MT BIN PHP GIM NH HNG CHN NG NG CC N CNG TRNH LN CN
TS. TRN NH NGC Vin KHCN Xy dng
Tm tt: Bin php gim nh hng chn ng do ng cc nhm bo v cc cng trnh
ln cn bng t p c kin ngh v trnh by trong bi bo. Kt qu nghin cu l
thuyt v thc nghim nhm khng nh tnh kh thi ca bin php cng c trnh by.
t vn
Mt trong cc bin php truyn thng nhm bo v cng trnh trc tc ng ca
chn ng l o ho gim chn. Chiu su ho gim chn thng c xc nh bng 1/3 ca
bc sng chn ng [1]. R rng tc dng ca vic o ho l c kh nng gim chn ng,
vy th tc dng p t (ngc li vi bin php o ho) s ra sao? Bi bo ny trnh
by kt qu nghin cu l thuyt v thc nghim v hiu qu gim chn ca phng php
t p. Tnh ton l thuyt
Tin hnh tnh ton cc bi ton truyn sng trong nn t gy nn bi ng cc
bng phn mm VIBRA_SP, kt qu cho thy tc dng ca c hai bin php o t v p
t trong vic gim nh hng chn ng do ng cc l tng t nhau. Trn cc hnh 1,
2 v 3 m t kt qu tnh ton cho cc trng hp: khng bin php gim chn, s dng
ho gim chn v s dng p t. Tc dng ca vic gim chn khi s dng phng php o
ho gim chn v p t c trnh by trong cc biu trn hnh 4 v hnh 5.
Hnh 2. Hnh nh vn tc dao ng phng ng ti thi im 0,2. Trng hp c bin
php gim chn h o
Hnh 1. Hnh nh vn tc dao ng phng ng ti thi im 0,2 s. Trng hp khng
c bin php gim chn
Thc nghim hin trng
Hin trng nh my n hnh Orion Hanel c s dng kim chng. Hnh 6 m t mt
bng b tr th nghim. Cc c ng ti Orion Hanel II l cc BTCT c tit din
l
0
10
20
30
40
50
0 2 4 6 8 10 12 14 16 18 20 Khong cch (m)
Vn tc dao ng (mm/s)
Ho gim chn
Khng bin php gim chn Gim chn bng ho
0
10 20
30 40
50
0 2 4 6 8 10 12 14 16 18 20 Khong cch (m)
Vn tc dao ng
(mm/s)
Ph ti mt t
Khng bin php gim chn Gim chn bng ph ti mt t
Hnh 4. Gi tr vn tc dao ng theo khong cch ca 2 trng hp tnh ton so
snh
Hnh 5. So snh gi tr vn tc dao ng theo khong cch ca bin php gim
chn bng ph ti mt t
Hnh 3. Hnh nh vn tc dao ng phng ng ti thi im 0,2 s. Trng hp c
bin php gim chn bng ph ti cht
trn mt t
350x 350 mm, chiu di cc l 32,0 m chia lm 4 on, mi on 8,0 m. Ba
ng cc l ba diezel 3,5 T, chiu cao ri ba ln nht l 2,5 m.
C 6 im o, trong im 2 v im 6 c b tr theo hng c ph ti cht trn mt t
theo phng truyn sng. im 3 v im 5 b tr trn hng khng c bin php gim
chn nhm so snh. Bng 1 trnh by cc gi tr vn tc, gia tc v bin dao ng o
c ti hin trng. Hiu qu gim chn cho tng tham s dao ng xc nh t o chn
ng c trnh by trn bng 2. .
Trong cc bng 1 v 2, cc tham s c ngha ln lt nh sau:
R khong cch t cc ng n im o; Vz, Vr, Vt ln lt l vn tc dao ng theo
cc phng ng, phng knh v phng
tip tuyn; Az, Ar, At ln lt l gia tc dao ng theo cc phng ng, phng
knh v phng
tip tuyn; Sz, Sr, St ln lt l bin dao ng theo cc phng ng, phng
knh v
phng tip tuyn; fzmin, fzmax l tn s dao ng ln nht v nh nht o c
theo ng; frmin, frmax l tn s dao ng ln nht v nh nht o c theo
knh.
Bng 1. Cc tham s dao ng o c khi ng cc s 2
R Vz Vr Vt Ad Ar At Sz Sr St fzmin fzmax frmin frmax on
im o m mm/s mm/s mm/s m/s2 m/s2 m/s2 m m m Hz Hz Hz Hz 1 10 6.63
2.79 7.19 0.66 0.44 0.79 119.00
45.40 127.37
8.59 15.60 9.16 17.2
2 10 7.40 4.51 8.67 0.66 0.59 0.88 151.00 62.90 163.5
8 7.25 13.90 8.11 11 1
3 10 8.37 6.64 10.68 1.22 0.97 1.56 198.00 101.0
0 222.2
7 9.09 16.40 8.47 21.20
4 23 3.69 2.22 4.31 0.47 0.34 0.58 66.60 59.80 89.51 10.60 11.00
6.87 10.40 5 23 2.78 2.78 0.31 0.31 47.60 47.60 5.9 10.5 2 6 23
5.66 4.58 7.28 0.53 0.41 0.67 71.20 65.60 96.81 12.40 13.10 5.94
12.1 4 23 3.24 2.90 4.35 0.63 0.47 0.79 44.80 27.80 52.72 11.20
28.20 9.66 21.4 5 23 3.72 3.72 1.22 1.22 25.20 25.20 3.99 47.4 3 6
23 4.44 6.11 7.55 0.53 1.63 1.71 57.40 49.60 75.86 14.00 27.60 5.68
35.2
Bng 2. Hiu qu gim chn ca ph ti cht trn mt t t o c Vz Vr Vt Ad Ar
At Sz Sr St
11% 32% 19% 46% 40% 43% 24% 37% 27%
Nh c
Hnh 6. V tr cc s 2 v v tr cc u o
Cc
H o BxLxD= 2x7x2
1
2
4
3
10 m 23 m
ng ct BxLxH= 3x7x1m
5
6
27 m 20 m
