Search

IMO Grain Regulations require a minimum level of acceptable stability for grain transportation, represented by the roll angle due to the conditional grain displacement, the residual restoring energy after such an assumed grain displacement and the initial metacentric height. Modern loading complexes for transshipment of grain crops are highly productive, which requires constant monitoring of the ship's position, including adjusting the length and tension of the mooring ropes. Along with mooring winches, windlass and capstan, dynamic mooring cleats are also involved in this process. The analysis of the mooring devices showed that the most effective for correcting the position of the vessel is the use of controlled bollards in combination with automatic winches. However, the experience of using the controlled bollards of known designs indicates that their designs contain solutions that significantly limit the possibilities of use in the rapidly changing position of the vessel or in difficult climatic conditions. The proposed design differs in that the pedestals have electromechanical stoppers with force sensors, the fingers are installed on the axes of rotation of the pedestals and are connected to the shafts of piezoelectric motors, which are rigidly attached to the base, and together with the stopper are connected to the control unit. Thus, the developed device will provide: expansion of the range of operating modes for the use of mooring bollards due to the use of piezoelectric motors; simplification of the design; no need to compensate for the influence of climatic factors on the bollard elements; no threat of environmental pollution by hydrocarbon working substances; improving maintainability due to the choice of a modular design. The use of the developed device will make it possible to quickly maintain a safe position of the ship during cargo operations. Thus, the developed device will provide: - expansion of the range of operating modes for the use of mooring bollards due to the use of piezoelectric motors; - simplification of design implementation; - no need to compensate for the influence of climatic factors on the bollard elements; - no threat of environmental pollution by hydrocarbon working substances; - increase in maintainability due to the choice of modular design and availability for technical diagnostics. The use of the developed device will allow to promptly maintain safety by the position of the vessel during cargo operations. [ABSTRACT FROM AUTHOR]

An actual test of medium-duty truck collision with twin anti-ram bollards of steel tube is analysed and simulated with different mass-spring-damper models to study bollard design requirements. Test data is obtained from test report of a medium-duty truck crashed into two fixed twin bollards at speed 78.3 km/h. Maximum impact load and impact height at that time is important in the analysis. Bollard height should be close to or larger than the vehicle's centre of gravity height to avoid climbing of the truck on the bollard. However, increasing impact height yields also increase in failure risk of bollard. Foundation is also critical in success of the bollard in successfully stopping the vehicle. The bollard should be fixed to the frame embedded in the concrete foundation so that the deformation in concrete be minimised. The bollard should be so stiff to stop the vehicle while most of the impact energy is absorbed by the vehicle through deformation of its frontal sections. A single-degree freedom linear mass-spring-damper model is the simplest model, but its results are not in line with test data. Single-degree non-linear model simulates the peak load but not the load history. However, using engine mass instead of truck mass in the single-degree model provides acceptable impact force data for the bollard. Two-degree freedom mass-spring damper linear model seems to simulate both truck's and bollard's deformation in a good manner. Non-linear analysis simulates the collision in a more realistic way, but it requires more data to be determined with testing. [ABSTRACT FROM AUTHOR]

Lack of shock absorption capability of conventional steel bollards causes significant vehicle damage and, consequently, high repair costs. This research studies a solution to reduce vehicle damage by inserting polylactic acid (PLA) honeycomb structures. A honeycomb-inserted bollard was designed based on numerical simulations using LS-DYNA, which yielded the bollard designed for actual vehicle-bollard collision experiments. Simulation efforts were focused on calculating the acceleration characteristics when a vehicle collides with steel and honeycomb-inserted bollards. Compared to the simulated steel bollards, 20 MPa yield-strength honeycomb-inserted bollard showed 0.017 s delay in the maximum acceleration occurrence time, reduction of the maximum acceleration of 37.4% of that of steel bollards, and a 13.1% reduction in the B-pillar maximum acceleration. Actual vehicle-bollard collision experiments, with a gyro-sensor installed at the test vehicle front bumper frame, also proved improved shock absorption characteristics of the honeycomb-inserted bollards. An experiment with honeycomb-inserted bollard showed a 0.783 s delay in the maximum acceleration occurrence time, a significant delay when compared to steel bollards. The maximum acceleration measured by the gyro-sensor was 0.35 × 103 m/s2 when the simulation predicted it to be 0.388 × 103 m/s2, proving the similarity in the simulations and experiments. Thus, this study of shock absorption characteristics promised reduced damage to vehicles and lower repair cost. [ABSTRACT FROM AUTHOR]

The blind encounter commuting risks, such as failing to recognize and avoid obstacles while walking, but protective support systems are lacking. Acoustic signals at crosswalk lights are activated by button or remote control; however, these signals are difficult to operate and not always available (i.e., broken). Bollards are posts installed for pedestrian safety, but they can create dangerous situations in that the blind cannot see them. Therefore, we proposed an obstacle recognition system to assist the blind in walking safely outdoors; this system can recognize and guide the blind through two obstacles (crosswalk lights and bollards) with image training from the Google Object Detection application program interface (API) based on TensorFlow. The recognized results notify the blind through voice guidance playback in real time. The single shot multibox detector (SSD) MobileNet and faster region-convolutional neural network (R-CNN) models were applied to evaluate the obstacle recognition system; the latter model demonstrated better performance. Crosswalk lights were evaluated and found to perform better during the day than night. They were also analyzed to determine if a client could cross at a crosswalk, while the locations of bollards were analyzed by algorithms to guide the client by voice guidance. [ABSTRACT FROM AUTHOR]

Lack of shock absorption capability of conventional steel bollards causes significant vehicle damage and, consequently, high repair costs. This research studies a solution to reduce vehicle damage by inserting polylactic acid (PLA) honeycomb structures. A honeycomb-inserted bollard was designed based on numerical simulations using LS-DYNA, which yielded the bollard designed for actual vehicle-bollard collision experiments. Simulation efforts were focused on calculating the acceleration characteristics when a vehicle collides with steel and honeycomb-inserted bollards. Compared to the simulated steel bollards, 20 MPa yield-strength honeycomb-inserted bollard showed 0.017 s delay in the maximum acceleration occurrence time, reduction of the maximum acceleration of 37.4% of that of steel bollards, and a 13.1% reduction in the B-pillar maximum acceleration. Actual vehicle-bollard collision experiments, with a gyro-sensor installed at the test vehicle front bumper frame, also proved improved shock absorption characteristics of the honeycomb-inserted bollards. An experiment with honeycomb-inserted bollard showed a 0.783 s delay in the maximum acceleration occurrence time, a significant delay when compared to steel bollards. The maximum acceleration measured by the gyro-sensor was 0.35 × 103 m/s2 when the simulation predicted it to be 0.388 × 103 m/s2, proving the similarity in the simulations and experiments. Thus, this study of shock absorption characteristics promised reduced damage to vehicles and lower repair cost.

The blind encounter commuting risks, such as failing to recognize and avoid obstacles while walking, but protective support systems are lacking. Acoustic signals at crosswalk lights are activated by button or remote control; however, these signals are difficult to operate and not always available (i.e., broken). Bollards are posts installed for pedestrian safety, but they can create dangerous situations in that the blind cannot see them. Therefore, we proposed an obstacle recognition system to assist the blind in walking safely outdoors; this system can recognize and guide the blind through two obstacles (crosswalk lights and bollards) with image training from the Google Object Detection application program interface (API) based on TensorFlow. The recognized results notify the blind through voice guidance playback in real time. The single shot multibox detector (SSD) MobileNet and faster region-convolutional neural network (R-CNN) models were applied to evaluate the obstacle recognition system; the latter model demonstrated better performance. Crosswalk lights were evaluated and found to perform better during the day than night. They were also analyzed to determine if a client could cross at a crosswalk, while the locations of bollards were analyzed by algorithms to guide the client by voice guidance.

World trade center attack, in year 2001, lead to enhanced research emphasis on the development of various protection systems to confine such terrorist attack possibly within a predesigned and predefined periphery. Amongst many forms of terrorist attacks, vehicular bombing is one of the most dangerous and frequently encountered threats to important civil and defense infrastructures. This unauthorized vehicle approaching a protected area can be effectively stopped using anti-ram bollard. In the present investigation, an anti-ram bollard is numerically analyzed under different vehicular impact speed to test simulate as per K4, K8 and K12 ratings. A comprehensive nonlinear finite element model is developed to simulate the performance of fixed anti-ram bollard subjected to vehicle impact using LS-DYNA ® . The bollard is modelled using piecewise linear kinematic plasticity model material model and effect of strain rate for the bollard material is neglected. Numerical investigation shows that both the impact force and the bollard deflection increases with the increase in truck impact speed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Inelastic transient finite element simulations based on an actual truck collision test are used to investigate the demands imposed during collisions between medium-duty trucks and anti-ram bollards constructed with concrete-filled steel tubes (CFT). The medium-duty truck is considered for crashing into a bollard at speed 50, 65, and 80 km/h, respectively, based on performance demands of bollards of different grades. Numerical results show that both the impact force and the bollard deflection increase with increasing the truck impact speed. When the speed is relatively high (e.g. 80 km/h), there is a risk of the truck climbing over the bollard, even with little damage to the bollard. The analyses show that the impact force along the height of the bollard is not uniform and may change during the impact process. Considering the complexity and computation time consumption, a simplified analysis based on a two-degree-of-freedom mass-spring-damper system model is developed to simulate the collision process. In the analysis, a bilinear spring is used to characterize the truck considering its “soft front and hard rear” characteristics when impacting bollards. Results show that the simplified analytical model is in good agreement with the finite element model using a detailed truck model. [ABSTRACT FROM AUTHOR]

Abstract: CSRs (Common Structural Rules for bulker and tanker), which came into effect in 2006, invoke the concept of the ultimate strength of hull girders. While numerous studies associated with the ultimate capacities regarding global hull girders and stiffened panels have been carried out, there are few application cases of the ultimate strengths for deck machineries and their supporting structures. In the present study, nonlinear finite element analyses have been performed to obtain ultimate capacities for a size 450 DIN type bollard including hull foundation structures for which elastic strength assessments based on allowable stress analyses were jointly carried out by a Mooring Fitting SWL Standardization Committee consisting of four major Korean shipbuilders (DSME, HHI, HHIC, and SHI) in 2003. The plastic hardening property is identified from a comparison of the results of ultimate strength simulations and a bollard tension tests performed by the committee. It is assumed that the ultimate load is the corresponding load point when the deformation slope of the bollard column reaches the critical slip angle. It is concluded that the reinforcements appear to be effective with respect to the allowable stress criterion, but are not substantially effective from the point of view of ultimate capacities. In other words, structural reinforcements based on allowable stress analyses may noticeably increase production costs, but do not remarkably raise the ultimate capacities. [Copyright &y& Elsevier]