$mathbb{Q}$-trivial generalized Bott manifolds

When the cohomology ring of a generalized Bott manifold with $mathbb{Q}$-coefficient is isomorphic to that of a product of complex projective spaces $mathbb{C}P^{n_i}$, the generalized Bott manifold is said to be $mathbb{Q}$-trivial. We find a necessary and sufficient condition for a generalized Bott manifold to be $mathbb{Q}$-trivial. In particular, every $mathbb{Q}$-trivial generalized Bott manifold is diffeomorphic to a $prod_{n_i>1}mathbb{C}P^{n_i}$-bundle over a $mathbb{Q}$-trivial Bott manifold.