In this study, the possibility to use Horasan mortar as a sliding interface material for pure friction aseismic isolation system is investigated. Both experimental and numerical studies are conducted to examine the effectiveness of using this material in structural isolation systems of buildings with no overturning moment, as it has shown some attractive experiences in time based on the existing related literature. Responses of four storey lightweight building are numerically investigated by finite element modelling in MATLAB; whereas the University Consortium on Instructional Shake Table (UCIST) is used to study the responses of the same building during experimental works. Comparison of both studies is shown to be in a good agreement in terms of resulting structural response accelerations, velocity and displacements. Approximately 28 - 31 % reduction of base floor acceleration is achieved; and the maximum sliding velocity and displacement are found to lie between 0.33-0.45 m/sec and 0.0353-0.0559 m respectively; which fall within the recommended standards’ limits. As a result, these findings demonstrate the effectiveness of using Horasan mortar as friction interface material which has additionally gained experience in more than ten centuries.
Operational Modal Analysis (OMA) is a one of the most popular method to extract the dynamic characteristics from ambient vibration response signals. In this study, the dynamic characteristics of a model of steel arch bridge with a bolt connection constructed in a 6.10 m span and 1.88 m height laboratory were determined by finite element method and operational modal analysis methods. Firstly, finite element model was created in SAP2000 software of model steel system and dynamic characteristic were obtained numerically. Then, accelerometers were placed where the displacements are high on points of the system and dynamic characteristics were determined by operational modal analysis method. The aim of this study is to obtain the dynamic parameters (frequency, damping ratio, mode shapes) of the model of the steel arch bridge accurately and reliably by operational modal analysis method by making use of ambient vibrations in the laboratory conditions. For this purpose, analytical analysis of the model of the steel arch bridge with finite element method and the dynamic parameters obtained as a result of the operational modal analysis of the model steel arch bridge were compared. Also, the modal assurance criterion (MAC) was used. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. At the end of this study, reasonable correlation is obtained between mode shapes, frequencies and damping ratios. Analytical and Operational modal frequencies differences between 0.139 %–7.170 %.
There are many varieties of the structural and architectural structures strengthened with different FRP composites are gaining popularity, and there is a growing need to understand and compare the behavior of these structures before-after GFRP composite strengthening. In this study, model steel structure was tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic response. After this, slabs of the model steel structure was strengthened with GFRP composite, and tested on the bench-scale earthquake simulator (The Quanser Shake Table) using ambient vibration, to determine the dynamic behavior. Finally, dynamic responses of model steel structure before and after GFRP composite strengthening, such as displacements and maximum-minimum acceleration, were compared. At the end of the study, it is seen that displacements had decreased along the height of the model steel structure. Also, it is seen from the earthquake analyses that GFRP strengthening is very effective on the dynamic responses of the model steel structure.
Usage of FRP composites for the retrofitting purpose of the structures against the harmful effect of dynamic loads are gaining popularity, it is used in a wide variety of disciplines including civil engineering. Thus, there is a great need to study the behavior of FRP composites for strengthening purposes of structures using empirical methods. In this study, a bench-scale steel structure model was strengthened with CFRP composite and tested using operational modal analysis. To conduct operational modal analysis a bench-scale earthquake simulator and ambient vibration emulator were used. Same steel structure model was tested without strengthening procedure. Obtained dynamic responses (maximum-minimum displacements and accelerations before and after application of CFRP) of steel structure model have compared to each other. This study shows that floor displacements of the model have been decreased along the height of the structure up to 41.43 %. Therefore, the results of the experiment confirm the effectiveness CFRP composites for the strengthening of steel structures.
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