Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and the September 11, 2001, attacks saw a sharp increase in the installation of bollards for security needs. Anti-ram installations include not just posts, but other objects designed to resist impact without presenting the appearance of a protective barrier, including large planters or benches that steel bollards. Once the design threat is determined the resistance necessary to stop it can be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes into consideration both the mass and the speed of an approaching attack vehicle, with the latter being considered the more significant.
In accordance with Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment from the surrounding website is required. “Street and site architecture will determine the highest possible approach speed,” he explained. “If you can find no strategies to your building with a long term-up, an attack vehicle cannot build-up high speed, and the resistance from the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is often measured employing a standard designed by the Department of State, known as the K-rating. K-4, K-8 and K-12 each make reference to the cabability to stop a truck of any specific weight and speed and stop penetration from the payload a lot more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not merely on the size and strength in the bollard itself, but also on the way it is actually anchored as well as the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Websites. The truck impacts 2 or 3 bollards at high speed, and the front from the vehicle often crumples, wrapping completely around the centermost post. Portion of the cab may disappear the truck, the top or rear end could rise several feet within the air, and front or rear axles might detach. The bollards and their footings are often lifted several feet upward. In all successful tests, the payload on the back from the truck will not penetrate more than 1 meter past the collection of bollards, thus satisfying the conventional.
The most basic security bollard is some 203-mm (8-in.), 254-mm (10-in.), or 305-mm (12 in.) carbon steel structural pipe. Some impact resistance is achieved even with a 102-mm (4-in.) pipe, depending on the engineering of their foundation. It is often loaded with concrete to improve stiffness, although unfilled pipe with plate stiffeners inside could possibly produce better resistance in the same diameter pipe. Without any form of internal stiffening, the pipe’s wall-thickness must be significantly greater. For fixed-type security bollards, simple pipe bollards could be functionally sufficient, if properly mounted. Undecorated pipe-type bollards will also be specially manufactured.
The biggest disadvantage of a plain pipe is aesthetics. A piece of painted pipe fails to truly blend into – a lot less enhance – most architectural schemes. However, this can be overcome by way of a decorative bollard cover. Many standalone bollards that do not have impact-resistance that belongs to them are designed with alternative mounting capability to slip over standard pipe sizes, forming an attractive and architecturally appropriate impact-resistance system. These decorative covers can also be offered to enhance specially designed (but non-decorative) pipe-type bollards.
Security Design Concepts
A lot of modern security design focuses on the threat of bomb attacks. The most important aspect in protecting against explosions is definitely the distance between the detonation and also the target. The force in the blast shockwave diminishes being a purpose of the square of the distance. The greater distance that can be placed involving the detonation and the protected structure – referred to as standoff distance – the greater the threat resistance or, conversely, the less blast resistance must be included in the structure. Therefore, creation of secure perimeter is step one within the overall form of blast resistance.
Standoff is valuable architecturally because it allows a building to be protected with out to look like a bunker. It also has economic impact, since it is frequently less costly to produce standoff rather than to bomb-proof the dwelling itself. Security bollards and similar anti-ram installations are designed and positioned to generate standoff by thwarting the delivery of explosives close to the target by way of a vehicle.
Any security design depends upon an estimate of the size of threat to get resisted – the ‘design threat.’ The force of the explosion that may be expected is directly related to the weight- and volume-carrying capabilities of the delivery vehicle. Explosives are measured with regards to tonnes of trinitrotoluene (TNT). By far the most potent molecular explosives such, as Composition 4 (i.e. C-4), are approximately another more robust than TNT, whereas a fuel and fertilizer bomb – like was used in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be produced about how much explosive power could be delivered by way of a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. according to its weight-and volume-carrying capacity.
You can find three basic varieties of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards may be mounted into existing concrete, or set up in new foundations. Manufactured bollards are usually created with their very own mounting systems. Standalone mountings can be as non-invasive as drilling into existing concrete and anchoring with epoxy or concrete inserts. Such surface-mounted bollards can be used purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards designed to protect against impact are usually embedded in concrete several feet deep, if site conditions permit. Engineering of the mounting is dependent upon design threat, soil conditions and other site-specific factors. Strip footings that mount several bollards have better resistance, spreading the impact load more than a wider area. For sites where deep excavation will not be desirable or possible (e.g. an urban location with a basement or subway beneath the pavement), steel bollard covers made with shallow-depth installation systems are accessible for both individual posts and groups of bollards. Generally speaking, the shallower the mounting, the broader it must be to resist impact loading.
A removable bollard typically features a permanently installed mount or sleeve below grade, whilst the sleeve’s top is flush with all the pavement. The mating bollard could be manually lifted out from the mount to permit access. This etxxdy is intended for locations in which the change of access is occasionally needed. It may include a locking mechanism, either exposed or concealed, to prevent unauthorized removal. Both plain and decorative bollards are for sale to this type of application. Most removable bollards are not intended for high-impact resistance and are usually not used in anti-ram applications.
Retractable bollards telescope down below pavement level, and might be either manual or automatically operated. Manual systems sometimes have lift-assistance mechanisms to help ease and speed deployment. Automatic systems might be electric or hydraulic and often include a dedicated backup power installation and so the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the requirement for defining space, among the basic tasks from the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to many different functions. The plethora of available options is vast when it comes to both visual style and performance properties. For security applications, a design professional with security expertise needs to be within the planning team.