Picnic bench design question

[chaoticbob]

I'm building a picnic bench to a design based on plans on the internet and onerous (but obviously necessary) researches in the gardens of local pubs. First time I've done anything like this, so please bear with me if my questions are naive!
This is where I'm at with the frame (a test bolt-up):

As it stands, the frame 'racks' slightly if pushed from the end - I guess that's to be expected, and I imagine it will be much more rigid when the top goes on and completes the triangles formed by the diagonal braces and the A frames. My worry is that the flanges on the ends of the diagonal braces are just butt joints secured by two 70mm deck screws. Any racking forces are going to try those joints. My gut feeling is that this a very weak spot in the design, especially as the screws go into (almost) end grain, although internet plans and observations tell me it's done like this.
So questions are: (a) am I worrying about nothing, and (b) if not, any suggestions for improving the design?
I should say that if this was going in my back garden I wouldn't worry, but it's destined for a public space so need to be proof against abuse.
Robin

 

[Inspector]

I'm no garden furniture designer but I'll toss in my suggestions for you to mull over.

I would skip the diagonal to the centre of the table and instead run one from each seat board position to the opposite side under the table. Offset them so they don't bend where they cross. Where they cross in the middle put a bolt through or a couple screws. That forms an "X" that is simpler and stronger than what you prototyped, even before the top goes on.

You can still put a cross piece across the middle to keep the top flat and if on it's side rather than edge, will not be hit by the knees of the person sitting in the middle of the seat. Set the end of it back an inch or so and bevel it and it will almost disappear visually.

At the "X" brace ends you run long screws in from the outside of the top and seat parts into them the parallel to the grain of the brace . Pilot drilling is a good idea too. Add the corner blocks on the inside of the table with a little caulking gun construction adhesive and the fasteners if you like. This kind of screw for the ends.
https://www.spax.com/en/products/constr ... /gid-3600/

 

[chaoticbob]

Thanks (belatedly) for your suggestions Inspector. That sounds like a more rigid design, though I've not seen it on any tables around here. Something to bear in mind for a MkII if it happens.
I think I've now answered my own question about joining end(ish) grain to to the flanges - either bed bolts (that's how Ikea do it, so must have something going for it!) or wooden cross dowels to give something for screws to bite into.
Robin.