Page 38 - DOUCE HYDRO 2013

38
Improvement
by using PSD
Case Comment F P3
(kN)
F other piers
(kN)
F total
(kN)
1 Only P3 17 400 0 17 400
2 STU 7 780 7 780 38 900
3 Dampers 7 500 1 500 13 500
4 PSD on P3 3 500 0 3 500
In service, the deck is submitted to forces such as frictions on sliding pot bearings (2.5% deck
weight). Therefore, for this example, the device’s preload for this bridge must be ≥ 2 500 kN.
This means that under any static horizontal force lower to 2 500 kN, the device acts as a fix
connection between the deck and the pier.
During an earthquake, when the seismic forces are exceeding the preload, the device will act as an elastic link
with a damping effect. In our example, we have installed a PSD in the central pier and we have let the 4 other
piers free.
A time history analysis has been achieved and gave
the following result:
Shear force on P3 = 3 500 kN for a max device compression of 35 mm
The PSD installed in P3 has to be able to fulfill
the following mechanical requirements:
(FP3 corresponds with the force applied on the central pier and F total is the amount of force applied on all the structure.)
Shear force in P3 was divided by approximately 2.2,
compared to the best of the other solutions.
In certain cases, the ratio can reach 5.
B R I D G E S