Bed frame question

I was given a queen bedframe. the headboard and
footboard are wooden and connected by 2 metal rails
only. The rails have an inward curve to them and no
middle bar support or crossbeam(?). I need to
reinforce the middle because I just bought deep
boxspring and mattress. Can I buy a universal beam ?
I'm worried because these rails are curved in and I've
never seen that before!