title: Buckling behaviour of cold-formed steel lipped channel sections with edge-stiffened web holes under eccentric compression loading

authors: Xi, Xianglun

subjects: cold-formed steel

abstract: Cold-formed steel (CFS) channel sections with web holes are being increasingly popular as vertical load-carrying members. Traditional unstiffened web holes can significantly reduce the
compression capacity, which limits their size and spacing. Recently, edge-stiffened web holes have gained popularity, particularly in New Zealand. These channels often experience eccentric compression loading due to combined lateral and gravity loads when used as vertical members. However, there's a lack of studies on how CFS channel sections with these web holes perform under such conditions.
This research focuses on numerically studying the structural behavior of CFS channel sections with plain webs, unstiffened web holes, and edge-stiffened web holes under eccentric
compression loading along both major and minor axes. Finite element (FE) models were developed to simulate these sections, considering material nonlinearity and initial imperfections. The FE analysis results closely matched experimental results in terms of compressive strength and failure modes.
The study also investigates how factors like section lengths, thickness, hole size, spacing, and load eccentricities influence the compressive capacity of these perforated channel sections.
To account for the effects of the aforementioned design variables on the capacity of these CFS channel members, a combined approach leverages the parametrization of Ansys and the
superior solver of Abaqus to conduct a comprehensive parametric study, including a total of 3078 FE models. Based on the FEA results from the parametric study, it appears that the direction of eccentricity (i.e., 𝑒𝑥< 0) emerges as the critical factor affecting the capacity of CFS channel sections with unstiffened or edge-stiffened web holes. Specifically, for 𝑒𝑥 < 0, the
compression capacity of the channel section with unstiffened web holes reduced by up to 20.55%, compared to a plain channel section; conversely, the channel section having edge-stiffened web holes had a maximum increase of 20.10%, compared to the same channel with unstiffened web holes. However, when 𝑒𝑥 > 0, the influence of different web openings became less significantly.
Finally, based on the FE results of the parametric study, an assessment of current design rules, including American Iron and Steel Institute (AISI-S100) and Australian/New Zealand Standard (AS/NZS-4600), was conducted. The assessment shows the design capacities under eccentric loading predicted by the interaction equation are conservative by 16%-33% on average for plain channels and unstiffened web hole channels. Consequently, new reduction factor interaction equations were proposed for predicting the eccentric compressive capacity of CFS channel sections with different web openings, and a reliability analysis was conducted to ensure the proposed equations could be reliable.

text: Buckling behaviour of cold-formed steel lipped channel sections with edge-stiffened web holes under eccentric compression loading Cold-formed steel (CFS) channel sections with web holes are being increasingly popular as vertical load-carrying members. Traditional unstiffened web holes can significantly reduce the
compression capacity, which limits their size and spacing. Recently, edge-stiffened web holes have gained popularity, particularly in New Zealand. These channels often experience eccentric compression loading due to combined lateral and gravity loads when used as vertical members. However, there's a lack of studies on how CFS channel sections with these web holes perform under such conditions.
This research focuses on numerically studying the structural behavior of CFS channel sections with plain webs, unstiffened web holes, and edge-stiffened web holes under eccentric
compression loading along both major and minor axes. Finite element (FE) models were developed to simulate these sections, considering material nonlinearity and initial imperfections. The FE analysis results closely matched experimental results in terms of compressive strength and failure modes.
The study also investigates how factors like section lengths, thickness, hole size, spacing, and load eccentricities influence the compressive capacity of these perforated channel sections.
To account for the effects of the aforementioned design variables on the capacity of these CFS channel members, a combined approach leverages the parametrization of Ansys and the
superior solver of Abaqus to conduct a comprehensive parametric study, including a total of 3078 FE models. Based on the FEA results from the parametric study, it appears that the direction of eccentricity (i.e., 𝑒𝑥< 0) emerges as the critical factor affecting the capacity of CFS channel sections with unstiffened or edge-stiffened web holes. Specifically, for 𝑒𝑥 < 0, the
compression capacity of the channel section with unstiffened web holes reduced by up to 20.55%, compared to a plain channel section; conversely, the channel section having edge-stiffened web holes had a maximum increase of 20.10%, compared to the same channel with unstiffened web holes. However, when 𝑒𝑥 > 0, the influence of different web openings became less significantly.
Finally, based on the FE results of the parametric study, an assessment of current design rules, including American Iron and Steel Institute (AISI-S100) and Australian/New Zealand Standard (AS/NZS-4600), was conducted. The assessment shows the design capacities under eccentric loading predicted by the interaction equation are conservative by 16%-33% on average for plain channels and unstiffened web hole channels. Consequently, new reduction factor interaction equations were proposed for predicting the eccentric compressive capacity of CFS channel sections with different web openings, and a reliability analysis was conducted to ensure the proposed equations could be reliable.

year: 2024-06-24

title: Isolation of cellulolytic anaerobic extreme thermophiles from New Zealand thermal sites

authors: Sissons, Christopher H.

subjects: biology

abstract: Avicel enrichment cultures from 47 thermal-pool sites in the New Zealand Rotorua-Taupo region were screened for growth and carboxymethyl cellulase activity at 75°C. Eight anaerobic cellulolytic cultures were obtained. The effect of temperature on carboxymethyl cellulase activity was measured, and bacteria were isolated from the five best cultures. Bacteria from two sources designated TP8 and TP10 grew at 75°C, accumulated reducing sugar in the growth medium and gave free cellulases with avicelase activity. Bacteria from sources designated Tok4, Tok8, and Wai21 grew at 75°C, accumulated no free sugars in the medium, and gave free carboxymethyl cellulases with virtually no avicelase activity. All were obligate anaerobic nonsporeforming rods which stained gram negative, grew on pentoses as well as hexoses, and gave ethanol and acetate as major fermentation end products. The isolated strain which produced the most active and stable cellulases (trivially designated TP8.T) had lower rates of free endocellulase accumulation at 75°C than did Clostridium thermocellum at 60°C, but its cellulase activity against avicel and filter paper in culture supernatants was comparable. Tested at 85°C, TP8.T carboxymethyl cellulases included components which were very stable, whereas C. thermocellum carboxymethyl cellulases were all rapidly inactivated. The TP8.T avicelase activity was relatively unaffected by Triton X-100, EDTA, and dithiothreitol. Evidence was obtained for the existence of unisolated, cellulolytic extreme thermophiles producing cellulases which were more stable and active than those from TP8.T.

text: Isolation of cellulolytic anaerobic extreme thermophiles from New Zealand thermal sites Avicel enrichment cultures from 47 thermal-pool sites in the New Zealand Rotorua-Taupo region were screened for growth and carboxymethyl cellulase activity at 75°C. Eight anaerobic cellulolytic cultures were obtained. The effect of temperature on carboxymethyl cellulase activity was measured, and bacteria were isolated from the five best cultures. Bacteria from two sources designated TP8 and TP10 grew at 75°C, accumulated reducing sugar in the growth medium and gave free cellulases with avicelase activity. Bacteria from sources designated Tok4, Tok8, and Wai21 grew at 75°C, accumulated no free sugars in the medium, and gave free carboxymethyl cellulases with virtually no avicelase activity. All were obligate anaerobic nonsporeforming rods which stained gram negative, grew on pentoses as well as hexoses, and gave ethanol and acetate as major fermentation end products. The isolated strain which produced the most active and stable cellulases (trivially designated TP8.T) had lower rates of free endocellulase accumulation at 75°C than did Clostridium thermocellum at 60°C, but its cellulase activity against avicel and filter paper in culture supernatants was comparable. Tested at 85°C, TP8.T carboxymethyl cellulases included components which were very stable, whereas C. thermocellum carboxymethyl cellulases were all rapidly inactivated. The TP8.T avicelase activity was relatively unaffected by Triton X-100, EDTA, and dithiothreitol. Evidence was obtained for the existence of unisolated, cellulolytic extreme thermophiles producing cellulases which were more stable and active than those from TP8.T.

year: 1987

title: Language, mātauranga Māori . . . and technology?

authors: Selby, Mereana

subjects: Māori language

abstract: In this paper, I report on a research project involving the creation of an e-learning environment for the teaching and learning of an aspect of te reo Māori, that is the preparation of mihi. It was found that learning in the context of an e-learning environment in which anonymity was assured, learners could learn in their own spaces and at their own pace and there was no pressure to perform in front of peers and tutors had the potential to reduce the potentially negative effects of whakamā.

text: Language, mātauranga Māori . . . and technology? In this paper, I report on a research project involving the creation of an e-learning environment for the teaching and learning of an aspect of te reo Māori, that is the preparation of mihi. It was found that learning in the context of an e-learning environment in which anonymity was assured, learners could learn in their own spaces and at their own pace and there was no pressure to perform in front of peers and tutors had the potential to reduce the potentially negative effects of whakamā.

year: 2006-09