Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing and also the September 11, 2001, attacks saw a sharp surge in the installation of bollards for security needs. Anti-ram installations include not just posts, but other objects created to resist impact without presenting the appearance of a protective barrier, such as large planters or benches that removable bollards for sale. Once the design threat is established the resistance required to stop it may be calculated. (See ‘Security Design Concepts’ – below). Specification of anti-ram perimeter takes into account both the mass and the speed of an approaching attack vehicle, with the latter being regarded the more significant.
According to Weidlinger Associates principal, Peter DiMaggio – an expert in security design – careful assessment of the surrounding site is required. “Street and site architecture will determine the highest possible approach speed,” he said. “If you can find no methods to the property having a long run-up, an attack vehicle cannot develop high-speed, and also the resistance from the anti-ram barriers can be adjusted accordingly.”
Anti-ram resistance is commonly measured using a standard developed 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 prevent penetration from the payload a lot more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not merely on the size and strength in the bollard itself, but additionally on the way it is anchored and also the substrate it’s anchored into.
Videos of bollard crash tests are featured on numerous manufacturer’s Web sites. The truck impacts several bollards at high speed, and the front from the vehicle often crumples, wrapping completely across the centermost post. Portion of the cab may fly off 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 often lifted several feet upward. In most successful tests, the payload on the back from the truck does not penetrate more than 1 meter beyond the line of bollards, thus satisfying the conventional.
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 loaded with concrete to boost 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 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 greatest drawback to a plain pipe is aesthetics. A bit of painted pipe does not truly blend into – a lot 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 very own are designed with alternative mounting capacity to slip over standard pipe sizes, forming an attractive and architecturally appropriate impact-resistance system. These decorative covers can also be offered to enhance specifically created (but non-decorative) pipe-type bollards.
Security Design Concepts
Much of modern security design focuses on the threat of bomb attacks. The most important element in protecting against explosions will be the distance involving the detonation and the target. The force in the blast shockwave diminishes being a function of the square in the distance. The greater distance which can be placed in between the detonation and the protected structure – called standoff distance – the higher the threat resistance or, conversely, the less blast resistance must be built into the structure. Therefore, introduction of secure perimeter is the initial step inside the overall design of blast resistance.
Standoff is valuable architecturally because it allows a building to be protected without needing to resemble a bunker. Additionally, it has economic impact, because it is frequently less costly to generate standoff 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 to the target by a vehicle.
Any security design depends on a bid of how big threat to become resisted – the ‘design threat.’ The force from the explosion which 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). 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 with a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. according to 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 may be mounted into existing concrete, or placed in new foundations. Manufactured bollards are usually designed with their very 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 for purely aesthetic installations and substantial visual deterrence and direction, but provide only minimal impact resistance.
Bollards created to protect against impact are usually a part of concrete several feet deep, if site conditions permit. Engineering in the mounting is dependent 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 with a basement or subway beneath the pavement), stainless steel bollard sleeves made out of shallow-depth installation systems are available for both individual posts and groups of bollards. Generally speaking, the shallower the mounting, the broader it ought to be to face up to impact loading.
A removable bollard typically features a permanently installed mount or sleeve below grade, as the sleeve’s top is flush using the pavement. The mating bollard can be manually lifted out of the mount to enable access. This etxxdy is supposed for locations where change of access is occasionally needed. It may include a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are for sale to this type of application. Most removable bollards usually are not designed for high-impact resistance and are usually not found in anti-ram applications.
Retractable bollards telescope down below pavement level, and might be either manual or automatically operated. Manual systems sometimes have lift-assistance mechanisms to help ease and speed deployment. Automatic systems might be electric or hydraulic and sometimes add a dedicated backup power installation and so the bollard remains functional during emergencies. Retractable systems are usually unornamented.
Bollards are as ubiquitous because they are overlooked. They speak with the necessity for defining space, among the basic tasks in the built environment. Decorative bollards and bollard covers provide a versatile solution for bringing pleasing form to many different functions. The range of available choices is vast with regards to both visual style and performance properties. For security applications, a design professional with security expertise ought to be within the planning team.