title: An improved and robust finite element model for simulation of  cold-formed steel built-up beams

authors: Birwadkar, Harsh Hemant

subjects: Cold-formed steel

abstract: Cold-formed steel (CFS) built-up sections are increasingly utilized in structural applications due to their lightweight properties, high strength-to-weight ratio, and enhanced moment capacity, which can be further improved by adding stiffeners to the webs or flanges. Accurately determining the moment capacity of these sections is important for practical use. This can be achieved through experimental testing or finite element analysis (FEA) using a four-point bending setup. However, conducting full-scale experimental tests is both expensive and time-consuming, and developing a full-scale finite element (FE) model to replicate these tests can be computationally intensive. 

To address these challenges, this study introduces an accurate, efficient, and robust numerical method that replicates the behaviour of CFS built-up sections, applicable to both back-to-back and face-to-face configurations. The proposed numerical methodology demonstrates excellent agreement with available test results in terms of moment capacity and failure modes, highlighting its potential for determining the moment capacity of built-up sections. The study further investigates two cross-sectional types—stiffened nested and unstiffened nested—to evaluate their behaviour and moment capacity. 

The proposed simplified model was subsequently used in an extensive parametric study to determine the moment capacity of stiffened and unstiffened nested sections. Parameters considered in the study include varying section thicknesses (0.75 mm to 3.00 mm), web depths (150 mm to 600 mm), section configurations (nested and stiffened nested), and screw spacings (75 mm, 150 mm, and 300 mm). Given that existing design standards, such as those from the American Iron and Steel Institute (AISI 2016) and the Australian/New Zealand Standards (AS/NZS 2018), lack specific guidelines for calculating the moment capacity of these sections, this research aims to fill that gap. Furthermore, to simulate practical scenarios, models incorporating screws in the webs (screw-web model) were developed and compared against the simplified model. The results of the parametric study revealed that the moment capacity of the built-up sections is significantly influenced by section thickness, web depth, and section configuration. Screw spacing, however, had a less significant impact. Notably, the moment capacity of the screw-web model was lower than that of the simplified model, emphasizing the importance of bimoment and warping deformation in connection design. 

The study concludes that the developed simplified model provides a computationally efficient tool for predicting the moment capacity of built-up beams, offering valuable insights for designers and engineers. Additionally, the nested section configuration is recommended for achieving higher moment capacity compared to the stiffened nested section.

text: An improved and robust finite element model for simulation of  cold-formed steel built-up beams Cold-formed steel (CFS) built-up sections are increasingly utilized in structural applications due to their lightweight properties, high strength-to-weight ratio, and enhanced moment capacity, which can be further improved by adding stiffeners to the webs or flanges. Accurately determining the moment capacity of these sections is important for practical use. This can be achieved through experimental testing or finite element analysis (FEA) using a four-point bending setup. However, conducting full-scale experimental tests is both expensive and time-consuming, and developing a full-scale finite element (FE) model to replicate these tests can be computationally intensive. 

To address these challenges, this study introduces an accurate, efficient, and robust numerical method that replicates the behaviour of CFS built-up sections, applicable to both back-to-back and face-to-face configurations. The proposed numerical methodology demonstrates excellent agreement with available test results in terms of moment capacity and failure modes, highlighting its potential for determining the moment capacity of built-up sections. The study further investigates two cross-sectional types—stiffened nested and unstiffened nested—to evaluate their behaviour and moment capacity. 

The proposed simplified model was subsequently used in an extensive parametric study to determine the moment capacity of stiffened and unstiffened nested sections. Parameters considered in the study include varying section thicknesses (0.75 mm to 3.00 mm), web depths (150 mm to 600 mm), section configurations (nested and stiffened nested), and screw spacings (75 mm, 150 mm, and 300 mm). Given that existing design standards, such as those from the American Iron and Steel Institute (AISI 2016) and the Australian/New Zealand Standards (AS/NZS 2018), lack specific guidelines for calculating the moment capacity of these sections, this research aims to fill that gap. Furthermore, to simulate practical scenarios, models incorporating screws in the webs (screw-web model) were developed and compared against the simplified model. The results of the parametric study revealed that the moment capacity of the built-up sections is significantly influenced by section thickness, web depth, and section configuration. Screw spacing, however, had a less significant impact. Notably, the moment capacity of the screw-web model was lower than that of the simplified model, emphasizing the importance of bimoment and warping deformation in connection design. 

The study concludes that the developed simplified model provides a computationally efficient tool for predicting the moment capacity of built-up beams, offering valuable insights for designers and engineers. Additionally, the nested section configuration is recommended for achieving higher moment capacity compared to the stiffened nested section.

year: 2024

title: Economical genotyping of little blue penguin (Eudyptula minor) clades from feather-based DNA

authors: Clark, Alan J.

subjects: Clades

abstract: Determination of clade membership is a crucial requirement for many research questions addressing phylogeography, population structure, mating patterns, speciation, and hybridisation. The little blue penguin (Eudyptula minor) can be separated into two deeply divergent clades. However, assigning clade membership in little blue penguins requires molecular methods. Genetic sequencing can be used to identify clade membership but is expensive. Here, we present an economical alternative to the use of sequencing to determine little blue penguin clade membership. We extracted DNA from feathers using a method that produced reasonable quantities of DNA. We then amplified the D-loop section of the mitochondrial control region from total genomic DNA extracts, using the primers 'C L-tRNAglu' and 'D H-Dbox' followed by digestion with the restriction enzyme AluI. When visualised on a gel, distinctive banding patterns clearly indicated clade membership. We sequenced a subset of our samples and verified the accuracy of this method. The methods we present should facilitate little blue penguin research through a cost-effective approach to clade analysis as well as a successful technique to extract DNA from feathers when blood or tissue samples are not available.

text: Economical genotyping of little blue penguin (Eudyptula minor) clades from feather-based DNA Determination of clade membership is a crucial requirement for many research questions addressing phylogeography, population structure, mating patterns, speciation, and hybridisation. The little blue penguin (Eudyptula minor) can be separated into two deeply divergent clades. However, assigning clade membership in little blue penguins requires molecular methods. Genetic sequencing can be used to identify clade membership but is expensive. Here, we present an economical alternative to the use of sequencing to determine little blue penguin clade membership. We extracted DNA from feathers using a method that produced reasonable quantities of DNA. We then amplified the D-loop section of the mitochondrial control region from total genomic DNA extracts, using the primers 'C L-tRNAglu' and 'D H-Dbox' followed by digestion with the restriction enzyme AluI. When visualised on a gel, distinctive banding patterns clearly indicated clade membership. We sequenced a subset of our samples and verified the accuracy of this method. The methods we present should facilitate little blue penguin research through a cost-effective approach to clade analysis as well as a successful technique to extract DNA from feathers when blood or tissue samples are not available.

year: 2013

title: Housing, mental health, and homelessness: Exploring lived experiences of homelessness to identify barriers to sustainable housing for vulnerable populations

authors: Cresswell, Caitlin Grace

subjects: Homelessness

abstract: Homelessness has become a much talked about topic in Aotearoa New Zealand in 2018 and the preceding years. This thesis explores the experiences of five people who have mental illness and have lived experience of homelessness in Aotearoa New Zealand, and two staff members who work closely with people who experience both mental illness and homelessness. The theoretical frameworks that inform this thesis are narrative research, social constructionism and humanistic psychology. Particular attention was paid to using theoretical frameworks and interview methods that suited Māori (the indigenous population of Aotearoa New Zealand) due to the inequities experienced by Māori in mental health and homelessness, and the majority of participants identifying as New Zealand Māori. Participants’ narratives were gathered using semi- structured interviews. This study argues the importance of a humanistic perspective being used for research on homelessness. In contrast to traditional psychology, humanistic psychology emphasises respecting individual participants’ voice and narratives about their personal experiences of homelessness while considering the environment that influence these narratives. The participants’ narratives reflected their desire to be viewed as more than their life circumstances and illness through the sharing of their life stories. While there has been growing public awareness about mental illness, stigma still exists about mental illness which influences social narratives and how people who have mental illness understand their experiences. I argue that people who are vulnerable to homelessness, like those who experience mental illness, should have better protection from homelessness. To achieve this, I argue that structural barriers to finding, gaining and sustaining housing need to be addressed,
iii
including the design of welfare and housing services. Additionally, there needs to be recognition that the solutions to homelessness are complex and require a whole of system approach to effectively address and prevent homelessness. Recognising the complex nature of homelessness and it’s solutions will help bring a focus to establishing predominantly preventative solutions while also providing emergency housing for people in need.

text: Housing, mental health, and homelessness: Exploring lived experiences of homelessness to identify barriers to sustainable housing for vulnerable populations Homelessness has become a much talked about topic in Aotearoa New Zealand in 2018 and the preceding years. This thesis explores the experiences of five people who have mental illness and have lived experience of homelessness in Aotearoa New Zealand, and two staff members who work closely with people who experience both mental illness and homelessness. The theoretical frameworks that inform this thesis are narrative research, social constructionism and humanistic psychology. Particular attention was paid to using theoretical frameworks and interview methods that suited Māori (the indigenous population of Aotearoa New Zealand) due to the inequities experienced by Māori in mental health and homelessness, and the majority of participants identifying as New Zealand Māori. Participants’ narratives were gathered using semi- structured interviews. This study argues the importance of a humanistic perspective being used for research on homelessness. In contrast to traditional psychology, humanistic psychology emphasises respecting individual participants’ voice and narratives about their personal experiences of homelessness while considering the environment that influence these narratives. The participants’ narratives reflected their desire to be viewed as more than their life circumstances and illness through the sharing of their life stories. While there has been growing public awareness about mental illness, stigma still exists about mental illness which influences social narratives and how people who have mental illness understand their experiences. I argue that people who are vulnerable to homelessness, like those who experience mental illness, should have better protection from homelessness. To achieve this, I argue that structural barriers to finding, gaining and sustaining housing need to be addressed,
iii
including the design of welfare and housing services. Additionally, there needs to be recognition that the solutions to homelessness are complex and require a whole of system approach to effectively address and prevent homelessness. Recognising the complex nature of homelessness and it’s solutions will help bring a focus to establishing predominantly preventative solutions while also providing emergency housing for people in need.

year: 2018