Post-Transformer RMS Voltage for This Circuit?
If you want 30Vdc, the peak AC voltage has to be 30V + 2 diodes = 31.4Vpk. The RMS is this divided by sqrt(2) = 22.2V RMS. This takes no account of ripple. If you factor ripple into the equation then you can assume the 30V is in fact 30V +/-1V. This equates to half the supply being 15V +/-0.5V i.e. 1Vp-p ripple.

So now the peak AC voltage is 31V + 2 diodes = 32.4Vpk. The RMS is then 22.9V.

As this appears to be the "correct" answer I can see that when you added onto the 30V the peak ripple you used twice as much - remember the ripple is peak-to-peak and only half of that counts towards pushing up the peak AC voltage.