untitledEffect of Bilateral Excitation on the Effect of Bilateral Excitation on the Seismic Performance of Reinforced Seismic Performance of Reinforced Concrete Bridge ColumnsConcrete Bridge Columns
US - Japan Young Researchers Symposium June 11, 2005, University of Tokyo
Department of Civil Engineering Tokyo Institute of Technology
Hidenori OGIMOTO Kazuhiko KAWASHIMA Gakuho WATANABE Seiji NAGATA
Extensive damage of columns in the 1995 Kobe earthquake
BackgroundsBackgrounds
Bridge columns are designed independently in longitudinal and transverse directions.
Seismic performance of bridge columns has been decided based on an unilateral cyclic loading test.
In Current Japanese Seismic Design
Columns are subjected to bilateral seismic excitation. Under a real earthquake …
Model ColumnsModel Columns
Lateral Force
Loading Orbits in the Cyclic Loading TestLoading Orbits in the Cyclic Loading Test
Unilateral Diagonal
3.5% Drift
La te
La te
Hysteresis under the Circular Orbit LoadingHysteresis under the Circular Orbit Loading X-direction Y-direction
Circular
X
Y
Method for reproducing behavior of bridge column under the earthquake experimentally
Hybrid Loading TestHybrid Loading Test
NS NS
JMA Kobe Record 1995 Kobe Earthquake
In the experiments, the acceleration amplitude was reduced to 30%-50% of the original.
Sylmar Parking Lot Record 1994 Northridge Earthquake USA
10 0
-1 0
A cc
el er
at io
n (m
/s 2 )
Bilateral Excitation, Kobe 40%
Effect of Bilateral Excitation
Local Buckling Cracks
Kobe 40%
80 0
-4 0
0 30
0 -4
Kobe 40% Sylmar 50%
Lateral Force
Plastic Hinge
Reinforce bar
La te
La te
Experiment Analysis
X-direction Y-directionX
Experiment
Analysis
-40 40-80 0-1 50
Conclusions
The flexural strength and ductility capacity of the column under the bilateral loading is smaller than those under the unilateral loading The above results in larger response displacement of the columns under the bilateral excitation than the unilateral excitation in the hybrid loading test. Fiber element analysis correlates the general trends of the column responses. However, correlation on the residual drift is poor.
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Effect of Bilateral Excitation on the Capacity of RC Bridge
More important in bridges than buildings because More important in bridges than buildings because of the lesser degree of static indeterminateof the lesser degree of static indeterminate Possibly overestimating the strength and ductility Possibly overestimating the strength and ductility capacities of bridge columnscapacities of bridge columns Always encounter this effect in skewed and Always encounter this effect in skewed and curved bridgescurved bridges More realistic evaluation is required to meet the More realistic evaluation is required to meet the performance goals in the performanceperformance goals in the performance--base base seismic designseismic design
Computed Hysteresis under the Unilateral Loading
-150
0
150
-4 -2 0 2 4 La
te ra
-50 -25 0 25 50
-2 0 2
-2 0 2
-15 0 15
-1 0 1
-50 -25 0 25 50
-2 0 2
-2 0 2
-15 0 15
-1 0 1
-40 40-80 0-1 50
Vertical Actuator
Actuator 1
Actuator 2
Actuator 1
x x
y
The error in measuring strength of stability of bridge pier experimentally
Actuator 1
Actuator 2
x x
Pvsinθvv P2sinθ22
The error in measuring strength of stability of bridge pier experimentally
PP−− effect effect by horizontal Actuatorby horizontal Actuator
PP--delta Effect by Actuatorsdelta Effect by Actuators