There are three basic varieties 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 usually created with their very own mounting systems. Standalone mountings can 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 control impact are generally baked into 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 over a wider area. For sites where deep excavation will not be desirable or possible (e.g. an urban location having a basement or subway beneath the pavement), bollards created using shallow-depth installation systems are available for both individual posts and groups 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, while the sleeve’s top is flush with the pavement. The mating bollard may be manually lifted from the mount to enable access. This technique is supposed for locations where change of access is occasionally needed. It can add a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are available for this kind of application. Most removable bollards are not created for high-impact resistance and 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 relieve and speed deployment. Automatic systems may be electric or hydraulic and often incorporate a dedicated backup power installation therefore the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous since they are overlooked. They talk to the necessity for defining space, among the basic tasks of the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to many different functions. The plethora of available options is vast in terms of both visual style and performance properties. For security applications, a design professional with security expertise ought to be included in the planning team.
According to Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment in the surrounding site is required. “Street and site architecture determines the highest possible approach speed,” he stated. “If there are no strategies to your building having a long haul-up, an attack vehicle cannot develop high-speed, and the resistance of the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is often measured employing a standard designed by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each refer to the ability to stop a truck of a specific weight and speed preventing penetration from the payload 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 also 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 Websites. The truck impacts 2 or 3 bollards at high-speed, and the front in the vehicle often crumples, wrapping completely round the centermost post. Portion of the cab may fly off the truck, the front side or rear end could rise several feet within the air, and front or rear axles might detach. The bollards and their footings are often lifted several feet upward. In every successful tests, the payload on the back from the truck does not pauxnp more than 1 meter past the line 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 even with a 102-mm (4-in.) pipe, depending on the engineering of the foundation. It is usually filled with concrete to boost stiffness, although unfilled pipe with plate stiffeners inside could possibly produce better resistance within the same diameter pipe. Without any type of internal stiffening, the pipe’s wall-thickness must 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.