| Abstract [eng] |
Steel structures designed for mounting traffic control devices – traffic lights and associated equipment – are analysed in this thesis. The main aim of the work is to investigate the strength of these structures and to assess the possibilities of reducing their member cross-sections in order to achieve more efficient use of material. The theoretical part reviews scientific and technical literature on lightweight steel structures, their application to traffic light and road sign supports, and discusses the relevant requirements of Eurocodes and Lithuanian technical regulations as well as their application to the design of structures supporting traffic control devices. The methodological part describes the numerical modelling of three types of supports – a frame truss, a cantilever truss and a cylindrical-conical cantilever – using the software Autodesk Robot Structural Analysis Professional 2021 and the Finite Element Method. The models take into account the self-weight of the structure and the mounted equipment, wind and ice loads, and Ultimate Limit State load combinations are formed in accordance with Eurocode provisions and national regulations. In the research part it is determined that the initial support configurations are characterised by relatively low member utilisation ratios: the average utilisation of the frame truss members is about 7 %, of the cantilever truss – about 15 %, and of the cylindrical-conical cantilever – about 47 %, which indicates a high safety reserve and inefficient use of steel. Using a trial-and-error approach, smaller cross-sections of the support members are selected: bar diameters are reduced in the frame and cantilever truss structures, and tube wall thicknesses are reduced in the cylindrical-conical cantilever. After changing the profiles, the average utilisation ratio of the frame truss members increases to approximately 18 %, of the cantilever truss – to about 28 %, and of the cylindrical-conical cantilever – to about 60 %, while the utilisation ratios of the most highly loaded members approach but do not exceed the allowable limit. The results show that by rationally adjusting the cross-sections of support members without changing the topology of the structures, it is possible to significantly reduce steel consumption while maintaining the required structural reliability. |
