There are 3 basic kinds 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 designed 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 made to protect against impact are usually a part of concrete several feet deep, if site conditions permit. Engineering from the mounting depends 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 will not be desirable or possible (e.g. an urban location using a basement or subway underneath the pavement), bollards made with shallow-depth installation systems are available for 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, while the sleeve’s top is flush with the pavement. The mating bollard may be manually lifted from the mount to enable access. This system is intended for locations where change of access is occasionally needed. It can include a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are for sale to this sort of application. Most removable bollards usually are not designed for high-impact resistance and therefore 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 might be electric or hydraulic and often include a dedicated backup power installation and so the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous as they are overlooked. They speak to the necessity for defining space, one of many basic tasks of the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to a variety of functions. The range of available choices is vast with regards to both visual style and performance properties. For security applications, a design professional with security expertise needs to be included in the planning team.
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 determines the maximum possible approach speed,” he stated. “If you can find no methods to your building having a long term-up, an attack vehicle cannot develop high-speed, and the resistance from the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is normally measured utilizing a standard designed by the Department of State, called the K-rating. K-4, K-8 and K-12 each make reference to the ability to stop a truck of a specific weight and speed and stop penetration of the payload more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not only on the size and strength in the bollard itself, but additionally on the way it is anchored as well as the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Websites. The truck impacts 2 or 3 bollards at high-speed, and the front of the vehicle often crumples, wrapping completely around the centermost post. Part of the cab may disappear the truck, the top or rear end could rise several feet within 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 from the truck will not pauxnp a lot more than 1 meter past the collection of bollards, thus satisfying the conventional.
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 having a 102-mm (4-in.) pipe, depending on the engineering of their foundation. It is often loaded with concrete to boost stiffness, although unfilled pipe with plate stiffeners inside may actually produce better resistance in 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 are also specially manufactured.