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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]