How can I repair my built-in luggage closet shelving?

Question

This is a built in (probably 50yo) set of wooden shelves in a basement sort of utility closet (off a finished room, but sort of in similar space as the mechanicals, I.e. non finished closet). The shelving has always been used for light supplies like luggage, sleeping bags, etc. and I would like to keep using it for the like. The problem is shelves starting to detach and warp.

As you can see, the front post is very insubstantial, but intact. And then the shelves themselves are pretty flimsy, but also intact. However the nails are ripping out connecting the front of the shelves to the front post.

However, other than that, the shelves are pretty nice in terms of using the whole space in width/height and are also fairly deep. Each shelf is 18"h by 30" deep by 48" wide.

CAVEAT: Please realize I'm not mechanically adept; I don't have a table saw.

Answer 1

Do your planned cleaning.

Plywood is actually very strong, but it does bend and warp. I would keep it.

The center support is actually very well suited for the lightweight stuff you plan to store on the shelves. Keep it.

The only issue is the 2 middle shelves are sagging. These need support. Get a length of 1x2 much like the center support. An 8 foot piece will work. Cut the piece to fit on the underside of the front of the center shelves. spanning the entire length from left end support to the right end support.

Attach the 1x2 on edge with screws from the plywood down into the 1x2. This will take the sag out of the plywood. Then attach the 1x2 to the center support with a screw. Run a screw at an angle through the front of the 1x2 into the side support wood at both ends. ( see the blue line on the pic. excuse the squiggle, not tech design educated.)

You have now taken the sag out of the shelves and given them more support. Drive the nails that are sticking out back into the wood. Done.

Answer 2

Personally, I think the easy button here is to just double up on the central vertical member, which looks like 1x2.

Remove any "little blocks" from the central post. Measure a piece of 1x2 that runs from the floor to the bottom of the first shelf. You can use the non-sagged sides of the shelf to measure this. Set one end of the new piece where the post meets the shelf (where the "little block" was), and the other on the floor. Hammer the bottom end of the piece in til it's vertical, i.e. flush against the post. Screw both together...don't need many screws, probably two—top and bottom—is enough. That way the new piece actually supports the shelf from below.

Repeat for each shelf; instead of being jammed against the floor, the subsequent pieces will be jammed against the top of the shelf below.

(The failure in design here was that the post relies on screws into a plywood edge for support.)

Edit: added sketch (including side view) of what I mean. Grey box is concrete floor, blue is existing shelf members, red is new 1x2 attached to the existing central post.