With the increasing span length and cable lenghts of cable stayed bridges efficient dampers are more and more required for stabilizing the stay cables and bridge girder. In co-operation with our customers we at Dellner Dampers develop efficient hydraulic dampers to solve this problem.
On long-span cable stayed bridges you can have the appearance of vibration problems. Those vibrations are induced by traffic load, e g braking of heavy vehicles and/or aerodynamic effects on the stay cables cause by wind, rain, snow and ice – often in combination.
In order to reduce those vibrations on of the most effective ways
is to equip the cables with Dellner Dampers hydraulic (a k a viscous)
dampers. All of our dampers are tuned individual for each bridge
and each cable. It is important that the dampers have the correct
tuning so that the response force is optimal.
The position of the dampers are in the vicinity of bridge deck and cable anchors. Dellner Dampers bridge dampers can be fitted both internally and externally.
Dellner Dampers Bridge Dampers are available in three different base designs depending on the bridge and cable lengths. They are delivered with a customised damping characteristic for each cable.
Type 45 – Fmax 20 kN
Type 62 – Fmax 30 kN
Type 62 Heavy Duty - Fmax 50 kN
Type 80 – Fmax 70 kN
The damper is a twin tube hydraulic telescopic damper. The required damping force is generated by viscous losses when oil being forced through a calibrated flow restriction. The inner cylinder contains only oil while the reservoir between the housing and the cylinder contains oil and air. Both ends of the damper are equipped with a spherical bearing or a pin bearing.
We have performed fatigue, salt spray and temperature tests of our dampers. The fatigue test was performed in a servo hydraulic testing machine, MTS 100 kN, 1.1 with a control unit, Instron 8500+. At start and after approximately 100 000, 500 000, 1 million and 2 million cycles the damper characteristics were recorded in load vs. displacement diagrams.
When the testing had reached 2 million cycles no significant change in maximum or minimum load could be registered. Besides that almost no visible change, that occurred during testing, was noticed. It’s noticeable that the equilibrium temperature did not change much during the testing procedure.
The overall test results were very good. We have also performed an accelerated corrosion test on our dampers. The test was perfomed as a 500 hrs salt spray test with good results.
The operational function of the dampers have also been tested at different temperatures from
-40°C to + 60°C. The performance was according to specification at all temperatures.