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 referendum incentive compatibility hypothesis: Some new results using information messages

authors: Stefani, Gianluca

subjects: contingent valuation

abstract: We report results from a laboratory experiment that allows us to test the incentive compatibility hypothesis of hypothetical referenda used in CV studies through the public or private provision of information messages. One of the main methodological issues about hypothetical markets regards whether people behave differently when bidding for a public good through casting a ballot vote than when they are privately purchasing an equivalent good. This study tried to address the core of this issue by using a good that can be traded both as private and public: information messages. This allows the elimination of confounding effects associated with the specific good employed. In our case information dispels some of the uncertainty about a potential gain from a gamble. So, the approximate value of the message can be inferred once the individual measure of risk aversion is known. Decision tasks are then framed in a systematic manner according to the hypothetical vs real nature of the decision and the public vs private nature of the message. A sample of 536 university students across three countries (I, UK and NZ) participated into this lab experiment. The chosen countries reflect diversity in exposure to the practice of advisory (NZ) and abrogative (Italy) referenda, with the UK not having any exposure to it. Under private provision the results show that the fraction of participants unwilling to buy information is slightly higher in the real treatment than in the hypothetical one. Under public provision, instead, there is no statistical difference between real and hypothetical settings, confirming in part the finding of previous researchers. A verbal protocol analysis of the thought processes during choice highlights that public provision of information systematically triggers concerns and motivations different from those arising under the private provision setting. These findings suggest that the incentive compatibility of public referenda is likely to rely more on affective and psychological factors than on the strategic behaviour assumptions theorised by economists.

text: The referendum incentive compatibility hypothesis: Some new results using information messages We report results from a laboratory experiment that allows us to test the incentive compatibility hypothesis of hypothetical referenda used in CV studies through the public or private provision of information messages. One of the main methodological issues about hypothetical markets regards whether people behave differently when bidding for a public good through casting a ballot vote than when they are privately purchasing an equivalent good. This study tried to address the core of this issue by using a good that can be traded both as private and public: information messages. This allows the elimination of confounding effects associated with the specific good employed. In our case information dispels some of the uncertainty about a potential gain from a gamble. So, the approximate value of the message can be inferred once the individual measure of risk aversion is known. Decision tasks are then framed in a systematic manner according to the hypothetical vs real nature of the decision and the public vs private nature of the message. A sample of 536 university students across three countries (I, UK and NZ) participated into this lab experiment. The chosen countries reflect diversity in exposure to the practice of advisory (NZ) and abrogative (Italy) referenda, with the UK not having any exposure to it. Under private provision the results show that the fraction of participants unwilling to buy information is slightly higher in the real treatment than in the hypothetical one. Under public provision, instead, there is no statistical difference between real and hypothetical settings, confirming in part the finding of previous researchers. A verbal protocol analysis of the thought processes during choice highlights that public provision of information systematically triggers concerns and motivations different from those arising under the private provision setting. These findings suggest that the incentive compatibility of public referenda is likely to rely more on affective and psychological factors than on the strategic behaviour assumptions theorised by economists.

year: 2007-06

title: Opening address

authors: Levy, Michelle Patricia

subjects: Maori

abstract: In 2002, the Māori and Psychology Research Unit at the University of Waikato made a valuable contribution to the teaching and practice of psychology in Aotearoa, via the Māori Graduates of Psychology Symposium. The symposium in 2002, with its theme of “Making a Difference” was designed to: provide an opportunity for exposure to role models; bring together Māori graduates of psychology to network and share information; and through the publication and dissemination of the Symposium proceedings provide a resource for teaching and practice in psychology. With over 100 delegates and 30 presentations, the 2002 symposium was widely acknowledged as a success. It resulted in the compilation of proceedings which have become a valuable resource in psychology. 
While there have been informal gatherings and ongoing networking over the past five years, there have been no formal gatherings since that time. We at the Māori and Psychology Research Unit consider it timely in 2007, five years on, to convene another Symposium. Our conversations with Pacific psychologists and recognition of the ties which exist between us as Pacific nations, saw our focus expand to include Pacific psychologists and psychologies.

text: Opening address In 2002, the Māori and Psychology Research Unit at the University of Waikato made a valuable contribution to the teaching and practice of psychology in Aotearoa, via the Māori Graduates of Psychology Symposium. The symposium in 2002, with its theme of “Making a Difference” was designed to: provide an opportunity for exposure to role models; bring together Māori graduates of psychology to network and share information; and through the publication and dissemination of the Symposium proceedings provide a resource for teaching and practice in psychology. With over 100 delegates and 30 presentations, the 2002 symposium was widely acknowledged as a success. It resulted in the compilation of proceedings which have become a valuable resource in psychology. 
While there have been informal gatherings and ongoing networking over the past five years, there have been no formal gatherings since that time. We at the Māori and Psychology Research Unit consider it timely in 2007, five years on, to convene another Symposium. Our conversations with Pacific psychologists and recognition of the ties which exist between us as Pacific nations, saw our focus expand to include Pacific psychologists and psychologies.

year: 2008