The downside to this installation method, when used with a rigid bollard, is that the anchors are generally not strong enough to withstand anything more than a minor collision. The plate anchors often are pulled up and possibly the plate bends, leaving a post which leans and is no longer able to properly serve its purpose. Plate mounted bollards often require constant maintenance and replacement.
The second method for installing bollards involves using a longer steel pipe and burying a portion of it deep in the ground. This method gives the bollard far more strength than surface mounted, however it can be very expensive to install if the surface is concrete and already poured. Installation in this case requires coring a hole in the surface using an expensive diamond bladed coring saw. These machines and their blades are expensive and require water cooling, creating a mess during installation. Once the concrete is cored and the bollard is in place, the hole must be Security bollards backfilled with concrete to secure the bollard. For added strength, these bollards are often filled with concrete, as well. Though the bollard pipe itself is relatively inexpensive, this installation method is costly and time consuming.
Although very strong, there are significant disadvantages to core installations. Most importantly, there is no give to this system upon impact. Though desired in high security applications, any vehicle impacting such a bollard will be significantly damaged and its passengers at risk of injury. Loads carried by fork trucks can also be thrown given the jarring impact likely to occur. Further, the bollard or its foundation can be damaged by such an impact, again leaving a tilted and less effective barrier requiring costly maintenance to correct. Often the steel bollard itself is beyond repair and must be replaced with an entirely new bollard.
Designed and patented in Europe by Belgian inventor Gerard Wolters is a unique system which solves many of the problems associated with traditional foundation mounted bollards. Simply put, the system uses a compressed rubber base to act as an energy absorbing mass. This elastomer allows the bollard to tilt slightly when impacted, in the range of 20 degrees from vertical, then return upright while still stopping the colliding vehicle.
The design consists of four major pieces:
This system is attached to concrete using concrete anchor screws. These anchors affix the base component over the adapter, which pre-compresses the elastomer against the ground. The base and adapter pieces are made of a special ductile cast iron, which makes the pieces less brittle than typical cast iron, and also has a very low (-40 degrees) brittleness temperature. The steel pipe which serves as the bollard post is a typical steel pipe inserted into the adapter. Standard pipe is used to give the end user the flexibility to weld fencing using standard components if necessary. Concrete fill is not required inside the bollard pipe, though is permitted. In fact, sign posts can be inserted into the post and concrete filled in place.
Upon collision, the pipe and adapter are allowed to tilt within the base, forcing the adapter to further compress the elastomer in the direction of the impact. The elastomer absorbs much of the energy of the impact and lengthens the deceleration time of the vehicle. The elastomer is of sufficient strength to then rebound, usually pushing the vehicle away from the bollard and returning to an upright position. The tilt of the pipe is limited to approximately 20 degrees at which point the bollard will become rigid.
Bollards are designed in a variety of sizes, each of which is appropriate for various expected collision speeds and masses. Further, modular connectors which can be used to create fencing and guards out of multiple base units have been created to eliminate welding. By using multiple base units, the ultimate strength of the rebounding bollard unit can be increased.
These new bollards utilize the much simpler method of surface installation, greatly reducing installation costs, while maintaining the flexibility to move bollards as conditions warrant. This is accomplished without the normal disadvantage of lack of strength, as the elastomer within the bollard system greatly reduces the maximum impact forces applied to the base anchors. This is because deceleration of an impacting vehicle is much less severe than during an impact with a rigid bollard. Energy is transferred to the elastomer instead of directly to a rigid post, reducing the harsh impact of a relatively immovable object.
This leads directly to the most important advantages of the new bollard system and that is the reduction of damage to both offending vehicles and to the bollard system itself. Direct damage to vehicles is reduced due to the reduction of peak impact force seen by the vehicle. Not only will this avoid damage to the vehicle, but also the chance of injury to a passenger is likewise reduced. In the case of a fork lift in a factory or warehouse, the chance of a thrown load is also reduced, avoiding the potential for bystander injury and stock loss.
Finally, damage to the bollard and its foundation is reduced. Because the post is constructed of strong steel pipe, it maintains its strength, but because of its forgiving nature, much less force is transferred to the foundation. This simplifies and eliminates maintenance while preserving an aesthetically pleasing facility.