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Old April 25th, 2007, 07:48 AM   #61
gladisimo
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No, whisper concrete is a type of concrete that must be manufactured and synthesized in a quiet environment, because soundwaves (around the frequency of human speech) greater than 50 dB or so vibrates throughout the molecules.

If this occurs before the cement molecules form, it will result in a dangerously reduced tensile strength compared to properly manufactured concrete.

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Old May 16th, 2007, 10:35 PM   #62
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Why do concrete middle crashbarriers get quite common

Why do those ugly concrete crashbarriers ge quite common, i find some shiny metal crashbarriers why more interesting as such concrete crashbarriers which get quite common. but many new motorways have concrete crashbarriers instead of metal crashbarriers, why is that? In bulgaria they still use metal though.
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Old May 16th, 2007, 10:39 PM   #63
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I like the metal ones too. They're safer in a crash, because they will bend. Concrete doesn't bend. Concrete might be cheaper, it don't know that for sure. However, it looks very ugly and American. (no offense to Americans, but they have a LOT of these Jersey barriers)
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Old May 16th, 2007, 10:50 PM   #64
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Quote:
Originally Posted by Chris1491 View Post
I like the metal ones too. They're safer in a crash, because they will bend. Concrete doesn't bend. Concrete might be cheaper, it don't know that for sure. However, it looks very ugly and American. (no offense to Americans, but they have a LOT of these Jersey barriers)
it indeet looks way to American
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Old May 16th, 2007, 11:18 PM   #65
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Hm i thought they are safer, but well i dont know, in the older part of egnatia odos in greece they used metal barriers, and they did generally in the 80s-90s roads, but after 90s they use those jersey barriers, i have no clues why atm but gimme a min and i ll be back with info
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Old May 16th, 2007, 11:24 PM   #66
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Yes its actually safer as it seems, here is some info from wiki:

Quote:
A Jersey barrier or Jersey wall separates lanes of traffic (often opposing lanes of traffic) with a goal of minimizing vehicle crossover in the case of accidents. It is also used as defense against car bombs.

It was originally developed at Stevens Institute of Technology in Hoboken, N.J. (under the direction of the New Jersey State Highway Department[1]) to divide multiple lanes on a highway by the state of New Jersey in the United States. A Jersey barrier stands 3 feet tall and is made of poured concrete. Their widespread use on the highway has led to many other uses as a general barrier (for instance, during general construction projects or constructing temporary walkways). They are also known as K-rails (especially in Western states or when used temporarily during roadway construction - K-rail is the California Department of Transportation specification for temporary concrete traffic barriers) or traffic dividers.
A Jersey barrier is a concrete barrier originally developed as a highway median.
A Jersey barrier is a concrete barrier originally developed as a highway median.

The design of the Jersey barrier was specifically intended to minimize damage and reduce the likelihood of a car crossing into oncoming lanes in the event of a collision. For the more common shallow angle hits, the Jersey barrier is intended to minimize sheet metal damage by allowing the vehicle tires to ride up on the lower sloped face.

For higher impact angles, the Jersey barrier is actually a multistage barrier. The front bumper impacts the upper sloped face and slides upwards. This interaction initiates lifting of the vehicle. If the bumper is relatively weak, the front end starts to crush before any uplift occurs. Then, as the vehicle becomes more nearly parallel with the barrier, the wheel contacts the lower sloped face. Most of the additional lift of the vehicle is caused by the lower sloped face compressing the front suspension. However, wheel side-scrubbing forces provide some additional lift, particularly if the barrier face is rough. Therefore, exposed aggregate and other rough surface finishes should be avoided. Modern vehicles have relatively short distances between the bumper and the wheel; as a result, bumper contact is followed almost immediately by wheel contact.

It is only necessary to lift the vehicle enough to reduce the friction between the tires and the paved surface. This aids in banking and redirecting the vehicle. If the vehicle is lifted too high into the air, it may yaw, pitch, or roll, which can cause the vehicle to roll over when the wheels come in contact with the ground again. Concrete safety shape barriers should be adjacent to a paved surface so that the wheels cannot dig into the soil and cause the vehicle to overturn.
http://en.wikipedia.org/wiki/Jersey_barrier
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Old May 16th, 2007, 11:31 PM   #67
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Here on the N50 2+1 project, they have used a moving Jersey Barrier constructor. Like you put some concrete in the machine at the front, and at the back you'll get a barrier instantly. This whole machine drives slowly. Works great, but i haven't seen that before.

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Old May 16th, 2007, 11:58 PM   #68
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I guess the "New Jersey" is installed by greater traffic, and as there's more and more traffic in our world, we get more and more of the rather ugly concrete barriers.
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Old May 17th, 2007, 12:11 AM   #69
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I've seen three different types of barriers: Cable, metal guard rail, and concrete Jersey barriers. They are all used depending on the traffic situation. The most common criteria used in decisions is the road configuration and vehicle speed. Each also provides varying degrees of safety and stopping power. Cable barriers are at the bottom, metal guard rails in the middle, and concrete barriers at the top.

To answer the question of why are they used so frequently, I would venture to guess that more and more situations are requiring the particular benefits of concrete barriers.
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Old May 17th, 2007, 12:17 AM   #70
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Quote:
Originally Posted by Verso View Post
I guess the "New Jersey" is installed by greater traffic, and as there's more and more traffic in our world, we get more and more of the rather ugly concrete barriers.
If they could manage to design it to look like plastic it would look better, there are some concrete and metal crashbarriers together at some sides of the struma motorway in bulgaria where it is dangerous, concrete and metal at the side doesn´t look very bad.
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Old May 18th, 2007, 08:44 AM   #71
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Metal guard rails indeed look aesthetically better than concrete barriers, but the latter are simply safer. Besides, I noticed that in America they are installed only if there is not enough space separating opposing traffic. If there are five metres between the opposing traffic that moves at the combined speed of 230+ km/h, then I will personally feel safer if there is a concrete divider.
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Old May 18th, 2007, 10:09 AM   #72
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Concrete MEDIANs, in particular, are safer than metal rails. Concrete medians are designed so that a car that hits it from the side (instead of head on, which is the most likely way a crash will take place), instead of flying over to the other side, will deflect the car
Metal rails, on the other hand, might not have sufficient strength to deflect a car's weight.
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Last edited by gladisimo; May 18th, 2007 at 01:17 PM.
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Old May 18th, 2007, 12:48 PM   #73
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just a few reasons on top of my head:

- better security in case of crash
- lesser risk of seeing an accidented car crossing the barrier from opposite direction
- metal barriers slice motorcyclists in 2 in case of fall (they are called "head-cutters" by the laters)
- when reasonably high (which is usually the case in urban areas, here at least) they conceal the lights of the cars from opposite direction, which is really enjoyable when you drive at night!
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Old May 19th, 2007, 02:27 AM   #74
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Voila! Nicely summed up.
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Old May 19th, 2007, 08:15 AM   #75
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How about this kind of barrier? Metal barrier filled with gravel.
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Old May 19th, 2007, 10:57 AM   #76
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I prefer steel. Its more flexible.

http://www.myvideo.de/watch/1402430
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Old May 19th, 2007, 01:17 PM   #77
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Quote:
Originally Posted by pflo777
I prefer steel. Its more flexible.
http://www.myvideo.de/watch/1402430
That lory on your video could easily break the steel rail and end up in the opposite lanes. With concrete barrier it is simply impossible even though the damage to the vehicle will be greater.

Here is what steel rail can do to a car:







Once in Bay Area I saw how a small lory hit the concrete divider. It didn't look good for the lory itself, but the driver was OK and what is the most important - the lory did not get to the other side.
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Old May 19th, 2007, 01:26 PM   #78
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Ofcourse they have to use dual metal barriers, otherwise forget it, in bulgaria the motorways ahve dual metal barriers like the pics of the struma motorway so i don´t know, it´s safer but yeah, it is not as safe as concrete.
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Old May 19th, 2007, 04:33 PM   #79
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http://www.tfhrc.gov/pubrds/marapr00/concrete.htm

From the US Federal Highway Administration website. A very detailed page about how concrete barriers work.

In Ontario, (my home jurisdiction), the highway department has been pretty feverishly replacing the old steel barrier (w-style) with new concrete tall wall barrier (which is a and thicker version of a jersey barrier). They always cite the improved safety of the concrete barriers in all of their press releases.

In this photo, the old w-style barrier has just been pulled out, to be replaced with permanent concrete:
http://www.onthighways.com/hwy_410-4...loor_South.jpg
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Old May 19th, 2007, 07:40 PM   #80
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A lot of freeways here have enough room for cable barriers and a large amount of grass - the cable barriers have only been introduced in the past few years.

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