title: Effect of spacers on axial capacity of cold-formed steel back-to-back gapped channel sections

authors: Divi, Seshagiri Rao

abstract: The use of cold-formed steel (CFS) gapped back-to-back channel sections is becoming popular, especially in New Zealand and South-East Asia. Introducing a gap between the back-to-back channels enhances resistance to lateral-torsional buckling. Previous research has investigated gapped built-up channel sections with spacers but hasn't determined the optimal number of spacers relative to length. Also, little attention has been given to how transverse spacing affects the axial capacity of these sections. This study fills those gaps by developing and validating a non-linear elastoplastic finite element (FE) model against experimental data. A parametric study of 1000 FE models examine the effects of column length, CFS section thickness, materials properties, and spacer spacing, on the axial capacity of gapped built-up columns. Key findings include: (1) Up to a column length of 4000 mm, three equally spaced spacers optimize compressive strength in gapped sections. (2) Optimal transverse spacing aligns with the channel web depth, offering no significant strength increase beyond 1.5 times the web depth. (3) Gapped sections show a substantial average increase (424%) in compressive strength over single-channel configurations, and a moderate improvement (125%) compared to non-gapped built-up sections. (4) FEA results closely match the predictions of AS/NZS4600:2018, differing by only 5% in compressive strength.

text: Effect of spacers on axial capacity of cold-formed steel back-to-back gapped channel sections The use of cold-formed steel (CFS) gapped back-to-back channel sections is becoming popular, especially in New Zealand and South-East Asia. Introducing a gap between the back-to-back channels enhances resistance to lateral-torsional buckling. Previous research has investigated gapped built-up channel sections with spacers but hasn't determined the optimal number of spacers relative to length. Also, little attention has been given to how transverse spacing affects the axial capacity of these sections. This study fills those gaps by developing and validating a non-linear elastoplastic finite element (FE) model against experimental data. A parametric study of 1000 FE models examine the effects of column length, CFS section thickness, materials properties, and spacer spacing, on the axial capacity of gapped built-up columns. Key findings include: (1) Up to a column length of 4000 mm, three equally spaced spacers optimize compressive strength in gapped sections. (2) Optimal transverse spacing aligns with the channel web depth, offering no significant strength increase beyond 1.5 times the web depth. (3) Gapped sections show a substantial average increase (424%) in compressive strength over single-channel configurations, and a moderate improvement (125%) compared to non-gapped built-up sections. (4) FEA results closely match the predictions of AS/NZS4600:2018, differing by only 5% in compressive strength.

year: 2024

title: Questionnaire-Derived Sleep Habits and Academic Achievement in First Year University Students

authors: Driller, Matthew W.

subjects: grades

abstract: This study aimed to determine the effect of sleep quantity and quality via the Pittsburgh Sleep Quality Index (PSQI) on students' academic achievement in their first year of university study. In this cross-sectional study, 193 students (102 female, 91 male, mean ± SD; age = 19.3 ± 2.9 y) from an undergraduate Health degree in New Zealand completed the PSQI four weeks prior to the end of the semester in their first year of university study. Results from three core subjects in the first semester were averaged and correlations between the PSQI and academic success were evaluated using Spearman's rho (ρ). The group were also trichotomized using a PSQI global score of ≤5 as the threshold for "good" sleepers (n = 62, 32%), a score of 5-8 for "moderate" sleepers (n = 63, 33%) and a score ≥8 to characterize "poor" sleepers (n = 68, 35%). Overall, students averaged 7 h 37 min of self-reported sleep duration with an average bedtime of 22:55 p.m. and wake time of 8:01 a.m. There was a significant, small inverse relationship between academic performance and bedtime (p = 0.03, ρ = -0.14), with those going to bed earlier having superior academic success. The trichotomized data demonstrated no significant differences in academic performance between students with poor, moderate and good sleep quality (p = 0.92). Later bedtimes were associated with lower academic performance in a group of first year university students. However, there were no other relationships observed between academic success and self-reported sleep quality or quantity as determined by the PSQI. Enhancing awareness of the impact of sleep timing on academic success should be prioritized and strategies to improve sleep hygiene should be promoted to university students.

text: Questionnaire-Derived Sleep Habits and Academic Achievement in First Year University Students This study aimed to determine the effect of sleep quantity and quality via the Pittsburgh Sleep Quality Index (PSQI) on students' academic achievement in their first year of university study. In this cross-sectional study, 193 students (102 female, 91 male, mean ± SD; age = 19.3 ± 2.9 y) from an undergraduate Health degree in New Zealand completed the PSQI four weeks prior to the end of the semester in their first year of university study. Results from three core subjects in the first semester were averaged and correlations between the PSQI and academic success were evaluated using Spearman's rho (ρ). The group were also trichotomized using a PSQI global score of ≤5 as the threshold for "good" sleepers (n = 62, 32%), a score of 5-8 for "moderate" sleepers (n = 63, 33%) and a score ≥8 to characterize "poor" sleepers (n = 68, 35%). Overall, students averaged 7 h 37 min of self-reported sleep duration with an average bedtime of 22:55 p.m. and wake time of 8:01 a.m. There was a significant, small inverse relationship between academic performance and bedtime (p = 0.03, ρ = -0.14), with those going to bed earlier having superior academic success. The trichotomized data demonstrated no significant differences in academic performance between students with poor, moderate and good sleep quality (p = 0.92). Later bedtimes were associated with lower academic performance in a group of first year university students. However, there were no other relationships observed between academic success and self-reported sleep quality or quantity as determined by the PSQI. Enhancing awareness of the impact of sleep timing on academic success should be prioritized and strategies to improve sleep hygiene should be promoted to university students.

year: 2021-12-28

title: Empirical analysis of Pacific, Māori and ethnic pay gaps in New Zealand

authors: Cochrane, William

abstract: A descriptive profile of the four ethnic groups, by gender, is provided to illustrate the heterogeneities across populations in terms of a number of variables grouped into the following categories: individual characteristics, educational attainment, region, household and job-related characteristics. The main empirical analysis involves estimation of the statistical contribution of observed factors (within each of the aforementioned categories) towards explaining the ethnic pay gaps. As this research is primarily aimed as an input towards the Pacific Pay Gap Inquiry being conducted by the Human Rights Commission, we focus our summary of the key findings on the Pacific – European pay gap.
This includes variables on permanent contract status, an indicator if in part-time work, occupation, and industry. These results are therefore likely an indication of the strong role of occupational segregation in the labour market. An additional factor that had a relatively strong contribution to the pay gap, particularly for the Pacific – European female gap, was educational attainment. Overall, even after accounting for differences in job-related characteristics and educational attainment, amongst a number of other observed factors, it was still found that only 27 percent of the pay gap for Pacific males (relative to Europeans) could be explained; and the corresponding proportion for females was 39 percent. The remaining portion of the Pacific Pay Gap is likely to reflect a range of causes that cannot be quantified or disentangled in this analysis – such as not including other factors of importance as they weren’t observed in the data (for example, literacy proficiency or field of study for qualification attained); ethnic differences in preferences for non-wage components of the job; unconscious bias; and discrimination.

text: Empirical analysis of Pacific, Māori and ethnic pay gaps in New Zealand A descriptive profile of the four ethnic groups, by gender, is provided to illustrate the heterogeneities across populations in terms of a number of variables grouped into the following categories: individual characteristics, educational attainment, region, household and job-related characteristics. The main empirical analysis involves estimation of the statistical contribution of observed factors (within each of the aforementioned categories) towards explaining the ethnic pay gaps. As this research is primarily aimed as an input towards the Pacific Pay Gap Inquiry being conducted by the Human Rights Commission, we focus our summary of the key findings on the Pacific – European pay gap.
This includes variables on permanent contract status, an indicator if in part-time work, occupation, and industry. These results are therefore likely an indication of the strong role of occupational segregation in the labour market. An additional factor that had a relatively strong contribution to the pay gap, particularly for the Pacific – European female gap, was educational attainment. Overall, even after accounting for differences in job-related characteristics and educational attainment, amongst a number of other observed factors, it was still found that only 27 percent of the pay gap for Pacific males (relative to Europeans) could be explained; and the corresponding proportion for females was 39 percent. The remaining portion of the Pacific Pay Gap is likely to reflect a range of causes that cannot be quantified or disentangled in this analysis – such as not including other factors of importance as they weren’t observed in the data (for example, literacy proficiency or field of study for qualification attained); ethnic differences in preferences for non-wage components of the job; unconscious bias; and discrimination.

year: 2022-07