Fire Safety of Plane Steel Truss according to System Reliability Analysis Combined with FORM Method: The Probabilistic Model and SYSREL Computation

Abstract

This article focuses on the reliability analysis of the plane steel truss under fire conditions. The safety of the structure was estimated by system reliability analysis combined with First Order Reliability Method (FORM). The authors created the C++ code, which enables us to prepare the advanced probabilistic model for bearing capacity in the selected time of fire duration. Searching cut-sets for system analysis was performed in the C++ code, where stiffness matrix spectral analysis was employed. It was found that a probabilistic model has significant influence on the reliability indices. The research showed that depending on the probabilistic model, the sensitivity of the reliability index to individual variables is different.

The safety of steel space truss under fire conditions according to the system reliability analysis.

“…In this way, it is possible to get the reliability index for the whole structure, not for individual members. The utility of this method for plane trusses was checked by the author in previous publications [17][18]. The present research has an initial character and there is tested if the system reliability analysis is an appropriate tool to assess the safety of spatial steel truss under persistent design situation and under fire influence.…”

The probabilistic model for system reliability analysis of a steel plane and spatial trusses

“…In other words, the cut-sets are such sets of elements whode failure determines the failure of the whole structure. The method of searching cut-sets for plane trusses was presented in the previous author's papers (Kubicka et al, 2019;Kubicka, 2022;Kubicka and Sokol, 2023). Generally, the method is based on spectral matrix stiffness analysis and is appropriate for both persistent and accidental (fire) design situation.…”