  A new class of micromechanically motivated chain network models for soft
biological tissues is presented. On the microlevel, it is based on the
statistics of long chain molecules. A wormlike chain model is applied to
capture the behavior of the collagen microfibrils. On the macrolevel, the
network of collagen chains is represented by a transversely isotropic eight
chain unit cell introducing one characteristic material axis. Biomechanically
induced remodeling is captured by allowing for a continuous reorientation of
the predominant unit cell axis driven by a biomechanical stimulus. To this end,
we adopt the gradual alignment of the unit cell axis with the direction of
maximum principal strain. The evolution of the unit cell axis' orientation is
governed by a first-order rate equation. For the temporal discretization of the
remodeling rate equation, we suggest an exponential update scheme of
Euler-Rodrigues type. For the spatial discretization, a finite element strategy
is applied which introduces the current individual cell orientation as an
internal variable on the integration point level. Selected model problems are
analyzed to illustrate the basic features of the new model. Finally, the
presented approach is applied to the biomechanically relevant boundary value
problem of an in vitro engineered functional tendon construct.
