title: Numerical investigation of cold-formed steel channels with edge-stiffened and unstiffened elongated web holes under shear

authors: Chandramohan, Dinesh Lakshmanan

subjects: elongated web holes

abstract: Over the past decade, cold-formed steel (CFS) channel sections having edge-stiffened circular web holes have been developed in New Zealand. Such edge-stiffened holes increase the strength of the CFS channel sections, compared to an equivalent section having unstiffened web holes, while still allowing full building service integration. In the case of shear, previous research has found that the use of edge-stiffened web holes significantly improves the shear strength of such channel sections. However, no studies are available in the literature investigating the shear strength of CFS channel sections with edge-stiffened elongated web holes. The issue is addressed herein. Non-linear finite element (FE) analyses are used to investigate the shear strength of CFS channel sections with a shear span aspect ratio of 2.0. The FE models were validated against the experimental test results of sections having unstiffened elongated web holes and edge-stiffened circular web holes; good agreement in terms of the load-displacement curves and failure behaviour was shown. Using the validated FE models, a parametric study was conducted, comprising 2124 finite element analyses (FEA) results. The parametric results were then compared to the design predictions of the American Iron and Steel Institute (AISI 2016), and Australia/New Zealand Standards (AS/NZS 2018) and Wanniarchchi et al. (2017) for unstiffened elongated web holes, showing that the design predictions are unconservative in comparison results. Moreover, the direct strength method (DSM) approach of Pham et al. (2020a and 2023) provides conservative results for channels with unstiffened elongated web holes. It was also found that the design equations proposed by Chen et al. (2022) for edge-stiffened circular web holes were unconservative in predicting the shear strength of channels having edge-stiffened elongated web holes. Therefore, design equations in the form of a shear reduction factor and a modified DSM approach for CFS channel sections having unstiffened and edge-stiffened elongated web holes were proposed. Finally, a reliability analysis was carried out to ensure that the proposed equations are reliable to predict the shear strength of CFS channel sections with edge-stiffened and unstiffened web holes.

text: Numerical investigation of cold-formed steel channels with edge-stiffened and unstiffened elongated web holes under shear Over the past decade, cold-formed steel (CFS) channel sections having edge-stiffened circular web holes have been developed in New Zealand. Such edge-stiffened holes increase the strength of the CFS channel sections, compared to an equivalent section having unstiffened web holes, while still allowing full building service integration. In the case of shear, previous research has found that the use of edge-stiffened web holes significantly improves the shear strength of such channel sections. However, no studies are available in the literature investigating the shear strength of CFS channel sections with edge-stiffened elongated web holes. The issue is addressed herein. Non-linear finite element (FE) analyses are used to investigate the shear strength of CFS channel sections with a shear span aspect ratio of 2.0. The FE models were validated against the experimental test results of sections having unstiffened elongated web holes and edge-stiffened circular web holes; good agreement in terms of the load-displacement curves and failure behaviour was shown. Using the validated FE models, a parametric study was conducted, comprising 2124 finite element analyses (FEA) results. The parametric results were then compared to the design predictions of the American Iron and Steel Institute (AISI 2016), and Australia/New Zealand Standards (AS/NZS 2018) and Wanniarchchi et al. (2017) for unstiffened elongated web holes, showing that the design predictions are unconservative in comparison results. Moreover, the direct strength method (DSM) approach of Pham et al. (2020a and 2023) provides conservative results for channels with unstiffened elongated web holes. It was also found that the design equations proposed by Chen et al. (2022) for edge-stiffened circular web holes were unconservative in predicting the shear strength of channels having edge-stiffened elongated web holes. Therefore, design equations in the form of a shear reduction factor and a modified DSM approach for CFS channel sections having unstiffened and edge-stiffened elongated web holes were proposed. Finally, a reliability analysis was carried out to ensure that the proposed equations are reliable to predict the shear strength of CFS channel sections with edge-stiffened and unstiffened web holes.

year: 2024

title: Effect of microwave pre-treatment on air-drying orange (Beauregard) kumara slices

authors: Deng, Lingze

subjects: Orange sweet potato

abstract: The effects of slice thickness, microwave pre-treatment, and drying temperature on drying orange kumara slices were investigated. The highest drying rate, with minimal loss of colour, occurred at 80°C. Slice thickness did not significantly influence colour but drying time increased with slice thickness. The drying curves fitted the Page thin-layer drying model. Two minutes microwave pre-treatment significantly reduced overall drying time and improved colour but increased shrinkage.

text: Effect of microwave pre-treatment on air-drying orange (Beauregard) kumara slices The effects of slice thickness, microwave pre-treatment, and drying temperature on drying orange kumara slices were investigated. The highest drying rate, with minimal loss of colour, occurred at 80°C. Slice thickness did not significantly influence colour but drying time increased with slice thickness. The drying curves fitted the Page thin-layer drying model. Two minutes microwave pre-treatment significantly reduced overall drying time and improved colour but increased shrinkage.

year: 2017

title: Indigenous epistemology in a national curriculum framework?

authors: Macfarlane, Angus

subjects: curriculum competencies

abstract: In this article, a group of four indigenous Māori educators and one non-Māori educator comment on a proposed amendment to the New Zealand National Curriculum Framework to replace the current separate sets of skills, values and attitudes with five generic performance-based key competencies. The paper discusses important parallels between western/European sociocultural theorizing on human development and learning (on which the key competencies seemed to be based), and the values, beliefs and preferred practices that are embodied within an indigenous Māori cultural worldview (Te Ao Māori). A Māori worldview is characterized by an abiding concern for the quality of human relationships that need to be established and maintained if learning contexts are to be effective for Māori students, and for these relationships to balance individual learning and achievement against responsibilities for the well-being and achievement of the group. Within such a worldview, education is understood as holistic, collective, experiential and dependent upon a free exchanging of teaching and learning roles. The article describes five specific cultural constructs within this worldview that highlight Māori traditional understandings of human development and learning and teaching, and aligns and compares these constructs with the five key competencies proposed. The article argues that the worldviews of Māori people in New Zealand provide an extensive and coherent framework for theorizing about human development and education, and are able to contribute strongly and positively to the development of a national school curriculum for the benefit all students. Implications for other contexts can also be drawn.

text: Indigenous epistemology in a national curriculum framework? In this article, a group of four indigenous Māori educators and one non-Māori educator comment on a proposed amendment to the New Zealand National Curriculum Framework to replace the current separate sets of skills, values and attitudes with five generic performance-based key competencies. The paper discusses important parallels between western/European sociocultural theorizing on human development and learning (on which the key competencies seemed to be based), and the values, beliefs and preferred practices that are embodied within an indigenous Māori cultural worldview (Te Ao Māori). A Māori worldview is characterized by an abiding concern for the quality of human relationships that need to be established and maintained if learning contexts are to be effective for Māori students, and for these relationships to balance individual learning and achievement against responsibilities for the well-being and achievement of the group. Within such a worldview, education is understood as holistic, collective, experiential and dependent upon a free exchanging of teaching and learning roles. The article describes five specific cultural constructs within this worldview that highlight Māori traditional understandings of human development and learning and teaching, and aligns and compares these constructs with the five key competencies proposed. The article argues that the worldviews of Māori people in New Zealand provide an extensive and coherent framework for theorizing about human development and education, and are able to contribute strongly and positively to the development of a national school curriculum for the benefit all students. Implications for other contexts can also be drawn.

year: 2008