Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and also the September 11, 2001, attacks saw a sharp rise in the installation of bollards for security reasons. Anti-ram installations include not only posts, but other objects designed to resist impact without presenting the appearance of a protective barrier, including large planters or benches that where to buy bollards. Once the design threat is determined the resistance needed to stop it may be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes into consideration both the mass as well as the speed of an approaching attack vehicle, with the latter being considered the more significant.
In accordance with Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment from the surrounding website is required. “Street and site architecture will determine the maximum possible approach speed,” he stated. “If you can find no methods to the building with 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 employing a standard designed by the Department of State, known as the K-rating. K-4, K-8 and K-12 each refer to the ability to stop a truck of any specific weight and speed and prevent penetration of the payload greater than 1 m (3 ft) past the anti-ram barrier. Resistance depends not merely on the size and strength of the bollard itself, but additionally on the way it really is anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Web sites. The truck impacts several bollards at high speed, and also the front from the vehicle often crumples, wrapping completely round the centermost post. Part 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 often lifted several feet upward. In most successful tests, the payload on the back of the truck fails to penetrate greater than 1 meter past the line of bollards, thus satisfying the conventional.
The simplest 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 usually filled with concrete to increase stiffness, although unfilled pipe with plate stiffeners inside could possibly 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 might be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.
The largest downside of a plain pipe is aesthetics. A piece of painted pipe does not truly blend into – much less enhance – most architectural schemes. However, this can be overcome by a decorative bollard cover. Many standalone bollards which do not have impact-resistance of their own are created with alternative mounting capability to slip over standard pipe sizes, forming an attractive and architecturally appropriate impact-resistance system. These decorative covers may also be offered to enhance specially engineered (but non-decorative) pipe-type bollards.
Security Design Concepts
Much of modern security design focuses on the threat of bomb attacks. The most significant aspect in protecting against explosions is the distance between the detonation and the target. The force in the blast shockwave diminishes as being a function of the square of the distance. The greater distance that can be placed in between the detonation as well as the protected structure – called standoff distance – the higher the threat resistance or, conversely, the less blast resistance needs to be included in the dwelling. Therefore, development of secure perimeter is the initial step in the overall form of blast resistance.
Standoff is valuable architecturally as it allows a building to become protected without needing to look like a bunker. Additionally, it has economic impact, since it is frequently less costly to produce standoff rather than bomb-proof the structure itself. Security bollards and similar anti-ram installations are created and positioned to create standoff by thwarting the delivery of explosives close to the target by way of a vehicle.
Any security design depends on a quote of how big threat to get resisted – the ‘design threat.’ The force from the explosion that may be expected is directly related to the weight- and volume-carrying capabilities from the delivery vehicle. Explosives are measured in relation 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 about how much explosive power may 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.
There are 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 frequently created 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 as purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards created to control impact are usually a part of concrete several feet deep, if site conditions permit. Engineering from the mounting depends on design threat, soil conditions as well as 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 is not really desirable or possible (e.g. an urban location with a basement or subway beneath the pavement), stainless steel pipe bollards made out of shallow-depth installation systems are for sale to both individual posts and groups of bollards. Generally speaking, the shallower the mounting, the broader it ought to 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 may be manually lifted out from the mount to enable access. This etxxdy is meant for locations in which the change of access is occasionally needed. It could include a locking mechanism, either exposed or concealed, to stop unauthorized removal. Both plain and decorative bollards are available for this sort of application. Most removable bollards are certainly not designed for high-impact resistance and are usually not utilized in anti-ram applications.
Retractable bollards telescope down below pavement level, and may 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 so the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the need for defining space, one of the basic tasks of the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to many different functions. All the different available options is vast when it comes to both visual style and gratification properties. For security applications, a design professional with security expertise needs to be within the planning team.