resilient bridge columns with copper-based shape memory...
TRANSCRIPT
Resilient Bridge Columns with Copper-Based Shape Memory Alloy Reinforcement
M. ‘Saiid’ Saiidi, PhD, P.E., Professor, Director, CATBI
Sebastian Varela, PhD student
CEE Dept. - University of Nevada, Reno
Overall Objective: Develop resilient bridge columns to allow bridge functionality after strong earthquakes
4 span bridge tested in 2008 • 110 ft. (33 m) long, 7.5 ft. (2.30 m) wide
• 266,000 lbs (120 Ton) total weight
Figures: Cruz-Noguez & Saiidi (2011)
Advanced materials: ECC Engineered Cementitious Composite: superior tensile ductility; reduces damage
Steel-RC SMA-RC SMA-ECC
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0 0.01 0.02 0.03
Str
ess
(ksi
)
Strain
DfD ECC 56d tests - Target: 6 ksi
Sp. 1Sp. 2Sp. 3Sp. 4Sp. 5Sp. 6
Advanced materials: SMA NiTi (Nickel-Titanium) Superelastic Shape Memory Alloy (SMA).
0 1 2 3 4 5 6 70
20
40
60
80
Str
ess
(ksi
)
Strain (%)
NiTi sample test to fracture
Advanced materials: SMA CuAlMn (Copper-Aluminum-Manganese) SMA: cheaper and easier to machine than NiTi
0 5 10 150
10
20
30
40
50
60S
tres
s (k
si)
Strain (%)
CuAlMn sample test to fracture
NiTi vs. CuAlMn SMA
•Both exhibit good superelastic properties.
•NiTi is more expensive.
•CuAlMn has lower yield strength and elastic modulus.
•No studies on seismic performance of CuAlMn-reinforced members.
Cu-CIP column model • ¼ Scale.
• Detailed according to AASHTO 2011 LRFD seismic.
• ECC and SMA only in the plastic hinge.
• Footing, column body and head were RC.
Other details • 7.7 ksi (54 MPa) ECC on test day.
• Footing concrete = 5.5 ksi (38.5 MPa)
• Column and head conc. = 6.5 ksi (45.5 MPa)
• Round CuAlMn SMA rods provided by Furukawa Techno Material, Co. Ltd. (Japan) and machined in the U.S.
Varela, S., and M. Saiidi (2015), "Dynamic performance of novel
bridge columns with superelastic CuAlMn shape memory alloy and
ECC." International Journal of Bridge Engineering, Vol.2 No. 3.
Test setup and procedure
Shake table
Rigid link
Spreader beam
Mass-rig
Motion
Hydraulic rams
N S W
E
Input ground motions
0 5 10 15-1
0
1
Accele
rati
on
(g) RRS 228 (Rinaldi Receiving Sta.)
0 5 10 15-40-20
0204060
Velo
cit
y(f
t/s)
Unscaled time (s)
0 0.5 1 1.5 20
0.5
1
1.5
2
2.5
3
Period, T (s)
Sp
ectr
al
accele
rati
on
, S a (
g)
Target versus achieved spectra
Target
AchievedRun 7
Run 6
Run 5
Run 4
Run 3
Run 2
Run 1
Run 7: 1.57x Rinaldi =290% x DE
Observed damage after Run 7
Run 7 - N Run 7 - S
Figure 16. Broken SMA bars on the north side after cover removal.
A
B
A
B
Hysteretic behavior and parameters
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Lateral displacement (in.)
Lat
eral
fo
rce
(kip
s)
Run 1
Run 2
Run 3
Run 4
Run 5
Run 6
Run 7
Envelope
Bilin-idealized
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12
-40
-30
-20
-10
0
10
20
30
40
50
Drift (%)
Lat
eral
fo
rce
(kN
)
Run
#
Max.
Drift +
Max.
Drift -
Res.
Drift
+ II+
1 0.48% -0.49% 0.01% 0.5 <0
2 1.06% -1.33% 0.03% 1.0 <0
3 2.39% -2.66% 0.02% 2.2 0.16
4 4.03% -3.07% 0.04% 3.7 0.36
5 5.80% -2.82% 0.08% 5.4 0.58
6 9.53% -2.23% 0.22% 8.9 >1
7 11.80% -2.71% 0.39% 11.0 >1
Analytical studies: OpenSees
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Lat
eral
fo
rce
(kip
s)
Run 1
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 2
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 3
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 4
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 5
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 6
-4 -2 0 2 4 6 8
-10
-5
0
5
10
Run 7
Lateral displacement (in.)
Analytical
Experimental
Conclusions Minimal damage and minor loss of capacity.
Nonlinear behavior took place in the plastic hinge region, no yielding or damage elsewhere.
Simple 2-D fiber model was able to match key test results with reasonable accuracy. Refinement of modeling method is warranted.
Using superelastic CuAlMn and ECC in the plastic hinge regions of bridge columns could allow bridges to stay functional after strong earthquakes.
Design guidelines under development.
