title: Comparative study of novel cold-formed steel sections for pedestrian bridges under varying structural configurations

authors: Mangelkar, Shridhar

subjects: Abaqus

abstract: The use of Cold-Formed Steel (CFS) in bridge engineering has received considerable interest due to its favorable properties, including a lightweight structure, a high strength-to-weight ratio and affordability. As an innovative alternative to traditional materials such as hot-formed steel, timber, and reinforced concrete, CFS shows significant potential in pedestrian bridge construction. The research investigates the performance of CFS pedestrian bridges, with the aim of advancing lightweight, prefabricated, and environmentally sustainable infrastructure in New Zealand. 

The research primarily focuses on evaluating the feasibility of using CFS for pedestrian bridges by investigating deflection behavior, stress distribution and overall structural performance under standard loading conditions via finite element analysis (FEA). In total, six types of bridge models --Flat Pratt Truss, Box Truss, Tub Girder, Flat Foot, Box Bridge, and the Modular Panel Bridge-- were thoroughly analyzed under a 5 kPa load. The mesh sensitivity study was conducted to ensure that the simulation results were independent of mesh size, achieving numerical convergence without excessive computational cost, and the simulation procedure is validated by comparing with experimental data sourced from an existing Glass Fiber Reinforced Polymer (GFRP) pedestrian truss bridge. In this study, six Cold-Formed Steel (CFS) pedestrian bridge models were investigated under identical 5 kPa loading, a span/200 deflection criterion as defined by the SNZ-HB-8630:2004 code, consistent boundary conditions, and a yield stress limit of 550 MPa, but with varying spans and geometries. (1) For the Flat Pratt Truss bridge spanning 6 meters, the effect of span on deflection and stress was investigated, revealing a maximum deflection of 0.8 mm and a maximum stress of 77.14 MPa, both well within allowable limits; however, the extremely low stress utilization indicates material overconsumption. (2) For the Modular Panel bridge spanning 7.2 meters, the influence of modular assembly on load distribution was examined, resulting in a higher deflection of 65.88 mm and stress levels reaching 639.4 MPa, exceeding the yield strength. (3) For the Box Truss bridge spanning 6.7 meters, the impact of closed-section geometry on stiffness was studied, demonstrating minimal deflection of 20.3 mm and uniformly distributed stress around 535 MPa. (4) For the Tub Girder bridge spanning 15 meters, the effect of large span on flexural performance was analyzed, identifying significant midspan deflection of 37.5 mm with stresses exceeding the yield strength. (5) For the Flat Foot bridge spanning 30 meters, the influence of extreme span on structural integrity was evaluated, showing excessive deflection of 58.92 mm, though still within the serviceability limits, while the maximum stress of 582.4 MPa surpassed the material yield strength. (6) For the Box Bridge spanning 10 meters, the effect of simple box-section design on structural efficiency was assessed, resulting in a deflection of 13.9 mm and stresses exceeding 550 MPa, demonstrating full material utilization. Among all, the Box Truss bridge was found to offer the most favorable balance between satisfying the deflection serviceability limit and achieving a more uniform stress distribution.

text: Comparative study of novel cold-formed steel sections for pedestrian bridges under varying structural configurations The use of Cold-Formed Steel (CFS) in bridge engineering has received considerable interest due to its favorable properties, including a lightweight structure, a high strength-to-weight ratio and affordability. As an innovative alternative to traditional materials such as hot-formed steel, timber, and reinforced concrete, CFS shows significant potential in pedestrian bridge construction. The research investigates the performance of CFS pedestrian bridges, with the aim of advancing lightweight, prefabricated, and environmentally sustainable infrastructure in New Zealand. 

The research primarily focuses on evaluating the feasibility of using CFS for pedestrian bridges by investigating deflection behavior, stress distribution and overall structural performance under standard loading conditions via finite element analysis (FEA). In total, six types of bridge models --Flat Pratt Truss, Box Truss, Tub Girder, Flat Foot, Box Bridge, and the Modular Panel Bridge-- were thoroughly analyzed under a 5 kPa load. The mesh sensitivity study was conducted to ensure that the simulation results were independent of mesh size, achieving numerical convergence without excessive computational cost, and the simulation procedure is validated by comparing with experimental data sourced from an existing Glass Fiber Reinforced Polymer (GFRP) pedestrian truss bridge. In this study, six Cold-Formed Steel (CFS) pedestrian bridge models were investigated under identical 5 kPa loading, a span/200 deflection criterion as defined by the SNZ-HB-8630:2004 code, consistent boundary conditions, and a yield stress limit of 550 MPa, but with varying spans and geometries. (1) For the Flat Pratt Truss bridge spanning 6 meters, the effect of span on deflection and stress was investigated, revealing a maximum deflection of 0.8 mm and a maximum stress of 77.14 MPa, both well within allowable limits; however, the extremely low stress utilization indicates material overconsumption. (2) For the Modular Panel bridge spanning 7.2 meters, the influence of modular assembly on load distribution was examined, resulting in a higher deflection of 65.88 mm and stress levels reaching 639.4 MPa, exceeding the yield strength. (3) For the Box Truss bridge spanning 6.7 meters, the impact of closed-section geometry on stiffness was studied, demonstrating minimal deflection of 20.3 mm and uniformly distributed stress around 535 MPa. (4) For the Tub Girder bridge spanning 15 meters, the effect of large span on flexural performance was analyzed, identifying significant midspan deflection of 37.5 mm with stresses exceeding the yield strength. (5) For the Flat Foot bridge spanning 30 meters, the influence of extreme span on structural integrity was evaluated, showing excessive deflection of 58.92 mm, though still within the serviceability limits, while the maximum stress of 582.4 MPa surpassed the material yield strength. (6) For the Box Bridge spanning 10 meters, the effect of simple box-section design on structural efficiency was assessed, resulting in a deflection of 13.9 mm and stresses exceeding 550 MPa, demonstrating full material utilization. Among all, the Box Truss bridge was found to offer the most favorable balance between satisfying the deflection serviceability limit and achieving a more uniform stress distribution.

year: 2025

title: Redistribution and Recognition for Migrants and Refugees in Aotearoa New Zealand: Neo-Liberal and Multicultural Discourses in NGO Claims-Talk

authors: Fraser, Rebecca Mary

subjects: Redistribution

abstract: Located in demographically diverse Aotearoa New Zealand, this thesis provides evidence that claims made by non-governmental organisations (NGOs) on behalf of refugees and migrants are defined by discourses that interact to provide improved outcomes, but also reproduce marginalisation. My core argument contends that while the parameters of social justice in society are framed by the key concerns of redistribution and recognition, as Nancy Fraser (1997) has asserted, these concerns are also discursively constructed. In order to develop a fuller understanding of redistribution and recognition, the thesis maps them to the key discourses within the settlement sector, described as those of neo-liberalism and multiculturalism. The former (even while it is currently influenced by a turn towards social cohesion) draws on economic ideologies and remains the dominant state discourse of Aotearoa New Zealand. The latter has been identified internationally as a discourse relating to the settlement of migrant and refugee minority cultures within a state. Neo-liberalism and multiculturalism offer distinct and comprehensive responses to social justice. As this thesis demonstrates, redistribution is positioned discursively as either a modest safety net or as a right to rectify structural and/or historical injustice. The discourses also provide alternative conceptions of how to recognise the migrant or refugee individual: as either a culture-free market oriented individual, or a culture-bearing community member. It is in the tension of these two discourses that NGOs frame their claims for redistribution and recognition. This thesis comprises a critical discourse analysis which investigates the claims-talk of NGOs in this environment, identifying what NGOs involved in the resettlement of migrants and refugees say when making claims to the state. Drawing on interviews with ten different actors working within nine NGOs, a small survey of thirteen NGOs, and information displayed on websites of seven NGOs – some of the largest working in the settlement sector – I establish the ways in which questions of social justice are discursively constructed in Aotearoa New Zealand. I further determine how these NGOs negotiate conflict and alignment between the discourses, to consider the points at which their negotiations fail or succeed in building better social justice. I find that NGOs use the discourses of neo-liberalism and multiculturalism strategically, frequently deploying them together, or using one to counter potential or perceived negative effects from the other. Lastly, I identify points of unresolved tension in the discourses, particularly regarding the positioning of ‘need’ as a claim upon the state. This thesis thus extends existing scholarship on multiculturalism, neo-liberalism, and recognition and redistribution, and draws together these diverse bodies of theory to elucidate the complex nature of claims-making in the settlement sector in Aotearoa New Zealand.

text: Redistribution and Recognition for Migrants and Refugees in Aotearoa New Zealand: Neo-Liberal and Multicultural Discourses in NGO Claims-Talk Located in demographically diverse Aotearoa New Zealand, this thesis provides evidence that claims made by non-governmental organisations (NGOs) on behalf of refugees and migrants are defined by discourses that interact to provide improved outcomes, but also reproduce marginalisation. My core argument contends that while the parameters of social justice in society are framed by the key concerns of redistribution and recognition, as Nancy Fraser (1997) has asserted, these concerns are also discursively constructed. In order to develop a fuller understanding of redistribution and recognition, the thesis maps them to the key discourses within the settlement sector, described as those of neo-liberalism and multiculturalism. The former (even while it is currently influenced by a turn towards social cohesion) draws on economic ideologies and remains the dominant state discourse of Aotearoa New Zealand. The latter has been identified internationally as a discourse relating to the settlement of migrant and refugee minority cultures within a state. Neo-liberalism and multiculturalism offer distinct and comprehensive responses to social justice. As this thesis demonstrates, redistribution is positioned discursively as either a modest safety net or as a right to rectify structural and/or historical injustice. The discourses also provide alternative conceptions of how to recognise the migrant or refugee individual: as either a culture-free market oriented individual, or a culture-bearing community member. It is in the tension of these two discourses that NGOs frame their claims for redistribution and recognition. This thesis comprises a critical discourse analysis which investigates the claims-talk of NGOs in this environment, identifying what NGOs involved in the resettlement of migrants and refugees say when making claims to the state. Drawing on interviews with ten different actors working within nine NGOs, a small survey of thirteen NGOs, and information displayed on websites of seven NGOs – some of the largest working in the settlement sector – I establish the ways in which questions of social justice are discursively constructed in Aotearoa New Zealand. I further determine how these NGOs negotiate conflict and alignment between the discourses, to consider the points at which their negotiations fail or succeed in building better social justice. I find that NGOs use the discourses of neo-liberalism and multiculturalism strategically, frequently deploying them together, or using one to counter potential or perceived negative effects from the other. Lastly, I identify points of unresolved tension in the discourses, particularly regarding the positioning of ‘need’ as a claim upon the state. This thesis thus extends existing scholarship on multiculturalism, neo-liberalism, and recognition and redistribution, and draws together these diverse bodies of theory to elucidate the complex nature of claims-making in the settlement sector in Aotearoa New Zealand.

year: 2011

title: Kōura in the Rotorua Te Arawa Lakes and potential effects of catfish

authors: Kusabs, Ian

abstract: I am going to talk about kōura and the novel sampling method we are using, then talk about the population characteristics of kōura in the Rotorua Te Arawa Lakes, including results from my PhD research, the Lake Taupō experience with catfish, which Michel Dedual has more than adequately described, and also future work.

text: Kōura in the Rotorua Te Arawa Lakes and potential effects of catfish I am going to talk about kōura and the novel sampling method we are using, then talk about the population characteristics of kōura in the Rotorua Te Arawa Lakes, including results from my PhD research, the Lake Taupō experience with catfish, which Michel Dedual has more than adequately described, and also future work.

year: 2017