Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and the September 11, 2001, attacks saw a sharp surge in the installation of bollards for security reasons. Anti-ram installations include not just posts, but other objects designed to resist impact without presenting the look of a protective barrier, including large planters or benches that commercial bollards. Once the design threat is determined the resistance necessary to stop it may be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes under consideration both the mass and also the speed of an approaching attack vehicle, with the latter being considered the more significant.
Based on Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment from the surrounding site is required. “Street and site architecture determines the maximum possible approach speed,” he stated. “If you will find no methods to your building using a long run-up, an attack vehicle cannot build-up high-speed, and the resistance of the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is commonly measured utilizing a standard designed by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each refer to the ability to stop a truck of the specific weight and speed preventing penetration of the payload more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not only on the size and strength of the bollard itself, but in addition on the way it really is anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Internet sites. The truck impacts 2 or 3 bollards at high-speed, and also the front in the vehicle often crumples, wrapping completely around the centermost post. Portion of the cab may disappear the truck, the front or rear end could rise several feet within the air, and front or rear axles might detach. The bollards and their footings are occasionally lifted several feet upward. In most successful tests, the payload on the back of the truck fails to penetrate a lot more than 1 meter past the type of bollards, thus satisfying the typical.
The simplest security bollard is a piece of 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 full of concrete to improve stiffness, although unfilled pipe with plate stiffeners inside might actually produce better resistance within the same diameter pipe. Without any form of internal stiffening, the pipe’s wall-thickness needs to 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 greatest drawback to a plain pipe is aesthetics. Some painted pipe will not truly blend into – a lot less enhance – most architectural schemes. However, this could be overcome by a decorative bollard cover. Many standalone bollards which do not have impact-resistance of their own are made with alternative mounting capacity to slip over standard pipe sizes, forming a stylish and architecturally appropriate impact-resistance system. These decorative covers can also be available to enhance specifically created (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 involving the detonation and also the target. The force in the blast shockwave diminishes as being a function of the square from the distance. The more distance that may be placed involving the detonation as well as the protected structure – called standoff distance – the higher the threat resistance or, conversely, the less blast resistance has to be built into the structure. Therefore, creation of secure perimeter is the initial step inside the overall design of blast resistance.
Standoff is valuable architecturally since it allows a building to be protected with out to resemble a bunker. It also has economic impact, because it is frequently cheaper to produce standoff rather than to bomb-proof the structure itself. Security bollards and similar anti-ram installations are made and positioned to create standoff by thwarting the delivery of explosives close to the target with a vehicle.
Any security design depends on a quote of how big threat to be resisted – the ‘design threat.’ The force from the explosion which can be expected is directly linked to the weight- and volume-carrying capabilities of the delivery vehicle. Explosives are measured with regards to tonnes of trinitrotoluene (TNT). 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 – including was utilized in Oklahoma City – is considerably less powerful than TNT. Reasonable approximations can be made about how exactly much explosive power may be delivered by way of a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based upon its weight-and volume-carrying capacity.
You will find three basic types of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards can be mounted into existing concrete, or installed in new foundations. Manufactured bollards are frequently made with their 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 control impact are often a part of concrete several feet deep, if site conditions permit. Engineering from the mounting depends on design threat, soil conditions and other site-specific factors. Strip footings that mount several bollards have better resistance, spreading the impact load over a wider area. For sites where deep excavation is not really desirable or possible (e.g. an urban location using a basement or subway under the pavement), stainless steel bollard sleeves made out of shallow-depth installation systems are accessible for both individual posts and groups of bollards. Generally speaking, the shallower the mounting, the broader it should be to face up to impact loading.
A removable bollard typically includes a permanently installed mount or sleeve below grade, while the sleeve’s top is flush using the pavement. The mating bollard may be manually lifted out from the mount to enable access. This etxxdy is intended for locations where change of access is occasionally needed. It could incorporate a locking mechanism, either exposed or concealed, to stop unauthorized removal. Both plain and decorative bollards are available for this kind of application. Most removable bollards are not designed for high-impact resistance and are usually not utilized in anti-ram applications.
Retractable bollards telescope down below pavement level, and could be either manual or automatically operated. Manual systems sometimes have lift-assistance mechanisms to help ease and speed deployment. Automatic systems may be electric or hydraulic and quite often include a dedicated backup power installation and so the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous since they are overlooked. They speak to the requirement for defining space, one of many basic tasks in the built environment. Decorative bollards and bollard covers give you a versatile solution for bringing pleasing form to a number of functions. The range of options is vast when it comes to both visual style and gratification properties. For security applications, a design professional with security expertise should be contained in the planning team.