Construction Management & Economics

Wang, Ching-Hwang; Huang, Yu-Chun

doi: 10.1080/014461998372547pmid: N/A

A new scheduling method is presented in this paper which overcomes the inability of the line of balance (LOB) method to control the interval times between adjacent activities in a repetitive construction unit. The interval times are analysed and then expressed as functions of the number of repetitive construction units, the difference between construction times of adjacent activities and the sequence of repetitive construction units. In order to overcome the LOB problem, this paper presents a new scheduling method, the multistage linear scheduling (MLS) method, based on the concept of a multistage decision process. With the MLS method, the project's completion time is smaller or equal to that estimated with the LOB method. The sum of construction times of each activity in all units is the same as that estimated with the LOB method. However, no interval times are generated. The adjacent activities in a repetitive construction unit can progress continuously (not allowed under the LOB method). Therefore, the MLS method can be used to schedule a repetitive project which has necessary practical constraints on the interval times. This results in the retention of construction quality, safety and efficiency.

Kumaraswamy, Mohan M.; Chan, Daniel W. M.

doi: 10.1080/014461998372556pmid: N/A

Projects can be delayed for a large number of reasons. The third phase of an investigation into such factors focused on the causes of construction delays in Hong Kong. A questionnaire was based on 83 factors identified in previous phases of the investigation. Analysis of the responses reveals differences in perceptions of the relative significance of factors between clients, consultants and contractors. There was general agreement about the relative importance of delay factors such as unforeseen ground conditions. Improving productivity is a useful approach to controlling delays. Important factors affecting productivity itself are thus examined in more depth, with a view to enhancing productivity and reducing delays. The conclusions of this phase of the investigation include a ranking of factors and factor categories that are perceived by different groups of project participants to contribute to delays. For example, higher-ranking factors, such as unforeseen ground conditions, and factor categories such as project-related factors, are found to merit special management attention in countering construction delays. The high degree of disagreement as discerned between the groups of clients, consultants and contractors is indicative of their experiences, possible prejudices and lack of effective communication. It is also confirmed that productivity and other non-scope factors such as effective communications should supplement the project scope factors incorporated into the construction time prediction models that were proposed in the previous phases of this investigation.

Ranasinghe, Malik

doi: 10.1080/014461998372565pmid: N/A

A probabilistic framework is developed to analyse a risk management approach adopted by an insurance firm. The analysis shows that when the insurance firm classifies a client as ‘superior’ and ‘most acceptable’, the probability of the insurer having to pay out on those claims is negligible. Even for a policy that is classified as ‘acceptable’, the highest probability of a claim is only 12%. When the probability of a claim is over 50%, the client is considered to be ‘unacceptable’ for an insurance policy. Based on that analysis, the insights that the engineering construction industry can gain from risk management in the insurance firm with respect to project duration and cost are highlighted. It is shown that, in responding to risks and uncertainty, the engineering construction industry should not allocate contingency at a predetermined probability of success for global variables such as project cost or duration as suggested in the literature, but at the input level. It is suggested that the predetermined probability of success value to allocate contingency at the input level should be at least 70%. Then, the contingency available for project cost and duration can ensure a high probability of success in the completion of the project.

Dawood, Nashwan

doi: 10.1080/014461998372574pmid: N/A

Variations in the durations of activities are commonplace in the construction industry. This is due to the fact that the construction industry is influenced greatly by variations in weather, productivity of labour and plant, and quality of materials. Stochastic network analysis has been used by previous researchers to model variations in activities and produce more effective and reliable project duration estimates. A number of techniques have been developed in previous literature to solve the uncertain nature of networks, these are: PERT (program evaluation and review techniques), PNET (probabilistic network evaluation technique), NRB, (narrow reliability bounds methods) and MCS (Monte Carlo simulation). Although these techniques have proved to be useful in modelling variations in activities, dependence of activity duration is not considered. This can have a severe impact on realistically modelling projects. In this context, the objective of the present research is to develop a methodology that can accurately model activity dependence and realistically predict project duration using a risk management approach. A simulation model has been developed to encapsulate the methodology and run experimental work. In order to achieve this, the following tasks are tackled: identify risk factors that cause activity variations using literature reviews and conducting interviews with contractors; model risk factors and their influence on activity variations through conducting case studies and identifying any dependence between them; develop a computer based simulation model that uses a modified Monte Carlo technique to model activity duration and dependence of risk factors; and run experimental work to validate and verify the model.

Tam, C.M.; Fung, Ivan W.H.

doi: 10.1080/014461998372583pmid: N/A

This research describes a study of safety attitudes, practices and characteristics of construction firms in Hong Kong and their relationship to safety performance on construction sites. Forty-five construction companies are compared and studied. Each adopts different safety management strategies. The 45 companies were composed of 11 small, 25 medium and 9 large-scale construction firms. Construction firms' safety performance is measured by site casualty rates. Based upon the information collected from the survey, the accident rates are first derived and compared with the industrial norms. Then the following safety measures, and strategies of contractors in Hong Kong and their associated safety performance, are compared: involvement of top management in safety management; safety orientation programmes for new workers; safety awards or incentive schemes; use of post-accident investigation systems; safety training schemes; safety committees; level of subcontracting. The first part of the research studies the relation between these measures and the safety performance using a number of tables. The results show that these practices have indeed improved site safety. The second part uses a multiple regression analysis to study the combined effect of these schemes and practices on safety performance. The study concludes that the provision of safety training, the use of directly employed labour, the use of post-accident investigation as a feedback, and promoting safety practices by safety award campaigns and incentive schemes, are the most effective tool in mitigating site casualties.

Brandon, Peter S.; Ribeiro, Francisco Loforte

doi: 10.1080/014461998372592pmid: N/A

This research is concerned with the development of a knowledge-based expert system for supporting human experts in assessing applications for the house renovation grant system. The development of the system followed the task structure analysis and the client-centred approach. The task structure analysis describes the system at knowledge level in terms of tasks, problem-solving methods and knowledge types. The implementation of the system followed the client-centred approach. The resulting system implements a framework that integrates case-based reasoning, abductive assembly, decomposition and associative methods. In addition, this framework combines different types of knowledge, which are required by the problem-solving methods. The implementation was carried out together with verification and validation, making it possible to have the system more valid after each stage of the client-centred approach. The system has demonstrated that various problem-solving methods are required for performing the different tasks of the assessment of application for the house renovation grant system. Therefore the system has proved to perform as accurately as human experts do for all of the tasks.

Mcdonald, Bruce; Smithers, Mark

doi: 10.1080/014461998372600pmid: N/A

The construction industry in Australia contributes approximately 15%, by volume, of all solid waste disposed in landfills each year. Similar volumes have been recorded in other countries. The Australian government, in common with many other countries, has legislation in place to reduce landfill requirements by 50% by the year 2000. As part of this programme an Australian division of a multinational construction company has developed a company policy with the aim of managing waste generated on site and, thereby, reducing the amount deposited in landfill sites. The programme has been supported by the Victorian Recycling and Resource Recovery Council. The first implementation of this policy was at the Dandenong Police and Court Complex in Melbourne. The effects of the programme have been compared against a similar project built concurrently. The results of the trial revealed substantial savings. A total volume of 15% less waste was generated on site prior to recycling and 43% less waste went to landfill. Cost savings of 50% were made in terms of waste handling charges. The savings resulted almost entirely from site based strategies for handling waste.

Noyce, David A.; Hanna, Awad S.

doi: 10.1080/014461998372619pmid: N/A

Constructors confronted with the need to compress or accelerate a construction schedule face the potential for extreme difficulties. Unfortunately, a limited knowledge base exists for determining the techniques, methods, or concepts to be employed in mitigating these potential negative outcomes of lower labour productivity rates and higher project costs. This paper explores the impacts of planned and unplanned schedule compression on labour productivity. Additional impacts of schedule compression related to project costs and schedule duration are also evaluated. Telephone interviews and questionnaire surveys primarily were used as the means for data collection to determine which methods of schedule compression identified are most effective in each of the aforementioned areas. Members of the National Electrical Contractors Association (NECA) were used as the data source for this investigation because of their diversified experience and because of the support received from NECA management. A number of schedule compression methods are presented that have been shown to be effective.

Chinyio, Ezekiel A.; Olomolaiye, Paul O.; Kometa, Simon T.; Harris, Frank C.

doi: 10.1080/014461998372628pmid: N/A

Clients' needs are inadequately evaluated in project schemes. Without a precise establishment of clients' preferences, the essential criteria for project implementation and especially contractor evaluation cannot be appreciated fully. It is not surprising therefore that subjective decisions have prevailed in tender evaluations and clients' needs have not been satisfied completely. Objective contractor evaluation will be realized only when clients' needs and contractors' capabilities can be quantified and matched reliably. The methodology described herein rests on identifying clients' needs preferences as comprehensively as possible at project inception and progressing to identifying contractors who can satisfy them optimally; relying on ‘multidimensional scaling’ and ‘cluster analysis’ techniques. The investigations suggest that clients' project needs are not along the traditional classifications of private, public and developer clients; a reclassification of clients into five needs-based groups is proposed. A new contractor evaluation methodology matching client satisfaction to attainment of established needs in project schemes has been developed for bidding purposes.

Wing, Chau Kwong; Raftery, John; Walker, Anthony

doi: 10.1080/014461998372637pmid: N/A

This note is written in response to Seymour, D., Crook, D. and Rooke, J. (1997) Construction Management and Economics, 15 (1), 117-19. We argue against their narrow focus on the interpretative approach. Also, Seymour et al. are incorrect in implying that the ‘rationalist approach’ is necessarily quantitative. Our contention is that the choice of research approach in construction management depends on the nature of the problem. However, whatever choice of approach is adopted, it is important that the problem and associated key concepts are defined clearly and that the methods used, underlying assumptions and limitations are transparent and defensible. It is difficult to argue in favour of any single approach based purely on epistemological grounds as what constitutes knowledge is still an unsolved philosophical issue. Since construction management is a practical subject, we suggest that the choice of approach should be a pragmatic one: the approach that is likely to generate practical solutions should be adopted. Seymour et al.'s suggestion serves only to limit our choice of research tools. Furthermore, a lot of the research issues in construction management are practical problems which involve generalization of experience and formulation of hypothesis that can generate empirically testable implications. For problems of this nature, testability of hypothesis and reproducibility of results are important, and the naturalist approach (which is labelled ‘rationalist paradigm’ in Seymour et al.) of discovering causal relationship is more likely to produce general practical solutions. However, this does not deny the value of the interpretative approach, as it may be more suitable for certain types of problem. Moreover, in practice, an understanding of human behaviour ‘from within’ often provides useful insights for formulation of empirically testable hypotheses, despite the philosophical incompatibility of the interpretative and naturalist approaches.