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 usually made 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 made to control impact are often embedded in concrete several feet deep, if site conditions permit. Engineering in the mounting depends on design threat, soil conditions as well as 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 desirable or possible (e.g. an urban location using a basement or subway beneath the pavement), bollards created using shallow-depth installation systems are available for both individual posts and teams of bollards. Generally speaking, the shallower the mounting, the broader it ought to be to face up to impact loading.
A removable bollard typically has a permanently installed mount or sleeve below grade, as the sleeve’s top is flush with all the pavement. The mating bollard may be manually lifted out of the mount to allow access. This method is intended for locations in which the change of access is occasionally needed. It may incorporate a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are available for this sort of application. Most removable bollards are not intended for high-impact resistance and are usually not found 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 help ease and speed deployment. Automatic systems may be electric or hydraulic and quite often incorporate a dedicated backup power installation therefore the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the necessity for defining space, among the basic tasks from the built environment. Decorative bollards and bollard covers give you a versatile solution for bringing pleasing form to many different functions. The range of available choices is vast with regards to 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 – an expert in security design – careful assessment of the surrounding website is required. “Street and site architecture will determine the maximum possible approach speed,” he stated. “If you can find no approaches to your building using a long term-up, an attack vehicle cannot develop high speed, as well as the resistance of the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is normally measured utilizing a standard designed by the Department of State, known as the K-rating. K-4, K-8 and K-12 each reference the ability 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 in 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 several manufacturer’s Internet sites. The truck impacts several bollards at high speed, and also the front in the vehicle often crumples, wrapping completely round the centermost post. Portion of the cab may disappear the truck, the front 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 will not pauxnp greater than 1 meter past the line of bollards, thus satisfying the conventional.
The easiest 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 its foundation. It is often loaded with concrete to increase stiffness, although unfilled pipe with plate stiffeners inside could possibly produce better resistance in the same diameter pipe. Without any kind of internal stiffening, the pipe’s wall-thickness must be significantly greater. For fixed-type security bollards, simple pipe bollards might be functionally sufficient, if properly mounted. Undecorated pipe-type bollards can also be specially manufactured.