Vibration Mitigation Engineering
Makatoke Viaduct Vibration Monitoring, National Park, NZ
The Makatote Viaduct was brought into service in 1908 on the North Island Main trunkline, 4.6 km south of Erua. It is a riveted steel structure with five towers supporting Pratt trusses. The viaduct is 262 metres long and 79 metres high.
It was recently observed that during the passage of trains there is excessive lateral movement of the lower chords of some trusses near the tower supports. The magnitude of the displacement appeared to be dependent upon the speed of the train and as a precautionary measure, train speeds have been restricted to 40 kph until the cause of the phenomenon was determined. This situation could only be temporary as it reduced the efficiency of the rail network.
Compusoft Engineering Ltd. (CEL) implemented a monitoring procedure to clearly investigate the extent of the bridge behaviour. It was acknowledged that such an approach without some direction could easily become an extensive and expensive task. Consequently as a first step it was decided that a prudent approach was to develop an analytical model using the structural engineering program SAP2000 of the viaduct and try to replicate the observed behaviour which would assist in the determining the optimal placing of recording equipment.
Oak Residences Liquid Tuned Damping System, Auckland, NZ
Compusoft Engineering Ltd. (CEL) was employed to design a Liquid Tuned Damping System to mitigate wind induced vibrations for the high rise building Oak Residences.
The design included interpretation of wind tunnel tests, initial design of dampers, the testing of prototype dampers, supervision of installation and tuning. The installation of the liquid damping system introduced an additional 2% damping to the structure limiting floor accelerations to an acceptable for wind storms.
Link to: Liquid tuned dampers for the mitigation of wind induced vibration publication
Auckland Sky Tower Dynamic Property Assessment, Auckland, NZ
Compusoft Engineering Ltd. (CEL) were engaged to identify the dynamic properties of the mast at the top of the Auckland Sky Tower.
The project involved the recording of wind induced vibrations at eight stations up the mast and accurately assessing the mode shapes, frequencies and damping of the mast. This was achieved prior to installation of the liquid tuned damping system so that liquid tuned dampers called be accurately filled prior to installation. These measurements were repeated after the installation of the dampers so that effectiveness of the dampers could be assessed.