One of the essential requirements of modern bridge design is to verify that the structure is safely resist wind loads, and do you suffer from excessive wind-induced vibration responses. Wind tunnel testing remains a tool 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 Structural Mechanics group frequenently uses the wind tunnel facilities (fluid mechanics laboratory) for aerodynamic testing of bridge decks. The wind tunnel has a 2m*3m test section with a 100 km/h max wind speed.

NTNU has developed a new system for forced vibration test of section models. The apparatus is capable of reproducing simulataneous horizontal, verical, and pitching motion of the bridge deck whilst measuring the aerodynamic forces. The apparatus is used in critical tests to develop new load models for bridges as well as investigating the accuracy of existing models. 

Forced vibration testing of a bridge girder section model. Video by NTNU/Ole Øiseth.

NTNU has also developed an active turbulence grid capable of generating stochastic freestream turbulence. This enables the study the aerodynamic forces exported on bridge decks in realistic conditions that are similar to those felt by suspension bridges in the field.

Through a collaboration with the Structural Mechanics Group at UCSD, the Structural Mechanics 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.

Numerically computed streamlines of the Hardanger bridge. Model and illustration by NTNU/Tore Andreas Helgedagsrud.