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This paper deals with experimental research of stability behaviour of laminated structural glass beams. The purpose of the research is the evaluation of lateral-torsional buckling resistance and actual behaviour of the beams due to absence of standards for design of glass load-bearing structures. The experimental research follows the previous one focusing on measuring of initial geometrical imperfections of glass members and experimental evaluation of flexural buckling resistance of structural glass columns. Within the frame of the research 9 specimens were tested. All of them were of the same dimensions - length 2400 mm and width 280 mm but different thicknesses - 12, 16, 20 mm. All the beams were composed of two annealed glass panes bonded together by PVB foil. Beams were loaded by couple of forces symmetrically situated to the mid-span and supports complied with fork boundary conditions. Specimens were loaded by constantly increasing force up to failure. During testing lateral deflection, vertical deflection, angle of torsion and normal stresses at mid-span were measured. Maximum bending moment achieved during testing has been adopted as lateral-torsional buckling resistance. From these values were calculated characteristics and design values according to the EN 1990. Experiment results were compared with lateral torsional buckling resistance calculated according to the buckling curves approach. [ABSTRACT FROM AUTHOR]

This paper deals with experimental research of axially loaded members made of structural (laminated) glass. The purpose of the research is the evaluation of buckling strength and actual behaviour of the columns due to the absence of standards for design of glass load-bearing structures. The experimental research follows the previous one focusing on measuring of initial geometrical imperfections of glass members. Within the frame of the research 15 specimens were tested. All of them were of the same geometry (length 1500 mm, width 150 mm and thickness 12 mm) but had different composition – monolithic glass or laminated double or triple glass made of annealed or fully tempered glass panes bonded together by PVB or EVASAFE foil. Due to rectangular cross section and considered boundary conditions, flexural buckling perpendicular to the weak axis of the cross section occurred. During the testing, lateral deflection and normal stresses at mid-span were measured. Maximum force achieved during the testing has been adopted as buckling strength. Euler's critical loads and equivalent geometrical imperfections were evaluated using a Southwell's method. The results of experiments were statistically evaluated according to the European standard for design of structures EN 1990, appendix D. There are significant differences between the specimens made of annealed glass or fully tempered glass and between the specimens laminated with using PVB or EVASAFE foil – the differences are in the values of buckling strengths and load – deflection, load - stress plots. The next step was to determine the design strength by calculation procedure based on buckling curves approach intended for design of steel columns. [ABSTRACT FROM AUTHOR]

This paper deals with the problems of analysis and the design of perforated thin-walled steel Sigma beams with respect to lateral torsional buckling (further LTB). The application of Sigma profiles is in the storage systems and expedient flooring structures as floor girders. In some cases, the beams are not laterally restraint and therefore the effect of lateral torsional buckling may occur. First the theoretical calculations according to the design procedure listed in European standard EN 1993-1-1 and Czech national annex NB.3 are being performed. These calculations are valid for the beams with the uniform cross-section only without any rules for the beams weakened by holes. Therefore the substitute cross-section is being established and the cross-section characteristics are defined as the weighted average of the characteristics for the full section and for the section weakened by holes. The calculated elastic critical moments for the substitute cross-section properties are verified by the FEM calculations on the beam with variable cross-section. This theoretical approach is verified by testing in laboratory conditions. The experiments are being carried out on the specimens of three different beam lengths. The test results are statistically evaluated according to EN 1090 and the characteristics bending resistances obtained from tests are compared with the values calculated according to EN 1993-1-1 and Czech national annex NB.3 using the cross-section characteristics of substitute cross-section. [ABSTRACT FROM AUTHOR]

As cold-formed steel profiles are increasingly used for load-bearing structural systems, their fire design requires specific attention due to their thin-walled nature and high slenderness. In some specific applications such as in storage hall floor systems, these structures are used without sheathing or thermal protection on the fire-exposed side. Yet, there is a lack of data from fire resistance tests on full-scale load-bearing thin-walled steel structures, especially with directly exposed steel. This article describes two standard fire resistance tests on full-scale light gauge steel frame floors made of cold-formed steel lipped channel girders and joists topped by chipboard panels. The experimental program was designed to investigate the fire resistance of the unprotected girders. A specificity of this program was that the girders were subjected to a low load level to probe the ability to achieve without passive fire protection a 30-min fire resistance rating typical for storage hall structures in the Czech Republic. The absence of protection resulted in differences in thermal gradients and bracing compared to common fire tests, as well as a very low degree of utilization leading to an expected failure temperature higher than 800 °C. The results showed that the two floors remained stable during the 30 min with limited deflections, but failed the deflection rate criteria after 24 and 22 min, respectively. Comparison is provided with the calculation methods from the Eurocodes. The presented results provide new data on the response of full-scale, unprotected cold-formed steel floor systems subjected to fire, which can be used to calibrate numerical models and fire design methods outside of the range currently covered by the codes. • Fire design of thin-walled steel structures requires specific attention. • Lack of data from fire resistance tests on full-scale thin-walled steel structures. • Some thin-walled structures are designed without the use of passive fire protection. • Calculation methods show good agreement with test data in temperature predictions. • The test results can be used to calibrate numerical models and fire design methods. [ABSTRACT FROM AUTHOR]