In diesem Beitrag werden Berechnungen und vergleichende experimentelle Ergebnisse des Stabilitätsverlusts von schlanken Stahlbetonstützen aus einer Versuchsreihe präsentiert. Das primäre Ziel der Arbeit war der Vergleich der Bemessungsmethoden bei der Ermittlung der globalen Zuverlässigkeit schlanker Stahlbetonstützen. Der Schlankheitsgrad der Stützen betrug λ > 90, wobei die untersuchten Stützen nach EN 1992‐1‐1 dimensioniert wurden. Die oben erwähnten experimentellen Untersuchungen dienten zudem als Grundlage für die Bewertung und Kalibrierung der deterministischen und probabilistischen nichtlinearen Modellbildung. Diese probabilistische Modellbildung der Normalkraft‐Momenten (N‐M)‐Beziehung und des Stabilitätsversagens ist eine Grundlage für die Entwicklung eines objektivierten Bemessungsansatzes und der zugehörigen Teilsicherheitsbeiwerte.

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In the past, research on the use of FRP in civil engineering has been focused on strengthening existing structures where FRP reinforcements were applied to the surface of concrete elements. Recently, the application of FRP reinforcements has been studied to replace steel reinforcements for use in areas of increased environmental loads, with a need to exclude the corrosion of the reinforcement or to ensure the electromagnetic neutrality of the individual elements of the load-bearing structure. The GFRP reinforcement ratio was verified considering failure modes in flexure and the bond of the GFRP reinforcement with concrete. Besides classical reinforcements, GFRP has also been used in prestressed variants, and the possibility of its use as permanent formwork has been verified. In terms of extending the use of non-metallic reinforcements, it is important to note the long-term exposure and possible degradation of the mechanical properties.

Standard for designing of concrete structures STN EN 1992-1-1 offers three methods of analysis of second order effects with axial load. Namely, a general method based on non-linear second order analysis and two simplified methods: Method based on nominal stiffness and method based on nominal curvature. According to three series of the experiments of slender concrete columns and after calibration of the non-linear calculations, the authors in following paper compare the global reliability of above mentioned design methods with parametric study. According to executed research is possible to say that the differences in reliability of the design methods are considerable in several cases of the slender concrete columns design.The experiments were executed in the Central laboratory of Faculty of Civil Engineering STU in Bratislava in cooperation with company STRABAG ltd. The series of columns differed only in strength class of concrete (C45/55 for S1, C70/85 for S2, C80/95 for S3) and each series included six tested samples. The geometry and reinforcement of the columns as well as the initial eccentricity of the axial force were design so, that the buckling failure of the columns occurred earlier than the design strength of materials in the most stressed cross-section ran out.

The evaluation of non-metallic reinforcing in slender concrete slabs is discussed in this article. The experimental campaign investigated the flexural behavior and the bending capacity of concrete slabs reinforced with Glass fiber reinforced polymer bars. A total of 6 slabs with a length of 1.36 m and cross-sectional dimensions of 0.50 x 0.04 m were tested until failure. The effective depth and reinforcement ratio are the same for all slabs. With an effective span of 1.3 m, the slabs were simply supported and tested in a four-point bending experimental setup. ATENA 3D, a finite element nonlinear solver, was used to simulate the experimental approach. The meshing was done using brick elements, and the calculation was performed with the Newton-Raphson method. The article compares the experimental program and nonlinear analysis performed in ATENA 3D program. The theoretical analysis outcomes are also introduced by calculating the deflection of the slab in the midspan. The correlation and a good agreement between numerical results and experimental outcomes are presented in the paper.