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This presentation discusses the potentials of probabilistic methods in offshore foundation installation, from the perspective of probabilistic ground models and data-driven site characterization. We discuss about methodologies for utilizing site-specific geotechnical (CPT) and geological data, aiming to construct an integrated ground model that can predict stratigraphic profiles and useful for geotechnical design parameters at any location within a 3D domain. The predicted parameters and stratigraphy are then used to predict the probability of potential pile tip damage, upon collision with a boulder.
The fire stability of carbon fiber reinforced polymer (CFRP) shell structures was investigated using an intermediate-scale test setup. The shell specimens are representative of typical load-bearing CFRPs in modern civil aviation. The CFRP shell specimens were exposed to a fully developed fire with direct flame impingement to one side at a heat flux of 182 kW/m2. Specimens were simultaneously loaded with constant compressive force equal to 40% of the ultimate failure load. CFRP shells and four different fire retarding configurations, using integrated protective layers, were investigated. Unprotected CFRP specimens failed after just 27 s. Specimens with integrated protective layers with low heat conductivity and high burn-through resistance showed the most promising results. An integrated titanium foil decelerated the decomposition of the epoxy matrix and increased the time to failure by 68% compared to the unprotected CFRP shell.
The torsional buckling of a cruciform column under compressive load with a vertex plasticity model
(2011)
The torsional buckling of a plastically deforming cruciform column under compressive load is investigated. The problem is solved analytically based on the von Kármán shallow shell theory and the virtual work principle. Solutions found in the literature are extended for path-dependent incremental behaviour as typically found in the presence of the vertex effect that is present in metallic polycrystals.
At the critical load for buckling the direction of straining changes by an additional shear component. It is shown that the incremental elastic–plastic moduli are spatially nonuniform for such situations, contrary to the classical J2 flow and deformation theories. The critical shear modulus that governs the buckling equation is obtained as a weighted average of the incremental elastic–plastic moduli over the cross-section of the cruciform.
Using a plasticity model proposed by the authors, that includes the vertex effect, the buckling-critical load is computed for a aluminium column both with the analytical model and a FEM-based eigenvalue buckling analysis. The stable post-buckling path is determined by the energy criterion of path-stability. A comparison with the experimentally obtained classical results by Gerard and Becker (1957) shows good agreement without relying on artificial imperfections as necessary in the classical J2 flow theory.
In practice usually thin-walled cylindrical silos are supported locally at the bottom rim of the shell. In this area a stress concentration may occur, which is responisble for buckling of the shell. In the currently applied codes, there is no information, how to analyze the load-bearing capacity of theselocally supported shells. In this paper, a new design formula is given for determining the load-bearing capacity.