SHEAR BEHAVIOUR AND DESIGN OF COLD-FORMED CHANNEL SECTIONS WITH ELONGATED OPENINGS BASED ON DIRECT STRENGTH METHOD

This thesis presents a detailed study on shear buckling and shear strength of high strength cold-formed channel sections with elongated openings. The main purposes are to investigate experimentally and numerically the shear behaviour of perforated cold-formed steel plain C-lipped sections and to further develop a Direct Strength Method (DSM) of design to predict the shear capacity of such sections. Firstly, in order to achieve the primary aims as stated, an experimental program of thirty tests was performed to observe the shear behaviour of channel members with both non-elongated and elongated web holes. Based on the capability of minimising the bending moments at two ends of the shear span, a testing apparatus namely ‘Dual Actuator Test Rig’ previously developed at the University of Sydney was used throughout the test program to capture a state close to pure shear and to obtain the predominantly shear capacity of perforated members with an aspect ratio (shear span / web depth) up to 2.0. The experimental results were used to study the shear strength reduction due to enlarged web openings. Further, these test results were also used as the input to the current Direct Strength Method (DSM) equations for further comparisons, calibrations and validations. Secondly, in order to achieve more insights into the shear behaviour of cold-formed members with elongated web openings, numerical nonlinear simulations based on the Finite Element Method (FEM) using ABAQUS/Standard were developed to compare with and calibrate against the experimental results. Moreover, to study shear buckling behaviour and to generate shear buckling loads which is also a required input to the DSM in shear, a simplified method for shear buckling analysis using simplified finite element (FE) models including web holes were introduced in this study. The buckling results obtained from these models were calibrated against those of the full FE models which have the same configuration as the actual tests. On the basis of the accuracy of the finite element modelling, the FE models for both shear buckling and shear strength analyses were employed for parametric studies to extend the result database used for further verification of new proposals in this study. Finally, on the basis of the results from experimental and numerical investigations, a new DSM design for cold-formed channel sections subjected to shear with both non-elongated and elongated web openings was introduced. The new proposal is based on the use of the existing DSM design rules for shear together with introduced modifications of the shear yield loads as a result of the Vierendeel mechanism approach. As a consequence of the parametric study for shear buckling analyses, a dimensional transformation was also proposed to determine the equivalent hole dimensions in design

Analysing the determinants of food security among farm households in northern upland Vietnam

The objective of this study is to analyse food security status and the factors affecting food security in Son La, a province in northern upland of Vietnam. The results suggest that 90% of the observed households experience food insecurity, in different levels including mild, moderate, and severe. Furthermore, the results from logistic regression analysis show that age, education, household size, and the number of livelihood related activities have a positive effect on food security. All the results above are consistent with those from previous similar studies. The findings from the study can provide relevant information to the development of food and agriculture policies in Son La and other mountainous provinces in Vietnam

Evaluative Thinking Amid Disaster

Evaluation and emergency medicine have appreciable parallels and are likely to intertwine as they each evolve, especially in response to disasters or other pervasive problems that can worsen into the future. Evaluative thinking—which largely involves critical thinking, valuing, and other dynamic processes—may be ubiquitously useful to practitioners, scholars, and others from both these fields of practice. In this dissertation, I referenced the dual systems theory of the human mind to conceptualize evaluative thinking as paradoxically fast (automatic) and slow (deliberate), and I characterized the COVID-19 pandemic as a disaster laden with societal games. Derived from game theory, societal games range from the formal ones played by disciplines and fields of practice to the informal and diffuse games of social movements and special interests. I sought to answer two research questions. First, what are the manifestations of evaluative thinking within and between evaluation and emergency medicine amid disaster? Second, what linguistic patterns emerge from evaluative thinking amid disaster? My research design was multimethod, involving Q-methodology and function word analysis. I used purposive sampling to obtain two samples—one representing the context of evaluation ( n = 32) and another representing the context of emergency medicine ( n = 31). All research participants were professionals working in settings related to health and disasters, emergencies, and/or crises. Amid disaster, I found six styles of evaluative thinking in the evaluation context ( clarere, justificare, movere, verificare, informare, ponderare ) and three styles in the emergency medicine context ( cernere, librare, delineare ). Using intuition to render judgments is the most automatic process in the verificare, cernere , and delineare styles. Considering the availability of resources is the most deliberate process in the ponderare and delineare styles, while challenging personal beliefs and opinions is the most deliberate process in the clarere and librare styles. Whereas reflecting specifically on closing the gap between current and desired states is most deliberate in the cernere style, it is most automatic in the ponderare style. Lastly, broad reflection is most deliberate in movere and informare , deliberate in justificare and librare , automatic in clarere and ponderare , and circumstantial in the remaining styles. Function words in the English language may be divided into eight categories. On average across evaluative thinking styles, rates of personal pronouns, impersonal pronouns, conjunctions, auxiliary verbs , and non-referential adverbs were higher during the speaking mode than writing mode, while the rates of articles, prepositions, and negations were similar between modes. There were significant mode x style interaction effects for prepositions and articles, though the mean rates of these function words were similar between modes for most styles. There were also significant interaction effects for conjunctions and auxiliary verbs , though the mean rates of these function words were higher during speaking than writing for most styles. Furthermore, the relatively higher rates of spoken (compared to written) pronouns, conjunctions, auxiliary verbs, and non-referential adverbs with the relatively similar rates of spoken and written articles, prepositions , and negations suggest that even with different styles of evaluative thinking and societal games at play, professionals working in disaster, emergency, or crisis settings gravitate toward talking with others in an accessible manner while maintaining a sense of authority that is inherent in their written work. In conclusion, this dissertation contributes to the empirical evaluative thinking literature by providing insights into the nature of evaluative thinking amid disaster, and it also comprises an initial foundation upon which to further probe linguistic signals that help evaluators and other professionals recognize and express different styles of evaluative thinking

Risk preferences and development revisited

A

Advanced deep flux weakening operation control strategies for IPMSM

This paper proposes an advanced flux-weakening control method to enlarge the speed range of interior permanent magnet synchronous motor (IPMSM). In the deep flux weakening (FW) region, the flux linkage decreases as the motor speed increases, increasing instability. Classic control methods will be unstable when operating in this area when changing load torque or reference speed is required. The paper proposes a hybrid control method to eliminate instability caused by voltage limit violation and improve the reference velocity-tracking efficiency when combining two classic control methods. Besides, the effective zone of IPMSM in the FW is analyzed and applied to enhance stability and efficiency following reference velocity. Simulation results demonstrate the strength and effectiveness of the proposed method