title: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements

authors: Abbaszadeh, Hadi

abstract: Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

text: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

year: 2025

title: Control of pests in Lake catchments – the Department of Conservation’s perspective

authors: Fairweather, Alastair

abstract: A key part of the Department of Conservation’s (DOC) work is to ensure the diversity of New Zealand’s natural heritage is maintained and restored. However, is a huge task and DOC’s resources cannot stretch to do everything everywhere. DOC therefore has to make decisions about what work to do and not do, juggling limited resources while meeting both biodiversity and community needs.
To help make these decisions, DOC has developed the Natural Heritage Management System (NHMS) Programme which identifies the highest priority sites (both terrestrial and freshwater) that need to be protected and where work needs to be done. For NHMS to correctly identify the priority sites and what work it needs to be done at the sites, it relies on good information. For the freshwater sites, the data came out of the Freshwater Ecosystems of New Zealand (FENZ) dataset. This data set describes the environmental and biological patterns in NZ’s freshwater ecosystems (rivers, lakes and wetlands). Once priority sites have been identified, it is important to understand what pressures the sites face and what activities, including pest control, need to be undertaken to reduce these pressures.
In this presentation, the Rotorua lakes, with particular reference to Lake Okataina, will be placed in the context of this prioritisation process, the pressures they face and pest control activities DOC has identified as necessary to ensure the priority lakes are protected.

text: Control of pests in Lake catchments – the Department of Conservation’s perspective A key part of the Department of Conservation’s (DOC) work is to ensure the diversity of New Zealand’s natural heritage is maintained and restored. However, is a huge task and DOC’s resources cannot stretch to do everything everywhere. DOC therefore has to make decisions about what work to do and not do, juggling limited resources while meeting both biodiversity and community needs.
To help make these decisions, DOC has developed the Natural Heritage Management System (NHMS) Programme which identifies the highest priority sites (both terrestrial and freshwater) that need to be protected and where work needs to be done. For NHMS to correctly identify the priority sites and what work it needs to be done at the sites, it relies on good information. For the freshwater sites, the data came out of the Freshwater Ecosystems of New Zealand (FENZ) dataset. This data set describes the environmental and biological patterns in NZ’s freshwater ecosystems (rivers, lakes and wetlands). Once priority sites have been identified, it is important to understand what pressures the sites face and what activities, including pest control, need to be undertaken to reduce these pressures.
In this presentation, the Rotorua lakes, with particular reference to Lake Okataina, will be placed in the context of this prioritisation process, the pressures they face and pest control activities DOC has identified as necessary to ensure the priority lakes are protected.

year: 2015

title: Problematic reasoning under the guise of anti-Māori talk: A case study of the Three Waters tweets

authors: Tan, Kyle K. H.

abstract: Drawing from a subset of Twitter/X quotes (or tweets) on the politically controversial Three Waters Reform, this study identified forms of anti-Māori discourse through a deductive analysis. A complementary analysis was conducted to unpack how problematic reasoning fueled racism against Māori. Our results revealed distinct and interconnected themes—“resources,” “culture,” “stirrer,” “privilege,” and “one people”—that portrayed Māori as undeserving, lacking expertise, threatening, and unworthy of equitable treatment, as New Zealand citizens are entitled to enjoy liberal democratic values. Anti-Māori speakers employed problematic reasoning tactics to obstruct the public from understanding the truth or to encourage others to form ill-informed opinions through emotions, supposed authority, and conspiracy. Exemplar tweets were provided to illustrate the myriad instances of false information related to patterns of anti-Māori discourse. Evidence from this study makes the case for addressing racism on social media and creating interventions to expand media literacy amongst the public to discern problematic reasonings.

text: Problematic reasoning under the guise of anti-Māori talk: A case study of the Three Waters tweets Drawing from a subset of Twitter/X quotes (or tweets) on the politically controversial Three Waters Reform, this study identified forms of anti-Māori discourse through a deductive analysis. A complementary analysis was conducted to unpack how problematic reasoning fueled racism against Māori. Our results revealed distinct and interconnected themes—“resources,” “culture,” “stirrer,” “privilege,” and “one people”—that portrayed Māori as undeserving, lacking expertise, threatening, and unworthy of equitable treatment, as New Zealand citizens are entitled to enjoy liberal democratic values. Anti-Māori speakers employed problematic reasoning tactics to obstruct the public from understanding the truth or to encourage others to form ill-informed opinions through emotions, supposed authority, and conspiracy. Exemplar tweets were provided to illustrate the myriad instances of false information related to patterns of anti-Māori discourse. Evidence from this study makes the case for addressing racism on social media and creating interventions to expand media literacy amongst the public to discern problematic reasonings.

year: 2025