Global Structural Stiffness and Random Vibration Response of One-Story Frame and Its Damage Effect

Abstract

Structural stiffness has been increasingly considered as a performance index or parameter indicating condition of structures in the fields of aerospace, civil, and mechanical engineering. In this paper, theoretical and experimental structural stiffness models are proposed, and random vibration responses of the structure are evaluated. As a demonstration, the proposed method is applied to a one-story frame structure generally used in many engineering applications, and the experimental results show that the structural stiffness increases as the thickness of girder augments. Due to the idealization and perfect column-girder joint conditions, the theoretically predicted structural stiffness value is always larger than that measured from the experiment. Since the experimental method includes all practical factors, the experimental values of structural stiffness represent real global stiffness of the structure. An empirical equation of structural stiffness for the one-story frame structure is thus obtained by fitting the experimental data. The experimental random vibration experiment is conducted and it demonstrates that the random vibration responses under the same excitation all decrease when the girder becomes thicker. The influence of crack damage in columns of the one-story frame on structural global stiffness and random vibration response is also experimentally investigated, and it shows that the structural stiffness reduces slightly when damage is present. For the example given where the damage locates at the midheight of columns and coincides with location of the inflection point, the local damage in the structure only imparts a little change on the structural global stiffness, and the random vibration responses of the intact and damage structures also exhibit little difference. The experimental structural stiffness model presented can be used to data-reduce the global structural stiffness from the random vibration experiment, and it can be in turn considered as a performance index to assess condition of or detect damage in the structures.