title: Moment capacity of cold-formed channel beams with edge-stiffened web holes, un-stiffened web holes and plain webs

authors: Sivaji, Vivekanandan

subjects: Science & Technology

abstract: Cold-formed steel (CFS) channel beams are an increasingly popular choice as load-carrying members in building structures. Such channel beams often include web holes for installation of services. Traditional web holes are normally punched and are un-stiffened. This can restrict the size and spacing of web holes. Recently, a new generation of CFS channel beams with edge-stiffened web holes has been developed and used widely in New Zealand. However, no experimental investigation has been reported in the literature for such channel beams under bending. In this paper, a total of 215 results comprising 16 four-point bending tests and 199 finite element analysis (FEA) are reported on the moment capacity of CFS channel beams with both edge-stiffened and un-stiffened web holes. For comparison, channel beams without web holes were also tested. For all specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was also developed, and the results showed good agreement with the test results. A parametric study was conducted using the validated FE model to investigate the effects of beam length, hole diameter, stiffener length and fillet radius on the moment capacity of CFS channel beams. It is shown that for the case of a channel beam with five edge-stiffened web holes, the moment capacity increased by as much as 14.5%, compared to that of a plain channel beam. For comparison, the same section with un-stiffened web holes had a 13.6% reduction in moment capacity, compared to that of a plain channel beam. Furthermore, the accuracy of current design guidelines in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZ) standards were verified by comparing the tests and FEA results against the design strengths for moment capacity of CFS channel beams without web holes. On the other hand, for CFS channel beams with web holes, the moment capacity obtained from tests and FEA were compared against the moment capacity calculated from the design equations of Moen and Schafer. Upon comparison, it was found that the AISI and AS/NZS can closely predict the moment capacity of CFS channel beams without web holes. The Moen and Schafer design equations were found to be over-conservative by around 11% and 28% for moment capacity of CFS channel beams with un-stiffened and edge-stiffened web holes, respectively.

text: Moment capacity of cold-formed channel beams with edge-stiffened web holes, un-stiffened web holes and plain webs Cold-formed steel (CFS) channel beams are an increasingly popular choice as load-carrying members in building structures. Such channel beams often include web holes for installation of services. Traditional web holes are normally punched and are un-stiffened. This can restrict the size and spacing of web holes. Recently, a new generation of CFS channel beams with edge-stiffened web holes has been developed and used widely in New Zealand. However, no experimental investigation has been reported in the literature for such channel beams under bending. In this paper, a total of 215 results comprising 16 four-point bending tests and 199 finite element analysis (FEA) are reported on the moment capacity of CFS channel beams with both edge-stiffened and un-stiffened web holes. For comparison, channel beams without web holes were also tested. For all specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was also developed, and the results showed good agreement with the test results. A parametric study was conducted using the validated FE model to investigate the effects of beam length, hole diameter, stiffener length and fillet radius on the moment capacity of CFS channel beams. It is shown that for the case of a channel beam with five edge-stiffened web holes, the moment capacity increased by as much as 14.5%, compared to that of a plain channel beam. For comparison, the same section with un-stiffened web holes had a 13.6% reduction in moment capacity, compared to that of a plain channel beam. Furthermore, the accuracy of current design guidelines in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZ) standards were verified by comparing the tests and FEA results against the design strengths for moment capacity of CFS channel beams without web holes. On the other hand, for CFS channel beams with web holes, the moment capacity obtained from tests and FEA were compared against the moment capacity calculated from the design equations of Moen and Schafer. Upon comparison, it was found that the AISI and AS/NZS can closely predict the moment capacity of CFS channel beams without web holes. The Moen and Schafer design equations were found to be over-conservative by around 11% and 28% for moment capacity of CFS channel beams with un-stiffened and edge-stiffened web holes, respectively.

year: 2020-12-01

title: The application of elemental fingerprinting techniques to identify population connectivity using austrovenus stutchburyi recruits

authors: Niemand, Clarisse

subjects: elemental fingerprinting

abstract: The density, distribution and dynamics of benthic bivalve populations are believed to be largely determined by the planktonic larval phase of the life history. As the hard parts of larvae, such as the prodissoconch (larval shell), develop and grow, ambient environmental conditions are recorded as chemical signatures (elemental fingerprints). If the chemical signals of reference sites are known, the larval signatures can be matched to reference sites, hereby reconstructing the origin of the larvae. The collection and identification of larval bivalves is extremely difficult, however, previous studies have shown that the prodissoconch is retained into the juvenile phase, thus enabling juveniles to maintain a record of the larval movement. Before elemental fingerprinting can be used as a larval tracking tool, site specific signatures must be evident in the shells. As a precursor study to test the application of elemental fingerprinting to track bivalve larvae, the presence of spatial variability in shell signatures as well as the scale at which these variations occurred, were established for New Zealand conditions. Furthermore, temporal stability of the shell signatures was explored, as temporal stability is crucial if the signals of shells collected at one time are to be used as predictors of unknown samples collected at a different time.
The venerid bivalve Austrovenus stutchburyi is a common and widespread constituent of New Zealand estuarine communities and were therefore selected as the study species. The chemical signatures of entire Austrovenus stutchburyi shells were examined to determine the inter-site spatial differences in elemental fingerprints of shells and also to characterise the temporal stability of the signatures. Furthermore, shells were ablated at two reference points (the prodissoconch and most recently formed shell material) to determine the intra-shell variation in the chemical signatures. Juvenile individuals were collected from 19 sites in the North Island of New Zealand as part of the whole shell spatial study. One site (in Tauranga Harbour) was examined for the temporal study, whilst four sites were used to compare intra-shell chemical variation. Whole shells were digested and analysed as solution based samples using inductively coupled
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ABSTRACT
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plasma-mass spectrometry (ICP-MS) for the spatial and temporal studies, and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for the point ablation intra-shell variation study.
Results showed that shell concentrations were sufficiently different to yield a classification success of 68% over 19 sites, however the classification success markedly increased as the number of sites included in the analysis decreased (e.g. 12 sites = 75%, 10 sites = 84%, 5 sites = 90%, 3 sites = 95%). Shells were successfully classified across all of the spatial scales that were tested (approximately 10 km to 1150 km). Temporal stability in chemical signatures was observed over a 44 day period. The chemical signatures were not correlated with ambient temperature or salinity, however more vigorous sampling is needed to accurately assess the relationship between shell elemental incorporation and environmental conditions. Intra-shell variation was also observed for some of the shells analysed from two of the four sites. These results were promising and indicated that there may be chemical variations between the larval shells and the more recently formed shell material, thus suggesting the possibility of external recruitment.
The results from this study emphasised the potential for the application of elemental fingerprinting techniques to track and better understand the larval transport and population connectivity for New Zealand invertebrate species, however more research is required before elemental fingerprinting can effectively be applied to New Zealand invertebrate species. With a fundamental understanding of the origin of bivalve recruits, restoration efforts following estuarine disturbance events can be effectively employed.

text: The application of elemental fingerprinting techniques to identify population connectivity using austrovenus stutchburyi recruits The density, distribution and dynamics of benthic bivalve populations are believed to be largely determined by the planktonic larval phase of the life history. As the hard parts of larvae, such as the prodissoconch (larval shell), develop and grow, ambient environmental conditions are recorded as chemical signatures (elemental fingerprints). If the chemical signals of reference sites are known, the larval signatures can be matched to reference sites, hereby reconstructing the origin of the larvae. The collection and identification of larval bivalves is extremely difficult, however, previous studies have shown that the prodissoconch is retained into the juvenile phase, thus enabling juveniles to maintain a record of the larval movement. Before elemental fingerprinting can be used as a larval tracking tool, site specific signatures must be evident in the shells. As a precursor study to test the application of elemental fingerprinting to track bivalve larvae, the presence of spatial variability in shell signatures as well as the scale at which these variations occurred, were established for New Zealand conditions. Furthermore, temporal stability of the shell signatures was explored, as temporal stability is crucial if the signals of shells collected at one time are to be used as predictors of unknown samples collected at a different time.
The venerid bivalve Austrovenus stutchburyi is a common and widespread constituent of New Zealand estuarine communities and were therefore selected as the study species. The chemical signatures of entire Austrovenus stutchburyi shells were examined to determine the inter-site spatial differences in elemental fingerprints of shells and also to characterise the temporal stability of the signatures. Furthermore, shells were ablated at two reference points (the prodissoconch and most recently formed shell material) to determine the intra-shell variation in the chemical signatures. Juvenile individuals were collected from 19 sites in the North Island of New Zealand as part of the whole shell spatial study. One site (in Tauranga Harbour) was examined for the temporal study, whilst four sites were used to compare intra-shell chemical variation. Whole shells were digested and analysed as solution based samples using inductively coupled
ii
ABSTRACT
iii
plasma-mass spectrometry (ICP-MS) for the spatial and temporal studies, and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for the point ablation intra-shell variation study.
Results showed that shell concentrations were sufficiently different to yield a classification success of 68% over 19 sites, however the classification success markedly increased as the number of sites included in the analysis decreased (e.g. 12 sites = 75%, 10 sites = 84%, 5 sites = 90%, 3 sites = 95%). Shells were successfully classified across all of the spatial scales that were tested (approximately 10 km to 1150 km). Temporal stability in chemical signatures was observed over a 44 day period. The chemical signatures were not correlated with ambient temperature or salinity, however more vigorous sampling is needed to accurately assess the relationship between shell elemental incorporation and environmental conditions. Intra-shell variation was also observed for some of the shells analysed from two of the four sites. These results were promising and indicated that there may be chemical variations between the larval shells and the more recently formed shell material, thus suggesting the possibility of external recruitment.
The results from this study emphasised the potential for the application of elemental fingerprinting techniques to track and better understand the larval transport and population connectivity for New Zealand invertebrate species, however more research is required before elemental fingerprinting can effectively be applied to New Zealand invertebrate species. With a fundamental understanding of the origin of bivalve recruits, restoration efforts following estuarine disturbance events can be effectively employed.

year: 2009

title: Place responsive and culturally responsive outdoor education in secondary schools: Examining teachers' perspectives and experiences

authors: Skipworth, Andrew James

subjects: place responsive

abstract: Sustainability, place and human connectedness have increasingly become the focus of research and professional dialogue in school-based outdoor education in Aotearoa New Zealand. These developments challenge traditional practices that privilege adventure and individualistic outcomes in outdoor education. At the same time, the implementation of culturally responsive practices within many secondary schools has further challenged teachers of outdoor education to ensure that pedagogical approaches and outcomes meet the needs of their diverse student population. An increasing number of educators appear to have adopted place responsive and culturally responsive pedagogies within their outdoor education programmes or units of work at the senior school level, yet there is limited research examining teachers’ perceptions and experiences in doing so.
Adopting an interpretive framework, and using qualitative research methods, this research focuses on the challenges faced and opportunities presented when secondary school teachers in Aotearoa New Zealand adopt place and culturally responsive pedagogies in outdoor education. Six teachers of senior level outdoor education from schools spread throughout Aotearoa New Zealand shared their stories. An inductive analysis of the interviews identified these teachers faced ongoing challenges with adopting new pedagogies in outdoor education, which was in part because many colleagues held perceptions that outdoor education was less important than other subjects and was primarily about having fun. In addition, the complexities of assessment at the senior level meant that teachers often faced challenges in formally assessing student learning. Teachers also found that undertaking change required shifts in mind-set which were further supported by targeted professional development, engagement in post-graduate study and talking with like-minded teachers. However, teachers’ adoption of place and culturally responsive approaches generated notable opportunities to align to the front end of the New Zealand curriculum, promote the holistic development of students and nurture cultural diversity.
This study highlights that undertaking curriculum and pedagogical change in outdoor education in secondary schools is a complex process, which is greatly influenced by the attitudes and perceptions of others. The potential alignment of place responsive and culturally responsive pedagogies became apparent, as did the need for more targeted professional development for teachers of outdoor education. Teachers’ adoption of these pedagogies also highlighted a greater capacity for authentic outdoor education experiences for students that also strengthened a commitment to their bicultural partnerships in schools. As the nature of education changes in schools, contemporary pedagogies in outdoor education have the potential to enhance the capacity of schools to facilitate learning that will meet the diverse needs of learners in Aotearoa New Zealand.

text: Place responsive and culturally responsive outdoor education in secondary schools: Examining teachers' perspectives and experiences Sustainability, place and human connectedness have increasingly become the focus of research and professional dialogue in school-based outdoor education in Aotearoa New Zealand. These developments challenge traditional practices that privilege adventure and individualistic outcomes in outdoor education. At the same time, the implementation of culturally responsive practices within many secondary schools has further challenged teachers of outdoor education to ensure that pedagogical approaches and outcomes meet the needs of their diverse student population. An increasing number of educators appear to have adopted place responsive and culturally responsive pedagogies within their outdoor education programmes or units of work at the senior school level, yet there is limited research examining teachers’ perceptions and experiences in doing so.
Adopting an interpretive framework, and using qualitative research methods, this research focuses on the challenges faced and opportunities presented when secondary school teachers in Aotearoa New Zealand adopt place and culturally responsive pedagogies in outdoor education. Six teachers of senior level outdoor education from schools spread throughout Aotearoa New Zealand shared their stories. An inductive analysis of the interviews identified these teachers faced ongoing challenges with adopting new pedagogies in outdoor education, which was in part because many colleagues held perceptions that outdoor education was less important than other subjects and was primarily about having fun. In addition, the complexities of assessment at the senior level meant that teachers often faced challenges in formally assessing student learning. Teachers also found that undertaking change required shifts in mind-set which were further supported by targeted professional development, engagement in post-graduate study and talking with like-minded teachers. However, teachers’ adoption of place and culturally responsive approaches generated notable opportunities to align to the front end of the New Zealand curriculum, promote the holistic development of students and nurture cultural diversity.
This study highlights that undertaking curriculum and pedagogical change in outdoor education in secondary schools is a complex process, which is greatly influenced by the attitudes and perceptions of others. The potential alignment of place responsive and culturally responsive pedagogies became apparent, as did the need for more targeted professional development for teachers of outdoor education. Teachers’ adoption of these pedagogies also highlighted a greater capacity for authentic outdoor education experiences for students that also strengthened a commitment to their bicultural partnerships in schools. As the nature of education changes in schools, contemporary pedagogies in outdoor education have the potential to enhance the capacity of schools to facilitate learning that will meet the diverse needs of learners in Aotearoa New Zealand.

year: 2017