Plywood deck design

[kaffy]

Good morning fellow engineers,

I am working on a plywood deck which will be loaded as shown in the attached file(screenshot of loading condition and CSA code.
I am going to check bending, plannar shear due to bending and deflection.
1:Is there any other criteria I need to check while specifying the thickness I need?
2:I am having a tough time understanding CSA 086 (orientation of applied force relative to face grain). Do they mean stress direction relative to face grain?
3: In attached file, based on my direction of grain, I am using 0 degree angle. Is that right? I could use 90 and make it conservative but I do not want to unnecessarily add the weight and cost.

Thank You
Kaffy

 

[rowingengineer]

Nothing attached, also I check ply wood for pinching point force's, however I most work in industrial buildings.

 

[kaffy]

My bad, Here is the attachment

 

[jayrod12]

How concentrated? What is causing the concentrated load?

 

[dik]

What are the plywood supports?

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-Dik

 

[kaffy]

Hi guys,
Support is steel and load is about 2000lb (dictated by code)

 

[jayrod12]

2000lbs over an area of what? It can't actually be a true point. Otherwise it would just pierce right through.

Lcoally, for floors of offices etc, it is 2000lbs over a 30"x30" loaded area.

The reason I was asking, was to help you determine how much of the plywood you could realistically account for the shear and bending.

You may be able to get plywood to work in these scenarios, however if you're expecting true point type loads, i.e. hard wheeled equipment, storage equipment on small feel, it may not be the best product without a concrete topping to help spread the load a bit.

 

[kaffy]

HellO,

So this is the elevator wood platform. We usually have a steel platform underneath made up of C channels(as shown in attachment). On the top of steel platform, we have a layer of plywood.
Now B44 code just say that while designing the platform, u have to assume a concentrated load. Having said that, it is passenger elevator, so in reality, there will never be concentrated load (it will be more like a floor of office) so it can't pierce through.

Most of the times, concentrated load = 625 lb ,

Thank You

 

[MotorCity]

A sheet of plywood will not be able to support a concentrated load of 2000 lb.

You may want to look at another option, such as a slab.

 

[le99]

In general, force makes zero degrees with wood grain is a force applied parallel to the grain, or in direction of the grain, such as compressive stress Link. Force makes 90 degrees to the grain is a force applied perpendicular/transverse to the grain, such as the load that produces bending stress Link.

If this is an outdoor deck open to foot traffic only, the design uniform live load is 40 psf (2018 IRC). You need to consider snow load, wind, and special items that cause concentrated loads, such as large planters, or deck-top pool.

 

[kaffy]

Hello Le99,

Table has a separate column for axial compression (at 0" and 90" angle), bending at (0" and 90"). If we follow the link, it should only have two columns. Bending(when force at 90), compression (when force is at 0").

Thank you

 

[le99]

See the attached sketch.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1643391909/tips/Untitled_mbxu4i.bmp[/url]

 

[kaffy]

I am okay with compression, but in bending, both scenario has force at 90"

Thank You

 

[jayrod12]

If this is meant for standard foot traffic only, there are plywood panels rated to support live loads of 100 psf and specified point loads of 2000 lbs. However, if this is a high traffic area, I'd be concerned with long term durability.

Is it a place where it snows? Are you going to have people bringing in a bunch of water/snow that could accelerate deterioration?

 

[hokie66]

Be sure to specify the direction of the plies. The outer plies must be in the direction of the bending. Plywood is not a homogeneous material.

 

[jjl317]

Not sure if applicable, but the APA (American Plywood Association) has several documents that include information on point loads, including on a technical note on caster loadings, and a research report on residential garages with plywood floors.

 

[le99]

@kaffy,

Think the force is really meant the stress - the resulting stress (compression or bending due to the applied force) is normal/parallel to the grain. Does this make sense?

 

[kaffy]

Sorry things got pretty confused on this thread. I will create a new thread with simple version of my question

 

[kaffy]

Here is the new link guys. Thank you very much

https://www.eng-tips.com/viewthread.cfm?qid=491479