There are three basic kinds 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 often created with their 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 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 of 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 spanning a wider area. For sites where deep excavation will not be desirable or possible (e.g. an urban location with a basement or subway underneath the pavement), bollards made with shallow-depth installation systems are accessible for both individual posts and sets of bollards. In general, the shallower the mounting, the broader it ought to be to resist impact loading.
A removable bollard typically has a permanently installed mount or sleeve below grade, whilst the sleeve’s top is flush with the pavement. The mating bollard can be manually lifted out from the mount to permit access. This method is supposed for locations in which the change of access is occasionally needed. It can incorporate a locking mechanism, either exposed or concealed, to stop unauthorized removal. Both plain and decorative bollards are accessible for this kind of application. Most removable bollards usually are not intended for high-impact resistance and they are not often utilized 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 quite often include a dedicated backup power installation therefore the bollard remains functional during emergencies. Retractable systems tend to be unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the need for defining space, among the basic tasks in the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to a variety of functions. All the different options is vast in terms of both visual style and satisfaction properties. For security applications, a design professional with security expertise ought to be within the planning team.
According to Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment from the surrounding website is required. “Street and site architecture determines the utmost possible approach speed,” he said. “If you will find no strategies to your building with a long run-up, an attack vehicle cannot build-up high speed, and the resistance in the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is commonly measured utilizing a standard designed by the Department of State, called the K-rating. K-4, K-8 and K-12 each reference the opportunity to stop a truck of the specific weight and speed and prevent penetration from the payload more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not only on the size and strength from 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 numerous manufacturer’s Web sites. The truck impacts several bollards at high-speed, and the front from the vehicle often crumples, wrapping completely round the centermost post. Portion of the cab may disappear the truck, the front side or rear end could rise several feet within 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 from the truck fails to pauxnp more than 1 meter past the line of bollards, thus satisfying the standard.
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 the foundation. It is often full of concrete to boost stiffness, although unfilled pipe with plate stiffeners inside might actually produce better resistance inside 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 might be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.