The nonlinear kinematics of thin shells is developed in full generality according to a
duality approach in which kinematics plays the basic role in the definition of the
model. The Kirchhoff–Love shell model is the central issue and is discussed in detail
but shear deformable and polar models are also considered and critically
reviewed. The analysis is developed with a coordinate-free approach which
provides a direct geometrical picture of the shell model. The finite and tangent
Green strains of the foliated continuum are explicitly expressed in terms of
middle surface kinematics. The new expressions contributed here do not
require the splitting of the velocity into parallel and normal components
to the middle surface, and provide a computationally convenient context.
Finite strain measures for the shell and their tangent and secant rates are
analyzed and consistency and nonredundancy properties are discussed. The
relations between the finite Green strain, its tangent and secant rates and the
corresponding shell strains, are provided. The differential and boundary
equilibrium equations of the shell are given in variational terms, both in unsplit
and split form. A new expression of the boundary equilibrium equations is
contributed and its mechanical soundness with respect to the classical one is
emphasized. Equilibrium in a reference placement for the shell model is briefly
discussed.