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 purposes. Anti-ram installations include not only posts, but other objects made to resist impact without presenting the appearance of a protective barrier, including large planters or benches that steel bollards for sale. 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 and the speed of an approaching attack vehicle, with the latter being regarded the more significant.
In accordance with 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 utmost possible approach speed,” he said. “If you will find no approaches to the property having a long run-up, an attack vehicle cannot build up high-speed, as well as the resistance from the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is normally measured employing a standard designed by the Department of State, called the K-rating. K-4, K-8 and K-12 each reference the ability to stop a truck of a specific weight and speed and stop penetration from the payload more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not merely on the size and strength from the bollard itself, but additionally on the way it is actually anchored and the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Web sites. The truck impacts 2 or 3 bollards at high speed, and the front in the vehicle often crumples, wrapping completely across the centermost post. Area of the cab may fly off the truck, the front or rear end could rise several feet inside 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 in the truck will not penetrate more than 1 meter beyond the type 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 despite having a 102-mm (4-in.) pipe, depending on the engineering of their foundation. It is often loaded with concrete to increase stiffness, although unfilled pipe with plate stiffeners inside might actually produce better resistance in the same diameter pipe. Without any form of internal stiffening, the pipe’s wall-thickness has to be significantly greater. For fixed-type security bollards, simple pipe bollards may be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.
The biggest drawback to a plain pipe is aesthetics. A bit of painted pipe does not truly blend into – much less enhance – most architectural schemes. However, this can be overcome with a decorative bollard cover. Many standalone bollards that 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
Much of modern security design focuses on the threat of bomb attacks. The most important factor in protecting against explosions is the distance involving the detonation as well as the target. The force in the blast shockwave diminishes being a function of the square of the distance. The more distance that may be placed between the detonation and also the protected structure – called standoff distance – the greater the threat resistance or, conversely, the less blast resistance has to be included in the dwelling. Therefore, creation of secure perimeter is step one inside the overall style of blast resistance.
Standoff is valuable architecturally because it allows a building to get protected with out to resemble a bunker. In addition, it has economic impact, because it is frequently less costly to create standoff rather than bomb-proof the dwelling itself. Security bollards and similar anti-ram installations are created and positioned to produce standoff by thwarting the delivery of explosives near the target with a vehicle.
Any security design depends on a quote of the dimensions of threat to be 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 in relation to tonnes of trinitrotoluene (TNT). By far 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 – like was utilized in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be produced about how much explosive power could be delivered by a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based on the weight-and volume-carrying capacity.
You will find three basic kinds 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 usually created with their own mounting systems. Standalone mountings may 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 designed to protect against impact are often a part of concrete several feet deep, if site conditions permit. Engineering from the mounting is dependent upon design threat, soil conditions along with 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 is not really desirable or possible (e.g. an urban location having a basement or subway under the pavement), stainless bollards created using shallow-depth installation systems are for sale to both individual posts and groups of bollards. Generally, the shallower the mounting, the broader it must 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 with all the pavement. The mating bollard may be manually lifted out of the mount to permit access. This etxxdy is supposed for locations in which the change of access is occasionally needed. It may add a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are accessible for this type of application. Most removable bollards are certainly not intended for high-impact resistance and are usually not utilized 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 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 requirement for defining space, among the basic tasks of the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to a number of functions. All the different options is vast in terms of both visual style and gratification properties. For security applications, a design professional with security expertise should be included in the planning team.