Wind tunnel testing - Research - Structural Dynamics - Department of Structural Engineering
Wind tunnel testing
Wind tunnel testing
wind tunnel tekst
One of the essential requirements of modern bridge design is to avoid excessive levels of wind-induced vibrations. Vibrations may occur due to vortex shedding at low mean wind velocities, due to the turbulence in the wind field during strong winds and due to the motion of the structure. Wind tunnel testing is of crucial importance since it is hard to obtain the coefficients in the aerodynamic load models for bridge decks with sufficient accuracy using computational methods.
The fluid mechanics laboratory has four wind tunnels. The largest wind tunnel is frequently used for wind tunnel testing of bridge decks. It has a 2 x 3 square meter test section with a 100 km/h max speed.
NTNU has developed a new system for forced vibration test of section models. The apparatus is capable of reproducing any bridge motion since the horizontal and servomotors and ball screws drive the vertical motion while a servomotor with planetary gear with 50:1 gear ratio drives the torsional motion. The apparatus is used to develop new load models for bridges and to study the accuracy of existing models. Both measured motion from the Hardanger Bridge monitoring project and simulated motion for very long span bridges are considered in the experiments.
The cross sections of the bridges milled in gurit glues to a very thin-walled aluminum pipe to make the section model very light and stiff. The surface of the models are refaced using either plaster and coating or a plastic film to get the right surface roughness.
Through a collaboration with the Structural Mechanics Group at UCSD, the Structural Dynamics group at NTNU also exploit the combination of wind-tunnel experimental testing and state of the art FSI methods to develop efficient tools for numerical simulation of wind forces and get a better understanding of these.
There are currently three PhD candidates working with wind tunnel testing: