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: The dynamics of ¹³C in several New Zealand lakes

authors: McCabe, Bruce

abstract: The main objectives of this study were to;
(i) Determine how the 𝜹¹³C of autochthonous production in fresh water lakes varies with productivity and trophic state.
(ii) Determine if such variations can be used for the investigation of lake palaeoenvironment.
(iii) Quantify the effect of anthropogenic activity on the productivity of Hamilton Basin lakes.
The viability of this project was assessed by monitoring the dissolved inorganic carbon chemistry of an eutrophic pond during a period of high insolation and algal productivity. These observations revealed that during the day, the Pc0₂ in the euphotic zone was reduced to levels low enough to affect. photosynthetic carbon isotopic fractionation, and hence plankton 𝜹¹³C values. The enrichment of ¹³C in the dissolved inorganic carbon (DIC) pool during periods of high
photosynthetic productivity also affects plankton 𝜹¹³C values. Analysis of diurnal changes in 𝜹¹³C and DIC concentration using the Rayleigh equation suggested that photosynthetic fractionation factors changed in response to changes in ambient P𝒸ₒ₂  levels.
The effect of lake trophic state on phytoplankton photosynthetic carbon isotopic fractionation was further investigated using closed system batch cultures of zooplankton-free natural algal populations collected from lakes of differing trophic state. The results indicated
that;
(i) There are considerable differences between algal communities, photosynthetic production and apparent CO₂  compensation points for cultures of algae from lakes of differing trophic state.
(ii) Plankton from a eutrophic lake were able to photosynthesise down to a low and had a variable photosynthetic carbon isotopic fractionation factor, (ep), which varied as a function of the P𝒸ₒ₂ .
(iii) Plankton from a mesotrophic lake were unable to reduce the Pc0₂   below 300ppm and exhibited a constant ∈p .
(iv) Carbon dioxide availability could be limiting plankton photosynthesis in productive eutrophic lakes, and may result in HCO₃⁻ use.
Phytoplankton 𝜹¹³C values and photosynthetic fractionation factors have the potential to be used to detect changes in plankton productivity and substrate use.
A study was made of the isotopic chemistry of the DIC and particulate organic matter, (POM), in six Hamilton Basin lakes with trophic states ranging from hypertrophic to oligotrophic-mesotrophic and dystrophic. From this study, it was concluded that;
(i) The isotopic chemistry of the DIC is a function of:
- catchment composition
- the relative amounts and 𝜹¹³C of inorganic carbon supplied from the atmosphere and biogenic sources.
- the mixing regime of the lake.
(ii) 𝜹¹³Cₚₒₘ varies seasonally in concert with changes in algal biomass.
(iii) Because variations in 𝜹¹³Cₚₒₘ result primarily from changes in the photosynthetic fractionation factor, ∆¹³C₍ₚₒₘ₋𝒸ₒ₂₍ₐq₎₎they can be used to detect changes in the productivity of lakes.
(i v) 𝜹¹³Cₚₒₘ values could not be used to rank lakes in order of increasing productivity because of the effect of systematic differences in the 𝜹¹³C 𝒸ₒ₂₍ₐq₎of different lakes.
(v) POM produced in the euphotic zone is incorporated in the sediment with only a small (-1%) change in its 𝜹¹³C, thus enabling sediment 𝜹¹³C values to be used to source organic carbon in the sediment and to investigate lake palaeoproductivity.
Large systematic variations were observed in sediment 𝜹¹³C values during the development of lakes. By assuming that the 𝜹¹³C 𝒸ₒ₂₍ₐq₎ had remained constant during lake development, an attempt was made to determine the palaeoenvironment of these lakes from sediment 𝜹¹³C values. It was concluded that the productivity of these lakes had undergone considerable changes during their development in response to climatically and anthropologically induced changes in the catchment vegetation. Low forest cover results in high or increased lake productivity, whilst dense forest cover led to low or reduced lake productivity. Lakes formed in the late glacial times had a high productivity, (low forest cover and high nutrient loading), which reduced as the forest cover developed. Peat development also affected some of the lakes.
An attempt was made to assess the effect of anthropogenic activity in the Hamilton Basin on the metabolism of the lakes from changes in the recent sediment 𝜹¹³C values and a comparison of present day 𝜹¹³Cₚₒₘ values with recent sediment 𝜹¹³C values. The results indicate that;
(i) Anthropogenic activity had a marked affect on lake metabolism, resulting in increased terrigenous inputs and/or increased productivity. This was particularly evident in Lake Hakanoa, where deforestation of the area by early Polynesian settlers resulted in a large increase in lake productivity.
(ii) Several of the lakes have very recently undergone a marked increase in their productivity, a result of European activity in the area. 
Thus, plankton productivity has a systematic affect on the 𝜹¹³C of the POM incorporated in lake sediments, which has the potential to be used in the investigation of lake palaeoproductivity, and in assessing the effect of anthropogenic activity on lake productivity.

text: The dynamics of ¹³C in several New Zealand lakes The main objectives of this study were to;
(i) Determine how the 𝜹¹³C of autochthonous production in fresh water lakes varies with productivity and trophic state.
(ii) Determine if such variations can be used for the investigation of lake palaeoenvironment.
(iii) Quantify the effect of anthropogenic activity on the productivity of Hamilton Basin lakes.
The viability of this project was assessed by monitoring the dissolved inorganic carbon chemistry of an eutrophic pond during a period of high insolation and algal productivity. These observations revealed that during the day, the Pc0₂ in the euphotic zone was reduced to levels low enough to affect. photosynthetic carbon isotopic fractionation, and hence plankton 𝜹¹³C values. The enrichment of ¹³C in the dissolved inorganic carbon (DIC) pool during periods of high
photosynthetic productivity also affects plankton 𝜹¹³C values. Analysis of diurnal changes in 𝜹¹³C and DIC concentration using the Rayleigh equation suggested that photosynthetic fractionation factors changed in response to changes in ambient P𝒸ₒ₂  levels.
The effect of lake trophic state on phytoplankton photosynthetic carbon isotopic fractionation was further investigated using closed system batch cultures of zooplankton-free natural algal populations collected from lakes of differing trophic state. The results indicated
that;
(i) There are considerable differences between algal communities, photosynthetic production and apparent CO₂  compensation points for cultures of algae from lakes of differing trophic state.
(ii) Plankton from a eutrophic lake were able to photosynthesise down to a low and had a variable photosynthetic carbon isotopic fractionation factor, (ep), which varied as a function of the P𝒸ₒ₂ .
(iii) Plankton from a mesotrophic lake were unable to reduce the Pc0₂   below 300ppm and exhibited a constant ∈p .
(iv) Carbon dioxide availability could be limiting plankton photosynthesis in productive eutrophic lakes, and may result in HCO₃⁻ use.
Phytoplankton 𝜹¹³C values and photosynthetic fractionation factors have the potential to be used to detect changes in plankton productivity and substrate use.
A study was made of the isotopic chemistry of the DIC and particulate organic matter, (POM), in six Hamilton Basin lakes with trophic states ranging from hypertrophic to oligotrophic-mesotrophic and dystrophic. From this study, it was concluded that;
(i) The isotopic chemistry of the DIC is a function of:
- catchment composition
- the relative amounts and 𝜹¹³C of inorganic carbon supplied from the atmosphere and biogenic sources.
- the mixing regime of the lake.
(ii) 𝜹¹³Cₚₒₘ varies seasonally in concert with changes in algal biomass.
(iii) Because variations in 𝜹¹³Cₚₒₘ result primarily from changes in the photosynthetic fractionation factor, ∆¹³C₍ₚₒₘ₋𝒸ₒ₂₍ₐq₎₎they can be used to detect changes in the productivity of lakes.
(i v) 𝜹¹³Cₚₒₘ values could not be used to rank lakes in order of increasing productivity because of the effect of systematic differences in the 𝜹¹³C 𝒸ₒ₂₍ₐq₎of different lakes.
(v) POM produced in the euphotic zone is incorporated in the sediment with only a small (-1%) change in its 𝜹¹³C, thus enabling sediment 𝜹¹³C values to be used to source organic carbon in the sediment and to investigate lake palaeoproductivity.
Large systematic variations were observed in sediment 𝜹¹³C values during the development of lakes. By assuming that the 𝜹¹³C 𝒸ₒ₂₍ₐq₎ had remained constant during lake development, an attempt was made to determine the palaeoenvironment of these lakes from sediment 𝜹¹³C values. It was concluded that the productivity of these lakes had undergone considerable changes during their development in response to climatically and anthropologically induced changes in the catchment vegetation. Low forest cover results in high or increased lake productivity, whilst dense forest cover led to low or reduced lake productivity. Lakes formed in the late glacial times had a high productivity, (low forest cover and high nutrient loading), which reduced as the forest cover developed. Peat development also affected some of the lakes.
An attempt was made to assess the effect of anthropogenic activity in the Hamilton Basin on the metabolism of the lakes from changes in the recent sediment 𝜹¹³C values and a comparison of present day 𝜹¹³Cₚₒₘ values with recent sediment 𝜹¹³C values. The results indicate that;
(i) Anthropogenic activity had a marked affect on lake metabolism, resulting in increased terrigenous inputs and/or increased productivity. This was particularly evident in Lake Hakanoa, where deforestation of the area by early Polynesian settlers resulted in a large increase in lake productivity.
(ii) Several of the lakes have very recently undergone a marked increase in their productivity, a result of European activity in the area. 
Thus, plankton productivity has a systematic affect on the 𝜹¹³C of the POM incorporated in lake sediments, which has the potential to be used in the investigation of lake palaeoproductivity, and in assessing the effect of anthropogenic activity on lake productivity.

year: 1985

title: Effects of industry on Maori cultural values: The case of the Tarawera River

authors: Dodd, Materoa

subjects: New Zealand

abstract: The research is a case study of the relationship between three tribes; Te Arawa, Tuwharetoa ki Kawerau and Ngāti Awa and the Tarawera River during the second half of the 20th century when the river was polluted with effluent from pulp and paper mills. It involves the cultural story of the Tarawera River as told by the iwi (tribes) of the river informed by Maori epistemologies and what has come to be known as a ‗kaupapa Maori research' approach. Reference is made to the history, legends, customs and lifestyle that have arisen from the relationship between iwi and the river. It includes comments on the pollution of the river from members of each iwi. The world views, experiences, and perceptions reported on here have forced a fundamental change on the iwi, a change that has affected their cultural and social relationship to the river. The price of economic development on the river has been cultural and ecological genocide. 
The cultural voice echoes a familiar story in indigenous communities. In the Maori context the research provides opportunities for further inquiry into determining the socio-cultural, economic and political future of the iwi of the river.

text: Effects of industry on Maori cultural values: The case of the Tarawera River The research is a case study of the relationship between three tribes; Te Arawa, Tuwharetoa ki Kawerau and Ngāti Awa and the Tarawera River during the second half of the 20th century when the river was polluted with effluent from pulp and paper mills. It involves the cultural story of the Tarawera River as told by the iwi (tribes) of the river informed by Maori epistemologies and what has come to be known as a ‗kaupapa Maori research' approach. Reference is made to the history, legends, customs and lifestyle that have arisen from the relationship between iwi and the river. It includes comments on the pollution of the river from members of each iwi. The world views, experiences, and perceptions reported on here have forced a fundamental change on the iwi, a change that has affected their cultural and social relationship to the river. The price of economic development on the river has been cultural and ecological genocide. 
The cultural voice echoes a familiar story in indigenous communities. In the Maori context the research provides opportunities for further inquiry into determining the socio-cultural, economic and political future of the iwi of the river.

year: 2010