|
Disaster waiting to happen? Using PVC for deck supports???
There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? |
Disaster waiting to happen? Using PVC for deck supports???
It probably depends on the diameter of the PVC tube. A 3" or 4" will not
have much strength, especially if there is not a continuous large diameter re-bar down the middle. I can see the PVC cracking in cold weather, particularly if the top is able to soak up some water that freezes. A 6" or 8" PVC tube with three or four re-bars, probably would be no more than a vinyl coated concrete column, and look good compared to bare concrete. The concrete will take most of the load. I can see the same problems with freezing water however. It could be difficult to make a connection with the foundation unless the post is run all the way down to the footing. "Thomas G. Marshall" . com wrote in message news:ib_Xj.134$ay2.84@trndny01... There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? |
Disaster waiting to happen? Using PVC for deck supports???
On May 18, 2:02 pm, "Thomas G. Marshall"
. com wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? I think you're right that there's cause for concern, I think you're wrong about the failure mechanism unless the footings are seriously sub-standard, and I think there's a lot of information left out. The diameter of the PVC, whether it's Schedule 40 or 80 or even the thin stuff that they use for drainage, how deep the footings are, how high above grade the deck is, etc. R |
Disaster waiting to happen? Using PVC for deck supports???
On Sun, 18 May 2008 12:36:06 -0700, RicodJour wrote:
I think you're right that there's cause for concern, I think you're wrong about the failure mechanism unless the footings are seriously sub-standard, and I think there's a lot of information left out. The diameter of the PVC, whether it's Schedule 40 or 80 or even the thin stuff that they use for drainage, how deep the footings are, how high above grade the deck is, etc. R If I remember correctly, Schedule 80 is called for on all deck support posts. |
Disaster waiting to happen? Using PVC for deck supports???
curt said something like:
On Sun, 18 May 2008 12:36:06 -0700, RicodJour wrote: I think you're right that there's cause for concern, I think you're wrong about the failure mechanism unless the footings are seriously sub-standard, and I think there's a lot of information left out. The diameter of the PVC, whether it's Schedule 40 or 80 or even the thin stuff that they use for drainage, how deep the footings are, how high above grade the deck is, etc. R If I remember correctly, Schedule 80 is called for on all deck support posts. Implication question: Is PVC meeting schedule-80 requirements considered acceptable for deck supports? |
Disaster waiting to happen? Using PVC for deck supports???
|
Disaster waiting to happen? Using PVC for deck supports???
"Thomas G. Marshall" . com
wrote in message news:z51Yj.138$ay2.70@trndny01... said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? My interpretation is that the dent thing is completely irrelevant. |
Disaster waiting to happen? Using PVC for deck supports???
Thomas G. Marshall . com wrote:
and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). Ignorance is bliss. I used PVC for my mail box post. Went down 18 inches, carved out a 3" foot lip, crisscrossed 8" bolt at 6" and 10", filled with concrete and rebar. My mail box was getting knocked down by cars sliding on ice. Someone was knocking down mail boxes with a baseball bat. The police found him when I told them to check for people with forearms. This clown broke his forearm and his wrist. But as a deck support, that's a joke. Dick |
Disaster waiting to happen? Using PVC for deck supports???
"Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. |
Disaster waiting to happen? Using PVC for deck supports???
|
Disaster waiting to happen? Using PVC for deck supports???
Thomas G. Marshall wrote:
said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt |
Disaster waiting to happen? Using PVC for deck supports???
JoeSpareBedroom wrote:
"Thomas G. Marshall" . com wrote in message news:z51Yj.138$ay2.70@trndny01... said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? My interpretation is that the dent thing is completely irrelevant. Your interpretation is incorrect. Matt |
Disaster waiting to happen? Using PVC for deck supports???
"Matt Whiting" wrote in message
. .. JoeSpareBedroom wrote: "Thomas G. Marshall" . com wrote in message news:z51Yj.138$ay2.70@trndny01... said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? My interpretation is that the dent thing is completely irrelevant. Your interpretation is incorrect. Matt OK. |
Disaster waiting to happen? Using PVC for deck supports???
Pete C. wrote:
"Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp |
Disaster waiting to happen? Using PVC for deck supports???
Matt Whiting wrote: Pete C. wrote: "Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp 8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total. |
Disaster waiting to happen? Using PVC for deck supports???
What am I missing here? The extra cost alone makes it not worth
doing. Not to mention how you would attach them without making it look jerry rigged. Even if you got past those two items, what would you make the rest of the deck out of to look right? I suppose if your only going 12" off the ground that it wouldn't matter but it sure sounds like your taking a step backwards. Lou |
Disaster waiting to happen? Using PVC for deck supports???
The concrete in steel lolly columns is to help keep them from collapsing in a fire. It also does provide much improved buckling resistance. Yes, buckling that would be caused by the heat of a FIRE. Check the temp that would cause steel to buckle. Now see what happens to concrete at that temp. Lou |
Disaster waiting to happen? Using PVC for deck supports???
On May 18, 8:45 pm, wrote:
On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. In a wood framed building? I guess if the fire started at the base of the column that might be a good argument, but in any real situation the house would be engulfed in flames long before the plastic temperature of the steel was reached. The concrete fill is to prevent buckling, partially from being dented, but also to prevent localized failure which can occur at lower loads than the straight compressive strength of the material(s) would indicate. http://en.wikipedia.org/wiki/Buckling R |
Disaster waiting to happen? Using PVC for deck supports???
On Sun, 18 May 2008 17:50:49 -0500, "Glenn" wrote:
"Matt Whiting" wrote in message . .. No, preventing buckling is a significant advantage provided by filling a steel column. Matt Whoa, if you are using a steel column, why the concrete? Sky scrapers sit on steel columns with out concrete in them. What am I missing? Perhaps four years of engineering school? Or even two semesters of structural member strength? g |
Disaster waiting to happen? Using PVC for deck supports???
RicodJour said something like:
On May 18, 8:45 pm, wrote: On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. In a wood framed building? I guess if the fire started at the base of the column that might be a good argument, but in any real situation the house would be engulfed in flames long before the plastic temperature of the steel was reached. The concrete fill is to prevent buckling, partially from being dented, but also to prevent localized failure which can occur at lower loads than the straight compressive strength of the material(s) would indicate. http://en.wikipedia.org/wiki/Buckling This makes sense to me, though I'm hardly as versed in structural analysis as the other denisins of this ng. Fire seems a concern, though secondary, only because the plasticity of steel could never be reached in a basement without the rest of the house already having been reduced to dust. Or so it seems to me. {shrug} |
Disaster waiting to happen? Using PVC for deck supports???
On May 18, 6:17*pm, (Dick Adams) wrote:
Someone was knocking down mail boxes with a baseball bat. The police found him when I told them to check for people with forearms. *This clown broke his forearm and his wrist. Good thing the clown was dumb as a the post he broke his arm on because if he'd had a lick of smarts at all he would've sued you for the injuries he sustained trying to bash in your mailbox... and he would've won. You're lucky. A friend of mine put boulders in his front yard because drunk drivers had missed the corner and ended up in his front yard on several occasions, and had hit both his house and his travel trailer at least once. The insurance company gave him 48 hours to have the boulders removed or they'd drop his policy. Long and short of it was, the boulders were a willful admission of wrongdoing/negligence in a lawsuit because they were put there to protect the house from drunk drivers. He could say they were decorative all he wanted, all they had to do in court was point out that the boulders were placed there AFTER the drunk hit his trailer, and he'd lose. |
Disaster waiting to happen? Using PVC for deck supports???
On May 19, 3:30 pm, wrote:
On May 18, 6:17 pm, (Dick Adams) wrote: Someone was knocking down mail boxes with a baseball bat. The police found him when I told them to check for people with forearms. This clown broke his forearm and his wrist. Good thing the clown was dumb as a the post he broke his arm on because if he'd had a lick of smarts at all he would've sued you for the injuries he sustained trying to bash in your mailbox... and he would've won. You're lucky. A friend of mine put boulders in his front yard because drunk drivers had missed the corner and ended up in his front yard on several occasions, and had hit both his house and his travel trailer at least once. The insurance company gave him 48 hours to have the boulders removed or they'd drop his policy. Long and short of it was, the boulders were a willful admission of wrongdoing/negligence in a lawsuit because they were put there to protect the house from drunk drivers. He could say they were decorative all he wanted, all they had to do in court was point out that the boulders were placed there AFTER the drunk hit his trailer, and he'd lose. Well I'm no attorney but, that doesn't sound right. A drunk driver doesn't premeditate getting drunk and running into a house so therefore creates an accident. An idiot smashing mailboxes does premeditate the conditions, planning and carrying out the plan to destroy private property. He could have sued but my bet is that it would have backfired. Lou |
Disaster waiting to happen? Using PVC for deck supports???
wrote:
On Sun, 18 May 2008 18:28:11 -0400, Matt Whiting wrote: wrote: On Sun, 18 May 2008 18:02:54 GMT, "Thomas G. Marshall" . com wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? The concrete in steel lolly columns is to help keep them from collapsing in a fire. It also does provide much improved buckling resistance. Yes, buckling that would be caused by the heat of a FIRE. No, buckling caused by heavy load as well. A column doesn't need fire to buckle. Matt |
Disaster waiting to happen? Using PVC for deck supports???
Pete C. wrote:
Matt Whiting wrote: Pete C. wrote: "Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp 8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total. Material properties don't depend on the size of the pipe. Did you even open the reference I provided? Do you understand MATERIAL properties? Matt |
Disaster waiting to happen? Using PVC for deck supports???
Matt Whiting wrote:
wrote: On Sun, 18 May 2008 18:28:11 -0400, Matt Whiting wrote: wrote: On Sun, 18 May 2008 18:02:54 GMT, "Thomas G. Marshall" . com wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? The concrete in steel lolly columns is to help keep them from collapsing in a fire. It also does provide much improved buckling resistance. Yes, buckling that would be caused by the heat of a FIRE. No, buckling caused by heavy load as well. A column doesn't need fire to buckle. Matt M: Although no one addressed the question, the geophysical stability of the location would be of some measured consideration. Performance of the columns on soil subject to liquefaction in a seismic event merits concern in the right circumstances. A first-hand look at the density of steel used in the recent rebuilds of L.A. freeway overpass supports is amazing. Whether the OP or owner has further interest in possible remedies for any shortcomings in this case is a another question. Regards, Edward Hennessey |
Disaster waiting to happen? Using PVC for deck supports???
Matt Whiting wrote: Pete C. wrote: Matt Whiting wrote: Pete C. wrote: "Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp 8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total. Material properties don't depend on the size of the pipe. Did you even open the reference I provided? Do you understand MATERIAL properties? Matt Do you understand that under testing in my 50T press, it took a load of ~37,500 PSI on the 1' length of 4" sch 40 PVC pipe before it failed? Material properties are irrelevant, that was the actual result of the test I noted. |
Disaster waiting to happen? Using PVC for deck supports???
Fire protection of structural steel is placed on the exterior of the
members, not within a pipe or tube. To make it simple, take a look at a typical pipe pile, driven empty, then filled with concrete, with a circular cage reinforcing only in the upper section (top 20-30'), a vertical bar or two near the center does nothing. As Matt and Rico have stated the concrete fill is to resist buckling. Tom "Stormin Mormon" wrote in message ... When I was in college, so many years ago. We learned that cement is strong for compressive loads (such as columns in the cellar). Steel is good for stretching loads (hanging a bridge from a frame). If your friend's use of concrete is to support weight, it may work very well. Concrete often has reinforcing bar, or rebar. This steel helps to combine the compression strength of concrete with the stretching strength of steel. -- Christopher A. Young Learn more about Jesus www.lds.org . "Thomas G. Marshall" . com wrote in message news:ib_Xj.134$ay2.84@trndny01... There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? |
Disaster waiting to happen? Using PVC for deck supports???
Pete C. wrote:
Matt Whiting wrote: Pete C. wrote: Matt Whiting wrote: Pete C. wrote: "Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp 8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total. Material properties don't depend on the size of the pipe. Did you even open the reference I provided? Do you understand MATERIAL properties? Matt Do you understand that under testing in my 50T press, it took a load of ~37,500 PSI on the 1' length of 4" sch 40 PVC pipe before it failed? Material properties are irrelevant, that was the actual result of the test I noted. 37,500 psi is a pressure, not a load. Material properties are not only relevant, they are essential to almost all structural engineering calculations (I know as I have a masters in civil/structural). And the behavior of a short column is MUCH different than a long column. Ever heard of Euler? A nearly pure compression test (which is what a 1' long 4" pipe comprises) has almost no relevance to the case of a column that has a substantially different slenderness ratio and thus subject to a buckling failure mode as well as possible bending moments due to eccentric loading. I didn't see a column length in the OP, but when "basement" is the description rather than "crawl space" it is likely that the length is at least 6' and possibly 8' or even more. This is far from being a 1' column. Concrete filled PVC could work if sized properly, but using the same size as the existing steel column is a fool's errand. Again, the OP didn't mention the size of either the steel or the PVC, but I'll bet there were likely nearly the same size. If that is the case, then the PVC is almost certainly inadequate, unless the steel column was grossly oversized for the required load. Matt |
Disaster waiting to happen? Using PVC for deck supports???
On May 20, 6:44*am, "Tom Cular" wrote:
Fire protection of structural steel is placed on the exterior of the members, not within a pipe or tube. To make it simple, take a look at a typical pipe pile, driven empty, then filled with concrete, with a circular cage reinforcing only in the upper section (top 20-30'), a vertical bar or two near the center does nothing. As Matt and Rico have stated the concrete fill is to resist buckling. Tom "Stormin Mormon" wrote in message ... When I was in college, so many years ago. We learned that cement is strong for compressive loads (such as columns in the cellar). Steel is good for stretching loads (hanging a bridge from a frame). If your friend's use of concrete is to support weight, it may work very well. Concrete often has reinforcing bar, or rebar. This steel helps to combine the compression strength of concrete with the stretching strength of steel. -- Christopher A. Young Learn more about Jesus *www.lds.org . "Thomas G. Marshall" . com wrote in messagenews:ib_Xj.134$ay2.84@trndny01... There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. *He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. *I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right?- Hide quoted text - - Show quoted text - And I would submit that it does a lot more than just provide the buckling resistance. Concrete is widely used to form structural support to hold up buildings, bridges, etc. Even in this deck example, what are the footers made of? They are essentially cylindrical concrete pillars. So, while the concrete does keep the steel pipes in a lolly column from buckling, which is clearly important, the concrete also carries some of the weight directly. If instead of concrete, you had some other means to keep the column from buckling, say an internal criss cross web of little rods, I would say the concrete filled lolly would carry substantially more weight. |
Disaster waiting to happen? Using PVC for deck supports???
Matt Whiting wrote: Pete C. wrote: Matt Whiting wrote: Pete C. wrote: Matt Whiting wrote: Pete C. wrote: "Thomas G. Marshall" wrote: There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I pointed out that I thought that the strength of a lolly was in the steel, and that the cement was there merely to ensure that it was never dented, causing it to fold like an aluminum can. I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. Was I right? There are code approved PVC pipe based deck support columns available. The compressive strength of PVC pipe is tremendous as long as you keep it from buckling. I once tested a 1' length of 4" sch40 PVC pipe in a hydraulic press and it too over 30 tons of force before it started to fail (Enerpac press with pressure gauge). The compressive strength of concrete is also very high. Combined strength is more than adequate and PVC handles cold pretty well also. I'd hardly call it tremendous. 8300 psi exceed most standard concrete, although high strength concrete is available now that substantially exceeds this value. And this falls FAR short of even standard A36 steel. http://www.harvel.com/piping-clear-pvc.asp 8300 psi? I come up with more like 37,500 psi since this was 4" dia sch 40 PVC pipe with no filling i.e. 60,000# load on something like 1.6 square inches of PVC total. Material properties don't depend on the size of the pipe. Did you even open the reference I provided? Do you understand MATERIAL properties? Matt Do you understand that under testing in my 50T press, it took a load of ~37,500 PSI on the 1' length of 4" sch 40 PVC pipe before it failed? Material properties are irrelevant, that was the actual result of the test I noted. 37,500 psi is a pressure, not a load. It is both. Material properties are not only relevant, they are essential to almost all structural engineering calculations (I know as I have a masters in civil/structural). And what I presented was not a structural engineering calculation it was simply the results of a real world test that point out that sch 40 PVC pipe is a lot stronger than most people think. And the behavior of a short column is MUCH different than a long column. Ever heard of Euler? No kidding, and again, I didn't present any structural engineering info, simply actual results of a real world test showing the surprising strength of PVC pipe. A nearly pure compression test (which is what a 1' long 4" pipe comprises) has almost no relevance to the case of a column that has a substantially different slenderness ratio and thus subject to a buckling failure mode as well as possible bending moments due to eccentric loading. Right, but again, I didn't present anything to the contrary. I indicated that code approved PVC pipe based deck supports were available, which they are, and an example showing that PVC pipe is stronger than people think. I didn't see a column length in the OP, but when "basement" is the description rather than "crawl space" it is likely that the length is at least 6' and possibly 8' or even more. This is far from being a 1' column. Concrete filled PVC could work if sized properly, but using the same size as the existing steel column is a fool's errand. Again, the OP didn't mention the size of either the steel or the PVC, but I'll bet there were likely nearly the same size. If that is the case, then the PVC is almost certainly inadequate, unless the steel column was grossly oversized for the required load. Probably, and I didn't suggest the OP's scenario was proper or safe. I simply noted that "Using PVC for deck supports" as in the subject line is possible and code approved if done properly, and not a "Disaster waiting to happen" as was also in the subject line. Can't seem to find a link to the product at the moment. Believe I read about it in Fine Homebuilding or perhaps JLC. |
Disaster waiting to happen? Using PVC for deck supports???
wrote in message ... On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. PVC burns doesn't it? |
Disaster waiting to happen? Using PVC for deck supports???
CWatters wrote:
wrote in message ... On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. PVC burns doesn't it? So does steel. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form . |
Disaster waiting to happen? Using PVC for deck supports???
"Thomas G. Marshall" . com wrote in message news:ib_Xj.134$ay2.84@trndny01... There was a person I was speaking to recently who was proud of what he considered to be a very bright move on his part. He had noticed that the lolly-columns in his basement had been filled with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). For what? |
Disaster waiting to happen? Using PVC for deck supports???
On May 20, 3:40*pm, CJT wrote:
CWatters wrote: wrote in message .. . On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. PVC burns doesn't it? So does steel. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. *Our true address is of the form .- Hide quoted text - - Show quoted text - Steel burns? I guess I learned something new today. |
Disaster waiting to happen? Using PVC for deck supports???
wrote in message
... On May 20, 3:40 pm, CJT wrote: CWatters wrote: wrote in message .. . On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. PVC burns doesn't it? So does steel. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form .- Hide quoted text - - Show quoted text - Steel burns? I guess I learned something new today. ============ Anything will burn at the right temp. |
Disaster waiting to happen? Using PVC for deck supports???
On May 20, 3:53*pm, "JoeSpareBedroom" wrote:
wrote in message ... On May 20, 3:40 pm, CJT wrote: CWatters wrote: wrote in message .. . On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: ...[snip]... The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Matt Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. PVC burns doesn't it? So does steel. -- The e-mail address in our reply-to line is reversed in an attempt to minimize spam. Our true address is of the form .- Hide quoted text - - Show quoted text - Steel burns? I guess I learned something new today. ============ Anything will burn at the right temp.- Hide quoted text - - Show quoted text - So there's no difference between burning and melting? |
Disaster waiting to happen? Using PVC for deck supports???
|
Disaster waiting to happen? Using PVC for deck supports???
He had noticed that the lolly-columns in his basement had been filled
with cement prior to being used. He assumed that the strength of the support was in the cement, and therefore concluded it was a good idea to try filling PVC tubes and using those as posts (note-not as sonno-tubes, but as fully structural support posts). I was concerned that the first major frost heave under his deck that is able to stress the ledger enough to pull outward a small amount would cause his pvc+cement "posts" to break. First, I'm no engineer, but a few thoughts did come to mind... You didn't mention the height of the deck or the span between support posts, but in general there shouldn't be much of a load on a deck (no walls, ceilings, roofing, etc.). Assuming a typical residential situation, of course. If the post footings are below the frostline in the area, they shouldn't heave anyway should they? But even so, PVC is fairly flexible, and even concrete flexes a small amount. With "typical" structural movements, I don't see this being an issue. They're not gonna "snap like twigs" at the first sign of stress. If the PVC is filled with concrete, I don't see why it would be any different than a cardboard sonotube, except you would not need to remove the PVC after the pour. Even if the PVC doesn't offer any structural support, the concrete piers inside the PVC should support the weight of the deck. If you're concerned about "flex" in the column, you should install rebar reinforcement whether you're using PVC, a sonotube, or even building a square box for the concrete pier. Unless this is a second story deck, or one perched out over a hillside, "most" decks only sit a foot or two off the ground and are supported by multiple pier posts. I doubt there will be any significant sideways loads to buckle the columns. A recent article in Fine Homebuilding showed a system that used PVC pipe to support a small shed (with no concrete). If it works for a shed, it's bound to be adequate for a deck. Unlike a steel post, PVC won't rust. However, regular PVC will be damaged by ultraviolet light from the sun, and will get brittle. You could avoid this by using grey PVC conduit which has protection against ultraviolet light. Around here, many decks are built with nothing more than a 4x4 post sitting in precast concrete pier blocks sitting on the ground and have lasted for decades. Also, many mobile homes sit on concrete blocks that are just dry stacked piers with no reinforcement (ours was setup that way for 13 years, with one end nearly four feet off the ground, and we survived two earthquakes with no problems). These are obviously UNDER engineered situations, but it's also possible to OVER engineer the support for a deck as well... Anthony |
Disaster waiting to happen? Using PVC for deck supports???
Thomas G. Marshall wrote:
RicodJour said something like: On May 18, 8:45 pm, wrote: On Sun, 18 May 2008 18:28:48 -0400, Matt Whiting wrote: Thomas G. Marshall wrote: said something like: The concrete in steel lolly columns is to help keep them from collapsing in a fire. ....so the preventing a dent thing is secondary, or not a concern...? No, preventing buckling is a significant advantage provided by filling a steel column. Uh, yes. And the buckling it prevents would be the result of fire. Filling the columns with cement is to protect the columns from buckling in a FIRE. In a wood framed building? I guess if the fire started at the base of the column that might be a good argument, but in any real situation the house would be engulfed in flames long before the plastic temperature of the steel was reached. The concrete fill is to prevent buckling, partially from being dented, but also to prevent localized failure which can occur at lower loads than the straight compressive strength of the material(s) would indicate.aconcern, though secondary, only because the plasticity of steel could never be reached in a basement without the rest of the house already having been reduced to dust. Or so it seems to me. {shrug} The problem with fire and steel beams/columns isn't so much from structural weakness when the steel becomes hot, although that would be a concern where the intention is to contain the fire for a length of time, but more from the actual expansion of the steel, either from it pushing other structural elements, or itself buckling when the expansion at both ends is restricted. -- scrum (\_/) Procrastinator bunny says: ( . .) "I'll conquer the internets tomorrow" C(")(") |
All times are GMT +1. The time now is 03:22 PM. |
|
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter