Flabel is formatted more like a modern structured course, Bruhn is more like a reference book, so that suggests where you can start, from that point of view.
I am not sure what fundamentals you want to build, so just doing hand-calcs from a textbook may not be the answer.
Assuming that you mean aluminum sheet-metal and riveted/bolted connections most common in 20th-century aircraft production, have you ever driven a rivet?
Have you drilled the hole, matched it to another mating piece, torqued the bolt, and load-tested the assembly to failure?
It's amazing how many engineers haven't done that stuff.

What kind of structure are you typically working on? (Wing? Fuselage? Control surfaces? Interiors? Landing gear....? ) New design or modifications?

How are your free body diagram skills? How is your familiarity with typical loadpath assumptions?
E.g. try freebody-ing a wing rib. Develop a shear and bending moment plot for it. Where would you take section cuts? How would you orient the section planes? How would you correct for flanges non-orthogonal to the cut plane? What failure modes would you check on the flanges... The web? The stiffeners?

Is that the sort of guidance you're after? Or something else?

I've also found these books by MICHAEL CHUN-YUNG NIU to be quite informative...

Airframe structural design : practical design information and data on aircraft structures

Airframe stress analysis and sizing

Composite airframe structures : practical design information and data

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

I'd start with your school/college/university texts, like for "Strength of Materials"

another day in paradise, or is paradise one day closer ?

You were told that your fundamentals are weak.

Your plan is to strengthen your stress analysis fundamentals knowledge.

Are you sure your plan is aligned with what your seniors are telling you?

Also an odd question: do You get excited about aero stress analysis... or is it just a job?

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

stressengineer26 went silent pretty fast...

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

Probably realized all he/she/ze was going to get was a lengthy list of rhetorical questions, or a printout from an IHS subscription.

Or read the FAQ page.