Determination of bending and lateral-torsional buckling displacements in castellated and circular opening steel beams by image processing

The points in high-web steel beams deviate irregularly due to lateral-torsional buckling, so it’s a challenging task to accurately measure displacements perpendicular to the loading and precise measurements cannot be made with fixed gauging devices. This study aimed to determine all displacements in high-web beams including those caused by buckling using an image processing technique. One castellated and one circular opening steel beam were produced and exposed to four-point bending tests. The vertical displacements were measured by LVDTs and transducers, and buckling displacements in the web and flanges at points spaced at certain intervals were measured by a total station device. Aside from that, both vertical and lateral deformations all over the beam were determined by a novel image processing technique using video recordings taken by two cameras (front and side). By the image processing technique, vertical displacements were detected with an accuracy of 98%, and deformations and displacements arising from lateral-torsional buckling on the web were detected with an accuracy of 99%. In conclusion, it is shown that the image processing technique can be easily and efficiently used for precise detection of both in-plane and out-of-plane deformations of castellated steel beams caused by bending moment and lateral torsional buckling.