Chun-Pong Sing

Determining the probability distribution of rework costs in construction and engineering projects

Rework arises due to design errors, changes and omissions during design and has been found to contribute to 52% of a projects cost overrun. The statistical characteristics of rework costs experienced from contract award in 276 construction and engineering projects were analysed. The skewness and kurtosis values of rework costs are computed to determine if the empirical distribution of the data follows a normal distribution. The empirical distributions for rework costs are found to be non-Gaussian. Theoretical probability distributions are fitted to the rework data. The Kolmogorov–Smirnov and Anderson–Darling non-parametric tests are used to determine the ‘Goodness of Fit’ of the selected probability distributions. A Generalised Pareto probability function is found to provide the best overall distribution fit for rework costs. The Generalised Pareto distribution is used to calculate the probability of rework being experienced for the selected sample. Projects with a contract value A

Probability Distribution Fitting of Schedule Overruns in Construction Projects

101 million. Larger projects may be better managed and longer completion times provide an opportunity to make adjustments to facilitate cost control. The anticipation that rework will occur using the probabilities that are derived can enable a quantitative risk assessment to be undertaken prior to the commencement of construction.

Multiplier Model for Forecasting Manpower Demand

The probability of schedule overruns for construction and engineering projects can be ascertained using a ‘best fit’ probability distribution from an empirical distribution. The statistical characteristics of schedule overruns occurring in 276 Australian construction and engineering projects were analysed. Skewness and kurtosis values revealed that schedule overruns are non-Gaussian. Theoretical probability distributions were then fitted to the schedule overrun data; including the Kolmogorov–Smirnov, Anderson–Darling and Chi-Squared non-parametric tests to determine the ‘Goodness of Fit’. A Four Parameter Burr probability function best described the behaviour of schedule overruns, provided the best overall distribution fit and was used to calculate the probability of a schedule overrun being experienced. The statistical characteristics of contract size and schedule overruns were also analysed, and the Wakeby (AU

Stock-Flow Model for Forecasting Labor Supply

101 m) models provided the best distribution fits and were used to calculate schedule overrun probabilities by contract size.

Assessing the impact of RFIs in electrical and instrumentation engineering contracts

To better manage and forecast the demand for labor in the construction industry, a mathematical model is developed using a distributed lag model and labor multiplier approach. The model is tested using economic statistics and manpower data derived from Hong Kong construction projects. The model can be used by public and private sectors to forecast future labor demand so that an optimal workforce can be attained.

Forecasting the Demand and Supply of Technicians in the Construction Industry

AbstractForecasting the supply of labor in the construction industry is pivotal to long-term economic growth. A labor supply model using a stock-flow approach was developed in this research for use in the construction industry. The model was tested using Hong Kong census statistics and data derived from interviews with 3,000 randomly selected construction workers. The findings were determined using a stock-flow model, which enabled the determination of future aging distribution trends and workforce supply for specific trade types. The developed stock-flow model can be effectively used in countries in which registration schemes for construction workers are in use.

A systems information model for managing electrical, control, and instrumentation assets

Using a case study, errors, omissions and information redundancy contained in the electrical and instrumentation (E&I) ‘As-built’ drawings for a Stacker Conveyor were examined. A total of 449 errors and omissions were identified within 42 documents. In addition, 231 cables and components appeared once among the 42 documents; 86 cables and components appeared twice and 12 cables and components appeared thrice. As a result of the errors, omissions and redundancy, requests for information (RFIs) were required. Retrospective analysis indicates that the indirect cost of raising the RFIs to the contractor was estimated to be approximately 9% of the cost of the E&I contract. To address the problems of errors, omissions and redundancy, it is suggested that there is a need to adopt an object orientated system information model (SIM) for E&I engineering design and documentation. It is demonstrated in the case study that the use of a SIM could bring significant improvements in productivity and reduce the cost of engineering design.

Toward productivity improvement in electrical engineering documentation

AbstractWorkforce forecasting is a strategic managerial practice that construction organizations should implement to ensure a balanced workplace. The workforce forecasting systems that have been developed are either qualitative or quantitative in nature. This paper develops a sustainable workforce model that utilizes both quantitative and qualitative data to improve the accuracy of workforce demand and supply forecasts. Using empirically derived data for off-site construction technicians in Hong Kong, the developed workforce forecasting system is used as a strategic managerial tool to predict and monitor workforce conditions.

Discussion of “State of Practice of Building Information Modeling in the Electrical Construction Industry” by Awad S. Hanna, Michael Yeutter, and Diane G. Aoun

Purpose – The purpose of this paper is to present a systems information model (SIM) that is akin to a building information model (BIM) and can be used by asset managers and staff to make more informed and quicker decisions about maintenance. Design/methodology/approach – The problems associated with managing assets are examined alongside recent international efforts to standardize methods of data collection for meeting the objectives of owners. A case study in the domain of electrical, control and instrumentation (ECI) documentation is examined in detail, with particular reference to the amelioration of errors and omissions in “as built” drawings in order to provide the underlying foundation to support effective asset management (AM). Findings – The findings show that object oriented data models such as SIM provide a robust structure for effective and efficient AM and associated leverage of benefits throughout the entire facility lifecycle of a project. In particular object oriented data enables appropria...

Personality and Occupational Accidents: Bar Benders in Guangdong Province, Shenzhen, China

Purpose - – The purpose of this paper is to determine the unproductive time and additional cost to re-engineer a safety control system for a Floating Production Storage Offloading vessel that was originally engineered and documented in computer-aided design (CAD). Design/methodology/approach - – The “As-Built” drawings contained numerous errors and omissions, which resulted in a “requests for information” being raised and productivity rates reduced – these costs and productivity losses are quantified. The use of CAD to originally engineer and document the safety control system was found to be inefficient as a 1: Findings - – The use of a SIM to re-engineer and document the new safety control system resulted in significant productivity benefits being achieved. Consequently, it is proffered that a paradigm shift from a 1: Originality/value - – The paper concludes by suggesting that future research is required to examine how processes and procedures can be re-designed to accommodate the use of a SIM.