Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and also the September 11, 2001, attacks saw a sharp surge 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, such as large planters or benches that steel bollards price. Once the design threat is established the resistance required to stop it may be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes under consideration both the mass and the speed of an approaching attack vehicle, with the latter being regarded the more significant.
Based on Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment of the surrounding site is required. “Street and site architecture will determine the highest possible approach speed,” he said. “If you will find no methods to your building having a long run-up, an attack vehicle cannot build-up high speed, and also the resistance in the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is normally measured utilizing a standard developed by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each refer to the opportunity to stop a truck of a specific weight and speed and stop penetration in the payload a lot more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not merely on the size and strength in 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 Websites. The truck impacts two or three bollards at high-speed, and also the front from the vehicle often crumples, wrapping completely round the centermost post. Portion of the cab may disappear the truck, the front side or rear end could rise several feet within the air, and front or rear axles might detach. The bollards along with their footings are occasionally lifted several feet upward. In every successful tests, the payload on the back of the truck does not penetrate greater than 1 meter past the collection of bollards, thus satisfying the standard.
The easiest 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 despite having 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 may actually produce better resistance within the same diameter pipe. Without any type 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 can also be specially manufactured.
The biggest downside of a plain pipe is aesthetics. A bit of painted pipe will not truly blend into – much less enhance – most architectural schemes. However, this can be overcome with a decorative bollard cover. Many standalone bollards which do not have impact-resistance that belongs to them are made with alternative mounting ability to slip over standard pipe sizes, forming an attractive and architecturally appropriate impact-resistance system. These decorative covers can also be available to enhance specially designed (but non-decorative) pipe-type bollards.
Security Design Concepts
Most of modern security design focuses on the threat of bomb attacks. The most important factor in protecting against explosions is the distance in between the detonation and also the target. The force in the blast shockwave diminishes as a function of the square of the distance. The greater distance that may be placed between the detonation as well as the protected structure – called standoff distance – the higher the threat resistance or, conversely, the less blast resistance must be included in the structure. Therefore, creation of secure perimeter is the initial step in the overall style of blast resistance.
Standoff is valuable architecturally as it allows a building to be protected without having to resemble a bunker. It also has economic impact, since it is frequently cheaper to create standoff than to bomb-proof the dwelling itself. Security bollards and similar anti-ram installations are made and positioned to produce standoff by thwarting the delivery of explosives close to the target with a vehicle.
Any security design is dependent upon a quote of the dimensions of threat to be resisted – the ‘design threat.’ The force of the explosion that may be expected is directly linked to the body weight- and volume-carrying capabilities from 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 stronger than TNT, whereas a fuel and fertilizer bomb – including was applied in Oklahoma City – is considerably less powerful than TNT. Reasonable approximations can be created regarding how much explosive power can be delivered by way of a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based upon the 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 set up in new foundations. Manufactured bollards are often created with their particular mounting systems. Standalone mountings could be as non-invasive as drilling into existing concrete and anchoring with epoxy or concrete inserts. Such surface-mounted bollards can be used for purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards made to control impact are often baked into concrete several feet deep, if site conditions permit. Engineering of the mounting depends upon design threat, soil conditions as well as other site-specific factors. Strip footings that mount several bollards provide better resistance, spreading the impact load more than a wider area. For sites where deep excavation is not really desirable or possible (e.g. an urban location having a basement or subway underneath the pavement), stainless steel bollard covers 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 must be to face up to impact loading.
A removable bollard typically has a permanently installed mount or sleeve below grade, while the sleeve’s top is flush with all the pavement. The mating bollard may be manually lifted out from the mount to enable access. This etxxdy is supposed for locations where the change of access is occasionally needed. It may incorporate a locking mechanism, either exposed or concealed, to prevent unauthorized removal. Both plain and decorative bollards are available for this sort of application. Most removable bollards are certainly not intended for high-impact resistance and therefore are not often 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 ease and speed deployment. Automatic systems might be electric or hydraulic and quite often add a dedicated backup power installation and so the bollard remains functional during emergencies. Retractable systems tend to be unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the need for defining space, one of the basic tasks from the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to a variety of functions. The plethora of available choices is vast in terms of both visual style and performance properties. For security applications, a design professional with security expertise needs to be within the planning team.