Experimental Study on Mechanical Behavior and Failure ...
Transcript of Experimental Study on Mechanical Behavior and Failure ...
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Experimental Study on Mechanical Behavior and Failure Mechanism of
Transmission Tower Structures ---Review and Reflect from the perspective of Resilience
Li Sun Institute of Structural Engineering
Chair of Structural Dynamics and Earthquake Engineering Prof. Dr. Božidar Stojadinović
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Electric Power Supply System: an Infrastructure Network
Users Transmission and Distribution Generation
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Research Background ◆Damage due to extreme ice load Rare ice disaster in South China in 2008
by courtesy of CMA
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Research Background
Failure due to unbalanced tension in cables Failure due to cable disconnect
Jiangxi Province
by courtesy of Prof. Qiang Xie
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Zhejiang Province
Failure due to unbalanced cable tension
by courtesy of Prof. Qiang Xie
Research Background
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◆Damage due to extreme wind load Xuyu, JiangSu Province, 2005
by courtesy of Prof. Qiang Xie
Research Background
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Outline ◆Test Program
◆Discussion on some issues
◆Reflection on test results
◆Conclusions and future works
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Diaphragm
Diaphragm
Diaphragm
2:3 1:2
1. Test Program ◆ Test prototypes
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Pw
C Gi Mw Gi T G1 G2
L L L Pw Pw
general load wind load ice load
◆ Loading types
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reaction frame
distribution beam oil jack
rigid foundation anchor bolt
rigid stand
grooves testing pedestal
rigid box beam
◆ Laboratory loading setup
wind-resistance
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3.45
m
Tongji University, Shanghai
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Six specimens
Two pairs of Double-panel specimens
One pair of Single-panel specimens
One pair
Another pair
ice-resistance
wind-resistance ◆ Test specimens
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◆ The principal failure mode --- Out-of-plane deformation….
by courtesy of Prof. Qiang Xie
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How long is the buckling length?!
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2. Discussion on some issues
◆ Are the tests of individual sub-assemblages are indicative of the overall behavior of the system?
◆ Are the cumulative second order effects have a significant impact on the buckling load distribution to individual members?
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3. Reflection on test results
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◆Why did the observed damage occur?
Principal failure mode: out-of-plane deflection and buckling
The location of tower stiffening diaphragms was not adequate
The design principles for distributing stiffening diaphragms in the tower body should be revisited
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◆How the out-of-plane deflection of diagonal bracings negatively affect the stability performance of the tower structure?
¬ From three perspectives:
I. Considering the main leg…
II. Considering the diagonal bracings…
III. Considering the INTERACTION between the main leg and the diagonal bracings…
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0 400 800 1200 1600 20000
20
40
60
80
100
120
140
121110
9
605958
f suw
f suo
0.9f suw
G1 (
kN)
ε (10-6)
57 58 59 60 9 10 11 12
without diaphragm with diaphragm57
I. Considering the main leg…
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0 20 40 60 80 100 120 140-2
0
2
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14 without diaphragm
with diaphragm
D (m
m)
G1 (kN)0 15 30 45 60 75 90 105
-1
0
1
2
3
4
5
6 without diaphragm
with diaphragm
D (m
m)
G1 (kN)
Ⅱ. Considering the diagonal bracing…
Axially loaded member…
single-panel double-panel
D
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Ⅲ . Considering the INTERACTION between the main leg and the diagonal bracing…
0 200 400 600 800 10000
400
800
1200
1600
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2400
Pw
G1
ε (10-6)
57 58 59 60 9 10 11 12
ε (1
0-6)
G2
121110
9
605958
without diaphragm with diaphragm57
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0 5 10 15 20 25 30 350
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32
Pw(k
N)
D(mm)
without diaphragm with diaphragm
◆What is the difference of load-carrying capacity? The case of wind resistance
Pw
Pw
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0 2 4 6 8 10 120
20
40
60
80
100
120
140
without diaphragm with diaphragm
G1(
kN)
D(mm)0 1 2 3 4 5 6 7 8
0
20
40
60
80
100
120
without diaphragm with diaphragm
G1(
kN)
D(mm)
The case of ice resistance
double-panel single-panel
◆What is the difference of load-carrying capacity?
G1
G1
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Conclusions: ◆ The out-of-plane deflection of diagonal bracing is
“critical” but difficult to avoid; ◆ The stability performance of both the individual member
and the overall tower structure is remarkably influenced by the out-of-plane deflection of diagonal bracings;
◆ Adding diaphragms on the vulnerable panels of tower structure would be a practical and effective retrofitting strategy.
4. Conclusions and Future Work
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Future work: 1. Investigation of dynamic response 2. Risk-informed performance analysis existing power network updated power network
retrofit existing component(s) updated Component(s) most cost-effective
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Thank you for your attention! Looking forward to working with all of you…
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Any question? Or comments?