Damage detection of two layer Space Dome Structures

Safari, Hadi (2018) Damage detection of two layer Space Dome Structures. Doctoral thesis, University of Mohaghegh Ardabili.

Preview

Text (شناسایی آسیب در سازه‌های فضاکار گنبدی دولایه) Hadi Safari.pdf Download (455kB) | Preview

Abstract

Damage is considered as a change in structure which affects its performance in the present and future. The nature of damage relates to the deference between two states of a system. In this view the first state relates to the intact structure and the next one is for damaged structure. Therefore, damage can be detected according to the comparison between the structure response of damaged and intact structure for preventing from early collapse of structure. Preserving the performance of space structures as of the most applicable covers of roofs in public places is an important issue. Because of large number of elements and joints and variety of geometrical choices in space structures comparing to other structures, introducing a fast and accurate damage localization and quantification method is essential. In the first stage, according to the decomposition of first mode shape of space structure, a two dimensional damage detection method is introduced. Frist mod shape of space structure is computed by applying experimental modal analysis. The image of vertical parameter of first mode shape that is called isosurface is generated and two dimensional continuous wavelet transform analysis is applied to define the sudden fractures in damaged regions of isosurface that is impossible to identify in the mode shape of structure. Large number of values appears when the mother wavelet passes through the boundaries of signal which is called boundary distortion. Also, disarrays of first mode shape computation and wavelet transform results of isosurface need to be erected to make the localization of damage possible. To this end, a two steps method is applied to overcome these issues. In the second stage, a damage quantification method is introduced base on finite element model updating to define the extent of damage in the structure elements and nodes. Objective function is based on comparison of measured modal and analytical modal results of damaged and intact structure respectively that should be minimized. Charged system search algorithm is applied as a fast and strong heuristic optimization method in the finite element model updating procedure. Three different double layer space structures are introduced to evaluate the applicability of proposed damage detection method. The speed and ability of proposed method on locating the damages and converging to the correct values of damage is assessed by applying purposeful damages in one or more regions of structure. The results of ten different scenarios reveals the applicability of the introduced hybrid damage detection method.

Actions (login required)

View Item