Flexural strength of cold-formed steel built-up box sections

Presented in this paper is a study involving finite element analysis to investigate the flexural strength of built-up box sections which have been extensively used in residential and commercial construction in North America. In the North American Specification for the Design of Cold-Formed Steel Structural Members [CSA, North American specification for the design of cold-formed steel structural members, S136, Canadian Standard Association, 2002], there is no guideline or design equation to calculate the flexural strength of this type of section. Both the Lightweight Steel Framing Design Manual [CSA, Supplement 2004 to the North American specification for the design of cold-formed steel structural members, S136, Canadian Standard Association, 2004] and Cold-Formed Steel Framing Design Guide [AISI, Cold-formed steel framing design guide", American Iron and Steel Institute, 1st ed., 2002, 2nd ed., 2007] have recommended that the flexural strength and moment of inertia of the built-up sections to be taken as the sum of the two components based on deflection compatibility of the components. However, this design approximation has yet to be justified by experimental or numerical study especially for the cases of eccentric and concentric loading. In this study, the proposed finite element model of the built-up box sections was validated with the experimental tests carried out by Beshara and Lawson [Beshara B, Lawson TJ. Built-up girder screw connection variation flexural tests, Internal Report, Dietrich Design Group, 2002]. The flexural strengths obtained from the finite element analysis were then compared with the nominal strength evaluated based on the current design method in order to assess its suitability. Parametric studies were carried out for more than 30 specimens to identify factors affecting the flexural strength of cold-formed steel built-up box sections. A recommendation is made for current design practice of evaluating the flexural strength of the box section when subjected to eccentric loading.     

Strain-mediated photoresponse of Fe–ZnO/rGO heterojunction photodetector by magnetic-field-assisted interface engineering

Journal of Materials Science: Materials in Electronics - Magnetic field-modulated interface engineering has been attained in Fe doped zinc oxide/reduced graphene oxide (rGO) layered thin films,...     

Analysis of infilled frames using A coupled finite element and boundary element solution scheme

The behaviour of infilled frames subjected to horizontal loads is analysed by an iterative numerical procedure. The stiffness of the structural system is determined with variations in geometrical and mechanical characteristics. The analysis is carried out utilizing the boundary element method (BEM) for the infill and opportunely dividing the frame into finite elements, so as to transform the mutual interactions of the two subsystems into stresses distributed along the boundary for the infill and into nodal actions for the frame. This makes it possible to take into account the separation arising between the two substructures when mutual tensile stresses are involved. At first, infills without openings are considered, using BEM with constant elements for two-dimensional problems in elasticity. The results are compared with those obtained using the simplified equivalent pin-jointed strut model, which is very common in the literature. Subsequently, using an analogous procedure, panels with openings are considered. For these systems, for which no satisfactory simplified models exist, the loss of stiffness in relation to the size of the opening is evaluated.     

Interfacial properties of phosphate glass fibres/PLA composites: Effect of the end functionalities of oligomeric PLA coupling agents

Polylactic acid (PLA) oligomers as coupling agents have shown higher interfacial shear strength in phosphate based glass fibres/PLA composites. To influence bonding on the glass fibre surface, short chain PLA oligomers with different end groups were used as coupling agents. The low molecular weight PLA with a sodium salt terminal group, a carboxylic acid end group and also with one, two and five hydroxyl groups were produced and applied on the fibre surface through a condensation reaction. Mechanical properties of the sized fibres/PLA composites were found to be increased. XPS and TG analyses showed the presence of the coupling agents on the fibres surface. SEM analysis further confirms the presence of the agents.     

Measuring the randomness of micro- and nanostructure spatial distributions: Effects of scanning electron microscope image processing and analysis

The quantitative characterisation of the degree of randomness and aggregation of surface micro- and nanostructures is critical to evaluate their effects on targeted functionalities. To this end, the methods of point pattern analysis (PPA), largely used in ecology and medical imaging, seem to provide a powerful toolset. However, the application of these techniques requires the extraction of the point pattern of nanostructures from their microscope images. In this work, we address the issue of the impact that Scanning Electron Microscope (SEM) image processing may have on the fundamental metric of PPA, that is, the Nearest Neighbour Index (NNI). Using typical SEM images of polymer micro- and nanostructures taken from secondary and backscattered electrons, we report the effects of the (a) noise filtering and (b) binarisation threshold on the value of NNI as well as the impact of the image finite size effects. Based on these results, we draw conclusions for the safe choice of SEM settings to provide accurate measurement of nanostructure randomness through NNI estimation.     

Flexural behaviour of concrete corbels containing steel fibers or wrapped with FRP sheets

In the present paper an analytical and experimental investigation referring to the flexural behaviour of reinforced concrete corbels subjected to vertical forces is presented. For fixed shape and dimensions of the corbels the experimental investigation analyses the effects of the following: longitudinal and transverase steel reinforcements; fiber reinforced concrete (FRC) with hooked steel fibers; external wrapping retrofitting technique with a thin layer of carbon fiber sheet (CFRP). The analytical model based on equivalent truss structures, allows one to determine the bearing capacity of corbels, distinguishing the different ultimate states reached. The analytical results are then compared with experimental values, showing good agreement.     

Scope of Sustainable Pretreatment of Cotton Knit Fabric Avoiding Major Chemicals

ABSTRACT

The present effort attempted to avoid basic chemicals, namely NaOH and H₂O₂ in scouring and bleaching of cotton knit fabric in order to reduce the chemical load and processing cycles without compromise of dyeing performance. Single jersey single lacoste cotton knit fabrics treated with detergent and wetting agent at 120°C temperature for 20 minutes revealed 5.8% weight loss. FTIR graphical data validated the weakening and moving out of characteristic bands of wax and pectin-based cotton impurities in the region of 1740–1200 cm^?1. The color differences of 1.5% and 1% dyed samples confirmed pass value (CMC ΔE ≤ 1) when treated at 105°C temperature for 20 minutes. The grading for color fastness to wash, perspiration, rubbing and light was 4–5 to 5. No deterioration in strength and morphological changes were experienced for the treated samples.     

Various dimension reduction techniques for high dimensional data analysis: a review

Artificial Intelligence Review - In the era of healthcare, and its related research fields, the dimensionality problem of high dimensional data is a massive challenge as it contains a huge number...