Longitudinally stiffened plates are commonly used to increase the resistance to plate buckling. Closed cross‐section stiffeners provide high values of the torsional stiffness and thus are very efficient to avoid their premature lateral torsional buckling. With the current software tools, it is easy to assess the critical stress for the elastic global mode, taking into account the beneficial effect of these high values of torsional stiffness for stiffeners with closed cross‐sections. However, the torsional stiffness of longitudinal stiffeners is not considered in the analytical formula proposed by Annex A of EN 1993‐1‐5 for the assessment of the global buckling critical stress. A study is presented here where the effect of the torsional stiffness of longitudinal stiffeners on the plate buckling criterion of EN 1993‐1‐5 has been analysed. 216 configurations of stiffened plates were calculated through finite element GMNIA non linear analyses. Their compressive strength thus obtained were compared to their resistance to plate buckling as predicted by EN 1993‐1‐5, either by considering their torsional stiffness with EBPlate software or by completely ignoring it. The study clearly shows that EN 1993‐1‐5 leads to unsafe results when the torsional stiffness is taken into account in the calculations. Finally, it is concluded that the torsional stiffness of longitudinal stiffeners has to be ignored in the design of stiffened plates according to EN 1993‐1‐5.

Abstract:The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix. OPEN ACCESSMaterials 2014, 7 6046

Concentrically braced frames (CBF) represent a very effective structural form against horizontal loading. They provide high lateral resistance at the same time limiting lateral displacements. Thanks to their simpler connection details and smaller cross sections, they are economic alternatives to the costly moment resisting frames. Nevertheless, concerning the seismic design, current Eurocode 8 provisions require a quite high level of complexity for the dissipative design of CBF structures. The global aim of this research is to find an optimal balance between safety and economy for the design of CBF structures, located in low-tomoderate seismic regions. New design rules will be proposed which will have less stringent local ductility and structural homogeneity requirements than current medium ductility class (DCM), and provide necessary safety level limiting the complexity and costs associated with anti-seismic design. This paper presents the results of the preliminary numerical analysis that has been realized thanks to the research fund received from European commission with the contract MEAKADO RFSR-CT-2013-00022. 3599

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