HEALTH & SAFETY ENGINEERING
Design and testing of a crash bollard system by Ang Choon Keat, Lim Siew Fern and Lim Jiunn Jie, Prostruct Consulting Pte Ltd, Singapore A crash bollard system is a type of physical security measure used to prevent forced entry by vehicles as well as to provide adequate stand-off distance between the target and a VehicleBorne Improvised Explosive Device (VBIED). Thus, the design of a crash bollard system will have to take into consideration high energy vehicle impacts and the need to minimise postimpact penetration. This article briey describes the design objectives, code provisions and methodologies related to designing and testing of a crash bollard system. Introduction Terrorism remains a serious threat in the world today. A terrorist attack is a very disruptive force which can destabilise the normalcy and unity of a society. The tactics of terrorism nowadays are getting more diverse, as a result of the relative ease of access to chemicals used to make explosives. Attacks can be made by individuals such as suicide bombers, or by vehicles - the latter is becoming more common in the wake of recent terror events. In the recent 2016 Nice attack in France, a cargo truck was deliberately driven into crowds, resulting in the deaths of close to 100 people and injuries to nearly 450. Another vehicle, driven by a suicide bomber hit a shopping area in Baghdad, in July 2016, causing hundreds of casualties. Therefore, protection against vehicle-borne explosive threats and vehicle impact threats has developed into an important requirement. A combination of security measures could be employed to protect the building from these attacks. It would involve active measures covering access control, security screening and surveillance, as well as passive measures such as barriers and bollards. Stand-off distance is one of the most effective ways to reduce the blast effects of a VBIED. This can be accomplished by designing blastresistant structures and/or vehicle security barriers (VSBs), to provide a hardened perimeter around the building. This would prevent or deter unscreened vehicles from approaching too close to a building by keeping
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them at a certain distance from the building. It can also mitigate the blast effects if a vehicle bomb is detonated at the perimeter. Crash bollards There are many barrier options that can be considered, when designing VSBs to protect against a VBIED. Typical designs consist of concrete mass barriers, cable barriers, bollards, crash gates etc. A crash bollard is a barrier system which is commonly used through-
out heavy industries and in building management, to protect assets. They usually consist of a steel post, either anchored to concrete, buried in the ground, or secured by a locking system, to protect the surrounding foundations when a bollard is struck. Crash bollards can be of a permanently fixed type or of a removable type that enables them to be inserted or removed from base frame sleeves, to facilitate vehicular access.
Figure 1: Crash bollards.
Figure 2: Fixed crash bollard system
THE SINGAPORE ENGINEER December 2016
Figure 3: Removable crash bollard system