Shved Y. Strength and deformability of a rectangular welded truss under force and temperature effects

The dissertation is dedicated to the current problem of determining the allowable loads on welded rectangular trusses, taking into account the impact of operational temperatures in both climatic and technological ranges. Solving this problem will facilitate the maximum utilization of the load-bearing capacity of structures and prevent their accidental failure during operation. Welded trusses are typically used in the construction of industrial, commercial, and sports facilities as intermediate supports for roofing structures, as well as for supporting technological equipment. The length of these trusses is usually 12-36 meters. Even under the influence of only climatic temperature fluctuations, internal stresses form in the elements of the structure and at the welded joints, which combine with stresses from force impact and reduce the overall calculated strength of the structure. The aim of the research is to identify the deformation parameters and conditions of failure of welded rectangular trusses under the combined action of force and temperature factors. The truss design and its loading scheme were selected, comprehensive experimental research methods were developed, and recommendations were formulated for determining the strength of the trusses both at the design stage and during operation. The research was conducted on a rectangular welded truss with parallel chords, supported at both ends from below and loaded with concentrated force at two points on the upper chord. Several design variants of trusses with different sizes and types of profiles were considered. Studies were carried out for both full-scale trusses and their physical models under conditions of static loads and temperature effects. The research results showed that the trusses lose stability and fail due to plastic deformation. Computer modeling was performed using the Ansys software package, which allowed assessing the behavior of the structure under the combined action of force and temperature effects. Full-scale studies of the mechanical properties of VSt3ps steel in the temperature range from 20 to 450°C made it possible to identify deformation and failure parameters of the structures with high accuracy. Based on the research results, an analytical dependency was developed to account for the temperature effect on the load-bearing capacity of welded rectangular trusses, and recommendations were formulated for their practical application in design and operation.