In recent years, there has been much discussion about the merits of the top-down design methodology. Studies show that a more successful design paradigm and, indeed, the one that human designers of circuits tend to use is one that combines bottom-up and top-down design. In this thesis we describe the development of a system that is able to combine the process of top-down refinement of a high-level design specification with the bottom-up process of speed assessment. The system is able to do so by virtue of the fact that its refinement algorithms always partition the circuit in a well-defined manner. We can therefore pre-characterize the speed of all such partition possibilities and use this information to guide the choice of partition. We then focus upon the problem of the accurate and efficient estimation of speed in VLSI circuits. Speed estimation has traditionally been performed by simulators and static timing analysers. Circuit simulation is both expensive and may exercise impossible paths, due to the fact that impossible input data was fed to the circuit or signals were diverted in the wrong direction through the circuit components. The path which a simulator tells us is the critical (slowest) path, may never be exercised during the circuit's normal use. Analysing the propagation of impossible data may therefore expose false critical paths and lead to pessimistic speed estimates. Static timing analysis is less expensive but assumes that every component in the circuit contributes its slowest possible delay. Pessimistic speed estimates result and, since the <I>slowest</I> rather than the <I>actual</I> delay contributions of some of the components are used, false critical paths may be discovered.

Many factors such as unforeseeable events, managerial or financial problems of Contractor, insufficient technical capacity of Engineer&#039 / s site team and so on may lead to delays in construction projects. Proper analysis of compensability and quantum of a delay event is very important. Any delay analysis application can be considered as a result of the combination of contract documents, scheduler, record keeping mechanism at site, communication among project participants, delay analyst and delay analysis methodology. The main purpose of this study is to analyze the shortcomings frequently encountered in implementation of delay analysis applications and propose an integrated solution which synthesizes the solution methods for each. For this purpose seventeen (17) shortcomings were identified and solution methods were suggested for each. Moreover, these shortcomings were attributed to the previously identified elements of delay analysis applications such as contract documents, scheduler etc. Furthermore, an integrated approach is developed which synthesizes the suggested solution methods at different stages of delay analysis applications in order to obtain accurate and reliable results. In order to test the validity of the proposed integrated approach on a real project, a resource and cost loaded construction schedule with approximately four thousand (4000) activities is created by using Primavera software which is currently being used to monitor &quot / Construction of One Reception Center and One Removal Center Project in Erzurum&quot / . In the case study, the necessary events are created in order to be able to compare the results of the proposed integrated approach and the likely result of erroneous delay analysis applications. It was apparently figured out that the proposed integrated approach has yielded accurate and reliable results and a comparison table was prepared showing the difference between the results of the proposed integrated approach and the likely result of an erroneous application.

Rework has been a primary cause of cost and schedule overruns in the construction of heavy industrial projects such as those related to oil and gas. It has been reported that the direct cost of rework is about 5% of total construction costs. Several research studies have analyzed the causes and effects of rework in construction projects, but almost no research exists to support decisions with respect of an effective strategy for mitigating the effects of rework on the cost and schedule of the project. This research introduces a new schedule analysis mechanism that considers the impact of rework on project delays and then optimises corrective actions for mitigating those delays. The proposed mechanism considers rework from three perspectives: (1) a schedule representation of the magnitude of rework as a negative percentage completed with respect to the activities affected, as documented on a specific schedule date, (2) a day-by-day delay analysis for quantifying and apportioning project delays among the parties responsible, and (3) an optimization mechanism for determining the best mitigation strategy for recovering rework at a minimum additional cost. The proposed mechanism can represent and mitigate rework caused by both the Owner and the Contractor. The proposed schedule analysis mechanism has been applied to a case study in order to demonstrate its usefulness and applicability. The resulting mechanism offers a quantitative approach to the consideration of rework in delay analysis and the optimization of corrective action, which are important aspects of effective project control.

Rework has been a primary cause of cost and schedule overruns in the construction of heavy industrial projects such as those related to oil and gas. It has been reported that the direct cost of rework is about 5% of total construction costs. Several research studies have analyzed the causes and effects of rework in construction projects, but almost no research exists to support decisions with respect of an effective strategy for mitigating the effects of rework on the cost and schedule of the project. This research introduces a new schedule analysis mechanism that considers the impact of rework on project delays and then optimises corrective actions for mitigating those delays. The proposed mechanism considers rework from three perspectives: (1) a schedule representation of the magnitude of rework as a negative percentage completed with respect to the activities affected, as documented on a specific schedule date, (2) a day-by-day delay analysis for quantifying and apportioning project delays among the parties responsible, and (3) an optimization mechanism for determining the best mitigation strategy for recovering rework at a minimum additional cost. The proposed mechanism can represent and mitigate rework caused by both the Owner and the Contractor. The proposed schedule analysis mechanism has been applied to a case study in order to demonstrate its usefulness and applicability. The resulting mechanism offers a quantitative approach to the consideration of rework in delay analysis and the optimization of corrective action, which are important aspects of effective project control.

Delay is a common problem of construction sector. Recent improvements in the sector increased the competition and this led the construction projects to be more complex than before and difficult to be completed in time. This situation not only increased the delay problems, but also made the analysis of delays difficult and that caused further problems as disputes between parties to the contract. Sound knowledge in delay analysis subject is needed to enhance the solution of the delay problem in construction projects. So, this study aims to share knowledge in delay analysis issue by construction of a delay analysis ontology that provides direct and comprehensive knowledge. The constructed ontology may ease the information sharing process and provide a base for the usage of information in computers for different purposes especially in risk and claim management processes. It may enable companies to create their own knowledge bases and decision support systems that may achieve improvement in the knowledge and its usability. To meet this objective, detailed literature review on delay subject is carried out and an ontology on delay analysis issue is created. The created ontology is validated through its comparison with three different case studies.

It is a known fact that construction projects do not often complete on time due to several reasons related with the unexpected changes in the project conditions, external factors or performance of project participants. Since construction projects are unique and limited information is available at the beginning of the projects, prediction of delays is a difficult task. However, if the delays can be assessed at the early stages, their impacts might be minimized, some of the delays can even be eliminated. This study introduces a delay assessment methodology which can be used to predict delays both at the activity level and project level. Fuzzy logic and fuzzy network analysis form the basis of this methodology. A software has been developed using the proposed delay assessment methodology and a delay taxonomy developed by Bilgin (2011). Project management teams can use the developed tool to predict delays and also evaluate impacts of delays on a project`s schedule.

Delay is one of the most common problems in the steel construction industry. At the time of bidding steel contractors plan tasks and assign resources according to the site visits, the information given in the contract and specifications related with the project. However, as the project progresses some conditions of the work may change. These changes may affect originally planned means and methods. Finally, the affected activities cause the project total cost and duration to increase. In steel construction projects, if not managed properly in accordance with the contract, changes are likely to result in claims between the project participants. In this study, a delay analysis methodology which is based on time impact analysis is proposed. The aim of this methodology is to quantify impacts of work changes on the schedule and cost of steel construction projects and identify the responsible parties for these changes. A risk breakdown structure is presented to help decision-makers to identify probable sources of risk factors that usually result in time and cost overruns. The potential sources of change are categorized into 3 groups: contractor-related, owner-related and external factors. By using this structure, contractors may classify changes and assign the impacts of changes to the appropriate parties. The proposed methodology comprises of 3 steps: identification and quantification of delays, allocation of these delays to responsible parties and using TIA to calculate overall impact of changes on time and cost. The major benefits of this methodology are / a) its ability to handle and quantify changes in a step by step procedure, b) it provides a graphical representation of actual progress, and c) it helps decision-makers to give reliable decisions by monitoring the impact of changes during the project&amp / #8217 / s life cycle. Construction professionals may use it to apportion impact of changes in a systematic and reliable way. Moreover, reports generated by using this methodology can provide evidence during the claim management process. An application of this methodology on a steel project demonstrates the superiority of the process in explaining the dynamic nature of changes and in apportioning the impacts between different parties in a systematic way.

The management of terminal yards requires quite complex day-to-day operations when hundreds of trains could be entered and/or exited marshalling yards every day. More specifically, multi-dimensional decisions are necessary to be taken in daily basis for management of operations. Manual solutions might cause inefficiency in the yard’s operation and consequently to the network. Nowadays, many freight trains in Sweden fail to follow their scheduled plan. In particular, a small portion of trains are following the scheduled arrival and departure time while the majority of trains run ahead of schedule.This master thesis aims to conduct evaluation of internal procedures within a marshalling yard in terms of time, examine the magnitude of delays from the scheduled departure time, and to identify the key reasons causing the delay during departure and their main implications. Furthermore, the master this aims to investigate ways of optimizing operations to increase system punctuality. The Malmo’s marshalling yard was used as a case study.The methods are used for this master thesis are a qualitative as well as a quantitative assessment. A literature review has been conducted using journal papers, conference papers and technical reports from other relevant projects as well as on-site visit and interviews. In order to manipulate the data for the research, the software Planimate was used and a simulation model is built based on operations in Malmo’s marshalling yard. Three scenarios are performed. The first one is considered without any usage of automation. The second one, automation is applied in the case of the arrival yard and the third one, automation is applied in the arrival and the departure yard.The findings from the qualitative research show that there are several factors cause delays, either network failures such as the late arrival of trains in the yard or internal factors as the reduced railway capacity. Also, as the simulation model has been demonstrated, any application of automated processes within the marshalling yard’s operations will be beneficial because will speed up the internal processes. For instance, the third scenario turns out the best scenario among the others because time is reduced almost to half time compared to the first scenario.

Many construction contracts require contractors to use the Critical Path Method (CPM) scheduling technique as a management tool. In such projects, many participating parties commonly attempt to appropriate float time shown in the CPM schedules in order to advance their own interests. Under current scheduling practices, float time is considered "free" and therefore does not belong to any one party in the construction process. As a result of this conception, when a project delay occurs, float ownership and its utilization can become a major source of dispute. This ambiguous interpretation of total float ownership can be clarified by improving contract language with regard to scheduling specifications in the area of total float management. The purpose of this research dissertation is to introduce a comprehensive practice of float pre-allocation and management terms, for the application of scheduling specifications in the CPM-based construction contract. The proposed concept for managing "total float" involves pre-allocating a set amount of total float on the same non-critical path of activities to the two contractual parties - owner and contractor. For the sake of equity, this research adopts an equal (50-50) allocation concept, which allocates to each party one-half of the total float. This new concept for pre-allocating and managing "total float" involves recommending contract clauses to direct its use and to explain the manner in which responsibility for any resulting delay will be assigned. Six examples of factual situations are provided to illustrate the assigning of responsibility for delays. The features of proposed concept are then compared to those of other theories presently being used. Such a comparison provides insight as to which features have not worked well in the past - and how those of the proposed concept can change this. A Delphi survey is used to validate the total float pre-allocation concept of equal allocation. The survey shows that the concept could significantly increase involved parties' awareness of total float consumption and thus help resolve any potential disputes regarding it. This dissertation considers suggestions obtained from the survey and recommends them for future study. The simple step of inserting new scheduling language into the construction contract documents assures that all participants will become more aware of the fact that when they consume floats, they introduce the potential of increasing project completion times. / Ph. D.

Delay and disruption (DD) to contractors’ progress, often resulting in time and cost overruns, are a major source of claims and disputes in the construction industry. At the heart of the matter in dispute is often the question of the extent of each contracting party’s responsibility for the delayed project completion and extra cost incurred. Various methodologies have been developed over the years as aids to answering this question. Whilst much has been written about DD, there is limited information on the extent of use of these methodologies in practice. The research reported in this thesis was initiated to investigate these issues in the UK, towards developing a framework for improving DD analysis. The methodology adopted in undertaking this research was the mixed method approach involving first, a detailed review of the relevant literature, followed by an industry-wide survey on the use of these methodologies and associated problems. Following this, interviews were conducted to investigate the identified problems in more depth. The data collected were analysed, with the aid of SPSS and Excel, using a variety of statistical methods including descriptive statistics analysis, relative index analysis, Kendall’s concordance and factor analysis. The key finding was that DD analysis methodologies reported in the literature as having major weaknesses are the most widely used in practice mainly due to deficiencies in programming and record keeping practice. To facilitate the use of more reliable methodologies, which ensure more successful claims resolution with fewer chances of disputes, a framework has been developed comprising of: (i) best practice recommendations for promoting better record-keeping and programming practice and; (ii) a model for assisting analysts in their selection of appropriate delay analysis methodology for any claims situation. This model was validated by means of experts’ review via a survey and the findings obtained suggest that the model is valuable and suitable for use in practice. Finally, areas for further research were identified.