Ảnh hưởng của một số dạng kết cấu gia tăng độ cứng đến các đặc trưng động lực học của đập bê tông trụ chống

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<b>ANH HUONG CUA M O T SO DANG K H CAU GIA TANG DO CUVG </b>

<b>DEN CAC DAC TRUNG DONG LUC HOC CUA DAP BE TONG TRU CHONG </b>

Nguyen Nggc Thang'

<i><b>Tdm tit: Kit cdu dap hogc lu&ng chdn cd tru chong Id dgng kit cdu co dp mdnh l&n theo phuang ngang </b></i>
<i>(phuang tuyen dap), do do khd ndng cua chiing chju tdi trgng, dgc biit Id tdi trgng dpng ddt theo phuang </i>
<i>ndy kem hcm so v&i khi chiu tdi trgng Iheo cdc phuang khdc. Chinh vi v^, viic gia tdng dp eumg cua dgp trg </i>
<i>chdng theo phucmg tuyin dgp giup cdi thiin ddng ke khd ndng khdng chan cua chung. Npi dung cua bdi bdo </i>
<i>ndy di sdu vao phdn tich dnh hu&ng cua mpt so ket cdu gia tdng dp cung din dgc tnmg dpng luc hgc (chu ky </i>
<i>dao dpng rieng) cita dap bi long tru chong. </i>

<i><b>Tir khoa: Dgp irg chdng, dp cimg, dpng ddi, khdng chdn, dao dpng rieng </b></i>

1. Kbii niem ve cac ket cau gia tang do cirng
cua dap tru chong [1,3].

Sy cin thiet ciia viec bd tri cae kat cau gia ting
do cirng phy thudc vio cac diau kien thyc ta ciia
edng trinh (chieu eao eiia dgp, chiau day ctia try
chdng, hogt ddng dja chin ciia viing xay dyng cdng
trinh....). Tgi cae khu vyc cd nguy ca dgng dit, xuat
phit tir sy lim vi?c cita cdng trinh chiu tii trgng
dgng dat theo phuang ngang (dge theo tuyan dip) c6
the bd tri cic try chdng kep, cac tudng gia ting do
cimg, thanh giang thing (khi khau dp khdng qui Idn
va try chdng mdng) hogc eac vach cirng trong trudng
hgp try chdng rdng. Dieu ki?n dn dinh eiia try chdng
chdng udn dge thudng da dang dugc thda man trong
mgi trudng hgp vdi dgng ket ciu gia tang bit ky
(dim, sudn, vach). Cdn dieu ki?n dn dinh ciia cac try

chdng tuong ddi day (thudng ip dung trong cic dap
try chdng hi?n nay) ludn ludn dugc thda man ke ca
khi kbdng cd kit ciu gia ting dp eung (die biet ddi
vdi nhii'ng dip cd chieu cao dudi 70m). Cac sudn va
vich cirng thudng bo tri theo phuang thing dimg
hogc song song vdi mai ba ciia try chdng. Cae thanh
giing thing (dim giing) thudng bd tri thinh cic

hang song song vdi mii hg ciia try chdng. Lian ket
giira dim giing v i try chdng thudng li lien ket ngam
hoac lian kat khdp. Neu mii thugng luu dugc chia
thanh timg khoang, nen bd tri lien ket khdp giifa
dim giing va try chdng. Ddi khi tran cic dim giang
ngudi ta bd tri cae lian kat khdp d giua nhjp (dip
Beny Badel, Algeria). Cae thanh giing cd thi thing
(dim giang) hogc cong (vdm giing). Tren dap try
chlng Faux-la-Montagne cao 16m tgi Phap, ngudi ta
da ap dyng ea dim giing va vdm giang (hinh 1).
Tren dap nay, cic dim giang vi vdm giang dugc bo
tri trong cic khoang thanh bai bing theo phucmg
nam ngang. Trong mgt khoang, ngudi ta bo tri hoac
toan bg dam giang hoic toan bd vdm giing. Cac
khoang duge sip xip sao cho khoang cd dim giang
nim giifa 2 khoang ed vdm giang vi ngugc lgi.

Ngi dung bai bio trinb biy ket qui nghien ciru anh
budng ciia cic logi kit eau gia tang kbi nang khang
chin nbu dam giang, vdm giing den eac die tnmg
dgng hge eiia ket eau dap try chdng, ma cy tha d diy la
ehu ky va tin sd dao ddng riang eiia dgp ba tong try

chdng Iam viec ddng thdi vdi nen. Cic md binh dugc
tinb toan bing phan mam tinh ket cau SAP2000 v.l4.

<i>Dgi hQC Thiiy lgi </i>

<i>a) Nhin tir phia ihirmig Im, b) Nhin tir phia ha luu </i>
<i>Hinh 1. Ddp Iru chong Faux-la-Montagne (Phdp) </i>

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<b>2. Cac dang dao dgng rieng va chu ky dao </b>
<b>dgng rieng ciia dap be tong tru cb6ng co dam </b>
<b>giang v i vom gi^ng. </b>

Xet hai phuang in dap be tdng try chdng cd dim
giing hogc vdm giing (hinb 2) chiu tic dyng ciia tii
trgng dpng dit theo phuang tuyen dap trong ba
trudng bgp: giifa hai khoang cd ba dam giang, ba
vdm giing v i kbdng co giang. Chiau cao cua dap H=
32m; mai thugng hg luu mj = m2 = 0,5; kich thudc
mat cit ngang ciia dam giang v i vdm giang bang 30
cm X 30 cm. Mian tinb toin bao gom dap try chdng,
nen da ed do siu 70m, khoang each tir chan dip den
bien ciia nen bing 70 m (hinb 3). Cac dac trung ca
ly ciia nan bao gdm: md dun dan bdi ciia be tong
Eb=250'10^ KG/em^, trgng lugng riang ciia be tdng
•^b = 2,4 T/m^, he so poisson ciia be tdng jj.b=0,2 ; md
dun dan hoi cua nen di Eo thay ddi lin lugt bing
50'10^KG/cm^ 150-10^ KG/cm^ va 10^ KG/cm^; he
so poisson ciia nen da po - 0,2; trgng lugng riang
cua nin di yo = 2,68 T/m^ ; dp dinh C = 1,5KG/cm^
h? so ma sit giiia be tdng va nen da tgip- 0,75. Sd

dgng dao ddng rieng ciia dap try chdng duge khio
sat la 30 dgng dau tian. Do khudn khd cd han, trong
bii bao chi dua ra kat qui tinb toan chu ky dao dgng
riang ciia dap try chdng cd ket cau gia ting do ciing
khi md dun dan hoi ciia nen EQ=150'10 KG/cm
(bang 2.1).

Cac kit qua tiiJi toan trong trudng bgp md dun dan
hdi ciia nin di Eo bing 50-lO' KG/cm^ cho thay dim
giing va vdm giang anb budng kbdng dang ke den
trgng thai irng suit - biln dgng cua dip be tong try
chong. Sy cd mat cua cac dim giing lam giam di 14%
chu ky hai dgng dao dgng riang dau tian ctia dap try
chong (dge theo tuyln dip). 0 nhifng dgng dao ddng
rieng khac, cbu ky giam di klidng dang ka. Trong
trudng hgp dgp cd vdm giang, ehu ky dao dpng rieng
thay doi khdng nliu truong hgp tren. Chu ky hai dgng
dao dpng rieng diu tian (dgc theo tuyen dip) giam di
3-5% so vdi phuang an khdng cd giang.

<b>Tir dgng dao dgng rieng thti 3 din thti: 5 chu ky </b>
dao dgng rieng thay doi khdng dang ke (dudi 0,1%).
<b>Sau dd, tu dgng thir 6 den dgng thif 8 - dao dgng dgc </b>
theo pbuong ddng chiy, chu ky dao ddng rieng ting
din so phuang in khdng cd giing. Sy ra tang dang
kl (11%) quan sit duge d dgng thir 9, 10 va 11. Sau
<b>dd, chu ky ting Ien khdng nhilu (dudi 6%) tir dang </b>
<b>thir 12 din dgng thir 30. </b>

<b>Kit qui tlnb toin trong trudng hgp md dun dan </b>

<b>hoi ciia nen da Eo bing 15010^ KG/cm^ cho thay </b>

cho thay dam giang va vdm giing anh budng khdng
nbieu den trang thai img suit - bien dang cua dap try
chong. Khi dip co dim giang, cbu ky eiia hai dgng
dao ddng rieng dau tien giim di so vdi trudng hop
md dun dan hdi ciia nan Eo=50-1 O^KG/cm'. C) nhirng
dgng dao dgng bac cao chu ky thay doi khong dang
ka so vdi trudng hgp dip khdng cd giang.

Trong tnrdng hgp dap ed vom giang chu ky dao
ddng rieng thay ddi theo mgt dien bien kha trai
ngugc. Chu ky hai dgng dao ddng rieng dau tien
giam di 3% - 4% so vdi trudng hpp dap khdng cd
giang nhung d nhifng dang bac cao chu ky thay ddi
mgt cich ro ret. Chu ky tang nhieu nhat (tir 20% den
30%) d dang thti 4, 5, 6, khi dao dpng dpc phuang
theo ddng chay. Sau dd, chu ky dao dgng tang 10%
-18% tir dang thu 7 dan dang thic 16, va 2-6% tir dang
17 den dang 30 (khi xuat hien dao dpng doc theo
phuang ddng chiy, theo phuong tuyen dap va dao
dgng hon hgp).

Kat qua tinh toan chu ky dao ddng rieng ciia h?
dap - nan trong trudng hgp mo dun dan hoi cua nen
Eg = lO'^KG/cm^ (nen co tha eoi nhu tuyet doi cung)
cho thiy sy xuat bien ciia dim giing lam giam
11-13% chu ky 2 dgng dao dgng rieng dau tien (dge
theo tuyln dap). Tir dgng 3 dan dang thir 20 chu ky
dao dgng rieng thay ddi khong dang ke so vdi

phuang an dgp khdng cd giang (dudi 3%). Sau do tir
dang 21 den dang 30 chu ky dao dpng riang tang tir
7-13%. Khi dip CO vom giing chu ky ciia 2 dang
dao dpng riang dau tien (dpc theo tuyan dap) giam di
tir 3-4% so vdi dap khdng co giing. 6 dang thir 3
chu ky chi tang Ien 4% nhung d nhirng dang bac eao
hcm chu ky thay ddi mgt each dgt ngpt. Chu ky tang
nhilu nhat (40-50%) d dang thu 5 va thu 6 khi dap
dao dgng rieng dge theo phuong dong chay. Sau do
chu ky dao dgng tang 14 - 23% tir dang thu 7 den
dang thu 11, va 12 -16% tir dgng 12 din dang 17. Tir
dang 18 din dgng 30, khi xuat hi?n cic dao dgng
rieng dgc theo tuyln dip, theo phuang dong chay va
dao ddng h6n hgp, chu ky dao dgng ting khoang 6

-12%.

Kit qua tinh toan cho thiy dg cimg eiia nen it inh
hudng din dao dgng rieng ciia dap co dam giang so
vdi phuang an dap khong co giang. Chu ky giam di
<i>11% -14% d hai dang diu tian. 6 nhCfng dgng bac </i>
cao han chu ky dao dgng rieng thay ddi khdng dang
kl. Chi trong hgp nen rat cting EQ = 1.10 KG/cm
chu ky dao dpng riang tang 10% - 20% tir dgng thir
20trddi.

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<i>1 — ^ </i>

<i><b>r\ </b></i>

<i>ffi«/i 2. i'o' dd tinh ddp tru chdng cd kit cdu gai tang dp cirng theo phuang ngang </i>

Dp cirng cua nan inh hudng nhiau nhat den chu
ky dao ddng rieng khi dap cd bd tri vdm giang so vdi
phucmg in dap khdng cd giing. 6 hai dgng dau tian
chu ky dao ddng riang giim di khdng dang ke (dudi
3-5%) vdi cic gii tri md dun din hdi khac nhau ctia
nan. Nhung d nhiing dang bgc eao hon chu ky ting
ian mgt cich ro ret (40-50%). Nin cang cung thi su

chenh lech giiJa chu ky dao dgng rieng cua dip cd
vdm giing va dap khdng giing cang Idn.

c i n nhin mgnh tham ring, trong tat c i cic
trudng hgp su giim dgt nggt cua cbu ky dao dgng
rieng sau bai dang dao dgng dau tian ndi ian sy
thay ddi phuang dao dgng ciia h? "dap try
chdng-nen".

<i>Bdng 2.1. Chu ky dao dpng rieng ciia dap tru chong co kit cdu gia tdng dp cimg </i>
<i>khi mo dun dan hoi ciia nin Eo=1501(fKG/cm^. </i>

Dang dao
dpng rieng
1
2
3
4
5
6

7
S
9
10
11
12
13
14
15
16
17
18
19
20
21
22

Chu ky dao dong rieng (s)

Dap khong c6 giang
0.0945
0.0896
0.0488
0.0402
0.0390
0.0369
0.0361
0.0330
0.0325
0.0316

0.0309
0.0282
0.0277
0.0263
0.0254
0.0253
0.0252
0.0244
0.0242
0.0241
0.0239
0.0234

Dap CO vom giang
0.0905
0.0866
0.0490
0.0484
0.0480
0.0479
0.0401
0.0390
0.0369
0.0360
0.0329
0.0325
0.0316
0.0309
0.0282
0.0277

0.0263
0.0254
0.0253
0.0252
0.0244
0.0242

Dap CO dam giang
0.0814
0.0786
0.0483
0.0396
0.0390
0.0369
0.0357
0.0329
0.0323
0.0314
0.0309
0.0282
0.0277
0.0263
0.0254
0.0253
0.0252
0.0244
0.0242
0.0241
0.0239
0.0234

D Q chenh lech so voi phuang ^n dap
khOng c6 giang (%)
Dap c6 v6m giang

.4.2754
-3.3083
0.3902
20.4353
23.2425
29.9969
11.1357
18.0916
13.4714
13.8111
6.5279
15.0142
13.9728
17.3640
10.9850
9.3415
4.6032
4.1480
4.8531
4.3947
2.0802
3.1612

Dap CO dam giang
-13.9212

-12.2821
-1.1571
-1.3823
-0.0040
-0.0005 •
-0.8967
-0.3864
-0.6375
-0.6694
-0.0600
0
0.0397
-0.1492
-0.0122
0.0109
-0.0375
-0.0308
0.0001
-0.0043
-0.0127
-0.0462

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D^ngdao
d$ng rieng

23
24
25
26
27

28
29
30

Chu ky dao dOng rieng (s)

<i>B^p khong c6 giang </i>

0.0231
0.0231
0.0228
0.0226
0.0226
0.0223
0.0222
0.0213

D3p c6 v6m giang
0.0241
0.0239
0.0234
0.0231
0.0231
0.0228
0.0226
0.0225

Dap c6 dam giang
0.0231
0.0231

0.0226
0.0226
0.0225
0.0222
0.0221
0.0213

DO chenh lech so v6i phuong an dap
khOns c6 giang (%)
D§p c6 v6m giang

4.1851
3.7426
2.6946
2.3381
2.2507
2.2308
1.7871
5.8694

Dap c6 dam giang
0
-0.0126
-0.6930
0.0002
-0.0431
-0.2873
-0.4325
-0.0004

3. Ket luan

Tir kit qui tinh toan chu ky dao ddng riang ctia
dap try chdng cd bd sung cac kat ciu gia ting khi
ning khang chin, cd the dua ra mgt sd ket luan sau:

1. Cac kit ciu gia tang dg eung dudi dang giang
(dim giing vi vdm giing) anh hudng khdng ding ke
den trgng thii iing suit - biln dgng ciia dap ba tdng
try chong khi khdng cd ddng dit.

2. Chu ky dao dgng riang cua dip try chdng khi
CO dim giing giim ro r?t nhat (1 l-14%i) so vdi khi
khdng cd giing d hai dang dao dgng rieng dau tien.
6 nhirng dang bgc cao ban, chu ky thay ddi kbdng
ding kl.

3. So vdi khi khdng cd giing, chu ky hai dang
dao dpng rieng ctia dap try chdng khi cd vdm giang
giim khdng dang kl (3-5%). Cl nhCfng dang bgc cao
hgn, chu ky ting len kha dot nggt tiiy thudc vao dg
cijng ciia nin. Nen cang ciing, chu ky tang cing

nhilu (20-30%). Dg gia ting ciia chu ky dao dgng
rieng giim dan d nhifng dang tiep theo (tir dang thu
10-12 trd di), chiem khoing 6-10%.

4. Dg cung ciia nan it anh budng dan dao dgng
rieng eua dap cd dim giang so vdi khi khdng cd giang.

5. Dg Cling cita nan anh hudng nhiau nhat den
chu ky dao ddng rieng khi dap cd bd tri vom giang
so vdi phuong an dap khdng cd giing. Nan cang
cung thi sy cbc.ih l?ch giifa chu ky dao ddng rieng
eiia dip cd vdm giing va dap khdng giang cang Idn.

<i>() diy, ngi dung bai bao cung mdi dl cap den kat </i>

qui tinh toan cic die trung ddng (ehu ky va tan so
dao dgng riang) ciia dap try chdng cd bd sung giang.
Trong thyc tl xay dyng cac cdng trinh chju tai trgng
dgng dit, tran thi gidi da ap dyng nhieu loai ket cau
gia tang dg cirng khic dgng sudn va vach ciing. Vi?c
lya chpn loai kit ciu nio de ip dyng phy thugc vao
dilu ki?n ciia tirng cdng trinh cy the.

TAI LI$U THAM KHAO

<i>1. Ngd Tri Viing. Sd lay ki thudl thuy lgi tgp 2. NXB Xay dyng. </i>

<i>2. Nguyen La Ninh (2007), Dpng ddt vd thiil ki cdng Ulnh chiu dpng ddt, NXB Xay dyng. </i>

3. Grishin M.M., Rozanov N.P vi nnk. Dap ba tdng tren nen d i NXB Xay dyng. Moscow, 1974 (ban tieng Nga).

Summary

INFLUENCE OF SOME RIGIDITY-INCREASED STRUCTURES TO DYNAMIC
CHARACTERISTICS OF THE CONCRETE BUTTRESS DAMS

<i>The butaess dams or abutment walls are slender suuclures in the line ofdamsite, so their ability lo work </i>

<i>under load especially under seismic load in this direction is less effective than other directions. Therefore. </i>
<i>Ihe rigidity increasing of buttress dams in the line ofdamsite significantly improves their seismic resistance. </i>
<i>This paper includes the analysis of the infiuence of rigidity-increased structures lo the dynamic </i>
<i>characteristics (natural-vibration period and frequency) ofthe concrete buttress dams. </i>

<i><b>Keyword: buttress dam, earthquake, rigidity, natural-vibration period </b></i>

<i>Ngu&i phan biin: TS. Nguyen Quang Ciromg </i> <i>BBT nhgn bdi: 22/8/2013 </i>
<i>Phdn biin xong: 27/8/2013 </i>

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