Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and also the September 11, 2001, attacks saw a sharp rise in the installation of bollards for security reasons. Anti-ram installations include not only posts, but other objects created to resist impact without presenting the look of a protective barrier, such as large planters or benches that steel security bollards. Once the design threat is established 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 as well as the speed of an approaching attack vehicle, with the latter being considered the more significant.
In accordance with Weidlinger Associates principal, Peter DiMaggio – a professional in security design – careful assessment of the surrounding site is required. “Street and site architecture determines the maximum possible approach speed,” he said. “If you can find no methods to the building using a long term-up, an attack vehicle cannot build-up high speed, as well as the resistance in the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is often measured utilizing a standard designed by the Department of State, called the K-rating. K-4, K-8 and K-12 each reference the opportunity to stop a truck of any specific weight and speed preventing penetration from the payload greater than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not just on the size and strength of the bollard itself, but in addition on the way it is anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on a number of manufacturer’s Websites. The truck impacts several bollards at high speed, and also the front in the vehicle often crumples, wrapping completely across the centermost post. Portion of the cab may disappear the truck, the front or rear end could rise several feet inside 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 of the truck does not penetrate greater than 1 meter past the line of bollards, thus satisfying the typical.
The most basic 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 usually filled with concrete to improve stiffness, although unfilled pipe with plate stiffeners inside could possibly produce better resistance inside the same diameter pipe. Without any type 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 can also be specially manufactured.
The greatest disadvantage of a plain pipe is aesthetics. A piece of painted pipe does not truly blend into – significantly less enhance – most architectural schemes. However, this is often overcome by way of a decorative bollard cover. Many standalone bollards that do not have impact-resistance of their very own are made with alternative mounting ability to slip over standard pipe sizes, forming a stylish and architecturally appropriate impact-resistance system. These decorative covers can be offered to enhance specifically created (but non-decorative) pipe-type bollards.
Security Design Concepts
Most of modern security design focuses on the threat of bomb attacks. The most important factor in protecting against explosions is definitely the distance involving the detonation as well as the target. The force from the blast shockwave diminishes as a purpose of the square of the distance. The more distance which can be placed in between the detonation and also the protected structure – known as standoff distance – the greater the threat resistance or, conversely, the less blast resistance needs to be that are part of the structure. Therefore, creation of secure perimeter is step one in the overall design of blast resistance.
Standoff is valuable architecturally because it allows a building to become protected without needing to resemble a bunker. Additionally, it has economic impact, because it is frequently less expensive to generate standoff rather than to bomb-proof the structure itself. Security bollards and similar anti-ram installations are designed and positioned to generate standoff by thwarting the delivery of explosives near the target by way of a vehicle.
Any security design is dependent upon a quote of how big threat to get resisted – the ‘design threat.’ The force of the explosion that may be expected is directly associated with the load- and volume-carrying capabilities in the delivery vehicle. Explosives are measured in terms of 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 – like was used in Oklahoma City – is considerably less powerful than TNT. Reasonable approximations can be produced regarding how much explosive power may be delivered by a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based on the weight-and volume-carrying capacity.
You can find three basic types of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards may be mounted into existing concrete, or placed in new foundations. Manufactured bollards are frequently designed with their particular mounting systems. Standalone mountings may 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 protect against impact are often a part of concrete several feet deep, if site conditions permit. Engineering of 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 spanning 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), pipe bollard covers made with shallow-depth installation systems are for sale to both individual posts and sets of bollards. Generally, the shallower the mounting, the broader it should 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 using the pavement. The mating bollard may be manually lifted from the mount to permit access. This etxxdy is meant for locations in which the change of access is occasionally needed. It may incorporate a locking mechanism, either exposed or concealed, to prevent unauthorized removal. Both plain and decorative bollards are accessible for this kind of application. Most removable bollards are certainly not created 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 could be electric or hydraulic and quite often incorporate a dedicated backup power installation so the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous since they are overlooked. They speak to the need for defining space, one of the basic tasks from the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to a variety of functions. The plethora 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.