G. Ghodrati Amir, A. Zare Hosseinzadeh,
Volume 34, Issue 1 (7-2015)
Abstract
In this paper, a new vibration-based damage detection method for damage localization in shear frames is presented. For this purpose, a new damage index is proposed by means of static displacements estimated using only the first several mode data and Grey Relation Theory. The efficiency of the presented method has been demonstrated through studying several damage scenarios on three examples of shear frames with a different number of stories. The effects of various situations such as the existence random noises in the recorded data, number of available modes, different damage scenarios and irregularity in the structural characteristics have been studied on the applicability of the presented method. The obtained results show the robustness and good performance of the presented method in the damage diagnosis of shear frames. Some of the most important advantages of the suggested method can be summarized as its ability in damage localization by means of only the first mode data, low sensitivity to the random noises, and high speed and accuracy in estimating damage locations.
F. Hosseinlou,
Volume 40, Issue 2 (1-2022)
Abstract
Today many complex models, typically finite element models, have been employed in the analysis of jacket offshore structures. However, these comprehensive models are not readily adopted in engineering practice, especially during the preliminary design stage. As the dynamic analysis of jacket platforms is very complicated, it will be very advantageous to make a simplified computational method to assess dynamic performance of such structures. In this work a refined simplified model has been utilized to calculate dynamic responses of jacket platforms. In this regard, the model simplification based on the vibration modal data and Timoshenko’s beam equation has been employed to overcome the uncertainty problem in modeling. According to the curve fitting method on the set of frequency response functions to derive modal parameters, the concept of power spectrum density has been also used to confirm the proposed computational model.In this regard, first the behavior of the physical model in the frequency domainhas been presented and compared with the spectral results obtained from the simplified model based on Timoshenko beam. Because the modal test of the physical model was performed under the force of white noise, the dynamic responses of the simplified model were also extracted under the force of white noise using MATLAB software. In this paper, an applied mathematical model has been produced, and it has been demonstrated that the refined simplified model can reflect the real structural features.
