The Pseudo Local Flexibility Method for Hyper-static Beams: An Experimental Study

The local flexibility method (LFM), which can determine local stiffness variations of beam structures using measured modal parameters, is a promising approach for damage detection of structures using vibration signals. The LFM method is founded on virtual forces that cause nonzero stresses within a local part of the structure. In this study, non-local virtual forces which cause concentrated stresses in a local part and nonzero stresses in the other parts of a structure are employed. The theoretical basis of the proposed pseudo local flexibility method (PLFM) which uses the non-local virtual forces is derived. The effects of the number of modes on damage detection results of three damage scenarios of a numerical hyperstatic beam are studied. The results show that much fewer modes are required for the PLFM to estimate the damage locations and extents. Therefore, the feasibility of the PLFM is higher due to limited number of high quality modes can be identified in real world application, especially for ambient vibration measurement.