Thesis (M.Psych.Org.) - University of Queensland, 2007. / Includes bibliography.

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Construction Management in the Faculty of Engineering at the Cape Peninsula University of Technology 2014 / The study investigates the predominant factors that adversely affect the efficiency of construction labour in the South African construction industry. There is a significant number of studies on construction labour efficiency and productivity. Nonetheless, construction labour efficiency in developed and developing nations is widely reported to be inadequate, and thus adversely impacts the delivery of construction projects. Adequate utilisation of basic construction resources (construction materials and machinery) is significantly dependent on the efficiency of human assets in the construction industry. Hence, the utilisation of construction resources to achieve project objectives in the construction sector cannot be disconnected from the efficiency of construction employees. As a result, the study identified five objectives directed towards improving the efficiency of employees in the construction industry. The first objective identified construction-related factors affecting construction workers’ efficiency; the second objective highlighted design-related factors reducing the efficiency of construction labour; the third identified the impact of construction resources on construction labour efficiency; and the fourth ascertained the external factors affecting the efficiency of human assets in the construction industry. Finally, the last objective is directed towards developing a framework for improving the efficiency of the South African construction workforce. The research adopted a mixed methodological approach, utilising a quantitative questionnaire completed by construction professionals (architects, quantity surveyors, site engineers, project managers, contract managers and site manager). Due to the high level of awareness of site supervisors on labour performance in construction, the quantitative data obtained from construction professionals was subsequently validated using semi-structured interviews with site supervisors. The research questionnaire was designed to elicit the perceptions of construction professionals on various identified factors affecting construction workers’ efficiency on Gauteng and Western Cape construction sites in South Africa. With the aid of 35 unstructured questionnaire surveys, an exploratory study was undertaken within construction firms in Cape Town to ensure the validity of research instruments, where the inputs and comments of respondents were duly considered in formulating the questionnaire for the main study. In the main study, two hundred and sixty-five (265) questionnaires were administered via hand-delivered and electronic mail to construction professionals in the Western Cape and Gauteng provinces, South Africa. Sixty-two (62) questionnaires (23.39%) were duly completed, returned and analysed with Statistical Package for the Social Sciences (SPSS) version 22. Cronbach's alpha coefficient reliability test was subsequently conducted on scaled research questions to ensure reliability of the research questionnaire. The findings revealed that the major factors contributing to the shortfall of construction workers’ performance include; missing details in architectural working drawings, the communication ability of site managers, site managers’ coordinating skills, the effect of strikes on construction operations, the planning ability of site managers, slow response of architects to drawing questions, slow response of structural engineers to drawing questions, construction skills of site supervisors and, finally, shortages of construction materials. Improved construction productivity is a product of construction labour efficiency and enables the achievement of construction project objectives. Therefore, an adequate implementation of the framework presented in this study will not only enhance construction labour efficiency and heighten construction productivity during building production process, but will also increase the satisfaction of construction stakeholder on Gauteng and Western Cape construction projects.

M. Tech. / The financing needs of contractors, especially emerging contractors, need to be explored. In the case of the Small, Medium and Micro-Enterprises (SMMEs’) within the contracting sector, a type of “finance-PLUS” arrangement, which sees the lender, or an intermediary, offer additional support services to emerging enterprises, would be worth exploring. There are various perspectives and opinions on the format and context of the contribution. One of these perspectives embraces the obstacles involved in the entrepreneurial process hindering contribution and economic catalisation. This study follows a focused approach towards the investigation of a financial model for small, medium sized contractors in South Africa. Interviews were conducted and questioners were sent out to different constructors who have been successful in the business for more than five years and also contractors who are currently straggling and trying to survive and grow. Conclusions will be drawn from the analysis and recommendations will be made for further study and curriculum revision, if necessary. All types of businesses need capital before and after they start operating as well as for expansion purpose. The problem is people who have been listed on credit bureaus have their records count against them when they apply for a loan. A key factor mitigating against increased investment in the SMMEs’ sector is the structure of the financial sector. The findings of the study point to the fact that conventional financing mechanisms do not allow for cost-effective provision of finance to large numbers of entrepreneurs seeking small quantities of finance. Effects of poverty and lack of assets mean that many people do not have the collateral needed to access finance. The study also found that although there are different initiatives that are in place to assist small and medium size contractors the typical problems and challenges are still existing. The scopes of this study only focused on small, medium and micro-enterprise in the built environment (specifically the construction industry). In addition, the study focuses on the different financial programmes that are currently in place. An overarching concern is that previously disadvantaged individuals do not have adequate access to credit offered by formal financial institutions and therefore are forced to seek relatively expensive (and often inadequate) amounts of credit from alternative financial sources.

The construction industry continues to strive for new ways to improve construction operations. This requires better understanding and analysis of these operations, which necessitates a way to systematically capture and analyze the diverse elements involved. The dynamic nature of construction is very difficult to describe using existing computer simulation and modeling systems. What is needed is rather a common construction language and a comprehensive modeling system that can be used to capture and analyze construction operations and potentially lead to improvements. A new taxonomy and its use for modeling construction operations are developed here. This taxonomy identifies a hierarchical representation of construction projects based on operational considerations. The hierarchy consists of seven levels: product, assemblies and subassemblies, components, operations, processes, physics, and control. The hierarchical levels were established by looking in the ways that construction field operations are being carried out. The new modeling system successfully accounts for the geometric and physical representations of not only the product but also the processes involved in shaping the product. Six major blocks of construction knowledge are described and information about the interaction processes required to model construction operations in a logical way is provided. An overview of the current state of modeling and simulation techniques that are used to develop and evaluate construction operations is presented. The advantages and limitations of physical-based modeling, 4D-CAD, and virtual modeling techniques as an integral part of the developed taxonomy are identified. The potential uses of robotics and automation opportunities in construction are described. Also, distribution of work between humans and tools and equipment based on their physical and information contributions are reviewed and analyzed. Classifications of construction work at different levels of detail are described to identify which operations can be usefully modeled and the appropriate level of the model. Two practical case studies are discussed that show the capabilities and potential uses of the developed taxonomy. The first case study describes the modeling process of the fabrication, assembly, and erection of steel structures. The second exploratory case study shows the potential use of the developed modeling in improving the heat recovery system generator's (HRSG) erection process. Also, prototype models and 3D models of the HRSG assemblies are developed. Both case studies validate with great confidence the use of the developed taxonomy as a direct support tool that captures the diverse elements and enhances the modeling and analysis to improve construction operations. / Ph. D.

The construction industry has a significant impact on the environment, and from the extractionof raw materials to the construction process to the operation and maintenance of buildings, eachphase contributes to environmental degradation in various ways. Consequently, promotingreuse in the Swedish building sector holds excellent potential for substantially reducing wastegeneration and CO2 emissions, aligning with broader sustainability objectives. We are tryingto create a circular economy paradigm where construction materials and resources are reused,remanufactured, and recycled, minimizing waste and environmental impact. However,realizing the full benefits of the Circular Economy requires significant changes in thinking andthe adoption of innovative business models. The project aims to identify barriers to the reuseof concrete in Sweden's construction sector, along with their causes and effects. A literaturereview was conducted to understand various barriers, forming the basis for subsequentinterviews with experts in a similar field, which is qualitative and semi-structured. Aninnovative collaboration project named Återhus helps to facilitate a comprehensive approach,exploring the challenges hindering reuse practices to inform strategies to overcome thesebarriers and promote greater reuse. The overall results, analysis, and discussion from all thesestudies reinforce the comparison of the views and experiences of different stakeholder groupsand how these differences affect the overall implementation of reuse in construction. Theseinterviews identified barriers and grouped them into the following categories: standardization,economic, material handling, knowledge, and technical barriers. Many barriers are highlyinterconnected, and multiple connections were found within knowledge within the market, aswell as a lack of standardization within the people's knowledge, culture, and understandingtoward a new transition of circularity for reuse.

Titre de l'écran-titre (visionné le 11 janvier 2024) / Ce manuscrit présente un nouveau concept modulaire préfabriquée hybride en bois/aluminium. En particulier, ce document présente un concept de construction mixte dans lequel les éléments structuraux principaux sont préfabriqués en usine en combinant le bois et l'aluminium. La recherche démontre le potentiel des structures hybrides bois-aluminium en termes de durabilité, offrant des constructions modernes légères et résistantes aux séismes. Puisqu'elles sont plus légères et requirent moins de maintenance, les structures bois-aluminium se distinguent des autres structures hybrides. Ce document présente les résultats d'une analyse théorique et numérique sur une structure à plusieurs étages ainsi qu'expérimentale sur une poutre mixte aluminium-bois. / This manuscript presents a development of a new prefabricated and modular hybride timber-to-aluminium construction system. Particularly, this document presents a concept of composite construction in which the main structural elements are prefabricated in the factory by combining timber and aluminum. Research demonstrates the potential of wood-aluminium hybrid structures in terms of durability, offering modern constructions that are light and earthquake resistant. Timber-aluminum structures stand out from other hybrid structures because they are lighter and require less maintenance. This document presents the results of a theoretical and numerical analysis on a multi-story structure as well as an experimental one on an aluminum-timber beam.

La conception des profilés en acier est généralement influencée par l’apparition d’instabilités au niveau local et global de l’élément. Le voilement, le flambement, le déversement ont été source de nombreuses recherches dans le but d’optimiser les coûts des constructions en acier. Une estimation plus précise des charges de ruines réelles devrait permettre des gains, en pratique, de par l’allègement de structures typiquement conçues de façon excessivement sécuritaires. En effet, les règles de conception, proposées par les normes, mènent à une estimation des résistances locales et globales des profilés en I et en H, dont la précision peut être améliorée, et certains chercheurs ont ainsi orienté leur travail vers une optimisation de ces règles. Dans ce contexte, l’O.I.C. (Overall Interaction Concept) qui a été développé dans un premier temps pour les sections tubulaires en acier, permet la conception de tous types de géométries de sections, et cas de chargement, d’une manière simple et efficace. Les formules de résistances ont été développées à partir de résultats expérimentaux et numériques, ceux-ci permettant de prendre en compte, de manière continue, l’interaction entre résistance et instabilité. Cette thèse s’inscrit dans la démarche de l’O.I.C., de par le développement de formules de conception pour les sections en I et en H. Suite à une étude numérique réalisée à partir d’un modèle aux éléments finis, dont la précision a été préalablement vérifiée, des schémas de contraintes résiduelles et imperfections géométriques ont pu être recommandés, afin de garantir l’obtention de résistances fiables. Des études paramétriques furent menées sur des éléments courts, soumis à des cas de chargement simples, telles que la compression pure, la flexion d’axe fort, et la flexion d’axe faible, ainsi que des cas de chargements combinés. Des formulations prédisant la résistance, dans un format O.I.C., ont été ensuite proposées. Davantage d’analyses numériques ont été réalisées afin d’étudier la réponse globale des poutres en I et en H, sujettes au phénomène de déversement, et une équation prédisant leur résistance a été développée. Les formulations proposées ont montré une meilleure fiabilité que celle obtenue selon les directives de l’Eurocode, tout particulièrement dans le cas des sections élancées de classe 4, dont les règles de conception préconisées présentent un manque de précision important. La formulation développée selon l’O.I.C., dans le cas des chargements combinés, bien que d’apparence complexe, permet d’obtenir une estimation de la capacité locale de façon très précise, là où la norme a montré d’importantes lacunes. La performance de la formulation a été préférée à la simplicité, pour assurer son apport vis-à-vis de la précision des normes actuelles. C’est pourquoi ce travail doit être considéré comme une première étape vers une formulation complète de conception des poutres en I et en H, et de futurs travaux pourraient s’intéresser à leur simplification. / Design of steel profiles is generally ruled by the occurrence of local and global instabilities which havebeen of major interest for many years now to reduce costs within steel applications. Closer estimate of actual ultimate strengths shall allow for some savings in practice since some structures typically designed through conservative rules provided by standards such as the Eurocode shall be lightened. The designguide lines currently suggested in codes to predict local and global strengths of I and H-shapes are broadly known to exhibit some conservatism and researchers have been directing their efforts towards an optimisation of such design. Accordingly, the O.I.C. (Overall Interaction Concept) which was first developed for tubular sections,provides a general approach for steel design with a common and straightforward formulation for all load cases and cross-section’s geometries. O.I.C. design equations are derived based on strengths mostly achieved by means of full non-linear analyses since F.E. simulations can provide accurate predictions of actual ultimate strengths and continuously account for the Resistance – Instability interaction. Through the present thesis, design formulae for I and H-shapes were developed as part of the development of the O.I.C. Subsequently to an extensive numerical study through a F.E. model whose reliability was first established by means of comparisons with tests data, reasonable local geometrical imperfections as well as appropriate residual stresses patterns were chosen so that reliable ultimate strengths could be reached with the F.E.models. Then, parametric studies were carried out on short members subject to simple load cases such assimple axial force, major-axis bending or minor-axis bending and combined loadings. Observations on local strengths tendencies allowed the determination of key parameters so that O.I.C. based design proposals predicting the local strengths of hot-rolled and welded I and H-sections could be established. Numerical investigations then focused on the member strength of I and H-sections prone to suffer fromLateral Torsional Buckling so that an accurate design proposal including local/global coupling effects waseventually derived. Accuracy showed great benefits from these O.I.C. based design proposals compared to Eurocode rules,especially for slender sections. The design for which coherence and accuracy was preferred to simplicity has shown drastic efficiency for simple and combined load cases. Owing to the complex strength tendencies observed for sections subject to combined loadings, no consequent simplification of theproposals could be achieved without losing the benefits in accuracy compared to the Eurocode one. This work shall be considered as a first step towards a more coherent and accurate design for steel I andH-sections since further work may be needed towards a simplification of such proposal

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

A parametric design study of light weight mirror shapes with various support conditions was performed utilizing the finite element program NASTRAN. Improvements in the mirror performance were made based on the following design criteria: (1) minimization of the optical surface wavefront variations, (2) minimization of the self-weight directly related to cost of manufacturing, and (3) optimal location of support points. A pre-processor to automatically generate a finite element model for each mirror geometry was developed in order to obtain the structural deformations systematically. Additionally, a post-processor, which prepares an input data file for FRINGE (an optical computer code) was developed for generating the optical deflections that lead to the surface wavefront variations. Procedures and modeling techniques to achieve the optimum (the lightest and stiffest mirror shape due to self-weight) were addressed. Fundamental natural frequency analyses, for contoured back mirror shapes for a variety of support conditions, were performed and followed by comparisons of the results which were obtained from NASTRAN and a closed-form approximate solution. In addition, element validity and sensitivity studies were conducted to demonstrate the behavior of the element types provided in the NASTRAN program when used for optical applications. Scaling Laws for the evaluations of the optical performances and the fundamental frequencies were established.