Author, Institution: Deividas Martinavičius, Kaunas University of Technology
Science area, field of science: Technological Sciences, Civil Engineering, T002
Scientific Supervisor: Assoc. Prof. Dr. Mindaugas Augonis (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002)
Dissertation Defence Board of Civil Engineering Science Field:
Prof. Dr. Tadas Ždankus (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002) – chairperson
Prof. Dr. Mindaugas Daukšys (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002)
Dr. Joao Pedro Firmo (University of Lisbon, Portugal, Technological Sciences, Civil Engineering, T002)
Assoc. Prof. Dr. Darius Zabulionis (Vilnius Gediminas Technical University, Technological Sciences, Civil Engineering, T002)
Prof. Dr. Valdas Eidukynas (Kaunas University of Technology, Technological Sciences, Mechanical Engineering, T009)
The doctoral dissertation is available on the internet at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).
Steel-concrete structures have a higher stiffness and fire resistance than steel structures and are more slender than concrete structures. The closed section steel profile also acts as a formwork for the infill concrete. In some cases, the width-to-thickness ratios of steel cross-sections may be high because thinner steel panels tend to cost less. Steel profiles with high width-to-thickness ratios are susceptible to local buckling, and the design procedures of regular steel sections are well known. However, local buckling in composite structures is less severe compared to local buckling in regular steel sections. Some of the globally used design codes, such as EN 1994-1-1, feature no specific design rules and expressions for thin-walled steel-concrete cross-sections. Using the design expressions of the regular steel cross-sections, the resistance of the steel profile in the steel-concrete cross-section is underestimated. In this thesis, local buckling phenomena in thin-walled welded steel-concrete structures is analysed. State-of-the-art review is presented. Two-part experimental campaign is carried out. Axial load-shortening results of steel-concrete columns and moment-deflection results of steel-concrete beams are presented. Critical stress and ultimate stress results of steel panels in steel-concrete columns are calculated using various theoretical methods. Numerical analysis of steel-concrete columns and beams is carried out. The average normal stress-strain model for compressed steel panels undergoing local buckling in concrete-filled welded steel structures is proposed. The proposed model is used to obtain the theoretical moment-deflection curves of steel-concrete beams via the iterative layer method.