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Given the illustration above:

Are there any tips on how to ensure that the beam load is correctly distributed across the three posts?

All posts are adjustable (up/down) via hex nuts so I have full control over the height of each post.

[Edit for clarification]

My concern is how to ensure that all posts are actually loaded as they should given their respective position. For example, if I lower the middle post (via hex nut), almost all of the load will be on the outer posts. On the contrary, if I make the middle post higher than it should (via the hex nut), then it would be incorrectly offloading the outer posts. That said, I am trying to see how to properly adjust the heights of the three posts to ensure that each is bearing the load it is supposed to do.

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    I think perhaps the question shouldn't be about loading exactly (the posts should be over-engineered to withstand any range of loads put on them), but adjustment. If you asked about adjustment, I'd say put a string on the beam and push the middle up until the beam is flat. If the beam is crown up, simply snug the central post into position. – Aloysius Defenestrate Jul 29 '18 at 13:18
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I am no statics-engineer nor a framer or carpenter.

But.

You can use belleville washer stacks to adjust the load. The idea is that the washers are conic shaped and will flatten upon load. You insert the right number of washers for your purpose, designed to the load. You can then tighten each nut holding the load (between anchor and frame shoe), untill the washers sit at exactly the same height. You will now have exactly (within the uncertainity of the washers and your height measurement) equal load on all frame shoes. That may or may not be - but in your sketch looks like it would be - equal even load on all frame posts.

How wise or useful it is, I am not the man to ask.

Edit: This of course evens out a static load. If you move something heavy from one end to the other, it will not be even anymore (it might also shift, slightly, the height of the stack.)

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  • Since the OP indicated that the saddles are all already adjustable via bolts on threaded rods, I'm not sure how adding washers into the mix would have fixed his problem. – FreeMan Feb 22 at 12:15
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The load will NEVER be equally loaded on the three supports.

The center support will carry twice the load of the end supports. Likewise, the center support needs to be twice as strong, have twice the footing size, etc.

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  • I understand your point. Thanks for sharing your thoughts. My concern is how to ensure that all posts are actually loaded as they should given their respective position. For example, if I lower the middle post (via hex nut), almost all the load will be on the outer posts. On the contrary, if I make the middle post higher than it should (via the hex nut) it would be incorrectly offloading the outer posts. That said, I am trying to see how to properly adjust the heights of the three posts to ensure that each is bearing the load it is supposed to do. Hope this clarifies. – Andrew Hanson Jul 29 '18 at 6:21
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    @AndrewHanson Your synopsis would be true, except for the phenomenon of deflection of the wood member. If your concern is “how exact do the supports need to be to be fully loaded?” We call that “transferring the load”. Well...nothings perfect. I’d make all the connectors the same height (+-1/8”) and the beam will deflect when loaded, unless the beam is cambered so much that it does not touch a support when loaded. That is to say, the beam will deflect sufficiently to fully transfer the load to each bearing point. – Lee Sam Jul 29 '18 at 7:51
  • This type of bearing does not resist uplift forces, right? Seemingly most people don't worry about that. I know when I cut off some rotten posts supporting a porch roof I just put this same type of truncated pyramid concrete blocks under the posts. I didn't bother to secure the blocks to the slab although I have secured the posts to the blocks against lateral forces. The blocks themselves are just resting on an existing concrete slab and I'm depending on friction to resist lateral movement. I suppose I could have drilled the slab and the underside of the blocks and put in pins . . . – Jim Stewart Jul 29 '18 at 12:37
  • @JimStewart I agree, most people don’t worry about uplift or lateral loads. The op does show a hanger with a bolted fastener, but hasn’t worried about that issue...yet. – Lee Sam Jul 29 '18 at 14:59

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