Abstract:   A unified redundancy formulation for both the elastic redundancy and the geometrical redundancy is proposed to be applicable for cablestrut systems at prestressed state by considering the effect of prestresses. The updated Lagrange formulation is used to establish a nonlinear description of strain energy with respect to the displacement increment; a common linearization method is then adopted to reduce the numerical complexity. Based on this reasonable simplification, a unified evaluation for the redundancy is derived by using the principle of minimum potential energy, which is interpreted as a useful method for system identification at prestressed configuration. In comparison with existing studies, an explicit formula of geometrical redundancy is firstly presented and the physical meanings of redundancy are clearly addressed. Furthermore, it can be concluded that this proposed evaluation is valid for cablestrut systems with introduced pretensions.

Key words:  cablestrut structure; redundancy; principle of virtual displacements; principle of minimum potential energy; distributed static indeterminacy; distributed kinematic indeterminacy