Design of composite columns based on Eurocode – comparison between general and simplified methods

[EN] In this paper, the results of a comprehensive parametric study for the member capacity of columns subjected to axial forces on the one hand and axial forces plus bending moments on the other hand are presented, considering all relevant types of composite sections: a) concrete encased sections, b) partially encased sections, c) concrete filled rectangular and circular tubes. Different steel grades and concrete strength classes are also considered. Firstly, the different methods of design in the Eurocode are briefly summed up: a) simplified method, based on buckling curves, for axial forces only, b) simplified method, based on a section verification with 2nd order moments, including equivalent geometric imperfections, c) a general method, based on geometrical and material nonlinear calculations with 3D-FEM-models. In the main part of the paper, the buckling resistance of the columns, based on these 3 methods, are compared, over the whole range of relative slenderness, for different section types, material strengths and type of loading (N, N + Mz, N + My). Also in the case of columns subjected to bending moments about the strong axis and axial forces, buckling about both axis is studied in detail.Unterweger, H.; Kettler, M. (2018). Design of composite columns based on Eurocode – comparison between general and simplified methods. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 757-782. https://doi.org/10.4995/ASCCS2018.2018.7064OCS75778

Hardware-aware block size tailoring on adaptive spacetree grids for shallow water waves.

Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Though they directly yield an adaptive spatial discretisation, i.e. a mesh, it is often more efficient to augment them by regular Cartesian blocks embedded into the spacetree leaves. This facilitates stencil kernels working efficiently on homogeneous data chunks. The choice of a proper block size, however, is delicate. While large block sizes foster simple loop parallelism, vectorisation, and lead to branch-free compute kernels, they bring along disadvantages. Large blocks restrict the granularity of adaptivity and hence increase the memory footprint and lower the numerical-accuracy-per-byte efficiency. Large block sizes also reduce the block-level concurrency that can be used for dynamic load balancing. In the present paper, we therefore propose a spacetree-block coupling that can dynamically tailor the block size to the compute characteristics. For that purpose, we allow different block sizes per spacetree node. Groups of blocks of the same size are identied automatically throughout the simulation iterations, and a predictor function triggers the replacement of these blocks by one huge, regularly rened block. This predictor can pick up hardware characteristics while the dynamic adaptivity of the fine grid mesh is not constrained. We study such characteristics with a state-of-the-art shallow water solver and examine proper block size choices on AMD Bulldozer and Intel Sandy Bridge processors

T6SS intraspecific competition orchestrates Vibrio cholerae genotypic diversity

Vibrio cholerae is a diverse species that inhabits a wide range of environments from copepods in brackish water to the intestines of humans. In order to remain competitive, V. cholerae uses the versatile type-VI secretion system (T6SS) to secrete anti-prokaryotic and anti-eukaryotic effectors. In addition to competing with other bacterial species, V. cholerae strains also compete with one another. Some strains are able to coexist, and are referred to as belonging to the same compatibility group. Challenged by diverse competitors in various environments, different V. choleare strains secrete different combination of effectors - presumably to best suit their niche. Interestingly, all pandemic V. cholerae strains encode the same three effectors. In addition to the diversity displayed in the encoded effectors, the regulation of V. cholerae also differs between strains. Two main layers of regulation appear to exist. One strategy connects T6SS activity with behavior that is suited to fighting eukaryotic cells, while the other is linked with natural competence - the ability of the bacterium to acquire and incorporate extracellular DNA. This relationship between bacterial killing and natural competence is potentially a source of diversification for V. cholerae as it has been shown to incorporate the DNA of cells recently killed through T6SS activity. It is through this process that we hypothesize the transfer of virulence factors, including T6SS effector modules, to happen. Switching of T6SS effectors has the potential to change the range of competitors V. cholerae can kill and to newly define which strains V. cholerae can co-exist with, two important parameters for survival in diverse environments

T6SS intraspecific competition orchestrates Vibrio cholerae genotypic diversity

Vibrio cholerae is a diverse species that inhabits a wide range of environments from copepods in brackish waterto the intestines of humans. In order to remain competitive, V. cholerae uses the versatile type-VI secretion system (T6SS) tosecrete anti-prokaryotic and anti-eukaryotic effectors. In addition to competing with other bacterial species, V. cholerae strainsalso compete with one another. Some strains are able to coexist, and are referred to as belonging to the same compatibility group.Challenged by diverse competitors in various environments, different V. choleare strains secrete different combination of effectors– presumably to best suit their niche. Interestingly, all pandemic V. cholerae strains encode the same three effectors. In additionto the diversity displayed in the encoded effectors, the regulation of V. cholerae also differs between strains. Two main layersof regulation appear to exist. One strategy connects T6SS activity with behavior that is suited to fighting eukaryotic cells, whilethe other is linked with natural competence – the ability of the bacterium to acquire and incorporate extracellular DNA. Thisrelationship between bacterial killing and natural competence is potentially a source of diversification for V. cholerae as it hasbeen shown to incorporate the DNA of cells recently killed through T6SS activity. It is through this process that we hypothesizethe transfer of virulence factors, including T6SS effector modules, to happen. Switching of T6SS effectors has the potential tochange the range of competitors V. cholerae can kill and to newly define which strains V. cholerae can co-exist with, two importantparameters for survival in diverse environments

Block Fusion on Dynamically Adaptive Spacetree Grids for Shallow Water Waves

Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Even though they directly yield a mesh, it is often computationally reasonable to embed regular Cartesian blocks into their leaves. This promotes stencils working on homogeneous data chunks. The choice of a proper block size is sensitive. While large block sizes foster loop parallelism and vectorisation, they restrict the adaptivity's granularity and hence increase the memory footprint and lower the numerical accuracy per byte. In the present paper, we therefore use a multiscale spacetree-block coupling admitting blocks on all spacetree nodes. We propose to find sets of blocks on the finest scale throughout the simulation and to replace them by fused big blocks. Such a replacement strategy can pick up hardware characteristics, i.e. which block size yields the highest throughput, while the dynamic adaptivity of the fine grid mesh is not constrained—applications can work with fine granular blocks. We study the fusion with a state-of-the-art shallow water solver at hands of an Intel Sandy Bridge and a Xeon Phi processor where we anticipate their reaction to selected block optimisation and vectorisation

Reframing pension policy: A comparative perspective on communicative discourse in Austria and Germany

Bismarckian pension systems are usually depicted as path-dependent. Nonetheless, many formerly traditional Bismarckian systems shaped by public old-age provision have recently been reformed towards capital-funding and privatization, therefore paving the way for structural change usually not accounted for by path-dependency literature. However, the extent of those reforms varies drastically, even between relatively similar countries like Austria and Germany. Those very similar countries, previously organising their pension systems through a social insurance principle (Bismarckian pension systems), having the same welfare regime (conservative), being subject to demographic and budgetary pressure with roughly the same economic performance, have taken drastically different paths in the beginning of 21th century. This master thesis now aims to address this research puzzle through empirically assessing the power of ideas and discourse in explaining policy change. The main argument of this research is that policy actors and entrepreneurs in Germany were able to implement wide ranging reforms because they successfully handled the policy and political stream, framing communicative discourse until privatized, funded pension policies were seen as a cognitively and normatively acceptable solution, while their Austrian counterparts failed to do so. Methodologically, this master thesis tries to present evidence through a discourse analysis of 357 newspaper articles published during the specific reform periods in which privatization was considered as a policy alternative in Austria as well as Germany. Ultimately, evidence suggests that ideas and discourse can indeed make a difference. Not everything happens behind closed doors, even in corporatist, multi- actor systems. Policy entrepreneurs indeed act as discoursive actors and engage in communicative discourse to promote their favoured policy ideas. Pension reform in Germany involved a long and decisive framing process. In Austria, such an open attempt to frame communicative discourse towards privatization and capital funding was not visible. Ideas incompatible with the hegemonic discourse have had a hard standing because they were cognitively and normatively not accepted and provoked decisive action by opposing discoursive actors, suggesting that the framing process has to begin early enough and has to be coherent and consistent. Respectively, strong opposing discoursive actors can also defend the hegemonic discourse through quick and decisive action