What is ballad? What are its cheif characteristics?briefly fiscuss "Load ullin's daughter" as a ballad?
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BOLLARD TYPES AND IDEAL APPLICATIONS
This post is the first of a five part article which describes traffic bollards types and their common uses. This post discusses bollard types and introduces the four main uses for traffic bollards.
Traffic bollards come in four main types:
Embedded BollardsSurface Mounted BollardsRebounding BollardsRetractable / Removable Bollards
Each type is specifically designed for its purpose and has its own benefits and limitations. Within those groups, there are sub-groups which I will discuss as well. Also, bollards that fit in those categories can also fall into other sub-categories less dependent on function and more on aesthetics. Architectural Bollards might be any of the above, but are also designed to also include pleasant or unique shapes. A Lighted Bollard is simply a bollard with a light source built in either to add conspicuity to the bollard or to light the surrounding area.
Embedded Bollards
Embedded Bollards are simply bollards which are embedded deep into the ground. This is usually for added strength and security. Embedded bollards can be made out of any common bollard material, be it steel, concrete or even wood, however the bollard will only be as strong as the foundation in which it is buried.
A steel post filled with concrete and buried very deep within a reinforced concrete foundation will be strong indeed. On the contrary, a wooden post buried in soft sand or dirt will not provide as much protection.
Costs for this type of bollard can be significant when coring out existing concrete or asphalt surfaces. It also potentially weakens the foundation, and therefore may not even be appropriate in an application such as a structural concrete parking deck. On the other hand, when placing a bollard in an unpaved area, this is perhaps the least expensive and simplest approach.
Surface Mounted Bollards

This type of bollard uses some sort of anchor system, usually mechanical, to mount the bollard to the surface. Although this is an inexpensive method of installation, it also is not a very secure method. Upon impact, the anchors are often the weakest link and quickly give way, leaving a tilted bollard and damaged foundation. However, when the purpose of the bollard is more to provide a mere presence or psychological barrier, this type of installation is most cost effective. It also may be necessary to use shear bolts in a post-tensioned concrete structure in order to prevent impact to the bollard to potentially compromise the building.
The next type of bollard, the rebounding bollard, is often surface mounted, but overcomes the strength and damage issues associated with standard surface mounted bollards.
Rebounding Bollards
A relative newcomer to the bollard field, rebounding bollards use energy absorption technology to provide the strength of some embedded bollards, with the low installation costs and flexibility of surface mounted bollards. When a rebounding bollard is impacted, it is allowed to tilt as some mechanism, be it an elastomer or spring system, more slowly absorbs and dissipates the energy of the vehicle. The bollard then ideally returns to its original position undamaged and fully functional. Some barriers use advanced polymers which do not yield like metal or concrete might under extreme load.
A further advantage of this type of system is that damage to vehicles, passengers and loads is reduced due to the more gradual absorption of impact energy. Imagine crashing a vehicle into a large concrete bollard. Since there is almost no give, it is much like hitting the proverbial brick wall; all energy is immediately felt by the vehicle and its passengers. With a flexible bollard system, that energy might be dispersed over several hundred milliseconds. While that doesn't sound like much, it makes a great deal of difference to the peak forces felt.
Some bollards in this type are actually not intended to provide traffic denial capabilities at all. As such, they are used mainly as sign markers and psychological barriers. These are extremely prevalent in the United Kingdom.
.
This post is the first of a five part article which describes traffic bollards types and their common uses. This post discusses bollard types and introduces the four main uses for traffic bollards.
Traffic bollards come in four main types:
Embedded BollardsSurface Mounted BollardsRebounding BollardsRetractable / Removable Bollards
Each type is specifically designed for its purpose and has its own benefits and limitations. Within those groups, there are sub-groups which I will discuss as well. Also, bollards that fit in those categories can also fall into other sub-categories less dependent on function and more on aesthetics. Architectural Bollards might be any of the above, but are also designed to also include pleasant or unique shapes. A Lighted Bollard is simply a bollard with a light source built in either to add conspicuity to the bollard or to light the surrounding area.
Embedded Bollards
Embedded Bollards are simply bollards which are embedded deep into the ground. This is usually for added strength and security. Embedded bollards can be made out of any common bollard material, be it steel, concrete or even wood, however the bollard will only be as strong as the foundation in which it is buried.
A steel post filled with concrete and buried very deep within a reinforced concrete foundation will be strong indeed. On the contrary, a wooden post buried in soft sand or dirt will not provide as much protection.
Costs for this type of bollard can be significant when coring out existing concrete or asphalt surfaces. It also potentially weakens the foundation, and therefore may not even be appropriate in an application such as a structural concrete parking deck. On the other hand, when placing a bollard in an unpaved area, this is perhaps the least expensive and simplest approach.
Surface Mounted Bollards

This type of bollard uses some sort of anchor system, usually mechanical, to mount the bollard to the surface. Although this is an inexpensive method of installation, it also is not a very secure method. Upon impact, the anchors are often the weakest link and quickly give way, leaving a tilted bollard and damaged foundation. However, when the purpose of the bollard is more to provide a mere presence or psychological barrier, this type of installation is most cost effective. It also may be necessary to use shear bolts in a post-tensioned concrete structure in order to prevent impact to the bollard to potentially compromise the building.
The next type of bollard, the rebounding bollard, is often surface mounted, but overcomes the strength and damage issues associated with standard surface mounted bollards.
Rebounding Bollards
A relative newcomer to the bollard field, rebounding bollards use energy absorption technology to provide the strength of some embedded bollards, with the low installation costs and flexibility of surface mounted bollards. When a rebounding bollard is impacted, it is allowed to tilt as some mechanism, be it an elastomer or spring system, more slowly absorbs and dissipates the energy of the vehicle. The bollard then ideally returns to its original position undamaged and fully functional. Some barriers use advanced polymers which do not yield like metal or concrete might under extreme load.
A further advantage of this type of system is that damage to vehicles, passengers and loads is reduced due to the more gradual absorption of impact energy. Imagine crashing a vehicle into a large concrete bollard. Since there is almost no give, it is much like hitting the proverbial brick wall; all energy is immediately felt by the vehicle and its passengers. With a flexible bollard system, that energy might be dispersed over several hundred milliseconds. While that doesn't sound like much, it makes a great deal of difference to the peak forces felt.
Some bollards in this type are actually not intended to provide traffic denial capabilities at all. As such, they are used mainly as sign markers and psychological barriers. These are extremely prevalent in the United Kingdom.
.
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