Why do manufacturers make ridiculous claims?

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I mean, really ridiculous. It's insulting. Case in point: http://www.grassypavers.com /
They'll support 97,000 PSF?! Most interesting - particularly in light of the fact that the IRC allows a prescriptive soil bearing capacity of 12,000 PSF for crystalline bedrock.
R
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That is what I've always refered to as "fun with math". Like in statistics, you can take any set of quanitative data and by cherry picking the scale you can greatly exaggerate the results.
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On Mon, 18 Jun 2007 06:35:09 -0500, TVeblen wrote:

Or as the Duke of Wellington once said, "There are lies, there are damned lies and then there are statistics".
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The material works well for temporary overflow parking areas, but heavy use results in dirt. Growies need sunlight and water. EDS
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Most likely they are attempting to make the potential buyer aware that the pavers are stronger than the roofing components they are covering. Green buildings are the future in certain cases.
Point in fact is, there's nothing wrong with this type of advertising; engineers know that a roof is only as strong as its weakest link....... they are simply stating htat this isn't it.

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Roofing components...? They're designed to be driven on - used in landscaping. Saw no mention of living roof ballast, thought they would obviously be able to handle _foot_ traffic on a roof.

Point of fact - it's a bunch of crap. They're saying that _one_ square foot of their _plastic product_ would support 2/3s of an M1 Abrams battle tank. Puh-lease. The stuff would be dust.
It's a simple, straightforward lie in advertising. They're either misrepresenting the load capacity intentionally or through ignorance. Neither is acceptable.
R
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There's a new trend to develop green roofs (covered with grass). Used on some commercial buildings made to be walked on by the tenets, also used to make a roof greener for a penthouse. That's where I've seen these types of products used, but not to any real extent.
As far as the loading goes, did you see that its designed to use a base of 6-7 inches of stone aggregate, covered with a bed of gravel 2' thick, with the hollows filled with pea gravel covered over with a 6" sand cover. The plastic pavers are used as a stabilizer for the gravel.
There should no problem in carrying a load of 675 psi using the method advertised on the website. I don't think you read through the entire specifications completely.
As far as what they advertise for loading, 674 psi is high, but not unheard of. "> Roofing components...? They're designed to be driven on - used in

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Dennis wrote:

It's not a new trend. There have been roof gardens aand roof top swimming pools for decades. What I love to do is visit these roof gardens couple decades on.....It's not just the psi, it's also wheher or not your substrate (elastomeric, whatever) is meant to be wet all the time when you water mr. roof garden.When you are doing drainage into aggregate like you suggest, it's not wicking into ground water, it's wicking eventually onto your substrate. Essentially, then , what you have to design is a swimming pool that is designed never to be kept clean on top of a roof...And the best way to conquer such an issue is to give that water somewhere to go and to do it without clogging it with the dirt...

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Forget left field, you've jumped the fence and are hanging out in the bleachers. Typical undisturbed prescriptive lsoil bearing capacity loads, according to the IRC, are in the range of a ton or two per SF. In other words, their paving plastic grid, resting on gravel (assume five tons PSF bearing capacity for gravel to show I'm not being unreasonable), increases the bearing capacity by TEN times. That sound right to you? If so, I sure hope you don't do your own calculations.
R
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Good Morning,
Interesting thread.
http://www.grassypavers.com/MPI%20Study%20Data%20and%20Explanation.pdf ot http://www.grassypavers.com/specs.htm and select the load data sheet link.
While I'm not the sharpest tool in the shed, I do like to hear good feed back on the products I sell. I am a dealer for the product and I own the site http://www.grassypavers.com . I use data given to me for the site. If it is incorrect I would like to update the info so it correctly represents the product.
You guys obviously know your stuff in the load arena. I would love some feedback on this load data from MPI. Is it crap? if so why? This is where the facts come from we use on the site (actually from the 4 page brochure on the specs page). I will be glad to send samples out to anyone that would be willing to conduct these tests to see how our products hold up.
I would also be willing to take feedback and a real world writeup on soil load capacities and what benefits any kind of pavers provide for that soil base.
I want everyone to know about the product and I want that info to be correct. Architects, Designers and End users a like should have factual information in making decisions and choosing products.
So I hope ya'll don't still want to take out behind the shed. My goal is to provide factual data for our products. They are a good solution and are more durable than people think.
Please keep up the thread. I like a good debate.
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Most of the responses you are reading here appear to be from kids who are not associated with engineering nor with how engineered products are marketed (note the off-topic preoccupation with the falsely-accused Duke Lacrosse college kids).
Some are arguing that the underlying soil is not strong enough to support a truck, which is of course ridiculous. The substrate conditions would be engineered to take the assumed reactions necessary, while the manufacturers product is design to provide a soil base and drainage stratum. It is assumed that the underlying soils would be considered in any installation, and improved if needed. This product's advantage is only in the addition of adding grass to such areas; already deemed capable of withstanding the loading of vehicular traffic.
Reviewing the test reports provided, it appears to me (my opinion) that the testing performed by the University of Southern Mississippi is completely within established guidelines and have sufficient credibility. The only additional qualification I would ask to see is the signature of a licensed professional, registered in the state where the tests were conducted or from the state where the product is manufactured. I work in plan review for a nationally recognized testing laboratory and review test reports similar to this product, on a regular basis.
As always, the best results is the feedback from existing installations. If you still have any concerns over the product's durability, I would recommend contacting the manufacturer to see what problems and failures are occurring in the field.

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A lot of words that don't say very much, and what they do say is misleading.
Obviously the product is intended for creating a drivable green surface. Thanks for clarifying that - the name grassy paver had confused me.
"It is assumed that the underlying soils..." That's your idea of engineering? ASSuming bearing capacity and soil conditions?
An 18 wheeler typically weighs in at around 80,000 pounds maximum load (federally mandated maximum). An average semi tire has approximately 60 square inches of contact area - that's ~7.5 SF of tire contact area per truck, or roughly 10,000 PSF.
If that grassy paver stuff has a rating of TEN times the maximum load allowed on federal highway - with the graded, layered and compacted base - why the nifong do they use asphalt and concrete for roads?
Your grasp of the numbers is as faulty as the manufacturer's claims. Move on - please. This is getting embarrassing.
R
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With gravel on the bottom, inside the hex spaces and on top, how much load do you think the plastic forms are actually carrying?
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it's the weakest link principle
don't pay me no mind, Im just agreeing with you
Tony
why he keep asking about the damn gravel now if his HEAD was in the plastic, yeah, maybe 100G
just kidding!
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RIco-
I visited the website & emailed the guy (he posted below) about the claims being made.
He sent me a link to some info from the mfr (he jut sells them)
looks like the mfr had some tests done on the plastic unit (filled & un-filled) AND the mfr (or their agent) did some hand waving based on the ASSTHO H-20 loading
And then extrapolated the results to some of insane psf number
the guy who signed the test report is some sort of clueless Phd.......reporting numbers with 6 or 7 "significant" figures, reporting psf's that no soil in the world could possibly support
Using the ASSTHIO loading & then extroplating to a generalized psf is like calc'ing the stress under a woman's high heel & extrapolating to a psf for floor loading!
Example:
120 pounds, assume .375" diameter heel tip, standing equally on both shoes,
540 psi translatesto >>>>>> 78,200 psf
makes as much sense as their test report & product claims
What they really have is a product that can take a higher "point load" (actually a local small patch distributed load) than normal (unconfined / un-reinfornced) soil.
With the plastic grid & grass roots, you wind up with a reinforced soil that (IMO) is at best is a few times stronger (locally) than regular soil MAYBE 20 or 30 psi
but it ain't asphalt or concrete!
cheers Bob
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wrote:

hehheh You obviously don't wear heels. You forgot to account for the sizable percentage of weight on the balls of the feet. Why do I suddenly feel like Reese Witherspoon in Legally Blonde?....................Bend....and Snap!
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I was considering the load case when "she's" rocking on her heels. :)
I didn't consider the dynamic effect of foot fall "impact" while walking
I think i also may have over estimated the heel tip diameter (I'm wearing flats today & didn't measure or reseach tip dia)
in any case I'm sure you get my example........heel tips are hard even oak floors so my number of ~540 psi is in the ball park
cheers Bob
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wrote:

<channeling Reeses again>Like I said, you obviously don't wear heels. Go get a pair, strap them on and try that stunt. (Make sure their not anybody's 'good ones'.)

Yes, probably the right order of magnitude. I'm just teasing you because you can work a calculator but not a pair of Jimmy Choos ; ) http://www.jimmychoo.com/pws/ProductDetails.ice?ProductID9893
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MB-
You have no idea what's in my closet.... :)
cheers Bob
I knew you were kidding me.
& I just pulled the example out of the air..... I divided the weight bu two but I also chose 120lbs (wishful thinking?) ...could have been 150+ :)
I refuse to go measure the heel tips...even too geeky for me.
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Well done, Bob! Let's see if they revise their claim to a number a couple of orders of magnitude more realistic.
R
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