To monitor static and dynamic responses of bridges, an image-based monitoring system using networking PTZ IP (Pan-Tilt-Zoom Internet Protocol) cameras has been developed. Triggers to acquire video or still-images are performed when structural events like vibrations or excessive displacements occur. Also, periodic or user-defined triggers can be performed. When a trigger occurs, the system collects bridge members' images along the pre-defined touring route of a group of presets and extracts relative displacements between images.

This study evaluates thermal movements of an existing bridge using digital image processing technologies. Digital images are acquired from smart phones. Thermal movements which extracted from bridge bearings' images are compared to the results of conventional displacement transducers. It is concluded that the image-based process for measuring thermal movements of bridges is accurate, practical and cost-effective.