Kinematically Admissible Failure Mechanisms for Plane Trusses

The reliability models of statically indeterminate steel trusses are analysed in this paper. The plane trusses are considered. For analysed structures types of reliability model are determined. Identification of system reliability is based on studies on the transformation from the safe structural system into the geometrically variable system (mechanism). These researches intended to determine the kinematically admissible failure mechanisms which contain minimal critical sets of elements. For analysed truss the formula setting out the number of mechanisms for any number of repeatable sections is determined. To identify the mechanism, spectral analysis of the linear stiffness matrix is used. This stage of the study, in conjunction with consideration of static loads, allows to determine the minimum critical set of rods corresponding to the most probable scenario of the structural damage. For these analysis the computer program based on the finite element method has been created within the Mathematica environment.