Search

Platform timber frame construction is considered an efficient building method for multistorey dwellings where timber walls and diaphragms provide the overall stability for the structure to resist lateral forces such as those generated by wind action. Although, so far, many research studies have been conducted on the racking performance of platform timber frame walls, there remain some gaps in knowledge in a number of key areas which this research has aimed to address. A quantitative assessment of the racking performance of partially anchored timber framed walls has been carried out via experimental test campaign. Timber framed walls, sheathed with oriented strand board (OSB) panels and/or British gypsum plasterboards (PB) were constructed from a combination of material types under different loading configurations and tested according to standardized procedure. The experimental study was designed to examine the influence of a range of geometrical parameters, such as (panel-to-frame) fastener size and spacing, wall length, arrangement of studs and horizontal members, and the effect of vertical loading on the racking strength and stiffness of the walls. When subjected to a vertical load, the wall's racking strength has been found to be more sensitive to variations in the fastener spacings, compared to the racking strength of similar walls without applied vertical loads. Conversely, it is racking stiffness to be more sensitive to variations in fastener spacings when no vertical load is applied to the wall. In such a case, the stiffness increase was up to three folds when the fastener spacing was reduced from 150 to 50 mm. However, such gain in stiffness did not occur in similar walls when they were subjected to a vertical loading of 25 kN, with stiffness increasing by only 24%.The comparison of experimental results, with the results from the UK design code formulae, showed that, on average, the design code underestimated the racking strength by 25% for walls under vertical loading of 25 kN and by 54% for walls without any vertical loading. The influence of test procedure on the racking performance of timber framed walls was also examined in an extensive experimental and analytical programme which investigated the compatibility and suitability of the test method in BS EN 594:2011 with the racking design method of BS 5268-6.1:1996. The research findings led to appropriate recommendations for determination of the design racking values from the test results. The effects of openings/discontinuities caused by windows and doors on racking performance of OSB walls with and without the use of trimmers, as well as spreaders were also examined. The results led to determination of a relationship between the size of the opening for a window or a door and the percentage reduction in the racking performance of the wall. Finally, this research examined the racking strength and stiffness of a recently developed shear wall referred to as "Mid-ply wall". Comparing the performance characteristics of the Mid-ply walls with the "standard walls", the Mid-ply walls performed significant ly better in both strength and stiffness terms, therefore providing a considerable potential for use in the UK and European timber frame construction.

The construction sector constitutes one of the most important sectors in the economy of any country. Contractor selection is a critical decision that is undertaken by client organisations and is central to the success of any construction project. For major construction projects, final contractor selection often follows the contractor selection stage. Contractor selection is a process which involves investigating, screening and determining whether candidate contractors have the technical and financial capability to be accepted to formally tender for construction work. The process should be conducted prior to the award of contract, characterized by many factors such as: contactor's skills, experience on similar projects, track- record in the industry, and financial stability. Several models and approaches have been developed to assist client organisations in the contractor selection decision making process. This thesis evaluates the current state of knowledge in relation to contractor selection models. The key features, strengths and limitations of each of these methods are critically evaluated. The key factors of particular interest to client organisations are assessed. This thesis reports on-going research which aims to develop improved contractor selection criteria and methods with specific application to make construction projects in the Libyan context. The aim of this thesis is to build a framework for contractor selection process in the Libyan Construction Industry (LCI) and to find out the major obstacles constraining its operations which so far have not yet been taken into account by the Libyan researchers. However, to address that, a huge investigation has taken place about the current statues for contractor selection in Libya, as well as, in developed and well developed countries. To achieve that, both, theoretical and empirical research was carried out between 2010 and 2013 in Libya. The theoretical study concentrated on the sector of construction industry (Cl) and its key issues, whereas the empirical study focused and explored on the Libyan Construction Industry (LCI) as the context for the study. Two case studies were utilized in this research. The case studies were used to provide more information about the current situation of the LCI and to identify the contractor selection procedures of construction projects in. Also, it assist the researcher to identify key research questions that can later be used in a questionnaire survey. This research was implemented through the administration of a questionnaire survey based on research questions that are required for the building of a framework for contractor selection procedure and the identification of the challenges and obstacles that are facing the clients in the selection process. The development of the framework includes, but is not limited to, contractor selection criteria, decision makers, consultant, clients and sub-contractor. Therefore, the data collection is based on responses from the public and private sector (clients, consultants, contractors and others that are involved in and are knowledgeable about the contractor selection process in the Libyan construction projects). Mean and analysis of variance (independent T-test) were used to manipulate the data from the questionnaire within the SPSS v.20 software environment. The resulting framework was subjected to a validation procedure which involved a structured Delphi technique process based on a focus group consisting of experts who were selected to help with validation of the framework and establishing the extent to which the framework is practical, clear, applicable and comprehensive. This research uses an integrated approach that combines AHP (Analytic Hierarchy Process) method and TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) method to evaluate and investigate the current existing practice of contractor selection in Libya. Also, the Delphi technique was used to establish a road map for contractor selection process. Twelve participants were selected to help with validation of the framework. Overall, this research found that the LCI was suffering from a total absence of contractor selection frameworks. This directly impacts on client satisfaction as well as government planning in the reconstruction of the country after the civil war in particular. To close this gap, this research was embarked upon to identify and explore the various contractor selection methods and frameworks that are utilized to support the guidance of contractor selection process toward success. As a consequence of this study, the Contractor Selection Process (CSP) is now very comprehensive and can now be a reference for any problem. Furthermore, this research will help decision makers and others involved to be more aware of and have a better understanding of the selection procedure in the LCI. This new understanding will help decision makers to make more efficacious decisions and to adopt good short and long term policies for contractor selection planning which can then be put into procedure. Even though this framework is built for the LCI, the research can be utilised in other countries that have a similar construction industry environment.

Abstract: In recent years, the performance of the construction industry warns of its increased need for better resource efficiency, improved productivity, less waste and increased value through sustainable construction practices. Existing literature reveals that construction-related spending accounts for 13% of the world’s Gross Domestic Product, but its annual productivity growth has increased by 1% over the past 20 years. The core concept of sustainable construction is to maximize value and minimize harm by achieving a balance between social, economic, technical, and environmental aspects, commonly known as the pillars of sustainability. The selection of structural material plays a vital role in building construction since it is the backbone of any structure. Also, the process of producing structural consumes massive amounts of nonrenewable natural resources. Reinforced concrete, structural steel, reinforced masonry, and timber represent the most commonly used structural materials. The decision of selecting the structural material for any construction project is traditionally made based mainly on technical and economic considerations with little or no attention paid to social and environmental aspects. Furthermore, the majority of the available literature on the subject considered a single sustainability aspect, not considering all four sustainability pillars together. When all pillars of sustainability are considered, the process of decision-making becomes more difficult and complicated due to the involvement of a large number of factors influencing the decision. Industry experts have also noted an unfulfilled need for a multi-criteria decision-making (MCDM) technique that can integrate all stakeholders’ (project owner, designer and constructor) opinions into the selection process. Hence, this research developed a Decision Support System (DSS) involving MCDM techniques to aid in selecting the most sustainable structural material considering the four pillars of sustainability. A hybrid MCDM method combining AHP, decision matrix, TOPSIS and VIKOR in a Fuzzy environment is used to develop the DSS. Multiple sub-criteria were identified and evaluated through a literature review and expert opinions. A hypothetical 8-story building was considered for a case study to validate the developed DSS. Notable differences were found in the final ranking of the alternatives of each team due to the significant differences in weights assigned to each sub-criterion based on experts’ preferences. The developed DSS is designed to be generic in nature, can be used by any group of industry practitioners and is expected to enhance objectivity and consistency of the decision-making process as a step towards achieving sustainable construction.

Cost overruns, schedule delays, and contractual claims are commonplace in construction projects. These issues often are the result of poor planning by the construction management team, or the improper alignment of field production management and control with the project schedule. To ensure that the schedule is properly executed in the construction process, the production management and control system must be manageable, intuitive and visually evident for all levels of management and trade supervisors. This need is especially critical for building construction, where client requirements often result in changing project demands, particularly for interior equipment and finishes. The various finish trades for a large building with many segments or floors may produce a large number of trade-location activities for the construction team to manage during construction. Thus, a good production plan is required to implement the schedule. Lott Brothers Construction Company has created a novel production management and control technique entitled, the Clear Flow Matrix (CFMx). The technique consists of a matrix integration of the trade activities and locations wherein time and workflow rhythm are represented through the progress of a unique Balanced Workfront, which balances client completion demand and trade contractor operations efficiency as trade work progresses through the building areas. The visual nature of CFMx and the Balanced Workfront provides the project participants with a production framework for managing production and documentation of trade-exchanges so critical for quality completion of the work in accordance with the contract schedule. The thesis discusses the theoretical underpinning of the CFMx and how the embedded concepts are used to produce this visual matrix framework for production management and control to deliver the project in full alignment with the master schedule. The thesis provides several example applications of the Clear Flow Matrix to various types of building construction projects. Data collected from the applications through jobsite observations of the work (Work Sampling Analysis) and questionnaire interviews of trade contractor foremen and project managers provide insights into the effectiveness of the Clear Flow Matrix in comparison with other production management techniques currently used in the construction industry.

Life cycle assessment (LCA) is considered as the most efficient methodology and has been widely accepted by previous researches in the area of energy analysis. Quantifying embodied energy (EE) and carbon (EC) is time-consuming and needs a lot of quantitative effort to ensure reliability of the data to be obtained and analysed. Hybrid-based LCA (hybrid LCA) is utilised - this incorporates input-output based LCA (I-O LCA) that calculate flow of building materials, products, and construction processes in the whole sector of economy and process-based LCA (process LCA) is used to quantify physical quantities of materials, products, or processes. Although hybrid LCA has been identified as improving completeness of EE and EC inventory data, this benefit was not empirically verified extensively, particularly in the Malaysian building construction industry. Therefore, the principal aim of this research was to develop LCEA methodology in order to systematically quantify EE and EC of building construction in Malaysia.

The construction industry has, for sometime, suffered from stagnant productivity, high accident rate, project delays, and poor quality. Research studies have shown that the major cause of these performance problems is the lack of effective communication. This research was launched to investigate the usefulness of a comprehensive information logistics model on construction process performance. In order to test and validate key components of the model, a prototype network system named Visual-based Integrated Wireless Site (V-IWS) was developed and tested on a mid-size building construction project. The system was designed to allow every project participant access to real-time visual images of the jobsite and share information interactively with each other as well as with a central database through the Internet. It was developed and evaluated for 7 months in 2003. During the same time, the communication channels adopted by the general contractor, R.N. Rouse, and on-site meetings were observed and analyzed. This analysis indicated that most of the information shared among participants of this project could be handled electronically by the V-IWS. It was demonstrated that the V-IWS: a) reduces production waste and non value-added activities such as material delivery time, b) eliminate the need for unnecessary site visits and meetings, c) adds significant value to project participants by automatically creating visual as-built and picture archives, d) provides operational how-to training for crew, and e) increases site safety and security through automated monitoring. The system is scaleable and more network devices can be added as the building grows. While this study proved technical feasibility of the V-IWS, it became evident that trust, collaboration and information sharing among participants were critical success factors. Due to the industry's traditional low-bid competition and aversion to change, it is crucial to understand how costs and benefits be distributed. Value sharing as well as technology adoption process need to be studied in order to ensure successful implementation of the system.

The premise of this thesis is that architecture indeed superseded the act of ordinary building. Beyond the idea of shelter or utilitarian accommodation, architecture is the art of embedding or encoding substantial humanist values which result in the form of the man-made architectural object.