Yazar "Atahan, Ali Osman" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • Küçük Resim Yok
    Öğe
    Finite element simulation and failure analysis of fixed bollard system according to the PAS 68:2013 standard
    (Pergamon-Elsevier Science Ltd, 2022) Apak, Mustafa Yurdabal; Ergun, Murat; Ozen, Halit; Buyuk, Murat; Ozcanan, Sedat; Atahan, Ali Osman; Yumrutas, Halil Ibrahim
    Fixed bollards are very significant elements in providing urban roadside safety. These structures, called passive systems, allow pedestrians and disabled people to use sidewalks effectively and safely, as well as they have a crucial role in protecting the above-ground assets of infrastructure facilities against run-off-road (ROR) crashes. In this study, structural and safety performance analyses of fixed bollards that protect natural gas above ground Reducing and Metering Station-B (RMS-B) type regulating stations used in many points in Istanbul were made. In this regard, finite element (FE) models of the steel pipe of the fixed bollard, the concrete of the foundation and the soil where the bollard was mounted were created. Existing fixed bollards have been verified with accident data. In the light of the calibration and validation, numerical models were created and combined with the vehicle models specified in PAS 68:2013 standard to simulate dynamic behaviours. The combined FE models were analysed applying LS-DYNA software. As a result of the numerical analysis, the fixed bollard system cannot safely stop the 30000 kg N3, 18000 kg N3 and 7500 kg N2 class vehicles, and cannot prevent them from damaging the RMS-B. Besides, the fixed bollard system cannot provide safety at the speed level of 48 km/h, considering the urban speed limit for 3500 kg N1 and 2500 kg N1G class vehicles. However, the fixed bollard system can safely stop 1500 kg and 900 kg M1 class vehicles up to 64 km/h speed limit. These analyses revealed that considering the regional traffic characteristics of Istanbul, the existing fixed bollard systems are not sufficient for the protection of hazardous roadside facilities and need to be improved. Fullscale crash tests should be carried out in future studies to validate the FE simulation models. Furthermore, various bollard designs should be developed, especially urban road requirements.
  • Küçük Resim Yok
    Öğe
    An innovative approach on the renewable hybrid barrier: combined use of wood and sand
    (Univ Federal Lavras-Ufla, 2021) Yumrytas, Halil Ibrahim; Birinci, Emre; Yorur, Huseyin; Atahan, Ali Osman
    Background: Wooden materials have been among the basic materials used in many different areas due to some advantages throughout the history. Roadside barriers, which are called passive safety structures, can be produced with different materials such as wood, steel, concrete, and plastic. In this study, Renewable Hybrid Barriers (RHB), a new type of barrier that is used wood in terms of aesthetics, renewability, high shock resistance, and used sand in terms of impact absorption capacity and low cost, produced by taking into account some of the disadvantages of other barrier types. These barriers are planned to be used especially in historical/touristic areas, scenic roads, and in urban areas as urban furniture. Real-time crash tests in accordance with EN 1317 (Road Restraint Systems) standard require high cost and long time. Therefore, the pendulum crash test mechanism frequently used in the literature was manufactured at which the experiments were carried out. Results: The results revealed that the RHBs which has 2 cm thick timber and sand used together, were sufficient and suitable in terms of both cost and necessary safety criteria. It was observed that impregnation and heat treatment applications did not have a considerable negative effect on the performance of RHBs which provide an opportunity to use RHBs for outdoor conditions.. Conclusion: In the light of the results of the study, the optimum wood timber thickness was determined as 2 cm regarding TB 31 test criteria. It is proposed that the crash tests for different wood species, timber thickness, and/or barrier dimensions should carry out in future studies. This study can serve as the basis for the next step, real-time real crash tests. Since the study includes an interdisciplinary subject, it is thought that it will inspire different studies.
  • Küçük Resim Yok
    Öğe
    A novel modular shallow mounted bollard system design and finite element performance analysis in ensuring urban roadside safety
    (Sage Publications Ltd, 2023) Apak, Mustafa Yurdabal; Ergun, Murat; Ozen, Halit; Buyuk, Murat; Yumrutas, Halil Ibrahim; Ozcanan, Sedat; Atahan, Ali Osman
    The safety of risky roadside zones such as kids' playgrounds, schools, bus stops, petrol stations, critical roadside facilities, and pavements are becoming a significant worldwide problem. This study focused on the roadside safety of critical above-ground assets of natural gas grids due to its consequences such as fire, blast, traffic interruptions, service downtime, and consumer displeasure during the repair process. In this regard, a novel modular shallow mounted bollard system was designed considering the disadvantages of conventional bollard systems in the literature and the demands/needs of related institutions. Numerical simulations were carried out to analyze the structural and safety performance capabilities of the originally designed bollard system following PAS 68:2013 standard. In addition, FE models were created and incorporated with the verified vehicle models to simulate dynamic behaviors. LS-DYNA software analyzed the FE models. As a result of the simulations, the newly developed fixed bollard design can safely stop vehicles that weigh 18,000 kg max., except for the 30,000 kg N3 class vehicle, up to 50 km/h. The results revealed that proposed bollard designs successfully met the standard requirements for the vehicle types and speed that represent general urban traffic characteristics. Thus, the new fixed bollard design will contribute to roadside safety in metropolitan areas by protecting critical hazardous roadside facilities. In the next stage, the newly designed barrier system should be optimized to lighten the system and reduce the costs.