18 Preliminary design of seismically isolated RC highway overpasses

shear stress Mpa
ver. stress Mpa
ver. stress Mpa
shear stress Mpa
George C. Manos, Stergios A. Mitoulis and Anastasios G. Sextos
0
-1
-1.5
-2
-2.5
-3
Vertical Load - Dual Bearing 150mm x 150mm
height of each bearing 95mm - Rubber height 70mm Specimen
heated for 20 days at 80 deg. C
-0.5 0 0.05 0.1 0.15 0.2
Test 3 H-cyclic
Test 4 H-cyclic
Test 5 H-cyclic
Test 6 H-cyclic
ver. strain
Vertical Preloading of
specimen prior to
shearing 2.0Mpa
Cyclic Hor. Load - dual bearing 150mm x 150mm
height of each bearing 95mm - Rubber height 70mm
Specimen heated for 20 days at 80 deg. C
0.5
Test 3 H-cyclic average
0.25
0
-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5
Vertical Preloading
of specimen prior
to shearing 2.0Mpa
-0.25
-0.5
shear strain
Test 4 H-cyclic average
0.1 - 1.0Hz
Figure 8c.
Figure 8d.
Figure 8. Results from compression as well as from combined pre-compression and shear for the elastomeric
specimen 150mm x 150mm before and after the artificial aging.
0
-0.5
-1
-1.5
-2
-2.5
Cyclic Hor. Load - Bearing 150mm x 150mm
height of each bearing 95mm - Rubber height 70mm
Vertical stiffness
Test 4 80 deg C
0 0.05 0.1 0.15 0.2
Test 5 80 deg C
Vertical Preloading
of specimen prior
to shearing 2.0Mpa
ver. strain
Test 3 80 deg C
Test 3 No heat
Test 4 No heat
Test 1 No heat
0.2 - 1.0Hz
Figure 9. Comparison of the vertical stress-strain response before and after artificial aging.
In figure 9 the comparison of the vertical stress-strain response for this elastomeric bearing
specimen before and after artificial aging is shown. As can be seen, this artificial aging process
resulted in a small decrease in the vertical stiffness for this elastomeric bearing. In figure
10 the effect of the artificial aging is depicted by comparing the cyclic shear stress-strain response
before and after the heat treatment. As can be seen in this figure, this artificial aging
process resulted in a very small increase in the shear stiffness for this bearing.
Cyclic Hor. Load - dual bearing 150mm x 150mm
height of each bearing 95mm - Rubber height 70mm
0.4
Test 1 H-cyclic no heat
Test 3 H-cyclic 80 deg C
0.2
Vertical
Preloading Vertical of
0
-0.4 specimen Preloading prior of to -0.2 0.0 0.2 0.4
shearing specimen 2.0Mpa prior to
-0.2
shearing 2.0Mpa
-0.4
0.2 - 1.0Hz
shear strain
Figure 10. Comparison of the shear stress-strain response before and after artificial aging.
12