lai
can
thiei phai kiem tra \a gidi ban van tdc gid ldi ban.
Cae hien tugng khf dan hdi
eiia
gid ndi chung lae dung va anh hudng theo eae
vai tro khae nhau vdi cae bd phan kei cau: dam cung, cot thap va cac day vang. Kei
eau dam
eirng
trong can day \'ang thudng duoc ehu trong xem
xei
tae dune
eiia
eae
hien
luone
Vortex-sheddine. Buffeiine va Flutter \a lien quan tdi tfnh loan tone the
kei cau eau. Con vdi kei eau

edl
thap thudne xem xet dudi tae dune eua eae hien
tugng Buffeting. Fluller \a
Galloping,
cung lien quan tdi tfnh loan long the kei
can
cau. Vdi eae day vang thudng dirge xem xet cue bg
dirdi
tae dung
eiia
hien
lugng
Vortex-shedding
\a
Galloping. Tdm lai trong thiei
ke
va tfnh toan tdng the kei eau
eau
da\
\ane.
eae hien tuone Fluller \a Buffeiine can phai duoc
ehii
trone xem xet
khi van tdc eid thiei ke
Idn
nham danh eia ket cau ed bi
neu\
hai do mai dn dinh
ddng lue \a hu hai kei can d
xan

toe gid eao
ha>
khdng. edn hien tugng
\*onex-
shedtling
can
ehii
trong
khi
\an tdc gid thiei
ke
trung binh \a thap nham danh eia
kel eau eo kha nang b| eong huong \di dai \an
ide
gid thong thudng ea\
ngu>
hai
moi \a anh huong tam ly
lia\
khdng.
\'ai iro
eua eae hien tugng khf dgng
lire
trong
thiet ke eau
da\
vane duac tdm
lai
irone
sadd

1.8.