There are 3 basic types 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 designed with their particular 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 as purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards designed to control impact are usually embedded in concrete several feet deep, if site conditions permit. Engineering from the mounting depends on design threat, soil conditions along with 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 under the pavement), bollards created using shallow-depth installation systems are accessible for 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 has a permanently installed mount or sleeve below grade, while the sleeve’s top is flush with all the pavement. The mating bollard may be manually lifted out of the mount to enable access. This method is supposed for locations in which the change of access is occasionally needed. It can include a locking mechanism, either exposed or concealed, to prevent unauthorized removal. Both plain and decorative bollards are for sale to this kind of application. Most removable bollards are certainly not designed for high-impact resistance and therefore 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 could 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 since they are overlooked. They speak to the requirement for defining space, one of many basic tasks in the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to a variety of functions. All the different 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 included in the planning team.
According to Weidlinger Associates principal, Peter DiMaggio – a specialist in security design – careful assessment of the surrounding site is required. “Street and site architecture determines the utmost possible approach speed,” he stated. “If you can find no approaches to the building with a long haul-up, an attack vehicle cannot develop high speed, and the resistance in the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is often measured utilizing a standard designed by the Department of State, known as the K-rating. K-4, K-8 and K-12 each make reference to the cabability to stop a truck of the specific weight and speed and stop penetration from the payload a lot more than 1 m (3 ft) beyond 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 the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Websites. The truck impacts several bollards at high-speed, as well as the front in the vehicle often crumples, wrapping completely around the centermost post. Area of the cab may disappear the truck, the top or rear end could rise several feet in the air, and front or rear axles might detach. The bollards and their footings are sometimes lifted several feet upward. In most successful tests, the payload on the back in the truck will not pauxnp a lot more than 1 meter beyond the line of bollards, thus satisfying the conventional.
The easiest 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 increase stiffness, although unfilled pipe with plate stiffeners inside may 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 might be functionally sufficient, if properly mounted. Undecorated pipe-type bollards will also be specially manufactured.