  Networks of elastic beams can deform either by stretching or bending of their
members. The primary mode of deformation (bending or stretching) crucially
depends on the specific details of the network architecture. In order to shed
light on the relationship between microscopic geometry and macroscopic
mechanics, we characterize the structural features of networks which deform
uniformly, through the stretching of the beams only. We provide a convenient
set of geometrical criteria to identify such networks, and derive the values of
their effective elastic moduli. The analysis of these criteria elucidates the
variability of mechanical response of elastic networks. In particular, our
study rationalizes the difference in mechanical behavior of cellular and fiber
networks.
