The thing about hammocks is that they create tremendous sideways forces. With the following configuration, you balance them well, but still create large tensions in the cables and a very large compressive load on the upright:
Plugging in 150 pounds for mg, 4 ft for the post height h, 3 ft for d and w, and 20° for theta, you end up with a hammock tension (T1) of 263 lbs, a guy line tension (T2) of 240 lbs, and a pole compressive load (Fa) of 420 lbs.
Changing the mg, h, w, d, and theta variables will result in new values for each of these forces. For example, increasing w in relation to h will result in a lower compressive load on the pole, and a lower tension in the guy lines. For all other variables constant, changing w to 6 ft results in T2 = 161 lbs, and Fa = 255 lbs.
For best results, you want to minimize the bending moment of the posts, since that's what tends to pull them out of the ground. So attach your guy lines at the same spot as the hammock on the upright posts, and then attach the other end as close to the ground as possible. You'll probably just need some very beefy stakes, rather than T-posts for the end of the guy lines attached to the ground.
@Ratchet Freak's suggestion of angling the base of the poles in toward the center will increase compressive load on the poles an minimize tension in the guy lines, since Fa will be pointing up and away instead of just up. However, you run the risk of adding buckling and twisting as a problem with that solution.
Might I suggest using a hammock stand instead? They're not too much more expensive, and they'll do a much better job remaining stable.
Without a picture, I am guessing you want to frame a wall out of steel studs and you are asking how to fasten the track between the concrete beams. The only way to do this is to either run your wall all the way up to the slab, or to span the concrete beams perpendicular with a piece of track or stud. Just cut tongues on either side of the track and install it legs up with a shutgun or rotohammer every four feet. Once you have these up you can secure your top track to this. You won't need to do this at either end of the track since the end stud, which should be attached to the wall will hold the track.
Best Answer
I think you probably ought to abandon the project at this point. Metal joists can be surprisingly light gauge steel. Sheet metal screws would not be strong and reliable enough for the pullout strength you need, especially holding a moving object.
Toggle bolts would probably be strong enough, I don't see the bolts ripping right out of the sheet metal, but I could see the sheet metal flexing enough to mess up the drywall and possibly deform the joist, which would be a very expensive repair.