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    Dynamic characteristics changes of masonry arches exposed to elevated temperature
    (Elsevier Ltd, 2024) Altunışık, Ahmet Can; Öztürk, Muhammed Mustafa; Genç, Ali Fuat; Günaydın, Murat; Kaya, Ali; Akbulut, Yunus Emrahan; Sunca, Fezayil
    In this study, the changes in the dynamic characteristics of masonry arches exposed to elevated temperatures were investigated experimentally and numerically. Firstly, the material properties were analyzed at different temperatures, ranging from 200°C to 800°C, through experimental tests. The constructed arch specimens were then subjected to heat to investigate the effects of elevated temperatures on their dynamic characteristics. Ambient vibration tests were performed before and after heating to identify natural frequencies and mode shapes. Furthermore, numerical models of the arches were developed, and a model updating procedure was implemented to minimize the differences between the numerical and experimental data. The findings indicated that elevated temperatures led to notable decreases in the compressive strengths of both the stone and the mortar. This decrease significantly degraded the stiffness of the masonry arch samples, consequently having a profound effect on their dynamic properties.
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    Estimating fundamental frequency of masonry arches under elevated temperature: Numerical analysis and validation using ambient vibration tests
    (Springer Nature, 2024) Altunışık, Ahmet Can; Öztürk, Muhammed Mustafa; Genç, Ali Fuat; Kaya, Ali; Akbulut, Yunus Emrahan; Sunca, Fezayil; Gunaydin, Murat
    In this study, the changing of dynamic characteristics of masonry arches at varying geometric parameters and temperature histories was investigated through a combination of experimental and numerical methods. First, the dynamic characteristics of laboratory-built arch models were determined both pre- and post-high-temperature test using ambient vibration testing. Then, the finite element (FE) models of the arches were developed for both, allowing for dynamic characteristics to be assessed numerically. To refine the accuracy of numerical models, FE analyses were adjusted based on experimental data. These updated FE models were used to investigate the dynamic characteristics of arches with different spans, heights, widths, and thicknesses under different temperature history scenarios. Finally, utilizing the data repository obtained, formulation and graphs/charts, providing valuable insights into the dynamic response of masonry arches under fire conditions, were developed and presented for practical application. The experimental study revealed that the natural frequencies of arches decreased by 55% with increasing temperature exposure.
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    Evaluating the high-temperature endurance of FRP-strengthened concrete using an innovative insulation system: Experimental investigation
    (Elsevier Ltd, 2023) Altunışık, Ahmet Can; Akbulut, Yunus Emrahan; Adanur, Süleyman; Kaya, Ali; Günaydın, Murat; Mostofi, Sara; Mosallam, Ayman
    Extensive research on fiber-reinforced polymer (FRP) composites has led to the presumption that this material is an effective solution for repairing and strengthening the reinforced concrete (RC) elements. The use of FRP significantly enhances the carrying capacity of elements under structural loads. However, the poor fire performance of this material poses a major concern, particularly in buildings. High temperature exposure can damage the adhesive bonding of polymer matrices and degrade their strength. Therefore, the use of thermal insulation is essential to ensure the safety of FRP-strengthened buildings. This study experimentally investigated the effectiveness of a recently developed thermal insulation system, “DYMAT® FIREWRAP”, in protecting the carbon and glass FRP wrapped concrete specimens. The tested insulation system comprised two different materials namely DYMAT® RS and Dymatherm. During the experiments, 50 concrete specimens with different strengthening and insulation configurations were prepared and exposed to high temperatures of 200 °C and 400 °C. The results highlight the importance of using thermal insulation on FRP repaired concrete elements. After high temperature exposure of 200 °C, the compressive strength losses of CFRP wrapped specimens were 12% lower than those of the non-insulated specimens. For GFRP strengthened specimens, the strength loss was 17% less than that for the non-insulated specimens. After high temperature exposure of 400 °C, the CFRP wrapped specimens experienced 27% less reduction in their compressive strength, and the strength loss for GFRP wrapped specimens was reduced by 32%. Among the considered configurations, the presence of the RS material as an inner layer played a major role in protecting the epoxy from deterioration. Dymatherm provided adequate protection; however, the number of layers did not significantly affect the high temperature endurance of the specimens.