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 purposes. Anti-ram installations include not just posts, but other objects designed to resist impact without presenting the look of a protective barrier, such as large planters or benches that steel security bollards. Once the design threat is established 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.
In accordance with Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment in the surrounding site is required. “Street and site architecture will determine the utmost possible approach speed,” he explained. “If there are no approaches to the property using a long term-up, an attack vehicle cannot build-up high speed, and the resistance in the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is commonly measured utilizing a standard designed by the Department of State, known as the K-rating. K-4, K-8 and K-12 each refer to the cabability to stop a truck of the specific weight and speed and stop penetration from 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 also on the way it 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 two or three bollards at high-speed, as well as the front of the vehicle often crumples, wrapping completely across the centermost post. Part of the cab may fly off 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 in the truck fails to penetrate more than 1 meter beyond the type of bollards, thus satisfying the typical.
The easiest 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 despite a 102-mm (4-in.) pipe, depending on the engineering of the foundation. It is often loaded with concrete to boost 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 needs to be significantly greater. For fixed-type security bollards, simple pipe bollards could be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.
The biggest drawback to a plain pipe is aesthetics. Some painted pipe will not truly blend into – a lot 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 designed with alternative mounting ability to slip over standard pipe sizes, forming a stylish and architecturally appropriate impact-resistance system. These decorative covers can be accessible to enhance specially engineered (but non-decorative) pipe-type bollards.
Security Design Concepts
A lot of modern security design focuses on the threat of bomb attacks. The most significant element in protecting against explosions will be the distance between the detonation and the target. The force from the blast shockwave diminishes being a function of the square from the distance. The better distance which can be placed involving the detonation and the protected structure – referred to as standoff distance – the higher the threat resistance or, conversely, the less blast resistance must be that are part of the structure. Therefore, creation of secure perimeter is the initial step within the overall form of blast resistance.
Standoff is valuable architecturally since it allows a building to become protected with out to look like a bunker. It also has economic impact, as it is frequently cheaper to create standoff than to bomb-proof the dwelling itself. Security bollards and similar anti-ram installations are created and positioned to create standoff by thwarting the delivery of explosives near the target with a vehicle.
Any security design depends upon an estimate of how big threat to become resisted – the ‘design threat.’ The force from the explosion which can be expected is directly associated with the body weight- and volume-carrying capabilities of the delivery vehicle. Explosives are measured in relation to tonnes of trinitrotoluene (TNT). Probably the most potent molecular explosives such, as Composition 4 (i.e. C-4), are approximately another 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 may be delivered with a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. according to the 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 installed in new foundations. Manufactured bollards are frequently 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 for purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards made to protect against impact are usually embedded in 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 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 with a basement or subway underneath the pavement), stainless bollard made with 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 has 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 from the mount to allow access. This etxxdy is meant for locations in which the change of access is occasionally needed. It may include a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are accessible for this kind of application. Most removable bollards are not created for high-impact resistance and they are usually not 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 ease and speed deployment. Automatic systems might be electric or hydraulic and often add a dedicated backup power installation therefore the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous as they are overlooked. They speak with 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 number of functions. The plethora of available choices is vast in terms of both visual style and gratification properties. For security applications, a design professional with security expertise needs to be contained in the planning team.