Bollards
are short vertical posts, usually made of steel, typically used to prevent
access and to protect pedestrians and assets from vehicle collision
damage. In so doing, vehicles (and their
passengers) that impact bollards face damage (and injury) due to the collision,
as well as damage to the bollard structure itself. A new bollard system, known as SoftStop® in
Europe and SlowStop® in the United States, solves this problem by allowing the
bollard to give slightly upon collision, greatly reducing the maximum impact
forces felt by both the colliding vehicle and the bollard system itself.
BOLLARD APPLICATIONS
Bollards
are used in a myriad of applications, for one of several purposes:
- Equipment Protection
- Utility Protection
- Building Protection
- Access Restriction
- Pedestrian Safety
One
needs only to keep a sharp eye to see bollards around us every day. In parking lots, driveways, and drive-thru
lanes, bollards are used to protect buildings, teller machines, utilities such
as gas meters, electrical equipment and fire hydrants, handicap parking signs,
gate entry keypads, and to restrict access to undesired areas. In factories and warehouses, bollards are
important for protecting pedestrians as well as guarding storage racks and
capital equipment from fork truck collisions.
Other
industries which find a heavy use of bollards include automated car wash
facilities, self-storage facilities, gas stations and convenience stores, propane
dispensing, and parking garages, among others.
THE PROBLEM
Foundation mounted bollards are typically
installed in one of two ways. The first,
least expensive way, is with a plate mounted bollard. These bollards are steel pipes welded to a
flat steel plate that can be anchored to a hard surface using concrete
anchors. This method of installation is
quick and inexpensive, requiring the installer to drill four to eight holes in
the concrete and bolt down the bollard with expansion or screw anchors.
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 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.
Another
disadvantage of this type of installation is that it is a permanent
installation with little flexibility for movement. In factory applications, equipment is often
moved and rearranged. Bollards used to
protect equipment or storage racks which are core-installed are not easily
moved. The concrete surrounding the
bollard must be broken out and the large remaining hole filled, leaving a
factory floor full of unsightly patches.
If the bollard itself is reusable after removal, the entire expensive
installation process is started over at the new location.
Some
designs have been created to attempt to solve these problems through the use of
plastic or spring loaded bollards, however these designs suffer from a lack of
strength. If the plastic is of
insufficient stiffness, the entire function of access denial is lost. On the other hand, very stiff plastic designs
have had difficulty with long term durability.
Minor collisions tend to wear away at such devices, and in outdoor
applications UV degradation becomes a concern.
REVOLUTIONARY NEW DESIGN
Designed and patented by Belgian
inventor Gerard Wolters as SoftStop® in Europe, the SlowStop® Bollard system is
a unique design which solves many of the problems associated with traditional
foundation mounted bollards. Simply put,
the SlowStop® 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° from vertical,
then return upright while still stopping the colliding vehicle.
- Elastomer
- Base
- Adapter
- Post
This
system is anchored 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°) brittleness temperature. The steel pipe which serves as the bollard
post is a typical steel pipe inserted into the adapter. In the US, standard ANSI schedule 40 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° at which point the bollard will become rigid.
SlowStop Bollards® are designed in a
variety of sizes, each of which is appropriate for various expected collision
speeds and masses. Further, they are available
with modular connectors which can be used to create fencing and guards out of
multiple base units. By using multiple
base units, the ultimate strength of the rebounding bollard unit can be
increased.
PERFORMANCE ADVANTAGES
SlowStop®
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. The
chart show below demonstrates the difference in impact forces felt by impacting
vehicles between a rigid bollard and the SlowStop® Bollard system. 
This leads directly to the most
important advantages of the SlowStop® 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 Schedule 40 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.
LIMITATIONS
SlowStop®
Bollards must be installed on concrete, as an asphalt surface is not of
adequate strength to anchor the bollard system.
Considering the replacement costs of damaged bollards, however, it may
be cost effective to pour a concrete pad and eliminate years of costly
maintenance and asphalt repair. As
previously mentioned, each bollard is sized for expected loads in terms of mass
and speed. Should that limitation be
exceeded, it is possible to break a component of the SlowStop® system. Most likely that involves the post, adapter,
or base. Fortunately, the SlowStop®
system is modular and easily repaired.
Posts can be replaced by loosening several set-screws, removing and
replacing, and re-tightening the set screws.
Adapter and Base components can be replaced by carefully removing the
concrete screw anchors and replacing the component.
CONCLUSION
The
SlowStop® Bollard system is a revolutionary new product which solves many of
the problems involved with bollard collisions as well as installation and
maintenance issues. Damage to vehicles,
passengers, vehicle loads, and the bollards themselves is greatly reduced due
to the absorption of impact energy by an elastomer hidden within the base of
the bollard. This elastomer allows the
bollard to tilt when impacted and return upright afterward. SlowStop® Bollards are quick and inexpensive
to install, flexible as they are easily moved, and simple to maintain should
there be the need. Safety fencing and
barriers are easily created using modular connectors, avoiding the need to weld
pipe together.
Further
information can be found at www.slowstop.com or by calling Impact Recovery Systems
at 1-800-736-5256 (210-736-4477).
