title: Web crippling behaviour of cold-formed stainless steel lipped channel sections with edge-stiffened web holes under two-flange loading conditions

authors: Opulencia, Maria Fe Glorieta

subjects: web crippling

abstract: In New Zealand, edge-stiffened holes have been recently introduced to cold-formed steel channels (CFS) to facilitate the installation of plumbing and electrical systems. Previous studies on cold-formed carbon steel (CFCS) channels have demonstrated that using edge-stiffened web holes provides nearly the same strength as an equivalent channel section with a plain web when facing web crippling. However, there is a lack of experimental or numerical investigations into the application of edge-stiffened web holes in cold-formed stainless steel (CFSS) channels in the existing literature.

This thesis builds upon previous studies conducted on CFCS channel sections. It presents a comprehensive numerical examination of the web crippling behavior of CFSS channel sections with edge-stiffened circular web holes under interior-two-flange (ITF) and end-two-flange (ETF) loading conditions. Three stainless steel grades were considered: EN 1.4509 (Ferritic), EN 1.4462 (Duplex), and EN 1.4301 (Austenitic). A parametric study involving 3,744 non-linear finite element (FE) models was developed for both fastened and un-fastened flange cases. The study covered the impact of different hole sizes, edge-stiffener lengths, channel inner radius, and the length of the bearing plates.

The results of the parametric study were used to establish new equations for web crippling strength and strength reduction factors through non-linear regression analysis. These proposed design equations outperformed predictions from American Society of Civil Engineers Specification (ASCE 8-02), American Iron and Steel Institute Specification, Australian/New Zealand Standard (AISI&AS/NZS), and Eurocode 3. Finally, a reliability analysis was conducted, revealing that the proposed design equations accurately predict the web crippling strength of CFSS channel sections with plain webs, unstiffened web holes, and edge-stiffened web holes under two-flange loading conditions.

text: Web crippling behaviour of cold-formed stainless steel lipped channel sections with edge-stiffened web holes under two-flange loading conditions In New Zealand, edge-stiffened holes have been recently introduced to cold-formed steel channels (CFS) to facilitate the installation of plumbing and electrical systems. Previous studies on cold-formed carbon steel (CFCS) channels have demonstrated that using edge-stiffened web holes provides nearly the same strength as an equivalent channel section with a plain web when facing web crippling. However, there is a lack of experimental or numerical investigations into the application of edge-stiffened web holes in cold-formed stainless steel (CFSS) channels in the existing literature.

This thesis builds upon previous studies conducted on CFCS channel sections. It presents a comprehensive numerical examination of the web crippling behavior of CFSS channel sections with edge-stiffened circular web holes under interior-two-flange (ITF) and end-two-flange (ETF) loading conditions. Three stainless steel grades were considered: EN 1.4509 (Ferritic), EN 1.4462 (Duplex), and EN 1.4301 (Austenitic). A parametric study involving 3,744 non-linear finite element (FE) models was developed for both fastened and un-fastened flange cases. The study covered the impact of different hole sizes, edge-stiffener lengths, channel inner radius, and the length of the bearing plates.

The results of the parametric study were used to establish new equations for web crippling strength and strength reduction factors through non-linear regression analysis. These proposed design equations outperformed predictions from American Society of Civil Engineers Specification (ASCE 8-02), American Iron and Steel Institute Specification, Australian/New Zealand Standard (AISI&AS/NZS), and Eurocode 3. Finally, a reliability analysis was conducted, revealing that the proposed design equations accurately predict the web crippling strength of CFSS channel sections with plain webs, unstiffened web holes, and edge-stiffened web holes under two-flange loading conditions.

year: 2024

title: Sensitive soils of the Puketoka Formation, Hamilton, New Zealand

authors: Kitchen, Emily

subjects: Puketoka Formation

abstract: Sensitive soils are known to cause significant issues in the infrastructure and civil engineering industry, and are prone to sudden, oftentimes catastrophic failures following long periods of stability. 
The Walton Subgroup soils deposited through volcanic activity and partially reworked by the ancestral Waikato River are identified within the Hamilton Basin. These materials are of interest to the engineering community, and consultancy groups in the Hamilton area, due to their identified sensitivity. The Puketoka Formation was focused on in this study.
Sampling of material was undertaken at two active construction sites in Hamilton: Dixon Road Roundabout, and Temple View Urban Development. A series of classification tests were completed to determine the samples’ mineralogical and geotechnical characteristics. 
Mineralogical testing found that all the materials were silt dominated (55.06 – 81.12 %), with sub-ordinate clay (13.10 – 18.85 %) and sand (5.56 – 25.35 %) fractions. The moisture contents were variable (49 – 65 %). The field moist bulk density varied throughout the samples (1069 – 1576 kg/m3), as did the oven dry bulk densities (645 – 1057 kg/m3). The porosity as a result also varied (36 – 51 %). The void ratios followed the same trend as the porosity values (0.56 – 0.88). The particle densities of the materials also showed variation (1935 – 2487 kg/m3). The activities of all three samples were variable, ranging from inactive (0.60) to active (1.79). The X-Ray Diffraction (XRD) analysis determined that the main clay mineral present within the samples was a kaolinite group clay, either halloysite or kaolinite. The Fieldes & Perrott NaF test to determine the presence of allophane was also completed on the samples. Both tests were negative, confirming the dominance of halloysite. Bulk analysis also determined other constituents of the samples to include quartz, plagioclase, augite and volcanic glass. Scanning Electron Microscopy (SEM) indicated the main halloysite morphologies present to be a combination of short and long tubules, spheroids, plates and book formations. The microstructure was analysed, and the main clay minerals, grains, microaggregates, and pores within the materials described. The microfabric was consistent for all three samples, with each showing an abundance of small pores (< 20 µm). These pores hold significant amounts of water in not readily accessible locations, leading to the highly porous, but poorly permeable nature of the materials. DRAB1 and TV1 showed microstructures consistent with Huppert (1986) and Beattie’s (1990) ‘matrix’ structures, whilst TV2 showed a more dominant ‘skeletal’ to ‘matrix’ structure. 
Atterberg limits testing found that the samples had a high liquid limit (59 – 75 %) and plastic limit (41 – 53 %), but a variable plasticity index (8 – 34 %) and liquidity index (0.1 – 2). This placed all three samples within the high plasticity “MH” category upon the Casagrande chart. Consolidated undrained triaxial testing of DRAB1 and TV1 indicated a characteristic normally consolidated response to shear, with the majority of cores showing shear band formation. Only TV1 at 170 kPa displayed an intermediate failure type, potentially occurring due to a combination of material being tested, confining pressure, and the low shear rate allowing time for pressure dissipation. The percentage of axial strain the cores failed at varied (1.81 – 16.35 %), and the peak deviator stress (129 – 277 kPa) and pore water pressure values (717.2 – 879.7 kPa) tended to increase as the confining pressures increased. Graphical outputs show a moderate strain, contractive (MSC) style of failure. The effective shear strength values produced were in keeping with the varying ranges of previously published values (effective cohesion: 0 – 37 kPa, effective friction angle: 27 - 38°). The permeability for all three samples was estimated to be ~10-9 – 10-10. Thin section analyses of failed core sections for DRAB1 at 270 kPa confining pressure and TV1 at 130 and 230 kPa confining pressures found that some degree of shear formation and propagation occurred. The calculated R’ angle for DRAB1 was closely observed in the thin section, however was not for TV1. This was hypothesised to have occurred due to a true shear band failure not occurring, rather the development of intermediate to juvenile shear bands within the soil. 
The sensitivity of the Puketoka Formation and wider Walton Subgroup is hypothesised to have been derived from the reworking and weathering the materials experienced. This in turn influenced the porosity and permeability of the materials, which I believe govern the sensitivity of the soils to a degree. Therefore, I believe the Puketoka Formation materials are representative of a silt-dominated, minimally reworked deposit of volcanic origin, that showed appreciable differences compared with the previously studied Tauranga soils. 
The remediation strategies used in the engineering industry were also analysed, and the suitability of the strategies in the context of the Puketoka Formation discussed. This assessment provides an overview of why traditional strategies for remediation may not be beneficial in some cases for the Walton Subgroup materials, which could be of benefit to key engineering groups that encounter these soil materials.
The results of this study provide a set of data which can be used as an initial reference point. The findings and hypotheses made could be of use to key groups including local engineering consultancies, who handle these materials regularly.

text: Sensitive soils of the Puketoka Formation, Hamilton, New Zealand Sensitive soils are known to cause significant issues in the infrastructure and civil engineering industry, and are prone to sudden, oftentimes catastrophic failures following long periods of stability. 
The Walton Subgroup soils deposited through volcanic activity and partially reworked by the ancestral Waikato River are identified within the Hamilton Basin. These materials are of interest to the engineering community, and consultancy groups in the Hamilton area, due to their identified sensitivity. The Puketoka Formation was focused on in this study.
Sampling of material was undertaken at two active construction sites in Hamilton: Dixon Road Roundabout, and Temple View Urban Development. A series of classification tests were completed to determine the samples’ mineralogical and geotechnical characteristics. 
Mineralogical testing found that all the materials were silt dominated (55.06 – 81.12 %), with sub-ordinate clay (13.10 – 18.85 %) and sand (5.56 – 25.35 %) fractions. The moisture contents were variable (49 – 65 %). The field moist bulk density varied throughout the samples (1069 – 1576 kg/m3), as did the oven dry bulk densities (645 – 1057 kg/m3). The porosity as a result also varied (36 – 51 %). The void ratios followed the same trend as the porosity values (0.56 – 0.88). The particle densities of the materials also showed variation (1935 – 2487 kg/m3). The activities of all three samples were variable, ranging from inactive (0.60) to active (1.79). The X-Ray Diffraction (XRD) analysis determined that the main clay mineral present within the samples was a kaolinite group clay, either halloysite or kaolinite. The Fieldes & Perrott NaF test to determine the presence of allophane was also completed on the samples. Both tests were negative, confirming the dominance of halloysite. Bulk analysis also determined other constituents of the samples to include quartz, plagioclase, augite and volcanic glass. Scanning Electron Microscopy (SEM) indicated the main halloysite morphologies present to be a combination of short and long tubules, spheroids, plates and book formations. The microstructure was analysed, and the main clay minerals, grains, microaggregates, and pores within the materials described. The microfabric was consistent for all three samples, with each showing an abundance of small pores (< 20 µm). These pores hold significant amounts of water in not readily accessible locations, leading to the highly porous, but poorly permeable nature of the materials. DRAB1 and TV1 showed microstructures consistent with Huppert (1986) and Beattie’s (1990) ‘matrix’ structures, whilst TV2 showed a more dominant ‘skeletal’ to ‘matrix’ structure. 
Atterberg limits testing found that the samples had a high liquid limit (59 – 75 %) and plastic limit (41 – 53 %), but a variable plasticity index (8 – 34 %) and liquidity index (0.1 – 2). This placed all three samples within the high plasticity “MH” category upon the Casagrande chart. Consolidated undrained triaxial testing of DRAB1 and TV1 indicated a characteristic normally consolidated response to shear, with the majority of cores showing shear band formation. Only TV1 at 170 kPa displayed an intermediate failure type, potentially occurring due to a combination of material being tested, confining pressure, and the low shear rate allowing time for pressure dissipation. The percentage of axial strain the cores failed at varied (1.81 – 16.35 %), and the peak deviator stress (129 – 277 kPa) and pore water pressure values (717.2 – 879.7 kPa) tended to increase as the confining pressures increased. Graphical outputs show a moderate strain, contractive (MSC) style of failure. The effective shear strength values produced were in keeping with the varying ranges of previously published values (effective cohesion: 0 – 37 kPa, effective friction angle: 27 - 38°). The permeability for all three samples was estimated to be ~10-9 – 10-10. Thin section analyses of failed core sections for DRAB1 at 270 kPa confining pressure and TV1 at 130 and 230 kPa confining pressures found that some degree of shear formation and propagation occurred. The calculated R’ angle for DRAB1 was closely observed in the thin section, however was not for TV1. This was hypothesised to have occurred due to a true shear band failure not occurring, rather the development of intermediate to juvenile shear bands within the soil. 
The sensitivity of the Puketoka Formation and wider Walton Subgroup is hypothesised to have been derived from the reworking and weathering the materials experienced. This in turn influenced the porosity and permeability of the materials, which I believe govern the sensitivity of the soils to a degree. Therefore, I believe the Puketoka Formation materials are representative of a silt-dominated, minimally reworked deposit of volcanic origin, that showed appreciable differences compared with the previously studied Tauranga soils. 
The remediation strategies used in the engineering industry were also analysed, and the suitability of the strategies in the context of the Puketoka Formation discussed. This assessment provides an overview of why traditional strategies for remediation may not be beneficial in some cases for the Walton Subgroup materials, which could be of benefit to key engineering groups that encounter these soil materials.
The results of this study provide a set of data which can be used as an initial reference point. The findings and hypotheses made could be of use to key groups including local engineering consultancies, who handle these materials regularly.

year: 2021

title: Harnessing Indigenous Tweets: The Reo Maori Twitter corpus

authors: Trye, David

subjects: Science & Technology

abstract: Te reo Māori, the Indigenous language of Aotearoa New Zealand, is a distinctive feature of the nation’s cultural heritage. This paper documents our efforts to build a corpus of 79,000 Māori-language tweets using computational methods. The Reo Māori Twitter (RMT) Corpus was created by targeting Māori-language users identified by the Indigenous Tweets website, pre-processing their data and filtering out non-Māori tweets, together with other sources of noise. Our motivation for creating such a resource is three-fold: (1) it serves as a rich and unique dataset for linguistic analysis of te reo Māori on social media; (2) it can be used as training data to develop and augment Natural Language Processing (NLP) tools with robust, real-world Māori-language applications; and (3) it will potentially promote awareness of, and encourage positive interaction with, the growing community of Māori tweeters, thereby increasing the use and visibility of te reo Māori in an online environment. While the corpus captures data from 2007 to 2020, our analysis shows that the number of tweets in the RMT Corpus peaked in 2014, and the number of active tweeters peaked in 2017, although at least 600 users were still active in 2020. To the best of our knowledge, the RMT Corpus is the largest publicly-available collection of social media data containing (almost) exclusively Māori text, making it a useful resource for language experts, NLP developers and Indigenous researchers alike.

text: Harnessing Indigenous Tweets: The Reo Maori Twitter corpus Te reo Māori, the Indigenous language of Aotearoa New Zealand, is a distinctive feature of the nation’s cultural heritage. This paper documents our efforts to build a corpus of 79,000 Māori-language tweets using computational methods. The Reo Māori Twitter (RMT) Corpus was created by targeting Māori-language users identified by the Indigenous Tweets website, pre-processing their data and filtering out non-Māori tweets, together with other sources of noise. Our motivation for creating such a resource is three-fold: (1) it serves as a rich and unique dataset for linguistic analysis of te reo Māori on social media; (2) it can be used as training data to develop and augment Natural Language Processing (NLP) tools with robust, real-world Māori-language applications; and (3) it will potentially promote awareness of, and encourage positive interaction with, the growing community of Māori tweeters, thereby increasing the use and visibility of te reo Māori in an online environment. While the corpus captures data from 2007 to 2020, our analysis shows that the number of tweets in the RMT Corpus peaked in 2014, and the number of active tweeters peaked in 2017, although at least 600 users were still active in 2020. To the best of our knowledge, the RMT Corpus is the largest publicly-available collection of social media data containing (almost) exclusively Māori text, making it a useful resource for language experts, NLP developers and Indigenous researchers alike.

year: 2022-02-14