Structural Connection Design (Metal to PVC)

In summary, a bolt through a composite metal panel and PVC adapter can shear the PVC if the bolt pull-out stress is too high. Rivet-nuts can be a safer option, but other types of threaded inserts exist that could be better suited for this application.
  • #1
banfillb
25
1
Hey All,

I am familiar with some of the practices of bolted connections between steel plates, or steel beams etc. I am currently facing a design problem at work dealing with a composite metal panel being screwed to a hallow PVC beam. The PVC beam is screwed into a hallow aluminum beam. However, for simplicity I will just consider the PVC section supported, and perform analysis on both the composite metal panel and the aluminum, and find the limiting factors. My problem is I can't seem to find any procedures dealing with PVC to metal connections.

Im looking for some links to information that might help me.

anything on tension, and shear would be helpful. Basically what I am looking for is at what force will the screw pull out of the PVC (stripping), and what downward force will cause the PVC to deform thus voiding the connection.

I've attached a RUFF sketch of what I'm talking about

Any info will be helpful. Thanks guys!
 

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  • #2
banfillb: You can assume your polyvinyl chloride (PVC) has tensile yield strength Sty = 44 MPa, and shear yield strength Ssy = 25 MPa. You could use a yield factor of safety of FSy = 2.0. Compute the PVC thread shear stress, tau, as follows.

tau = F/(0.625*pi*dp*t1),​

where F = bolt tensile force, pi = 3.14159, dp = dn – 0.75*p*sin(60 deg), dn = bolt nominal (major, outside) diameter, p = bolt thread pitch, and t1 = PVC tube wall thickness. To prevent PVC thread shear pull-out (stripping), ensure Ry does not exceed 100 %, where Ry = FSy*tau/Ssy.
 
  • #3
banfillb: Alternately, you might consider rivet nuts (also called jack nuts), such as part number JN605, JN610, 90186A313, or similar. Find one having a grip range corresponding to your PVC square tube wall thickness.
 
Last edited:
  • #4
Since the diagram doesn't offer much detail, such as dimensions, this might be way off track. It seems to me that the simplest and safest approach would be to run bolts straight through all three materials, with nuts on the back side of the aluminum beam.
 
  • #5
I have much more detailed drawings of what I am working with. I "dumbed" down the design just to get an idea of where to go with it. I will post some more detailed drawings of exactly what I'm talking about tomorrow when I get back to work.

Basically, if your familiar with the terms, it is a curtain wall mullion, with a PVC thermal break leg which has been extended outwards to create a continuous thermal barrier, separating the aluminum from outside cold air. Then the composite panels are attached to the mullion (frame) by means of screws into the fiberglass.

bolts inside of the tube will not work, because it would be nearly impossible to access the tube to hold bolts, etc. I should have mentioned this earlier.

But, I will post some more drawings tomorrow when I'm back in the office.

Thanks again guys!
 
  • #6
nvn said:
banfillb: Alternately, you might consider rivet nuts (also called jack nuts), such as part number JN605, JN610, 90186A313, or similar. Find one having a grip range corresponding to your PVC square tube wall thickness.

Very cool!
 
  • #7
OK here is an updated drawing of what is actually happening.

This is an overhead view of an aluminum curtain wall (window) frame. The blue is aluminum. The PVC adapter is being screwed into the aluminum through one wall via access holes. The composite panel bracket is being screwed into the other end of the PVC adapter, offset from the access holes.
 

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  • #8
Wowziewoo! That is indeed more detailed, and unfortunately far beyond my experience.
I like Nvn's suggestion. That is very reminiscent of what we Canuks call "drywall anchors", but of a much heavier duty.
 
  • #10
hi friends...i m Albertasen ..i m new bie here.
 
  • #11
It's kind of hard to help without knowing dimensions. Assuming that it's a low wind load, I'd be more worried about the composite panel bending than the stripping failure or shear failure (friction is helping here) of the bolt shafts. In terms of combining Al and PVC, there's no galvanic difference or corrosion potential, but you might want to insulate the bolts from the Aluminium. Although, they should be galvanised. Just something to be aware of.

Edit, just saw the updated diagram, that changes things...
 
  • #12
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1. What is the purpose of structural connection design?

The purpose of structural connection design is to ensure that the connection between two different materials, such as metal and PVC, is strong and secure. This is especially important in construction projects where the stability and safety of the structure depend on the strength of these connections.

2. What factors should be considered when designing a structural connection between metal and PVC?

Some factors to consider when designing a structural connection between metal and PVC include the type and thickness of the materials, the load or weight being supported, and the environmental conditions the connection will be exposed to. It is also important to consider any potential corrosion or compatibility issues between the two materials.

3. What are the common methods used for connecting metal to PVC?

The most common methods for connecting metal to PVC include adhesive bonding, mechanical fastening, and thermal joining. Adhesive bonding involves using a strong adhesive to bond the two materials together. Mechanical fastening involves using bolts, screws, or other fasteners to physically connect the two materials. Thermal joining involves using heat to fuse the two materials together.

4. How do I ensure the structural connection between metal and PVC is strong and durable?

To ensure a strong and durable structural connection between metal and PVC, it is important to follow proper design guidelines and use high-quality materials. It is also important to regularly inspect and maintain the connection to ensure it remains secure over time. Additionally, using corrosion-resistant materials and techniques can help extend the lifespan of the connection.

5. Are there any industry standards or codes for structural connection design?

Yes, there are several industry standards and codes that provide guidelines for structural connection design. These include the American Institute of Steel Construction (AISC) standards for steel structures, the American Society for Testing and Materials (ASTM) standards for PVC materials, and the International Building Code (IBC) for general building construction requirements. It is important to consult these standards and codes when designing structural connections between metal and PVC.

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