title: Full-scale experimental study on the stability of chords of cold-formed steel c-section roof trusses

authors: Rokocakau, Ulamila

abstract: The use of cold-formed steel (CFS) roof trusses is growing as a substitute for wood because of their advantages in quick fabrication, high strength-to-weight ratio, and lightweight nature [1]. However, the torsional buckling behaviour of these trusses remains inadequately understood. There have been experimental studies conducted for the behaviour of CFS roof trusses [2], wide-span roof trusses [1] and small-scale roof trusses [3]. The common failures in the previous studies of CFS roof trusses include distortion of heel plates, local buckling of the top chords [3] and flexural-torsional buckling becoming a concern in elevated temperatures [4]. The behaviour of CFS under loads applied away from the shear centre requires more testing due to its thin nature.
Through eight full-scale experiments, different truss configurations (back-to-back and linear), different lateral restraint spacing and internal support inclusions, this study investigates the structural behaviour of lipped channel (C-section) chords in CFS Howe roof truss assemblies. The experimental total load at failure exceeds factored predicted capacities by 12% and 34%, and factored design capacities by 34% and 60%, depending on lateral restraint spacing. Design equations, however, are conservative with predicted-to-experimental capacity ratios as low as 0.7 for wider spaced lateral restraints and 0.5 for closely spaced restraints. In 37.5% of cases, the design standards fail to predict the correct failure modes.
Observed failures during the experiments include lateral-torsional buckling, out-of-plane buckling, and inward torsional buckling. The single-channel linear truss system (face of web connected to back of chords) proved more robust than back-to-back system (back of web connected to back of chords), offering better torsional restraint and load-bearing capacity post-failure. Truss strength is enhanced by increased lateral restraints, but current design standards lack provisions for calculating member lengths with such restraints. Therefore, further research, including FEM analysis, is needed to address this gap and improve design accuracy.

text: Full-scale experimental study on the stability of chords of cold-formed steel c-section roof trusses The use of cold-formed steel (CFS) roof trusses is growing as a substitute for wood because of their advantages in quick fabrication, high strength-to-weight ratio, and lightweight nature [1]. However, the torsional buckling behaviour of these trusses remains inadequately understood. There have been experimental studies conducted for the behaviour of CFS roof trusses [2], wide-span roof trusses [1] and small-scale roof trusses [3]. The common failures in the previous studies of CFS roof trusses include distortion of heel plates, local buckling of the top chords [3] and flexural-torsional buckling becoming a concern in elevated temperatures [4]. The behaviour of CFS under loads applied away from the shear centre requires more testing due to its thin nature.
Through eight full-scale experiments, different truss configurations (back-to-back and linear), different lateral restraint spacing and internal support inclusions, this study investigates the structural behaviour of lipped channel (C-section) chords in CFS Howe roof truss assemblies. The experimental total load at failure exceeds factored predicted capacities by 12% and 34%, and factored design capacities by 34% and 60%, depending on lateral restraint spacing. Design equations, however, are conservative with predicted-to-experimental capacity ratios as low as 0.7 for wider spaced lateral restraints and 0.5 for closely spaced restraints. In 37.5% of cases, the design standards fail to predict the correct failure modes.
Observed failures during the experiments include lateral-torsional buckling, out-of-plane buckling, and inward torsional buckling. The single-channel linear truss system (face of web connected to back of chords) proved more robust than back-to-back system (back of web connected to back of chords), offering better torsional restraint and load-bearing capacity post-failure. Truss strength is enhanced by increased lateral restraints, but current design standards lack provisions for calculating member lengths with such restraints. Therefore, further research, including FEM analysis, is needed to address this gap and improve design accuracy.

year: 2025

title: The Neolithic of Vietnam

authors: Piper, Philip J.

subjects: Vietnam

abstract: The Neolithic in Mainland Southeast Asia is considered to be the period of human prehistory that commenced with the transition from hunting and gathering into mixed economies of foraging and farming. It lasted until the appearance of copper and bronze metallurgy and thus dates between circa 2500 and 1200 BC. In Vietnam, Neolithic sites and cultures are recorded especially around the edges of the Red River delta, along the northern and central coasts, and in the southern river basins between the Đông Nai and lower Mekong. This period of Vietnamese prehistory was characterized by the southward movements of East Asian Neolithic populations from southern China across Mainland Southeast Asia, the introduction of cereal cultivation (rice and foxtail millet), and the management of domesticated pigs and dogs. The Neolithic of Vietnam also reveals material culture relationships extending from southern China to central Thailand. Recent research is also starting to highlight social and cultural diversity during this period, together with the development of significant exchange networks.

text: The Neolithic of Vietnam The Neolithic in Mainland Southeast Asia is considered to be the period of human prehistory that commenced with the transition from hunting and gathering into mixed economies of foraging and farming. It lasted until the appearance of copper and bronze metallurgy and thus dates between circa 2500 and 1200 BC. In Vietnam, Neolithic sites and cultures are recorded especially around the edges of the Red River delta, along the northern and central coasts, and in the southern river basins between the Đông Nai and lower Mekong. This period of Vietnamese prehistory was characterized by the southward movements of East Asian Neolithic populations from southern China across Mainland Southeast Asia, the introduction of cereal cultivation (rice and foxtail millet), and the management of domesticated pigs and dogs. The Neolithic of Vietnam also reveals material culture relationships extending from southern China to central Thailand. Recent research is also starting to highlight social and cultural diversity during this period, together with the development of significant exchange networks.

year: 2022-02-14

title: Kaumtua Mana Motuhake: A study protocol for a peer education intervention to help Māori elders work through later-stage life transitions

authors: Oetzel, John G.

subjects: Science & Technology

abstract: Background
The Aotearoa/New Zealand population is ageing and numerous studies demonstrate with this phenomenon comes increases in non-communicable diseases, injuries and healthcare costs among other issues. Further, significant inequities exist between Māori (Indigenous peoples of Aotearoa/New Zealand) and non-Māori around poor ageing and health. Most research addressing these issues is deficit oriented; however, the current research project takes a strengths-based approach that highlights the potential of kaumātua (elders) by asserting mana motuhake (autonomy, identity and self-actualisation). We believe that the esteem of elders in Māori culture signals transformative potential. Specifically, this project utilises a ‘tuakana-teina’ (older sibling/younger sibling) peer-educator model, where kaumātua work with other kaumātua in relation to health and wellbeing. The objectives of the project are (a) to develop the capacity of kaumātua as peer educators, whilst having positive impacts on their sense of purpose, health and wellbeing; and (b) to enhance the social and health outcomes for kaumātua receiving the intervention.

Methods
The research is grounded in principles of Kaupapa Māori and community-based participatory research, and brings together an Indigenous community of kaumātua, community health researchers, and academic researchers working with two advisory boards. The project intervention involves an orientation programme for tuakana peer educators for other kaumātua (teina). The research design is a pre- and post-test, clustered staggered design. All participants will complete a baseline assessment of health and wellbeing consistent with Māori worldviews (i.e., holistic model). The tuakana and teina participants will be divided into two groups with the first group completing the intervention during the first half of the project and the second group during the second half of the project. All participants will complete post-test assessments following both interventions allowing comparison of the two groups along with repeated measures over time.

Discussion
The findings will provide an evidence base for the importance and relevancy of kaumātua knowledge to create contextually based and culturally safe age-friendly environments that facilitate engagement and participation by kaumātua for kaumātua. If the model is effective, we will seek to facilitate the dissemination and scalability of the intervention.

Trial registration
Australia New Zealand Clinical Trial Registry (ACTRN12617001396314); Date Registered: 3 October 2017 (retrospectively registered).

text: Kaumtua Mana Motuhake: A study protocol for a peer education intervention to help Māori elders work through later-stage life transitions Background
The Aotearoa/New Zealand population is ageing and numerous studies demonstrate with this phenomenon comes increases in non-communicable diseases, injuries and healthcare costs among other issues. Further, significant inequities exist between Māori (Indigenous peoples of Aotearoa/New Zealand) and non-Māori around poor ageing and health. Most research addressing these issues is deficit oriented; however, the current research project takes a strengths-based approach that highlights the potential of kaumātua (elders) by asserting mana motuhake (autonomy, identity and self-actualisation). We believe that the esteem of elders in Māori culture signals transformative potential. Specifically, this project utilises a ‘tuakana-teina’ (older sibling/younger sibling) peer-educator model, where kaumātua work with other kaumātua in relation to health and wellbeing. The objectives of the project are (a) to develop the capacity of kaumātua as peer educators, whilst having positive impacts on their sense of purpose, health and wellbeing; and (b) to enhance the social and health outcomes for kaumātua receiving the intervention.

Methods
The research is grounded in principles of Kaupapa Māori and community-based participatory research, and brings together an Indigenous community of kaumātua, community health researchers, and academic researchers working with two advisory boards. The project intervention involves an orientation programme for tuakana peer educators for other kaumātua (teina). The research design is a pre- and post-test, clustered staggered design. All participants will complete a baseline assessment of health and wellbeing consistent with Māori worldviews (i.e., holistic model). The tuakana and teina participants will be divided into two groups with the first group completing the intervention during the first half of the project and the second group during the second half of the project. All participants will complete post-test assessments following both interventions allowing comparison of the two groups along with repeated measures over time.

Discussion
The findings will provide an evidence base for the importance and relevancy of kaumātua knowledge to create contextually based and culturally safe age-friendly environments that facilitate engagement and participation by kaumātua for kaumātua. If the model is effective, we will seek to facilitate the dissemination and scalability of the intervention.

Trial registration
Australia New Zealand Clinical Trial Registry (ACTRN12617001396314); Date Registered: 3 October 2017 (retrospectively registered).

year: 2019