Search

The procedure for detecting the location and severity of damage of complex structural systems using their modal properties is an important tool of Structural Health Monitoring (SHM) of civil infrastructure. The herein presented research proposes procedures for damage detection based on two heuristic optimization methods: Simulated Annealing (SA) and Tabu Search (TS). In order to test the proposed procedures in different frequency ranges, experimental and numerical analyses were conducted on a steel grid bridge model in two configurations, according to the total mass of the structure, as well as for two simulated damage cases. The calibration of model parameters, according to experimentally extracted modal properties, is carried out using the proposed procedures. Numerical computations were conducted using ANSYS package and developed routines under MATLAB environment for model calibration and damage detection procedures. Experimental modal properties were extracted from ambient vibration measurements, as state-of- the art in SHM of complex structures, by the Frequency Domain Decomposition (FDD) technique, using ARTeMIS software. Both of the proposed procedures for model calibration and damage detection, with adopted objective functions including frequency and mode shape differences, exhibit accuracy, efficiency and robustness.

The historical masonry brick buildings are important structural symbols due to their old construction time. It is necessary to investigate the mechanical properties of the masonry brick building to evaluate the structural behaviour during service life. Here, the research focused on finding out the compressive strength of brick unit, mortar and brick prism model. Two types of mortar and brick unit are adopted, historical and traditional, and the comparison between the results is implemented. The historical brick and mortar used experimentally in this study were taken from the Imam Ali holy shrine structure (built 300 year before) during its rehabilitation. The traditional brick is Iranian yellow brick which is used in repairing process of two minarets now. The traditional mortar is the Iraqi gypsum which is available in the local market. The tests of mortar cubes and brick units are conducted according to Iraqi Standards and the British Standards is adopted for brick prism models. The experimental testing is carried out in the lab of faculty of engineering at university of kufa. The strain gauges and LVDT instruments are used with the acquisition system device to record and save data. The results of compressive strength and mass density for historical and traditional brick unit and mortar are exhibited. Also, the results of compressive strength, stress-strain curve, load-displacement curve and modulus of elasticity for historical and traditional brick prism models are displayed and discussed. In addition, the compressive strength of brick prism models using empirical equation are estimated. The comparison between the results of historical and traditional brick units, gypsum mortar types and brick prism models are carried out. The historical brick prism model has mechanical properties weaker than the traditional and there is a difference in the compressive strength of the historical brick prism model between the empirical equation and testing results.

This research represents the dynamic behavior of the steel tower structural model due to applying seismic load. The 3D finite element model is created using ANSYS-software to simulate the real structure used in experiment. The dynamic properties, natural frequencies and mode shapes, are extracted and compared with the experimental model values. The comparison is implemented to verify the FE analysis procedure of the tower model with experimental model results and they are accepted by 83% tuning ratio. The nonlinear seismic analysis is applied to the structural model using observed ground motion in 1999 Turkey Earthquake. The seismic load is applied in two cases; the first is in the x-direction of the structural tower model and the other in the y-direction of the model in a horizontal plane. The maximum response displacements in x and y-axis and load displacement hysteresis for both loading cases are exhibited. The results display that the tower structural model failed with large response displacement in the first few time of ground motion according to IBC-2018 and NBCC-2005. The collapse of the tower structural model occurred after time 18 sec and the applied seismic loading in x-axis has significant effect.

In this study the Vierendeel bridge structural model is adopted as a complex structure case study scaled from a real structure located near Cacak city in Serbia. Experimental analysis is conducted under simulation of ambient vibration using shaker device for exciting the model. Frequency Domain Decomposition (FDD) technique is applied using ARTeMIS software extractor to extract the modal properties, natural frequencies and mode shapes. As a comparative study, Enhanced Frequency Domain Decomposition (EFDD) is used to verify the extracted results from FDD. A finite element model is created in ANSYS software to simulate the adopted model to estimate modal properties numerically. Calibration process is implemented to converge the numerically estimated with the experimentally extracted modal properties. Two procedures written in MATLAB environment, for calibration and damage identification, are proposed using heuristics optimization, Simulated Annealing (SA) and Tabu Search (TS). Both of proposed calibration procedures exhibit high accuracy and efficiency due to good convergence between experimentally extracted and numerically updated values of natural frequencies extracted based on ambient vibration measurements.