Structural health monitoring of layered structure by strain measurements

Abstract

Structural health monitoring (SHM) of building structures is a very important technology in the effort to realize a sustainable society. Various studies on SHM have been carried out, and it is effective because it avoids accidents and predicts behaviour of structures. In this study, we proposed a method of SHM for a layered structure, in which the abnormal layer of the structure was identified by strain measurement. The main point of the study is that rotational degrees of freedom are constrained at both ends of the wall, so that the wall of each layer vibrates individually. First, in the normal condition, a location where the strain is almost zero on the outer wall of each layer is specified, and the strain at that point is constantly measured. Then, when an abnormality occurs in a certain layer, a significant value of strain appears in the abnormal layer where the strain is originally zero. We verify the proposed method by numerical simulation. We consider a three-layered structure, modelled as a cantilever beam. Abnormality is assumed to be the decrement of stiffness at a certain element, and it was shown that the effect of abnormality appeared throughout the structure in the natural vibration mode while it appeared locally in the strain measurement. The random response was then calculated by numerical integration, and the layer where the abnormality occurred could be identified by using the proposed method. Finally, we checked the applicability of the proposed method by experiment. As a result, it was shown that the method was possible to identify the layer where an abnormality occurred as well as numerical simulation.

Keywords

• shm
• strain measurement
• layered structure
• natural vibration mode
• random response