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Article Investigating of Dynamic Compressive Response of Plain and Fiber-Reinforced Concrete Structures at Various Strain Rates(SAGE Publications Ltd, 2025) Gunay, A.R.; Hafizoglu, H.; Akdeniz, E.; Kaya, C.Across the world, studies on building design are conducted at various scales. The behavior of structures under static loading has been the subject of various studies in the modern era, leading to the development of significant standards and application techniques. However, studies on the behavior of structures under dynamic loading have remained limited. This study investigated the dynamic compressive behavior of plain and fiber-reinforced C60 and C80 concrete samples through experimental studies at room temperature. In addition, this study also investigated dynamic deformation and fracture behavior of plain concrete samples by numerical studies. For this purpose, plain and fiber-reinforced C60 and C80 concrete samples were produced. Experimental studies covered both static and dynamic compression tests. Following the static tests, dynamic test samples with a diameter and length of 10 mm were produced from the static test samples by water jet cutting method and were dynamically compressed in the Split Hopkinson Pressure Bar (SHPB) test setup. Dynamic compression test results showed that the strength of plain and fiber-reinforced C60 and C80 concretes were obtained in the range of 74–162 MPa at an average strain rate of between 139 and 650 s−1. Experimental results also showed that the fiber addition affected the dynamic increase factor (DIF) and impact toughness of both C60 and C80 concretes in a good manner. To compare experimental and numerical results, a dynamic compression test condition was visualized with a high-speed camera and simulated with the Ls-Dyna software using the finite-element method. Numerical studies indicated a good correlation with dynamic compression results in terms of crack formation and fracture progress. © IMechE 2025.Article Effect of COVID-19 Infection on the Performance of Elite Adolescent Overhead Athletes(SAGE Publications Ltd, 2025) Uluǧ, Naime; Kodak, Seyde Büşra; Kodak, Muhammed Ihsan,; Karahan, Zehra Can; Kiliç, ErdenBackground: COVID-19 might have a negative impact on sports performance. There are few studies in the literature that assess how the sports performance of adolescent athletes is affected by COVID-19. Objective: This study aimed to compare the sports performance of adolescent overhead athletes who had COVID-19 infection with those who had not. Methods: The study involved adolescent elite overhead athletes from basketball, volleyball, handball, and tennis. Athletes’ performance were assessed using core muscle endurance, hand grip strength, upper extremity functional performance, reaction time and agility performance, and the 3-min step test. Results: Study included 47 adolescent overhead athletes (mean age 15.15 ± 1.51 years). The COVID-19 group showed significantly higher Borg Scale scores and decrease in oxygen saturation levels only after the step test (p = 0.02, p = 0.02, respectively). Additionally, COVID-19 group had lower grip strength in both right and left hands compared to the non-COVID group (p = 0.01, p = 0.05, respectively). No significant association was found between core muscle power and endurance, upper extremity functional performance, reaction time and agility performance (p > 0.05). Conclusions: Our results showed reduced hand grip strength and increased fatigue following COVID-19 infection in adolescent overhead athletes. Time period after COVID-19 infection had a negative correlation with sports performance and core endurance. © 2025 Elsevier B.V., All rights reserved.
