I am an engineer and have designed and installed a number of steel strap systems to stiffen floors. The first time took a bunch of calculations to determine fastener schedules and such, but wood is a nice material to place nails and screws into. Unlike metal to metal joints were deformation occurs in the fasteners weakening them, deformation in pinned (the engineering term for nailed or screwed) joints, the wood deforms and increase in bearing capacity from any slight crushing that occurs since the load is spread out in the wood over a larger area. The equations needed are the same ones used to develop the amount of weld bead required to create a fabricated steel I-beam.
It is that slight deformation that allow an I-beam made from wood, metal, or a combination of the two to bear loads.
Deformable bodies and how to design and engineer things for strength and efficient use of material is not always an obvious area for amateurs to delve into.
Doubling up a joist doubles the strength. Adding an 2x4 flat bottom edge of a 2x10 joist increase the strength also doubles the strength, and for a lot less material.
As for experience, I have a PE seal and over 30 years experience in composite structural design and electrical engineering. When I start having problems with a design I have two other structural engineers to fall back on.
Fasteners strength in tension (withdrawal) loading is so variable that it is assigned a load value of ZERO. Nothing. Only through bolted fasteners can be relied upon in this application. Unless you through bolt the angle (or a strap) you have not provided a reliable joint.
Even a flitch design (a steel plate between 2 pieces of lumber) requires as a minimum clenched nails, and I would never allow those. I require through bolted fasteners in tightly drilled holes. A reliable flitch beam con only be made by clamping all the layers together, and then drilling the fastener holes. This eliminates any tolerance stack up in the drilled holes.
It is possible to fasten steel to one side of a lumber section and through bolt, but the number of fasteners required to prevent buckling often results in weakening of the beam. The loads under each and every fastener on the wood side must be examined for bearing pressure and held to below about 30-70 PSI (depending on the actual wood species used). These joints also have a greater problem with loosening of the fasteners from dimensional changes in the wood weakening the beam. This effect is present I a full flitch, but is not as serious since the wood itself acts to spread out the loading and prevent buckling over the entire area of the flitch, instead of being concentrated strictly at the fasteners.
Is Silva going to be held responsible for his 'designs' forever? That is what a PE seal on a design entails.
I have spent many years fixing the screw ups from GCs and carpenters who have a Âworking knowledge of how to build. The most recent was a floor made from I-joist with a 24 foot span. The building code allows 1/360 deflection. Over a 24 foot span that is 0.8 inches. While structurally adequate, the floor was like a trampoline. So much for using span tables.
And by the way, fixing I-joist span problems is a lot harder than 2x joist span problems. In many cases the only fix is a perpendicular beam and a post. The web of an I-joist cannot sustain the loads of increasing the lower flange.
Q