Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing as well as the September 11, 2001, attacks saw a sharp increase in the installation of bollards for security needs. Anti-ram installations include not only posts, but other objects made 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 determined the resistance required to stop it can be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes into account both the mass as well as the speed of an approaching attack vehicle, with the latter being considered the more significant.
Based on Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment from the surrounding site is required. “Street and site architecture will determine the highest possible approach speed,” he stated. “If you will find no methods to the property with a long term-up, an attack vehicle cannot build up high-speed, and also the resistance of the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is commonly measured utilizing a standard developed by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each reference the opportunity to stop a truck of a specific weight and speed and prevent penetration in the payload a lot more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not only on the size and strength of the bollard itself, but in addition on the way it is actually anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Web 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. Area of the cab may disappear the truck, the front side or rear end could rise several feet inside the air, and front or rear axles might detach. The bollards as well as their footings are occasionally lifted several feet upward. In most successful tests, the payload on the back of the truck will not penetrate a lot more than 1 meter past the type of bollards, thus satisfying the typical.
The simplest security bollard is a bit of 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 the foundation. It is usually filled with concrete to increase stiffness, although unfilled pipe with plate stiffeners inside may actually produce better resistance inside the same diameter pipe. Without any type of internal stiffening, the pipe’s wall-thickness has 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 does not truly blend into – a lot less enhance – most architectural schemes. However, this can be overcome by a decorative bollard cover. Many standalone bollards that do not have impact-resistance that belongs to them 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 be available to enhance specially designed (but non-decorative) pipe-type bollards.
Security Design Concepts
Much of modern security design focuses on the threat of bomb attacks. The most important element in protecting against explosions is the distance in between the detonation and the target. The force of the blast shockwave diminishes as being a function of the square of the distance. The better distance that can be placed between the detonation and also 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, development of secure perimeter is the first step within the overall style of blast resistance.
Standoff is valuable architecturally because it allows a building to be protected without having to resemble a bunker. It also has economic impact, as it is frequently cheaper to produce standoff rather than to bomb-proof the structure itself. Security bollards and similar anti-ram installations are designed and positioned to create standoff by thwarting the delivery of explosives near to the target by a vehicle.
Any security design depends on a bid of the dimensions of threat to be resisted – the ‘design threat.’ The force of the explosion which can be expected is directly related to the load- and volume-carrying capabilities in 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 one third more powerful than TNT, whereas a fuel and fertilizer bomb – such as was used in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be produced about how exactly much explosive power could be delivered by 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 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 very own 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 purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards created to protect against impact are usually baked into concrete several feet deep, if site conditions permit. Engineering from 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 spanning a wider area. For sites where deep excavation will not be desirable or possible (e.g. an urban location using a basement or subway underneath the pavement), stainless steel pipe bollards made out of shallow-depth installation systems are available for both individual posts and teams of bollards. In general, 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, as the sleeve’s top is flush using the pavement. The mating bollard can be manually lifted out of the mount to permit access. This etxxdy is intended for locations in which the change of access is occasionally needed. It could add 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 usually are not created for high-impact resistance and they are not often used 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 sometimes 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 with the need for defining space, one of many basic tasks of the built environment. Decorative bollards and bollard covers give you a versatile solution for bringing pleasing form to many different functions. All the different options is vast with regards to both visual style and gratification properties. For security applications, a design professional with security expertise should be included in the planning team.