REAL TIME DISPLACEMENT MEASUREMENT OF A FLEXIBLE

BRIDGE USING DIGITAL IMAGE PROCESSING TECHNIQUES

Jong-Jae Lee¹ and Masanobu Shinozuka²

ABSTRACT

It is very difficult to measure the displacement of bridges. Since most bridges overpass the

sea or the river, installation of the conventional devices for displacement measurement is almost

impossible, or extremely costly, if not impossible. In this study, real-time displacement

measurement of a flexible bridge was made by using digital image processing techniques. This is

innovative, highly cost-effective and easy to implement, still maintaining the advantages of

dynamic measurements and resolutions. At first, the measurement point is marked with an

indication panel of known geometry. A commercial digital video camera is installed on a fixed

point beyond the bridge (e.g. on the coast) or on a pier (abutment), which can be regarded as a

fixed point. Then, the video camera takes a motion picture of the target marked at the

measurement point. Finally, the displacement of the target is calculated using the image

processing technique, which requires the texture recognition algorithms, projection of the

captured image, and calculation of the actual displacement using target geometry and number of

pixels moved. Feasibility tests on real-time displacement measurement by digital video camera

were carried out on a pedestrian bridge located at University of California, Irvine.

1 Post Doctoral Researcher, Department of Civil and Environmental Engineering, University of California,

Irvine, Irvine, CA 92697-2175, USA, Email: jongjael@uci.edu

2 Professor, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine,

CA 92697-2175, USA