experimental study on mechanical behavior and failure
TRANSCRIPT
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
Electric Power Supply System: an Infrastructure Network
Users Transmission and Distribution Generation
Research Background ◆Damage due to extreme ice load Rare ice disaster in South China in 2008
by courtesy of CMA
Research Background
Failure due to unbalanced tension in cables Failure due to cable disconnect
Jiangxi Province
by courtesy of Prof. Qiang Xie
Zhejiang Province
Failure due to unbalanced cable tension
by courtesy of Prof. Qiang Xie
Research Background
◆Damage due to extreme wind load Xuyu, JiangSu Province, 2005
by courtesy of Prof. Qiang Xie
Research Background
Outline ◆Test Program
◆Discussion on some issues
◆Reflection on test results
◆Conclusions and future works
Diaphragm
Diaphragm
Diaphragm
2:3 1:2
1. Test Program ◆ Test prototypes
Pw
C Gi Mw Gi T G1 G2
L L L Pw Pw
general load wind load ice load
◆ Loading types
reaction frame
distribution beam oil jack
rigid foundation anchor bolt
rigid stand
grooves testing pedestal
rigid box beam
◆ Laboratory loading setup
wind-resistance
3.45
m
Tongji University, Shanghai
Six specimens
Two pairs of Double-panel specimens
One pair of Single-panel specimens
One pair
Another pair
ice-resistance
wind-resistance ◆ Test specimens
◆ The principal failure mode --- Out-of-plane deformation….
by courtesy of Prof. Qiang Xie
How long is the buckling length?!
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?
3. Reflection on test results
◆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
◆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…
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…
0 20 40 60 80 100 120 140-2
0
2
4
6
8
10
12
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
Ⅲ . Considering the INTERACTION between the main leg and the diagonal bracing…
0 200 400 600 800 10000
400
800
1200
1600
2000
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
0 5 10 15 20 25 30 350
4
8
12
16
20
24
28
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
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
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
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
Thank you for your attention! Looking forward to working with all of you…
Any question? Or comments?