Detection of damage on structural connections of steel frames based on vibration measurement

Abstract

In other to improve the accuracy of the evaluation of aging structures, the method of vibration-based nondestructive testing (NDT) is widely applied in damage detection. This paper proposes an experiment to introduce a brief procedure of the damage detection by utilizing the method of vibration measurement. We adopt a two-story steel frame as experimental model with joints defects to imitate the damage situations. According to physical properties, if a structural frame is suffering from dramatic loads from exterior and having extraordinary deformation, the bending moment detected from the connections are quite large. Unfortunately, the influence of joint defects will pile up if the defects have been ignored. To date, structural health monitoring still strongly depends on the method of visual detection. The accuracy of this technique is related to the knowledge and experience of the researchers. In this paper, a global method of structural damage detection for the two-story steel frame will be proposed. Also, two popular technologies will be applied in this paper, the method of modal identification and model updating. The methods introduced in this paper can provide more dependable results of the structural damage detection than visual inspection can. In this paper, the joints of the steel frame are supposed as semi-rigid, which are built up as linear elastic rotational spring in the computer. To start with, the method of modal identification is used to establish the structural model into the computer by the measured modal parameters. Furthermore, based on the model updating method, the intact joints have pretty strong rotational stiffness, compared with the damaged joints have reduction strength of stiffness. The change of the performance of the joints will be revealed during the vibration measurement. The reduction of rotational stiffness at the connections indicates that there is the joint defect. This paper introduces both the methodologies applied in the damage detection and carry out several typical experiments on a two-story steel frame to prove the feasible of the project.