Abstracts Category : Other

Detection and localization of damage of civil structuresbased on ambient vibraton measurements

by Ahmed A Alalikhan

Civil Engineering - Vibration of steel structures /Graevinarstvo - Vibracije elinih konstrukcija Generally, damage detection of different types ofsteel structures is the main aspect that has been studied in thepresent work. Damage could be detected by different ways whichdepend on different procedures existed in literature. In thepresent work, the adopted concept of damage detection depends onthe procedure of comparison between the updated modal parameters(natural frequencies and mode shapes) of the FE model with theircorresponding experimental values. Hence, estimating of structuralmodal parameters experimentally and numerically are another aspectsthat are adopted in the present work. Based on ambient vibrationmeasurements (AVM) that implemented upon different types of steelstructures, experimental modal parameters are extracted usingARTeMIS software according to the frequency domain decomposition(FDD) technique. On the other hand, modal analysis by ANSYSsoftware is implemented to compute the numerical values of modalparameters which required during the procedure of damage detection.The process of damage detection is executed with the aid ofproposed Tabu Search (TS) optimization procedure to detect thelocation and severity of damage. This technique is relatively newand was not used before in the field of civil structure damagedetection which satisfies the state of the art in the present work.The proposed procedures of TS optimization are written andperformed in MATLAB environment. MATLAB has the ability ofsimultaneously handling the experimentally extracted modalparameters with their corresponding numerical values which arecontinuously updated by ANSYS software. The comparison between theestimated experimental and numerical modal parameters is executedaccording to values obtained by a certain proposed form called"objective function" which produces the value of error that used inthe comparison. Minimum value of error reflects the optimum valuethat indicates the closest result to the target (actual) value. Forthe sake of damage detection, another important aspect had beenadopted in the present work which is the calibration process byupdating of FE model. Due to several reasons, mismatch betweenmodal parameters of the experimental and numerical model is usuallyexist leading to erroneous results in the procedure of damagedetection. Hence, calibration process is aimed to produce numerical(updated) values of structural modal parameters as close aspossible to their corresponding experimental values. In this way,the convergence between the compared modal parameters is achievedwhich allows the procedure of damage detection to be implementedwith more accurate results...Advisors/Committee Members: Mikovi, Zoran, 1963-.