Laser measurement for slight deformation of a large-scale structure

Abstract

This article is to introduce the outline of our newly developed method of laser measurement for slight deformation of large-scale building or structure, which we call the automatic inspection for the six-degree-of-freedom movement-deformation of distributed interconnected measure-points. The basic principle is described as below: A certain number of measure-points are settle on the building that is waiting for inspection. In all measure-points, we select one as a datum point. For every two connected measure- points, we measure their relative displacement of six-degree-of- freedom, then, we calculate out the relative displacement of six- degree-of-freedom for every measure-point to datum point. By this way, we can know the deformation of the building. The measuring method of relative displacement for every two connected measure-points is presented as below: An indium steel pipe, which acts as a length rod and a displacement sensor, are used to inspect the distance of the two measure-point. A collimating laser beam and a two-dimensional PSD are used to inspect the other two dimensional linear displacement. A collimating laser beam, a reflector and a one-dimensional PSD are used to inspect the relative rotation in horizontal plane. A high precision photoelectric tiltmeter which is especially developed for this purpose is used to inspect the other two dimensional angular displacement. All those measurement are controlled by a central computer, and full automatic.