The proposed paper focuses on the method of estimating the reliability
index β (as a safety measure) of the spatial steel truss under fire
conditions. The whole procedure connected with computation of
temperatures of elements, effects of actions and bearing capacities is
realised in author-designed C++ code, prepared according to Eurocode.
The probabilistic model includes mechanical properties of steel (yield
strength), geometrical characteristics of bar cross-sections and effect
of actions. In the next step, the stiffness matrix spectral analysis is
realized. The code prepared by the author is being developed to be
useful for spatial structures. The program realization leads to finding
so called cut-sets, i.e. possible ways of transforming the structure
into mechanism. These sets of elements create a logical model, which
will be introduced to the SYSREL module, which is part of STRUREL
program. This is the software that was created in Munich University of
Technology to solve reliability problems. SYSREL module is dedicated to
conduct system reliability analysis connected with different reliability
methods including, among others, the FORM,SORM, Monte Carlo and Subset
Simulation method.