Sensitivity of Modal Parameters to Detect Damage through Theoretical and Experimental Correlation

Abstract

Early detection and localization damage allow increased expectation of reliability; safety and reduction of the maintenance cost. Modal tests including intact and simulated damage state was proposed to investigate steel beam health monitoring. It consists mainly of piezoelectric accelerometers, impact hammer, pulse analyzer with (modal analysis consultant software) and laptop for three cases. The first case is free-free vibration. The second case is boundary condition. The third case is boundary condition with static load. Artificial crack was cut in lower beam flange at mid span. Sensitivity of modal parameters to change of steel member condition was studied for natural frequency, mode shape and damping factor. Finite Element Analysis (FEA) using (ANSYS11) was conducted to study natural frequencies, mode shape and stresses. The steel beam is modeled by three dimensional structural solid element (solid 45). Finite Element results from (ANSYS11) are used to make comparisons between numerical solutions and experimental results in terms of natural frequencies and mode shapes. Improved FE to compute damping matrices is proposed and discussed. Results show that, modal frequencies, mode shapes and damping factor may be used to identify structural damage with saving time. Sensitivity of damping ratios is more sensitive than that of natural frequency.