×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

stress in two planks

stress in two planks

stress in two planks

(OP)
if i have two 8x10 can i combine them and calculate the stress over the combined thickensss
thanks

RE: stress in two planks

combine them how ... to get ...
16*10, 8*20, 10*16.

and then how are the loads oriented to the joint ?

and what is the primary load ... bending or compression ?

 

RE: stress in two planks

Good questions, rb1957.  My question is "since when is an 8x10 a plank?"

RE: stress in two planks

it'd be a very thick one, or a very narrow one ;)

RE: stress in two planks

Generally not.  If they're the same thickness and size, you could figure each carried half the load.  But that's not the same as figuring one plank twice as thick.

Consider why a cable if flexible, but a bar of the same size is not.

RE: stress in two planks

Bond, or fasten, the 2 8x10, then calculate as composite.
Otherwise, the above is accurate enough for practical purpose.  

RE: stress in two planks

For two beams combined, the bending stiffness will be determined by the addition of the 2nd Moment of Inertias, ie. bd^3/6. This assumes the worst case that there is no friction between them and they slide. If you bolt the two together, however, then the MOI will be based upon the combined thickness, ie. (2/3)bd^3

corus

RE: stress in two planks

I ususally assume each one carries half the load - assuming that the load rests rather evenly on each one.  Fasten together to act as one beam.

RE: stress in two planks

we're assuming this is a beam ... what if this is a column ?

if it is a beam, and they're just stacked on top of each other, and there's a point load on the upper one, then doesn't the lower beam provide a distributed reaction to the upper ? ... IMHO not the same as saying each reacts 1/2

RE: stress in two planks

Looks like technicalgirlca needs to provide a bit more information.

BA

RE: stress in two planks


It seems that technicalgirlca is not actively following this thread.  A clarification of the specific application is in order - beam or column?  orientation of the (2) 8x10s as rb1957 stated?

Ralph
 

RE: stress in two planks

Column will be lousier to address - side aways + compression. Difficult to justfied the 50/50 approach.

RE: stress in two planks

You can make them a composite wood beam using the shear flow equation VQ/Ib to determine the ingerstitial shear generated at the intersection from your particular loads.  Based on this shear value, you can determine the size and spacing of the thru-bolts to accomplish the composite action.  This is assuming that the members are placed one on top of the other.

However, if they are placed side by side, they are just the two original beams.  They should still be stitch bolted together, but this is mainly to get them to deflect uniformly, sharing the same load.

Mike McCann
MMC Engineering

RE: stress in two planks

if they're on top of each other, no.  unless you connect them and check horizontal shear.  

if they're side by side, technically no.....but you'd be splitting the load in half anyway between the two members, so numerically, it'll come out that way.  

whoops, msquared already said it.

LOL.

RE: stress in two planks

we've all said lot's of things ... but we need to OP to chime in ... beam or column ?

RE: stress in two planks

I think Mike has nailed it.   

BA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources