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 created to resist impact without presenting the look of a protective barrier, including large planters or benches that safety bollards for sale. Once the design threat is determined 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 as well as the speed of an approaching attack vehicle, with the latter being regarded the more significant.
In accordance with Weidlinger Associates principal, Peter DiMaggio – an expert in security design – careful assessment from the surrounding website is required. “Street and site architecture will determine the highest possible approach speed,” he said. “If there are no methods to the property having a long haul-up, an attack vehicle cannot build-up high-speed, and the resistance from the anti-ram barriers may be adjusted accordingly.”
Anti-ram resistance is commonly measured utilizing a standard designed by the Department of State, referred to as 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 of the payload more than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not only 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 a number of manufacturer’s Internet sites. The truck impacts 2 or 3 bollards at high-speed, and the front from the vehicle often crumples, wrapping completely around the centermost post. Area of the cab may fly off the truck, the top or rear end could rise several feet within the air, and front or rear axles might detach. The bollards along with their footings are sometimes lifted several feet upward. In most successful tests, the payload on the back from the truck does not penetrate a lot more than 1 meter past the collection of bollards, thus satisfying the conventional.
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 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 might actually produce better resistance inside the same diameter pipe. Without any kind of internal stiffening, the pipe’s wall-thickness must be significantly greater. For fixed-type security bollards, simple pipe bollards could be functionally sufficient, if properly mounted. Undecorated pipe-type bollards are also specially manufactured.
The largest drawback to a plain pipe is aesthetics. A bit of painted pipe will 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 which do not have impact-resistance of their own are made with alternative mounting ability to slip over standard pipe sizes, forming an attractive 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
A lot 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 and also the target. The force in the blast shockwave diminishes being a function of the square of the distance. The better distance that may be placed involving the detonation as well as the protected structure – called standoff distance – the higher the threat resistance or, conversely, the less blast resistance must be included in the structure. Therefore, introduction of secure perimeter is the first step in the overall style of blast resistance.
Standoff is valuable architecturally as it allows a building to become protected without having to resemble a bunker. Additionally, it has economic impact, because it is frequently less expensive to create standoff rather than bomb-proof the structure itself. Security bollards and similar anti-ram installations are created and positioned to generate standoff by thwarting the delivery of explosives close to the target by way of a vehicle.
Any security design depends on an estimate of how big threat to be resisted – the ‘design threat.’ The force of the explosion which can be expected is directly associated with the weight- and volume-carrying capabilities from 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 one third more robust than TNT, whereas a fuel and fertilizer bomb – like was used in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be produced about how exactly 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 will find three basic varieties of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards can be mounted into existing concrete, or set up in new foundations. Manufactured bollards are frequently designed with their very 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 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 and other site-specific factors. Strip footings that mount several bollards have better resistance, spreading the impact load more than 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), stainless steel bollard sleeves created using shallow-depth installation systems are available for both individual posts and teams 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, as the sleeve’s top is flush with the pavement. The mating bollard may be manually lifted out from the mount to allow access. This etxxdy is intended for locations in which the change of access is occasionally needed. It can include a locking mechanism, either exposed or concealed, to stop unauthorized removal. Both plain and decorative bollards are accessible for this sort of application. Most removable bollards usually are not designed for high-impact resistance and they 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 ease and speed deployment. Automatic systems could be electric or hydraulic and often include a dedicated backup power installation so the bollard remains functional during emergencies. Retractable systems tend to be unornamented.
Bollards are as ubiquitous as they are overlooked. They talk to the requirement for defining space, one of many basic tasks of the built environment. Decorative bollards and bollard covers give you a versatile solution for bringing pleasing form to many different functions. The plethora of available choices is vast with regards to both visual style and satisfaction properties. For security applications, a design professional with security expertise needs to be within the planning team.