Hi Bill.
The previous structure may well still be standing but even with 2 beams of that size you are under spec for any loading above self-supported load.
As A rule for a clear span, the calculation is span divided by 20 plus 20 mm or 1 inch. If you want to go with the 2 by beams I would suggest making them flitch beams by adding a section of either 18 gauge steel or 1/2 plywood and fixing these with coach bolt through the neutral axis- the middle.
The deflection is calculated with two factors dead load = structural weight - all components and live load, wind and snow. You can not always be sure that all the load with distributed evenly - UDL and not a point load. It might be OK. But as it is impossible to allocate 100% UDL I would size up.
Also, you are not showing any diagonal wind bracing to the corners of the side or rear structures. I assume the structure is open and not closed.
Just a thought- by no means a structural analysis.
The previous structure may well still be standing but even with 2 beams of that size you are under spec for any loading above self-supported load.
As A rule for a clear span, the calculation is span divided by 20 plus 20 mm or 1 inch. If you want to go with the 2 by beams I would suggest making them flitch beams by adding a section of either 18 gauge steel or 1/2 plywood and fixing these with coach bolt through the neutral axis- the middle.
The deflection is calculated with two factors dead load = structural weight - all components and live load, wind and snow. You can not always be sure that all the load with distributed evenly - UDL and not a point load. It might be OK. But as it is impossible to allocate 100% UDL I would size up.
Also, you are not showing any diagonal wind bracing to the corners of the side or rear structures. I assume the structure is open and not closed.
Just a thought- by no means a structural analysis.