There are 3 basic types 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 frequently designed 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 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 in 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 more than a wider area. For sites where deep excavation is not desirable or possible (e.g. an urban location having a basement or subway underneath the pavement), bollards made with shallow-depth installation systems are available for both individual posts and sets of bollards. Generally, 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 all the pavement. The mating bollard could be manually lifted from the mount to enable access. This method is supposed for locations where 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 type of application. Most removable bollards are not designed for high-impact resistance and therefore are not often found 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 relieve and speed deployment. Automatic systems could be electric or hydraulic and often include a dedicated backup power installation so the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous because they are overlooked. They speak to the need for defining space, one of the 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 gratification properties. For security applications, a design professional with security expertise ought to be contained in the planning team.
In accordance with Weidlinger Associates principal, Peter DiMaggio – a specialist 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 methods to your building having a long term-up, an attack vehicle cannot build-up high speed, and also the resistance in the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is normally measured using a standard created by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each make reference to the opportunity to stop a truck of a specific weight and speed and stop penetration from the payload greater than 1 m (3 ft) past the anti-ram barrier. Resistance depends not just on the size and strength from the bollard itself, but additionally 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 Web sites. The truck impacts several bollards at high-speed, and the front from 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 inside the air, and front or rear axles might detach. The bollards and their footings are often lifted several feet upward. In most successful tests, the payload on the back from the truck will not pauxnp more than 1 meter beyond the type of bollards, thus satisfying the typical.
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 despite a 102-mm (4-in.) pipe, depending on the engineering of its foundation. It is often filled with concrete to improve 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 needs to be significantly greater. For fixed-type security bollards, simple pipe bollards could be functionally sufficient, if properly mounted. Undecorated pipe-type bollards will also be specially manufactured.