Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and the September 11, 2001, attacks saw a sharp surge in the installation of bollards for security reasons. Anti-ram installations include not just posts, but other objects made to resist impact without presenting the appearance of a protective barrier, such as large planters or benches that steel bollard pricing. Once the design threat is established the resistance required to stop it can 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 considered the more significant.
Based on Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment of the surrounding website is required. “Street and site architecture will determine the maximum possible approach speed,” he said. “If you can find no approaches to your building using a long haul-up, an attack vehicle cannot build up high speed, and the resistance of the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is normally measured using a standard developed by the Department of State, called the K-rating. K-4, K-8 and K-12 each refer to the cabability to stop a truck of any specific weight and speed and prevent penetration in the payload more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not just on the size and strength from the bollard itself, but in addition on the way it is anchored and the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Internet sites. The truck impacts 2 or 3 bollards at high speed, and the front of the vehicle often crumples, wrapping completely around the centermost post. Portion of the cab may disappear the truck, the front or rear end could rise several feet in the air, and front or rear axles might detach. The bollards and their footings are sometimes lifted several feet upward. In all successful tests, the payload on the back from the truck does not penetrate a lot more than 1 meter beyond the line of bollards, thus satisfying the typical.
The easiest 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 a 102-mm (4-in.) pipe, depending on the engineering of its foundation. It is often full of concrete to boost stiffness, although unfilled pipe with plate stiffeners inside might actually produce better resistance in the same diameter pipe. Without any type of internal stiffening, the pipe’s wall-thickness must be significantly greater. For fixed-type security bollards, simple pipe bollards may be functionally sufficient, if properly mounted. Undecorated pipe-type bollards will also be specially manufactured.
The biggest drawback to a plain pipe is aesthetics. A piece of painted pipe does not truly blend into – significantly less enhance – most architectural schemes. However, this can be overcome by a decorative bollard cover. Many standalone bollards which do not have impact-resistance of their own are designed with alternative mounting capability to slip over standard pipe sizes, forming a beautiful and architecturally appropriate impact-resistance system. These decorative covers can be available to enhance specially engineered (but non-decorative) pipe-type bollards.
Security Design Concepts
A lot of modern security design focuses on the threat of bomb attacks. The most significant element in protecting against explosions will be the distance involving the detonation as well as the target. The force of the blast shockwave diminishes being a purpose of the square in the distance. The more distance that can be placed in between the detonation and also the protected structure – referred to as standoff distance – the higher the threat resistance or, conversely, the less blast resistance has to be included in the dwelling. Therefore, introduction of secure perimeter is the first step within the overall form of blast resistance.
Standoff is valuable architecturally because it allows a building to get protected without having to look like a bunker. It also has economic impact, because it is frequently less costly to create standoff rather than to bomb-proof the dwelling itself. Security bollards and other anti-ram installations are created and positioned to create standoff by thwarting the delivery of explosives near the target by way of a vehicle.
Any security design depends upon a bid of the dimensions of threat to get resisted – the ‘design threat.’ The force in the explosion that can be expected is directly associated with the weight- and volume-carrying capabilities from the delivery vehicle. Explosives are measured in relation 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 powerful than TNT, whereas a fuel and fertilizer bomb – including was applied in Oklahoma City – is considerably less powerful than TNT. Reasonable approximations can be created regarding how much explosive power could be delivered by a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based upon the weight-and volume-carrying capacity.
You will find three basic varieties 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 often 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 created to protect against impact are generally a part of concrete several feet deep, if site conditions permit. Engineering in the mounting depends upon design threat, soil conditions and other site-specific factors. Strip footings that mount several bollards have better resistance, spreading the impact load over a wider area. For sites where deep excavation will not be desirable or possible (e.g. an urban location having a basement or subway underneath the pavement), stainless bollards made out of shallow-depth installation systems are available for both individual posts and teams of bollards. Generally speaking, the shallower the mounting, the broader it must be to resist impact loading.
A removable bollard typically features 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 from the mount to enable access. This etxxdy is meant 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 created for high-impact resistance and they are usually not used 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 may be electric or hydraulic and often incorporate a dedicated backup power installation therefore the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous as they are overlooked. They speak with the necessity for defining space, one of many basic tasks of the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to a variety of functions. The plethora of options is vast when it comes to both visual style and performance properties. For security applications, a design professional with security expertise should be within the planning team.