  In this study, we introduce a new class of rational elliptic 3-folds, which
we refer to as "1/2 Calabi-Yau 3-folds". We construct elliptically fibered
Calabi-Yau 3-folds by utilizing these rational elliptic 3-folds. The
construction yields a novel approach to build elliptically fibered Calabi-Yau
3-folds of various Mordell-Weil ranks. Our construction of Calabi-Yau 3-folds
can be considered as a three-dimensional generalization of the operation of
gluing pairs of 1/2 K3 surfaces to yield elliptic K3 surfaces. From one to
seven $U(1)$s form in six-dimensional $N=1$ F-theory on the constructed
Calabi-Yau 3-folds. Seven tensor multiplets arise in these models.
