Experimental study on ferritic stainless steel simply supported and continuous beams

Development of efficient design guidance for stainless steel structures is key for the increased use of this corrosion-resistant material by considering both nonlinear behaviour and strain hardening into resistance prediction expressions, together with the moment redistribution in indeterminate structures. With the aim of analysing the bending moment redistribution capacity of ferritic stainless steel beams, a comprehensive experimental programme on continuous beams is presented. These tests contribute to the assessment of EN1993-1-4 specifications, where no plastic design is allowed, and the classical and new plastic design methods available in the literature for indeterminate stainless steel structures. Four three-point and eight four-point bending tests are also reported for the assessment of current codified and revised cross-sectional classification limits, analysing the different methods for the prediction of the ultimate bending capacities of ferritic hollow sections. Additional test results reported by other authors in different stainless steel grades and carbon steel are also studied and presented. The analysis indicates that Class 1 cross-sectional classification limits are too optimistic for ferritic stainless steels and further research is needed for the extension of plastic design to these grades, although promising predictions of ultimate loads are obtained for austenitic and lean duplex stainless steels.Peer ReviewedPostprint (author's final draft

Draft genome sequence of Mycobacterium brumae ATCC 51384

Here, we report the draft genome sequence of Mycobacterium brumae type strain ATCC 51384. This is the first draft genome sequence of M. brumae, a nonpathogenic, rapidly growing, nonchromogenic mycobacterium, with immunotherapeutic capacities

Pre-normative recommendations for the system-based direct design of stainless steel frames using advanced analysis

This document includes the pre-normative recommendations developed in the NewGeneSS research project for the design of stainless steel frames using advanced analysisThe research project NewGeneSS, the acronym of “NEW GENEration design methods for Stainless steel Structures” was financed by the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Actions (2018). The NewGeneSS project aimed at developing the basis of system-based direct design approaches for stainless steel structures in the European framework by calibrating suitable system safety factors from rigorous structural reliability considerations, and at delivering the pre-normative design recommendations included in this document.The project leading to this document has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant Agreement No. 842395 (NewGeneSS project).Preprin

A stiffness reduction method for the in-plane design of stainless steel members and frames according with EN 1993-1-4

Current design standards for stainless steel such as ASCE 8-02 and EN 1993-1-4 prescribe provisions for the design of cross-sections and members that account for material nonlinearities and strain hardening, although these features are not considered in the global design of structures. Recent studies have highlighted the need of accounting for material nonlinearities in order to design efficient and safe stainless steel structures, and it is expected that the forthcoming versions of the standards will incorporate updated rules for the global design of these structures. To contribute to this field, this paper presents a Stiffness Reduction Method (SRM) for the in-plane design of stainless steel members and frames with stocky sections based on the prescriptions given in the next version of EN 1993-1-4. The proposed approach predicts the ultimate capacity and internal forces in stainless steel structures by performing a second-order elastic analysis in which the stiffnesses of the members are reduced by a set of factors defined in this paper to account for the effect of the spread of plasticity, residual stresses and member imperfections. The accuracy of the presented method is assessed for individual stainless steel structural members (columns, beams, and beam-columns) with different cross-sections and material properties, and for austenitic stainless steel portal frames, against numerical results obtained from nonlinear analyses conducted on finite element models. A comparison between the proposed approach and the Direct Analysis Method prescribed in the upcoming AISC 370 Specification is also provided, showing that the results are comparable in the two approaches.The research presented in this paper was developed in the frame of the Project BIA2016-75678-R, AEI/FEDER, UE “Comportamiento estructural de pórticos de acero inoxidable. Seguridad frente a acciones accidentales de sismo y fuego”, funded from the MINECO (Spain). The financial support received from the Spanish Ministry for Science, Innovation and Universities through the FPI-MINECO PhD fellowship Ref. BES-2017-082958 (I. González-de-León) and from the European Commission through the Marie Sklodowska-Curie grant agreement No. 842395 (I. Arrayago) is also gratefully acknowledged.Peer ReviewedPostprint (published version

Effects of material nonlinearity on the global analysis and stability of stainless steel frames

In structural frames, second order effects refer to the internal forces and moments that arise as a result of deformations under load (i.e. geometrical nonlinearity). EN 1993-1-1 states that global second order effects may be neglected if the critical load factor of the frame acr is greater than or equal to 10 for an elastic analysis, or greater than or equal to 15 when a plastic global analysis is used. No specific guidance is provided in EN 1993-1-4 for the design of stainless steel frames, for which the nonlinear stress-strain behaviour of the material will result in greater deformations as the material loses its stiffness. A study of the effects of material nonlinearity on the stability of stainless steel frames is presented herein. A series of different frame geometries and loading conditions are considered. Based on the findings, proposals for the treatment of the influence of material nonlinearity on the global analysis and design of stainless steel frames are presented.Peer ReviewedPostprint (author's final draft

Description of stress-strain curves for stainless steel alloys

There is a wide variety of stainless steel alloys, but all are characterized by a rounded stress-strain response with no sharply defined yield point. This behaviour can be represented analytically by different material models, the most popular of which are based on the Ramberg-Osgood formulations or extensions thereof. The degree of roundedness, the level of strain hardening, the strain at ultimate stress and the ductility at fracture of the material all vary between grades, and need to be suitably captured for an accurate representation of the material to be achieved. The aim of the present study is to provide values and predictive expressions for the key parameters in existing stainless steel material models based on the analysis of a comprehensive experimental database. The database comprises experimental stress-strain curves collected from the literature, supplemented by some tensile tests on austenitic, ferritic and duplex stainless steel coupons conducted herein. It covers a range of stainless steel alloys, annealed and cold-worked material, and data from the rolling and transverse directions. In total, more than 600 measured stress-strain curves have been collected from 15 international research groups. Each curve from the database has been analysed in order to obtain the key material parameters through a curve fitting process based on least squares adjustment techniques. These parameter values have been compared to those calculated from existing predictive models, the accuracy of which could therefore be evaluated. Revised expressions providing more accurate parameter predictions have been proposed where necessary. Finally, a second set of results, containing material parameters reported directly by others, with information of more than 400 specimens, has also been collected from the literature. Although these experimental results were not accessible as measured raw data, they enabled further confirmation of the suitability of the proposed equations.Peer ReviewedPostprint (author's final draft

Mice with Pulmonary Tuberculosis Treated with Mycobacterium vaccae Develop Strikingly Enhanced Recall Gamma Interferon Responses to M. vaccae Cell Wall Skeleton

Whole heat-killed Mycobacterium vaccae is used as an immunotherapeutic agent in tuberculosis (TB), but the compound(s) that triggers its immunostimulatory ability is not known. Here, we show that among different subcellular fractions, the cell wall skeleton induced a prominent expression of gamma interferon in splenocytes from both non-TB and TB M. vaccae-treated mice

Experimental study on ferritic stainless steel trapezoidal decks for composite slabs in construction stage

The use of composite floor slabs is well established and provides an opportunity to promote the use of visually exposed composite slabs. Stainless steels, with the combination of good mechanical properties and excellent corrosion resistance, are key to this strategy, specially ferritic stainless steels, whose price is lower and more stable than that corresponding to the more widely used austenitic grades, due to their low nickel content whilst still maintaining good mechanical properties and aesthetic appeal. In addition, the emissivity of these grades contributes to lowering the heating and cooling requirements of buildings, reducing the costs associated to maintenance. Generally used as cold-formed members with high resistance-to-weight ratios, stainless steel decks are slender and highly sensitive to buckling phenomena and so the study of the structural performance of composite slabs using ferritic stainless steel decking is required due to the complex nonlinear behaviour of stainless steels, which is very different from that exhibited by carbon steel. Thus, this paper presents a comprehensive experimental programme on ferritic stainless steel trapezoidal decks for composite slabs under several structural configurations occurring during construction stage: simply supported decks under positive and negative bending moment, continuous decks and internal and end support tests. All the experimental results have been compared with the predicted ultimate loads in EN 1993-1-4, which remits to EN 1993-1-3 for carbon steel, and also with some previous tests on galvanized carbon steel decks. The paper concludes that EN 1993-1-3 provisions are applicable to ferritic stainless steels.Peer ReviewedPostprint (author's final draft

Experimental investigation on ferritic stainless steel composite slabs

Steel-concrete composite structures are well established in the construction of floors and roofing, being interesting solutions as steel decks act as formwork for relatively large spans and support the weight of the concrete and construction loads. However, the use of stainless steel decks in such structures has been very limited, although their mechanical properties, corrosion resistance, aesthetics and emissivity make them excellent for visually exposed composite floor slabs where the thermal capacity of the slab is mobilized as part of an energy saving strategy. This paper presents a comprehensive investigation on composite slabs with trapezoidal ferritic stainless steel decks in order to assess the performance of such structural members. Composite slabs made from EN1.4003 ferritic stainless steel and common C25/30 concrete were tested in two series of span lengths in order to determine the different parameters defining their ultimate longitudinal shear response. Reference tests on slabs with galvanized steel were also conducted with identical geometries and configurations. The m and k parameters used in the m-k Method and the design longitudinal shear strength tu,Rd corresponding to the Partial Connection Method have been determined according to EN 1994-1-1:2004. Finally, the behaviour of these composite slabs was compared with the performance shown by the conducted reference slabs with galvanized steel deck in terms of Ultimate and Serviceability Limit States.Peer ReviewedPostprint (author's final draft

Stereological estimations and neurochemical characterization of neurons expressing GABAA and GABAB receptors in the rat pedunculopontine and laterodorsal tegmental nuclei

To better understand GABAergic transmission at two targets of basal ganglia downstream projections, the pedunculopontine (PPN) and laterodorsal (LDT) tegmental nuclei, the anatomical localization of GABAA and GABAB receptors was investigated in both nuclei. Specifically, the total number of neurons expressing the GABAA receptor γ2 subunit (GABAAR γ2) and the GABAB receptor R2 subunit (GABAB R2) in PPN and LDT was estimated using stereological methods, and the neurochemical phenotype of cells expressing each subunit was also determined. The mean number of non-cholinergic cells expressing GABAAR γ2 was 9850 ± 1856 in the PPN and 8285 ± 962 in the LDT, whereas those expressing GABAB R2 were 7310 ± 1970 and 9170 ± 1900 in the PPN and LDT, respectively. In addition, all cholinergic neurons in both nuclei co-expressed GABAAR γ2 and 95–98% of them co-expressed GABAB R2. Triple labeling using in situ hybridization revealed that 77% of GAD67 mRNA-positive cells in the PPT and 49% in the LDT expressed GABAAR γ2, while 90% (PPN) and 65% (LDT) of Vglut2 mRNA-positive cells also expressed GABAAR γ2. In contrast, a similar proportion (~2/3) of glutamatergic and GABAergic cells co-expressed GABAB R2 in both nuclei. The heterogeneous distribution of GABAAR and GABABR among non-cholinergic cells in PPN and LDT may give rise to physiological differences within each neurochemical subpopulation. In addition, the dissimilar proportion of GABAAR γ2-expressing glutamatergic and GABAergic neurons in the PPN and LDT may contribute to some of the functional differences found between the two nuclei