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    Crashworthiness of the bollard system by experimentally validated virtual test
    (Pergamon-Elsevier Science Ltd, 2023) Yumrutas, Halil Ibrahim; Apak, Mustafa Yurdabal
    Shielding risky/vulnerable roadside zones in urban areas such as playgrounds, sidewalks, bus stations, oil/gas stations, and regulators of infrastructure facilities has been a significant focus point by engineers and local authorities in recent decades due to the boost of vehicular number and mobility. Bollard systems are regarded as one of the efficient countermeasures, especially for the zones that vehicles and pedestrians share. This paper discusses the performance of a steel bollard system by experimentally validated virtual crash tests following IWA 14-1 (Vehicle security barriers (VSB): Performance requirement, vehicle impact test method and performance rating), EN 1317 (Road Restraint Systems), and EN 16303 (Validation and verification process for virtual testing in crash testing against vehicle restraint system) standards. In this context, pendulum crash tests were performed, virtual pendulum crash tests were verified and modelled with the results of actual tests then full-scale virtual crashworthiness tests were conducted respectively. The penetration, Acceleration Severity Index (ASI), displacement, and deformation values of the bollard system were evaluated considering the relevant standards and the characteristics of urban traffic. Based on virtual test results with increased reliability, the bollard system has the capability to shield the roadside critical assets against M1 class 900 kg vehicles up to 50 km/h and M1 class 1500 kg vehicles up to 32 km/h.
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    Experimental and numerical comparative crashworthiness analysis of innovative renewable hybrid barrier with conventional roadside barriers
    (Taylor & Francis Ltd, 2023) Yumrutas, Halil Ibrahim; Ozcanan, Sedat; Apak, Mustafa Yurdabal; Anwer, Mohammed Jalil
    Guardrails are passive safety elements used in roadside safety. They are commonly manufactured as steel and concrete. There are also guardrail systems in which wood and steel materials are used together. This study investigated the crashworthiness performance of a newly developed F-shape type renewable hybrid barrier (RHB) system consisting of wood, steel and sand components. Commonly used steel guardrail and F-shape type concrete barrier were used for performance comparison. For this, a pendulum impactor has been set up. The impact performances of the aforementioned guardrails in the pendulum assembly were determined, then tests were carried out by modelling the pendulum system in the LS-DYNA environment for full-size crash testing and calibration. Calibration and validation were performed by comparing the Finite Element (FE) results with the pendulum results. Then, to determine the crashworthiness and safety of RHBs and compare them with steel and concrete barriers, full-size finite element models were created in the TB11 test standard specified in the European roadside safety standard - EN1317. As a result of the analysis, while providing the comfort of a concrete barrier after impact, RHBs perform close to the steel barrier in terms of safety. This study will be the first step before the prospective full-scale crash analysis.
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    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.
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    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.