What is the effect of wind loading on the suspension bridges?

Wind loading is a critical factor in the engineering design of slender structures such as long-span suspension bridges. This project investigates how wind affects cables and bridge decks, with a particular focus on special phenomena that are currently not well understood.

The Hålogaland Bridge in northern Norway is used as a case study in this project, where a comprehensive monitoring system is installed:

• 34 accelerometers
• 10 anemometers to measure wind speed 
• 22 temperature sensors 
• 36 strain gauges to monitor stress

Non-stationary wind loads

Non-stationary wind events, such as thunderstorm downbursts, can cause a sudden rise in wind speed, leading to unusually large dynamic responses. Traditional design codes do not take into account such special load scenarios. There is therefore a need to quantify their impact and frequency of occurrence on long-span bridges.

• Statistical methods are used to detect non-stationary wind events. 
• Dynamic response measurements show how the bridge behaves under these conditions.
• Meteorological data on rain and lightning gives insight into the atmospheric conditions.
• Wind tunnel tests provide aerodynamic properties of the bridges.

Next, these detections can be compared to numerical models and wind tunnel tests and help refine the models for future design codes.

Wind-induced cable vibrations

Cables can vibrate due to vortex shedding, causing repeated stress and potentially shortening its lifespan. Stockbridge dampers are installed to mitigate these vibrations, but because the technology is relatively new, failures have been reported. This research examines how wind-induced vibrations arise in hanger cables and explores effective mitigation strategies.

• Monitoring data yields information how both the hangers and the dampers vibrate in real-life conditions.
• Laboratory tests of Stockbridge dampers help us understand their energy dissipation capabilities.
• Simulations are used to tune numerical models and explore alternative damping configurations.

What Makes This Study Unique? 

Long-term field data from an actual, full-scale bridge allows for validation of numerical models, an opportunity that is rarely available. By enhancing our understanding of non-stationary wind loads and vortex-induced cable vibrations, this project aims to provide practical guidelines for bridge managers and help refine current design methodologies. Reducing uncertainties in wind modeling ultimately leads to more reliable structures capable of safely withstanding complex wind conditions.