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 set up in new foundations. Manufactured bollards are frequently made 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 made to control impact are often a part of concrete several feet deep, if site conditions permit. Engineering in the mounting depends on 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 is not desirable or possible (e.g. an urban location using a basement or subway underneath the pavement), bollards created using 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 face up to impact loading.
A removable bollard typically includes a permanently installed mount or sleeve below grade, while the sleeve’s top is flush with all the pavement. The mating bollard can be manually lifted out from the mount to allow access. This system is supposed for locations where 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 sort of application. Most removable bollards are certainly not created for high-impact resistance and are not often 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 relieve and speed deployment. Automatic systems may be electric or hydraulic and often incorporate 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 requirement for defining space, among the basic tasks of the built environment. Decorative bollards and bollard covers give you a versatile solution for bringing pleasing form to many different functions. All the different available options is vast when it comes to both visual style and performance properties. For security applications, a design professional with security expertise should be contained in the planning team.
In accordance with Weidlinger Associates principal, Peter DiMaggio – an expert in security design – careful assessment from the surrounding site is required. “Street and site architecture will determine the highest possible approach speed,” he stated. “If you will find no methods to the property with a long haul-up, an attack vehicle cannot build up high speed, and the resistance in the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is often measured using a standard designed by the Department of State, called the K-rating. K-4, K-8 and K-12 each reference the cabability to stop a truck of a specific weight and speed and stop penetration in the payload more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not merely on the size and strength of the bollard itself, but additionally on the way it is actually anchored as well as the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Internet sites. The truck impacts 2 or 3 bollards at high speed, and also the front of the vehicle often crumples, wrapping completely around the centermost post. Part of the cab may fly off the truck, the top or rear end could rise several feet in the air, and front or rear axles might detach. The bollards as well as their footings are sometimes lifted several feet upward. In most successful tests, the payload on the back of the truck fails to pauxnp more than 1 meter beyond the line of bollards, thus satisfying the conventional.
The most basic 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 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 kind of internal stiffening, the pipe’s wall-thickness needs to be significantly greater. For fixed-type security bollards, simple pipe bollards may be functionally sufficient, if properly mounted. Undecorated pipe-type bollards can also be specially manufactured.