Experimental investigation of bridges using targetless computer vision

A non-contact, targetless approach to determine the deflection of bridges using consumer grade video cameras is presented. A total of four bridges (two concrete bridges and two steel bridges) were selected for load testing, based on typical characteristics of load posted bridges in Texas. Each bridge was instrumented using strain gauges, string potentiometers, and accelerometers to measure the response of the bridge during various load tests. In addition to these conventional measuring devices, two cameras mounted on a tripod were used to record the bridge response during each load test. An image analysis algorithm was applied to determine the displacements from the unloaded bridge image and loaded bridge image. These tests demonstrated that computer vision has the potential to measure deflections during bridge load testing without the need for targets. This method provides an efficient alternative for field evaluation that eliminates the need to instrument the bridge, which can be a time-consuming process, especially when access is restricted.