Finding joint loads for a structure

[Ld3Ake]

Hi,

Does anyone have any experience about how to find the forces acting on a joint that is subjected to an out of plane load? For example I have a square panel that I want to attach to a frame around the perimeter, so I would like to work out the corresponding joint loads in shear and tension (i.e. pull through). Calculating the joint force is relatively easy when the forces are only in-plane and the structure can be idealised as 2D, such as a bridge. I can't find any hand calculations though on how to account for the transverse loading.

To that end, I've gone down the FEA route. Abaqus allows me to extract the loads using 1D connector elements and I've set this up for my global structure. However I have doubts about the reliability of these values so I wanted to see if there were any analytical techniques that I could use to help me check the results.

Also my end goal is further complicated by the fact that the panel geometry is long and thin such that deflections are non-linear and membrane stiffening are induced. However for the moment I would settle for modelling joints with a thick plate in order to validate the joints loads as that way classical plate theory assumptions can be used.

Thanks for any help

 

[desertfox]

please provide a sketch or drawing it speaks a 1000 words.

 

[Ld3Ake]

Sure no problem

The first shows the general assembly (the lines down the middles are where I applied BCs for this scenario)

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The second is an example of the job after it has been run, focussing specifically on the joint loads.

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The third is an exaggerated deflection showing what is happening at the joints.
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I'm convinced there must be some sort of analytical solution. They have been designing aircrafts, cars, buildings for the past 100 years and I'm sure they didn't just wait for in-service feedback to determine if their joints were up to spec or not.

 

[jayrod12]

most manufacturer's of the fasteners provide pull out and pull over values for different gauge materials. Choose a standard spacing and then choose the fastener that works, or alternatively use the smallest fastener capacity to determine the fastener spacing.

 

[desertfox]

Hi Ld3ake

Sorry I cannot open tif's on iPad can you make them PDF's please.

 

[Ld3Ake]

Ok, so the plot thickens. We are using a composite materials, and specifically a composite sandwich structure, so we are particularly interested in knowing if our panel is suitable for rivet fastening. We have done experimental coupon tests on our material for shear and pull out, so what we know the strength of our material. We just don't know whether that strength is sufficient for the desired application (other than going for a full scale field test).

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