How do I calculate the equivalent resistance of this kind of circuit?
As (nearly) always, try and simplify: -

Move from top left to top right by using two star to delta transformations to produce: -


Ra, Rb, Rc


and 


Rd, Re, Rf




Bottom picture is the simplified combination of the the above right.

Can you take it from here by doing another star to delta transform on 3 more resistors?