fibrelass vs. concrete

[ajk1]

thread507-310737
[tt]I have not been on this forum for some years. Nevertheless a question has recently arisen, that I seek to comment on, and woud like to hear engineering connents on, viz.
Someone on the cemetaary ccommittee at the place of worship that I attend, has proposed covering each new grave (at the level of the grass), with a fibreglas cover, instead of with a concrete cover as I believe is the custom that is sometimes followed where a grade level cover is provided; there is no requirement to have any grade level cover.
The proponent of the fibreglass cover has a business interest in manufactured fibreglass producta.

a)The mailn concern I have with this idea, is that wind gusst can lift the fibreglass cover and it can become a dangerours projectile that might injure someone even in relatively low velocity winds. I suppose a staked type hold-down system can be devised, but it seems to me it would be awkward.

b) My other concern is that the machinery used to excavate and backfill new adjacent graves may accidentally run over the fibreglass cover.

My opinion is that fibreglass is not a suitable cover.
For graves that are to be covered at ground surface level, concrete would be a better covering material (as has ttraaditionally been used where a grave cover is provided at grde level.

Any comments?


[/tt]

 

[phamENG]

Aren't those usually provided to prevent animals from digging up graves or flood waters from floating caskets? Pretty sure fiberglass won't help you much in either of those scenarios.

 

[ajk1]

to phamENG - thank you for your reply. What you say sounds logical Much appreciated.

 

[TugboatEng]

The resin in fiberglass ablates in sunlight and will degrade the surface appearance and leave sharp strands of glass that can cut or splinter into fingers that contact the surface. This issue can be resolved with coatings but must be managed.

 

[dik]

I think the coatings that prevent UV degradation have to be applied periodically 'forever'.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[epoxybot]

I agree with Tugboat. Concrete seems like a one and done. Fiberglass seems like a 25 year interval, ongoing maintenance cost.

 

[ajk1]

Does anyone have any advice on what the wind uplift suction (kPa or psf) on a cemetary grave fibreglas cover at ground level might be? The environment would genrerally be suburban or rural, although it could be urban depending on where the cemetary is located.
I am told by an friend that he has seen such pab=nel on ome garaves.
I suppose the formula from the 2015 National Building Code of Canada (NBC) would be:
p = IwCeCgCp q
where:
Iw=0.8 importance factor
Ce=0.9 exposurere factor
Cg=2.5 gust factor
Cp=?

But I don't know:
a) if this formula can be applied to a sheet lying on the ground?
b) what the approppriate value for Cp might be?
c) how the fibreglass panel would be held down against wind uplift?
d) whether the wind could act on the underside of the fibreglass panel as well as on the top side of the panel?
e) whether there might be a downturn at the edges of the panel?

Any helpful comments?

 

[ajk1]

TYPO: should say "I am told by a friend that he has seen fibreglass panels over some graves."

 

[BridgeSmith]

The panels would have to be anchored to the ground, maintained, and protected from damage. Why would you even consider using them? Just say no.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[ajk1]

Looking at the NRC 1995 -

CNRC User's Guide- NBC 1995 Structural Commentaries (Part 4):

CpCg:

​

From Commentary B, Figure B-9(a) External peak pressure coefficients, for roofs of 10° slope or less for design of cladding and secondary structural members I read the value for CpCg of about -1.75 for area 'r' the main area of the roof.
[/indent]
I know this is not the same as a sheet of fibreglass on the ground, but I it is the closest thing that I can find in the Code or its Commentary.

Ce:
I would expect that something at zero distance above the ground would have a smaller Ce value than 0.9 that I am using, which is the smallst value given in the Commentary, but I have no way of determining that (has any user of this Forum?).

I would expect that if the air can get under the fibreglass then there would also be an upward force acting under the fibreglass. I don't know the details at the moment. I can't go to the cemetery today because there is a major snow storm here in Toronto . We usually get little snow (unlike BUFFALO).

 

[ajk1]

If anyone has other sources of data that might be useful for this please don't hesitate to post them.
The only other way to determine what I seek is by a boundary layer wind tunnel like I recall they had at the University of Western Ontario, but I have lost track of them, and anyway I dont think that this would be worth the cost.

 

[phamENG]

Why are you still considering this?

Strike 1:
You have a suggestion to what I assume is a non-profit religious organization by a member of the same organization with a business interest in the organization following that suggestion. This is a textbook conflict of interest. Unless this person has suggested a different manufacturer with whom he has no ties and from whom he stands to gain nothing, the suggestion is at least unethical.

Strike 2:
For all of the use cases we've been able to come up with here, fiberglass is a less suitable material. Concrete is the best suited (though carved stone would look real nice).

Strike 3:
In all likelihood, fiberglass has the greater life cycle cost. I don't know a lot about the economics of cemeteries, but I'm pretty sure my family is not paying for upkeep around my recently deceased loved ones' graves. They paid a few thousand dollars decades ago and reserved a plot. That was it. So life cycle cost analysis will be even more critical here than for a building or a bridge where tapping additional revenue sources is a reasonable expectations. Once the cemetery is full, you have to rely on the ROI from money used to purchase plots, correct? I suppose for a church they can raise money from the congregation, but that's a pretty irresponsible use of the peoples' money.

1-2-3...you're outa here!

 

[ajk1]

I will drop the matter now, following your wise advice.
I was just trying to see if anyone could come up with a good reason for fibreglass cover panels.

 

[CarlB]

You might look into studies/design criteria for roof pavers, seems a similar concept.
Here’s one

https://iibec.org/wp-content/uploads/2017-cts-mooneghi-smith-irwin-chowdhury.pdf

 

[Ussuri]

I would also think they would get damaged by lawn mowing equipment.

We also used to use Mortsafes

https://en.wikipedia.org/wiki/Mortsafe

Although the original driver for these has long gone.

 

[dauwerda]

I got the impression ajk1 does not want to use the fiberglass option, but also has to convince an entire church board of the same thing - not an easy task, especially when there is a perceived cost savings involved.

Does said provider have pictures of installations that are 10+ years old? I can't imagine they weather all that great (my googling skills haven't been successful in finding pictures of any that are "old".

Based on what I see in the picture on this site (bottom right is fiberglass option) and others, there is a hole in each corner for stakes to hold it to the ground. That just screams impermanence to me, which I feel is the opposite of what your typical grave marker is going for.

The little bit of googling I did on the topic told me that headstones/footstones/grave covers were originally used due to the belief that they were needed to keep the soul anchored in place (with the body). I understand that although this may have been the initial thought and use, it has morphed into something else. However, a fiberglass cover that has to be staked to the ground to keep it from blowing away just doesn't seem to fit the entire tradition to me.

 

[BridgeSmith]

The little bit of googling I did on the topic told me that headstones/footstones/grave covers were originally used due to the belief that they were needed to keep the soul anchored in place (with the body).

Hmmm...I always thought they were so people would know where to visit the grave and so the body wouldn't get dug up by mistake.

Although I do know that there was a big fight over the placement of the grave marker of my wife's friend because the relatives on one side of the family wanted her name, etc. on the side facing away from where the body was buried, so they wouldn't have to walk on her grave to visit, leave flowers, etc., while the other relatives wanted the name facing East so that Jesus could find her to resurrect her at the Rapture. (He can resurrect a rotten corpse or a collection of bones, but can't find it without directions?)

Rod Smith, P.E., The artist formerly known as HotRod10

 

[ajk1]

To dauwerda - thanks very much for your comment.

Very interesting indeed that you have found pictures of fibreglass covers with holes at each corner, presumably to insert some sort of hold-down anchorage to keep the fibreglass cover from blowing away.

Why do you think that holes in each corner "screams impermeance"?
I would be interested in knowing, because this would be a good reason not to use fibreglass panels.


To Bridgesmith - thanks very much for your comment.

The bodies face east in the tradition that I follow, towards where the holy temple stood in Jerusalem.
The holy temple was destroyed a number of times, most recently by the Romans, and has never been rebuilt since.

 

[phamENG]

Sorry...the "you're outa here" was a joke/baseball reference.

The point of my last post was to sum up the reasons not to do it, my apologies if it was taken differently.

I agree with dauwerda's comment about impermanence...the only thing I anchor with stakes is a tent.

 

[ajk1]

LOL