title: An improved and robust finite element model for simulation of  cold-formed steel built-up beams

authors: Birwadkar, Harsh Hemant

subjects: Cold-formed steel

abstract: Cold-formed steel (CFS) built-up sections are increasingly utilized in structural applications due to their lightweight properties, high strength-to-weight ratio, and enhanced moment capacity, which can be further improved by adding stiffeners to the webs or flanges. Accurately determining the moment capacity of these sections is important for practical use. This can be achieved through experimental testing or finite element analysis (FEA) using a four-point bending setup. However, conducting full-scale experimental tests is both expensive and time-consuming, and developing a full-scale finite element (FE) model to replicate these tests can be computationally intensive. 

To address these challenges, this study introduces an accurate, efficient, and robust numerical method that replicates the behaviour of CFS built-up sections, applicable to both back-to-back and face-to-face configurations. The proposed numerical methodology demonstrates excellent agreement with available test results in terms of moment capacity and failure modes, highlighting its potential for determining the moment capacity of built-up sections. The study further investigates two cross-sectional types—stiffened nested and unstiffened nested—to evaluate their behaviour and moment capacity. 

The proposed simplified model was subsequently used in an extensive parametric study to determine the moment capacity of stiffened and unstiffened nested sections. Parameters considered in the study include varying section thicknesses (0.75 mm to 3.00 mm), web depths (150 mm to 600 mm), section configurations (nested and stiffened nested), and screw spacings (75 mm, 150 mm, and 300 mm). Given that existing design standards, such as those from the American Iron and Steel Institute (AISI 2016) and the Australian/New Zealand Standards (AS/NZS 2018), lack specific guidelines for calculating the moment capacity of these sections, this research aims to fill that gap. Furthermore, to simulate practical scenarios, models incorporating screws in the webs (screw-web model) were developed and compared against the simplified model. The results of the parametric study revealed that the moment capacity of the built-up sections is significantly influenced by section thickness, web depth, and section configuration. Screw spacing, however, had a less significant impact. Notably, the moment capacity of the screw-web model was lower than that of the simplified model, emphasizing the importance of bimoment and warping deformation in connection design. 

The study concludes that the developed simplified model provides a computationally efficient tool for predicting the moment capacity of built-up beams, offering valuable insights for designers and engineers. Additionally, the nested section configuration is recommended for achieving higher moment capacity compared to the stiffened nested section.

text: An improved and robust finite element model for simulation of  cold-formed steel built-up beams Cold-formed steel (CFS) built-up sections are increasingly utilized in structural applications due to their lightweight properties, high strength-to-weight ratio, and enhanced moment capacity, which can be further improved by adding stiffeners to the webs or flanges. Accurately determining the moment capacity of these sections is important for practical use. This can be achieved through experimental testing or finite element analysis (FEA) using a four-point bending setup. However, conducting full-scale experimental tests is both expensive and time-consuming, and developing a full-scale finite element (FE) model to replicate these tests can be computationally intensive. 

To address these challenges, this study introduces an accurate, efficient, and robust numerical method that replicates the behaviour of CFS built-up sections, applicable to both back-to-back and face-to-face configurations. The proposed numerical methodology demonstrates excellent agreement with available test results in terms of moment capacity and failure modes, highlighting its potential for determining the moment capacity of built-up sections. The study further investigates two cross-sectional types—stiffened nested and unstiffened nested—to evaluate their behaviour and moment capacity. 

The proposed simplified model was subsequently used in an extensive parametric study to determine the moment capacity of stiffened and unstiffened nested sections. Parameters considered in the study include varying section thicknesses (0.75 mm to 3.00 mm), web depths (150 mm to 600 mm), section configurations (nested and stiffened nested), and screw spacings (75 mm, 150 mm, and 300 mm). Given that existing design standards, such as those from the American Iron and Steel Institute (AISI 2016) and the Australian/New Zealand Standards (AS/NZS 2018), lack specific guidelines for calculating the moment capacity of these sections, this research aims to fill that gap. Furthermore, to simulate practical scenarios, models incorporating screws in the webs (screw-web model) were developed and compared against the simplified model. The results of the parametric study revealed that the moment capacity of the built-up sections is significantly influenced by section thickness, web depth, and section configuration. Screw spacing, however, had a less significant impact. Notably, the moment capacity of the screw-web model was lower than that of the simplified model, emphasizing the importance of bimoment and warping deformation in connection design. 

The study concludes that the developed simplified model provides a computationally efficient tool for predicting the moment capacity of built-up beams, offering valuable insights for designers and engineers. Additionally, the nested section configuration is recommended for achieving higher moment capacity compared to the stiffened nested section.

year: 2024

title: Characteristics and origin of black breccia and its relation to adjacent facies within the Martha hill deposit, Waihi

authors: Salsano, Gianluca Domenico

subjects: Waihi

abstract: The Coromandel Volcanic Zone [CVZ] was an active continental volcanic arc between 18 – 1.9 Ma that was responsible for bimodal andesitic–dacitic–rhyolitic volcanism. Following the emplacement of these volcanic formations, some became locally hydrothermally altered to generate ≈ 50 low sulphidation Au–Ag deposits within the CVZ (Hauraki Goldfield). The Martha Hill deposit is a rift–low sulphidation adularia–sericite gold deposit situated in the township of Waihi, New Zealand. Notably, the origin of a black breccia appearing in core logs at the Martha Hill deposit was previously unknown. The focus of this study was to identify the origin of the black breccia through analyses of three separate drill cores (pertaining to the black breccia), and to discover its significance in the paleo–geothermal field at Martha. Analytical techniques included core logging, microscopy, x–ray diffraction [XRD], x–ray flourescence for geochemical majors [XRF] and scanning electron microscopy [SEM]. Initial core logging and analyses recognised 10 new facies relating to the black breccia. These recognised facies fell under three separate categories; two facies for the weakly altered, five for the highly altered and three for the breccia facies. One of the weakly altered facies best reflects the andesite country rock of the Waipupu Formation. The other weakly altered facies is a foreign clast inclusion of a breccia deposited during the original emplacement of the andesite lavas. The five highly altered facies are related to the varying degrees and overprinting events of the paleo–hydrothermal fluid. One of the breccia facies related to the original emplacement of andesite lava as an autobreccia, whilst the other breccia facies was the product of hydraulic fracturing in the sub–surface. Based on core logging, petrographical and geochemical analyses, the black breccia was discovered to be related to diatreme formation. Diatreme formation can vary among deposits due to the post–eruptive hydrothermal environment (high versus low sulphidation) and the nature of the mechanism utilised to generate the diatreme (phreatomagmatism or hydrothermal eruption). However, the poorly sorted, matrix supported nature of the black breccia that was observed during core logging is widely associated with volume expansion (a hydrothermal brecciation mechanism responsible for diatreme formation). Diatreme formation is the result of an increase in temperature or depressurisation. Facies that may suggest the presence of a feeder dike responsible for generating volume expansion and phreatomagmatism was not observed during core logging, but may be present at greater depths or in other drill core. A more likely scenario for the formation of black breccia was due to depressurisation and volume expansion in the near surface due to hydrothermal eruptions. Indeed, initial steam bursts may have ejected cover materials at the surface resulting in depressurisation and boiling in the near–surface. Brecciation and fragmentation would have likely continued and propagated further downward until the steam supply rate was insufficient to further brecciate and uplift rock fragments. Carbonate veins (calcite) that were present during core logging indicates that the paleo–geothermal field reset after the formation of the black breccia and associated diatreme. The presence of adularia indicated by XRD analyses within the black breccia matrix, signifies that the paleo–hydrothermal fluid temperatures after the emplacement of black breccia was ≈ 180 – 350°C.

text: Characteristics and origin of black breccia and its relation to adjacent facies within the Martha hill deposit, Waihi The Coromandel Volcanic Zone [CVZ] was an active continental volcanic arc between 18 – 1.9 Ma that was responsible for bimodal andesitic–dacitic–rhyolitic volcanism. Following the emplacement of these volcanic formations, some became locally hydrothermally altered to generate ≈ 50 low sulphidation Au–Ag deposits within the CVZ (Hauraki Goldfield). The Martha Hill deposit is a rift–low sulphidation adularia–sericite gold deposit situated in the township of Waihi, New Zealand. Notably, the origin of a black breccia appearing in core logs at the Martha Hill deposit was previously unknown. The focus of this study was to identify the origin of the black breccia through analyses of three separate drill cores (pertaining to the black breccia), and to discover its significance in the paleo–geothermal field at Martha. Analytical techniques included core logging, microscopy, x–ray diffraction [XRD], x–ray flourescence for geochemical majors [XRF] and scanning electron microscopy [SEM]. Initial core logging and analyses recognised 10 new facies relating to the black breccia. These recognised facies fell under three separate categories; two facies for the weakly altered, five for the highly altered and three for the breccia facies. One of the weakly altered facies best reflects the andesite country rock of the Waipupu Formation. The other weakly altered facies is a foreign clast inclusion of a breccia deposited during the original emplacement of the andesite lavas. The five highly altered facies are related to the varying degrees and overprinting events of the paleo–hydrothermal fluid. One of the breccia facies related to the original emplacement of andesite lava as an autobreccia, whilst the other breccia facies was the product of hydraulic fracturing in the sub–surface. Based on core logging, petrographical and geochemical analyses, the black breccia was discovered to be related to diatreme formation. Diatreme formation can vary among deposits due to the post–eruptive hydrothermal environment (high versus low sulphidation) and the nature of the mechanism utilised to generate the diatreme (phreatomagmatism or hydrothermal eruption). However, the poorly sorted, matrix supported nature of the black breccia that was observed during core logging is widely associated with volume expansion (a hydrothermal brecciation mechanism responsible for diatreme formation). Diatreme formation is the result of an increase in temperature or depressurisation. Facies that may suggest the presence of a feeder dike responsible for generating volume expansion and phreatomagmatism was not observed during core logging, but may be present at greater depths or in other drill core. A more likely scenario for the formation of black breccia was due to depressurisation and volume expansion in the near surface due to hydrothermal eruptions. Indeed, initial steam bursts may have ejected cover materials at the surface resulting in depressurisation and boiling in the near–surface. Brecciation and fragmentation would have likely continued and propagated further downward until the steam supply rate was insufficient to further brecciate and uplift rock fragments. Carbonate veins (calcite) that were present during core logging indicates that the paleo–geothermal field reset after the formation of the black breccia and associated diatreme. The presence of adularia indicated by XRD analyses within the black breccia matrix, signifies that the paleo–hydrothermal fluid temperatures after the emplacement of black breccia was ≈ 180 – 350°C.

year: 2022

title: An old story, a new voice: Tertiary education in the Bay of Plenty region

authors: Amundsen, Diana Leigh

subjects: Bay of Plenty

abstract: In this article, I first critique neoliberal effects on the Aotearoa New Zealand tertiary education sector and then provide a close-up look at tertiary education in the Bay of Plenty region. Information is based on aspects of my doctoral research which was located across three tertiary education organisations comprising the Bay of Plenty Tertiary Education Partnership: The University of Waikato, Toi Ohomai Institute of Technology and, Te Whare Wānanga o Awanuiārangi.  The findings of this research examine connections across the partnership, delving into relevant aspects of universities, polytechnics and wānanga. I evaluate the historical, geographical, political and socio-cultural context of all three institutions. Lastly, I discuss campus connections between the partnership organisations. The emerging picture reveals an old story of expansion and growth with a new voice of tension between collaboration and competition in the face of a neoliberal education context. This article offers timely implications for contemporary and future University of Waikato campus connections and may appeal to academics, graduate students, policymakers and the general public.

text: An old story, a new voice: Tertiary education in the Bay of Plenty region In this article, I first critique neoliberal effects on the Aotearoa New Zealand tertiary education sector and then provide a close-up look at tertiary education in the Bay of Plenty region. Information is based on aspects of my doctoral research which was located across three tertiary education organisations comprising the Bay of Plenty Tertiary Education Partnership: The University of Waikato, Toi Ohomai Institute of Technology and, Te Whare Wānanga o Awanuiārangi.  The findings of this research examine connections across the partnership, delving into relevant aspects of universities, polytechnics and wānanga. I evaluate the historical, geographical, political and socio-cultural context of all three institutions. Lastly, I discuss campus connections between the partnership organisations. The emerging picture reveals an old story of expansion and growth with a new voice of tension between collaboration and competition in the face of a neoliberal education context. This article offers timely implications for contemporary and future University of Waikato campus connections and may appeal to academics, graduate students, policymakers and the general public.

year: 2019