Security Bollards and Post Covers
The aftermaths of the 1995 Oklahoma City bombing as well as 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 designed to resist impact without presenting the appearance of a protective barrier, like large planters or benches that metal safety bollards. 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 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 specialist in security design – careful assessment in the surrounding website is required. “Street and site architecture will determine the utmost possible approach speed,” he explained. “If you will find no approaches to the building having a long haul-up, an attack vehicle cannot build up high-speed, and also the resistance of the anti-ram barriers could be adjusted accordingly.”
Anti-ram resistance is often measured utilizing a standard created by the Department of State, referred to as K-rating. K-4, K-8 and K-12 each make reference to the opportunity to stop a truck of a specific weight and speed and prevent penetration in the payload greater than 1 m (3 ft) beyond the anti-ram barrier. Resistance depends not just on the size and strength in the bollard itself, but also on the way it is actually 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 from the vehicle often crumples, wrapping completely around the centermost post. Portion of the cab may fly off 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 often lifted several feet upward. In most successful tests, the payload on the back of the truck will not penetrate a lot more than 1 meter beyond the line of bollards, thus satisfying the standard.
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 even with a 102-mm (4-in.) pipe, depending on the engineering of their foundation. It is often filled with concrete to boost stiffness, although unfilled pipe with plate stiffeners inside may actually produce better resistance within the same diameter pipe. Without any type of internal stiffening, the pipe’s wall-thickness needs to be significantly greater. For fixed-type security bollards, simple pipe bollards might 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 will not truly blend into – a lot less enhance – most architectural schemes. However, this is often overcome with a decorative bollard cover. Many standalone bollards which do not have impact-resistance that belongs to them are made with alternative mounting capacity to slip over standard pipe sizes, forming a stylish and architecturally appropriate impact-resistance system. These decorative covers can be available to enhance specially designed (but non-decorative) pipe-type bollards.
Security Design Concepts
Most of modern security design focuses on the threat of bomb attacks. The most significant factor in protecting against explosions is the distance in between the detonation as well as the target. The force from the blast shockwave diminishes as a purpose of the square from the distance. The greater distance that may be placed between the detonation and also the protected structure – known as standoff distance – the higher the threat resistance or, conversely, the less blast resistance needs to be that are part of the structure. Therefore, development of secure perimeter is the initial step in the overall design of blast resistance.
Standoff is valuable architecturally because it allows a building to get protected with out to resemble a bunker. Additionally, it has economic impact, as it is frequently cheaper to generate standoff rather than bomb-proof the structure itself. Security bollards and other anti-ram installations are made and positioned to create standoff by thwarting the delivery of explosives close to the target by a vehicle.
Any security design depends upon a bid of the dimensions of threat to be resisted – the ‘design threat.’ The force in the explosion that may be expected is directly linked to the weight- and volume-carrying capabilities from the delivery vehicle. Explosives are measured in terms of tonnes of trinitrotoluene (TNT). The most potent molecular explosives such, as Composition 4 (i.e. C-4), are approximately another stronger than TNT, whereas a fuel and fertilizer bomb – like was utilized in Oklahoma City – is much less powerful than TNT. Reasonable approximations can be created about how exactly much explosive power may be delivered with a person carrying a backpack, a passenger vehicle, a pickup truck, a flatbed truck, etc. based on its weight-and volume-carrying capacity.
You will find three basic varieties of bollard mountings: fixed, removable, and operable (retractable or fold-down). Fixed bollards may be mounted into existing concrete, or set up in new foundations. Manufactured bollards are usually made 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 designed to control impact are generally a part of concrete several feet deep, if site conditions permit. Engineering of 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 desirable or possible (e.g. an urban location having a basement or subway beneath the pavement), stainless bollard created using shallow-depth installation systems are available for both individual posts and sets of bollards. Generally speaking, the shallower the mounting, the broader it ought to be to resist 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 may be manually lifted out from the mount to permit access. This etxxdy is supposed for locations in which the change of access is occasionally needed. It can incorporate a locking mechanism, either exposed or concealed, to avoid unauthorized removal. Both plain and decorative bollards are available for this kind of application. Most removable bollards are certainly not created 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 help ease and speed deployment. Automatic systems might be electric or hydraulic and often add a dedicated backup power installation so the bollard remains functional during emergencies. Retractable systems are generally unornamented.
Bollards are as ubiquitous because they are overlooked. They talk to the necessity for defining space, one of the basic tasks from the built environment. Decorative bollards and bollard covers offer a versatile solution for bringing pleasing form to many different functions. All the different options is vast when it comes to both visual style and gratification properties. For security applications, a design professional with security expertise should be contained in the planning team.