Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing as well as the September 11, 2001, attacks saw a sharp increase in the installation of bollards for security purposes. Anti-ram installations include not just posts, but other objects designed to resist impact without presenting the appearance of a protective barrier, including large planters or benches that bollard post. Once the design threat is determined the resistance needed to stop it may be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes under consideration both the mass and the speed of an approaching attack vehicle, with the latter being regarded the more significant.
Based on Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment in the surrounding site is required. “Street and site architecture determines the utmost possible approach speed,” he stated. “If there are no methods to the building with a long run-up, an attack vehicle cannot build up high speed, and the resistance from the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is commonly measured using a standard designed by the Department of State, called 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 of the payload a lot more than 1 m (3 ft) past the anti-ram barrier. Resistance depends not merely on the size and strength from the bollard itself, but also on the way it really is anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Internet sites. The truck impacts several bollards at high-speed, as well as the front of the vehicle often crumples, wrapping completely around the centermost post. Area of the cab may fly off the truck, the front side 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 every successful tests, the payload on the back from the truck fails to penetrate a lot 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 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 has to be significantly greater. For fixed-type security bollards, simple pipe bollards may be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.
The largest disadvantage of a plain pipe is aesthetics. Some painted pipe fails to truly blend into – a lot less enhance – most architectural schemes. However, this could be overcome by a decorative bollard cover. Many standalone bollards which do not have impact-resistance of their own are made with alternative mounting ability to slip over standard pipe sizes, forming a beautiful and architecturally appropriate impact-resistance system. These decorative covers can be accessible to enhance specially engineered (but non-decorative) pipe-type bollards.
Security Design Concepts
Much of modern security design focuses on the threat of bomb attacks. The most important aspect in protecting against explosions is the distance involving the detonation as well as the target. The force of the blast shockwave diminishes as being a function of the square from the distance. The greater distance which can be placed in between the detonation as well as the protected structure – known as standoff distance – the greater the threat resistance or, conversely, the less blast resistance needs to be included in the dwelling. Therefore, creation of secure perimeter is step one in the overall design of blast resistance.
Standoff is valuable architecturally as it allows a building to become protected without needing to resemble a bunker. In addition, it has economic impact, since it is frequently less costly to produce standoff rather than bomb-proof the dwelling itself. Security bollards and similar anti-ram installations are made and positioned to produce standoff by thwarting the delivery of explosives near the target by way of a vehicle.
Any security design depends on an estimate of the size of threat to get resisted – the ‘design threat.’ The force from the explosion that can be expected is directly related to the body weight- and volume-carrying capabilities of the delivery vehicle. Explosives are measured with regards to tonnes of trinitrotoluene (TNT). By far the most potent molecular explosives such, as Composition 4 (i.e. C-4), are approximately a third more robust than TNT, whereas a fuel and fertilizer bomb – like was utilized in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be made regarding how much explosive power could be delivered by way of a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based upon the weight-and volume-carrying capacity.
You can find three basic kinds of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards could be mounted into existing concrete, or placed in new foundations. Manufactured bollards are usually created with their own mounting systems. Standalone mountings could 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 made to control impact are usually embedded in concrete several feet deep, if site conditions permit. Engineering in the mounting depends on design threat, soil conditions and 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), stainless steel bollard sleeves made out of shallow-depth installation systems are for sale to both individual posts and teams of bollards. Generally, the shallower the mounting, the broader it must be to resist impact loading.
A removable bollard typically includes a permanently installed mount or sleeve below grade, whilst the sleeve’s top is flush with the pavement. The mating bollard may be manually lifted out from the mount to permit access. This etxxdy is intended 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 usually are not designed for high-impact resistance and are usually not used 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 quite often incorporate a dedicated backup power installation so the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous as they are overlooked. They speak to the need for defining space, among the basic tasks of the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to a number of functions. All the different options is vast in terms of both visual style and gratification properties. For security applications, a design professional with security expertise needs to be contained in the planning team.