Analytical, Numerical and Experimental Examination of Reinforced Composites Beams Covered with Carbon Fiber Reinforced Plastic: In the article, analytical, numerical (Finite Element Method) and experimental investigation results of beam that was strengthened with fiber reinforced plastic-FRP composite has been given as comparative, the effect of FRP wrapping number to the maximum load and moment capacity has been evaluated depending on this results. Carbon FRP qualitative dependences have been occurred between wrapping number and beam load and moment capacity for repair-strengthen the reinforced concrete beams with carbon fiber. Shown possibilities of application traditional known analysis programs, for the analysis of Carbon Fiber Reinforced Plastic (CFRP) strengthened structures.

The effect of temperature change on modal frequencies leads to erroneous results in the detection of structural damage. Therefore, quantifying the temperature dependency of modal frequencies is essential to improve the reliability of damage identification. Due to the irregular and time-dependent nature of temperature distribution, reliable correlations between air or surface temperatures and modal frequencies cannot be established. In this study, the dynamic behavior of a galvanized steel benchmark structure was investigated at two controlled temperature levels (2 °C and 32 °C) using experimental modal analysis (EMA). The structure was excited using a shaking table, while ambient vibration signals recorded at ground level were used as pre-recorded excitation input to the shaking table. Modal parameters were identified using Enhanced Frequency Domain Decomposition (EFDD). The results showed that mode shapes remained consistent across temperature levels, whereas natural frequencies decreased by an average of 2.43%. The identified dynamic parameters exhibited an approximately linear trend with temperature change. These findings highlight the importance of considering temperature effects in experimental modal analysis of galvanized steel structures to avoid false damage detection.

The aim of this research is to determine the effect of nanocoating retrofitting on the dynamic responses of industrial steel chimneys. A 20 m high industrial steel chimney was selected for nanocoating retrofitting. First, a three-dimensional finite element model of the chimney was created, and modal analysis was performed in SAP2000 software, and frequency values and mode shapes were obtained. Later, linear analyses of the chimney were made using the 1995 Kobe earthquake ground motion recording. Then, the outer surface of the chimney was retrofitted with a 1 mm MgO nanocoating, and dynamic analyses were made. Finally, the chimney’s dynamic responses before and after the MgO retrofit, such as minimum–maximum von Mises stresses and displacements, were compared. At the end of the study, it was observed that the displacements along the chimney height, especially maximum displacements, decreased from 150 mm to 140 mm, and the minimum von Mises stress at the bottom of the chimney decreased from 37.20 kPa to 30.19 kPa, and the maximum von Mises stress from 1519.27 kPa to 1332.33 kPa stresses in the analyses results. The decrease in frequency values revealed that MgO nanocoating had a positive effect on the stiffness of the chimney. It can be understood from this study that nanocoatings will be very useful in retrofitting industrial steel chimneys and have an effect on dynamic parameters.

Seismic retrofitting is widely used to enhance the dynamic performance of steel structures. This study experimentally investigates the effect of seismic damper retrofitting on a scaled steel frame using ambient vibration testing. Both as-built and retrofitted configurations were evaluated under low-amplitude excitations generated on a shake table. Modal parameters, including natural frequencies, mode shapes, and damping ratios, were identified using output-only Operational Modal Analysis (OMA) based on the Enhanced Frequency Domain Decomposition (EFDD) method. The results show a significant increase in damping ratios, with more than a 23-fold improvement in the first mode, along with mode-dependent frequency variations ranging from 17.63% to 142.74%. Mode shape comparison confirms strong consistency between configurations. The findings indicate that the integration of the damping devices enhanced the overall energy dissipation capacity of the scaled steel frame by increasing its global damping ratios and modifying the modal responses. The results suggest that output-only OMA can provide valuable insights into damper effectiveness, offering a practical alternative when controlled input excitation is not available.

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.

The purpose of this study is to ascertain how the dynamic reactions of a flexible biogas digester composed of PVC coated on PET polyester fabric are affected by nanocoating retrofitting. In this study, the effects of seismic movements on a ZrO₂-coated and uncoated PVC-PET biogas digester were investigated. A semi-sphere biogas digester that was 2.5 m high was chosen for development with nanocoating. Frequency values and mode shapes were acquired by first creating a three-dimensional finite element model of the biogas digester and then performing modal analysis in SAP2000 software. Later, the ground motion data from the 1994 Northridge earthquake were used to do linear assessments of the methane digester. Dynamic evaluations were then performed after a 0.25 mm ZrO₂ nanocoating was installed onto the digester’s exterior. Finally, the dynamic behavior of the biogas digester, characterized by minimum and maximum von Mises stresses and corresponding displacements, was evaluated before and after the ZrO₂ coating. By the end of the study, the maximum von Mises stress had decreased from 60.47 kPa to 15.18 kPa, while the minimum von Mises stress at the digester bottom was reduced from 11.41 kPa to 4.47 kPa. Additionally, the displacements along the digester height, particularly the maximum values, were reduced from 0.057 mm to 0.013 mm. The reduction in frequency values demonstrated that ZrO₂ nanocoating improved the biogas digester’s rigidity. This study makes it clear that nanocoatings will have an impact on dynamic parameters and be highly beneficial for improving biogas digesters.