forced vibration modal testing of ‘international bridge’ at wayne, new jersey, 21-23 july 2010...
Post on 16-Dec-2015
213 Views
Preview:
TRANSCRIPT
Department of Civil & Structural Engineering.
Forced vibration modal testing of ‘International Bridge’
at Wayne, New Jersey, 21-23 July 2010
Prof. James BrownjohnDr Ki-Young Koo
Dr Chris Middleton
The University of SheffieldDepartment of Civil and Structural Engineering
Vibration Engineering Section
Department of Civil & Structural Engineering.
Test grids for AVT and FVT using 19 sensors
234567891011131415161718192021
121122
123124
125126
127128
111112
113114
115116
117118
101102
103104
105106
107108
9192
9394
9596
9798
8182
8384
8586
8788
7172
7374
7576
7778
6162
6364
6566
6768
51
5253
5455
5657
58
41
42
43
44
45
46
47
48
21
22
23
24
25
26
27
28
11
12
13
14
15
16
17
18
Span 2: using 6 swipes with 2×16+triax by shaker
Span 1 Span 2
Single swipe with 19 sensors
Department of Civil & Structural Engineering.
The workers ….
Chris on data acquisition, and Ki on the cherry picker
Department of Civil & Structural Engineering.
The equipment ….QA 750 servo accelerometers, APS400 shaker
Department of Civil & Structural Engineering.
Single ‘swipe’ ambient test on walkway -during afternoon and 90+F
Department of Civil & Structural Engineering.
Displacement signals from double integration of acceleration.
Are we seeing real coupling of spans?
308 310 312 314 316 318 320-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
seconds
mm
C:\DOCS_TP\Proposals\Drexel\05-Testing\AMBIENT_SWIPES\displacement\fvt_20100721_31_dsa_scaled_0p1dis_mm_r
TP61TP62TP63TP64TP65TP66TP67TP68TP51TP52TP53TP54TP55TP56TP58TP57TP51z
Department of Civil & Structural Engineering.
Mode shapes obtained using NExT/ERA:(30 minute data set)
Clear evidence of coupling here mode: 1 f=3.75Hz zeta=0.71% mode: 2 f=4.3Hz zeta=2.3% mode: 3 f=5.27Hz zeta=0.94% mode: 4 f=5.96Hz zeta=0.66%
mode: 5 f=9.5Hz zeta=0.8% mode: 6 f=10.2Hz zeta=0.61% mode: 7 f=11.7Hz zeta=2.3% mode: 8 f=12.4Hz zeta=1.5%
mode: 9 f=14.2Hz zeta=1.1% mode: 10 f=14.9Hz zeta=0.4% mode: 11 f=15.1Hz zeta=0.91%
Department of Civil & Structural Engineering.
Single vehicle free decay and
small damping and frequency
variation1590 1600 1610 1620 1630 1640 1650 1660 1670 1680 1690
-3
-2
-1
0
1
2
3
seconds
m/s
ec2
C:\DOCS_TP\Proposals\Drexel\05-Testing\AMBIENT\ambient_20100721_5_DSA_scaled
TP5TP6TP7TP8TP9TP15TP16TP17TP18TP19
0 0.1 0.2 0.3 0.4 0.50
0.2
0.4
0.6
0.8
1
ch 20 (m/sec2)
damping vs amplitude; average damping: 0.6332%
/%
0 0.1 0.2 0.3 0.4 0.53.66
3.67
3.68
3.69
3.7
3.71 frequency vs amplitude; average frequency: 3.6824Hz
f /H
z
ch 20 (m/sec2)
3.66 3.67 3.68 3.69 3.7 3.710.4
0.6
0.8
1
1.2
1.4 damping vs frequency
/%
ch 20 f /Hz0 5 10 15 20 25
0
0.5
1
log-dec damping vs time
/%
ch 20 t /sec
Department of Civil & Structural Engineering.
Force vibration test/analysis methods~between 11PM and 5AM
• Excitation modes– Random (15 minutes)– Chirp (15 minutes)– Swept sine –for reference sensors only, during moves– Shaker shutdown –for reference sensors only, during moves
• Analysis methods– NExT/ERA on random excitation (MODAL) , f, – GRFP on chirp excitation (MODAL) , f, , m– OMAX on chirp excitation (MACEC) , f, , m– Circle-fit on swept sine (MODAL) f, , m– Log-dec free decay on shaker shutdown (MODAL) f,
Department of Civil & Structural Engineering.
5-swipe output only modal analysis using NExT/ERA (with 15 minute random excitation)
mode: 1 f=3.07Hz zeta=1.4% mode: 2 f=3.67Hz zeta=0.66% mode: 3 f=4.34Hz zeta=3.3%
mode: 4 f=5.14Hz zeta=0.66% mode: 5 f=5.17Hz zeta=0.59% mode: 6 f=9.42Hz zeta=0.76%
mode: 7 f=11.6Hz zeta=1.4% mode: 8 f=12Hz zeta=1.8% mode: 9 f=12.2Hz zeta=1.3%
Department of Civil & Structural Engineering.
Cross-section reveals increasing transverse mode order
mode: 1 f=3.07Hz zeta=1.4% mode: 2 f=3.67Hz zeta=0.66% mode: 3 f=4.34Hz zeta=3.3%
mode: 4 f=5.14Hz zeta=0.66% mode: 5 f=5.17Hz zeta=0.59% mode: 6 f=9.42Hz zeta=0.76%
mode: 7 f=11.6Hz zeta=1.4% mode: 8 f=12Hz zeta=1.8% mode: 9 f=12.2Hz zeta=1.3%
half-sine
full-sine
half-sine
Department of Civil & Structural Engineering.
Chirp excitation & response –on last swipe (4AM?), almost zero traffic
–Shaker induced response drowned by traffic effects
TP51z f/Hz
10
20TP101 f/Hz
10
20TP102 f/Hz
10
20TP103 f/Hz
10
20TP104 f/Hz
10
20
TP105 f/Hz
10
20TP106 f/Hz
10
20TP107 f/Hz
10
20TP108 f/Hz
10
20TP91 f/Hz
10
20
TP92 f/Hz
10
20TP93 f/Hz
10
20TP94 f/Hz
10
20TP95 f/Hz
10
20TP96 f/Hz
10
20
seconds
TP97 f/Hz
520 530 540 550
10
20
seconds
TP98 f/Hz
520 530 540 550
10
20
seconds
TP51x f/Hz
520 530 540 550
10
20
seconds
TP51y f/Hz
520 530 540 550
10
20
seconds
TP51z f/Hz
520 530 540 550
10
20
TP51z f/Hz
10
20TP61 f/Hz
10
20TP62 f/Hz
10
20TP63 f/Hz
10
20TP64 f/Hz
10
20
TP65 f/Hz
10
20TP66 f/Hz
10
20TP67 f/Hz
10
20TP68 f/Hz
10
20TP51 f/Hz
10
20
TP52 f/Hz
10
20TP53 f/Hz
10
20TP54 f/Hz
10
20TP55 f/Hz
10
20TP56 f/Hz
10
20
seconds
TP57 f/Hz
0 10 20 30
10
20
seconds
TP58 f/Hz
0 10 20 30
10
20
seconds
TP51x f/Hz
0 10 20 30
10
20
seconds
TP51y f/Hz
0 10 20 30
10
20
seconds
TP51z f/Hz
0 10 20 30
10
20
Department of Civil & Structural Engineering.
Good quality FRF; used for Global RFP curve fitting
0
0.2
0.4
0.6
0.8
1
1.2x 10
-3Modulus H2 (H1=red): ch20 vs ch1
-6
-4
-2
0
2
4x 10
-4 Real : ch20 vs ch1
-10
-8
-6
-4
-2
x 10-4 Nyquist : ch20 vs ch1
5 10 15 20-200
-150
-100
-50
0
Frequency /Hz
Phase : ch20 vs ch1
5 10 15 20-1.2
-1
-0.8
-0.6
-0.4
-0.2
0x 10
-3
Frequency /Hz
Imag : ch20 vs ch1
5 10 15 200.7
0.75
0.8
0.85
0.9
0.95
1
Frequency /Hz
Coh : ch20 vs ch1
Department of Civil & Structural Engineering.
Global rational fraction curve
fitting for two modes …
Department of Civil & Structural Engineering.
Modes 1,2 from GRFP
mode: 1 f=5.22Hz, zeta=0.42%
mode: 1 f=3.7Hz, zeta=0.54%
mode: 1 f=3.71Hz, zeta=0.92%
mode: 2 f=5.15Hz, zeta=0.56%
Department of Civil & Structural Engineering.
…. And using MACEC/OMAX
020
4060
80100
120
0
20
40
0
10
20
XY
Z
020
4060
80100
120
0
20
40
-10
0
10
20
XY
Z
Department of Civil & Structural Engineering.
How did we do?
Ambient Forced mode Walkway
AVT Random AVT
Shaker shutdown
GRFP Circle fit OMAX
f /Hz /% f /Hz /% f /Hz /% f /Hz /% m1 /t f /Hz /% m1 /t f /Hz /% m /t 0? 3.07 1.4 1 3.75 0.71 3.67 0.66 3.69 0.61 3.69 0.63 81 3.70 0.51 94 3.68 0.83 71 2 4.3 2.3 4.34 3.3 3 5.27 0.94 5.17 0.59 5.22 0.63 5.22 0.57 273 5.22 0.61 300 5.20 0.96 192 4 5.96 0.66 5 9.5 0.8 9.42 0.76 9.46 0.58 9.49 0.52 354 9.48 0.53 2075 6 10.2 0.6 7 11.7 2.3 11.6 1.4 11.7 1.64 285 8 12.4 1.5 12.2 1.3 12.2 1.2 12.2 0.96 130 12.16 1.26 102 9 14.2 1.1 10 14.9 0.4 11 15.1 0.91 15 0.77 15 0.51 266 15 0.51 1237 12 15.8 0.33 843
Department of Civil & Structural Engineering.
Lessons• Expected to be able to do two spans: took much longer to move
between swipes! Could have done one span per night• We could get good quality FRFs with light ‘automobile’ traffic• OMAX proved very effective• Walkway swipe was very valuable –dynamic link between spans, no
evidence of amplitude dependence• Orthotropic nature of deck revealed by set of swipes• Movement at piers was surprising, shame we couldn’t study
horizontal movement• Step-sine testing was tedious and not good value• Shaker testing did give OK FRFs
Department of Civil & Structural Engineering.
What we would do in future• Think seriously about the logistics of moving accelerometers• Probably foregoing the luxury of full realisation of mode shapes & use
reduced cross-deck measurements• Pay more attention to the bearings, which in any case are more
accessible• Estimate modal mass, frequency and damping from shaker chirp
excitation • Use either shaker shutdown or passage of heavy vehicle to obtain
reliable frequency and damping estimates.
top related