Abstract
Project
 delay is a global problem affecting construction and other industries in many
 countries. Its impact on planning and budgeting can be serious for all
 stakeholders involved and difficult to resolve. The purpose of this study is to
 analyze the reliability of duration estimates of public building projects based
 on actual duration of similar projects carried out in the past.Turkey is used
 as a case study for this purpose and data from 643 public building projects
 completed in Turkey were collected. The data include contract durations, actual
 durations as well as the total construction areas for all projects. Reference
 Class Forecasting (RCF) method is proposed and used to investigate whether it
 would be possible to produce reliable and realistic project duration forecasts
 based on such data. RCF can realistically predict the actual final duration of
 the projects of different reference classes for various levels of acceptable
 risks. Original estimates of the contract durations in Turkey are generally
 optimistic or underestimated. Government buildings with the highest average
 construction area required lower uplift values on the estimated durations to
 produce accurate and realistic forecasts.So far the RCF method has been broadly
 applied to predict project cost rather than duration. This paper describes it
 use for forecasting duration in building projects.
Highlights
The competitive nature of the construction industry exerts pressure on contractors to keep project duration and cost as low as possible [1]
Leu and Liu (2016) have identified three prediction models based on the total cost for large, medium, and small industrial building construction projects in Taiwan using backpropagation neural network (BP-NN), a type of Artificial neural network (ANN) and the results have demonstrated a considerable applicability of the proposed methodology [29]
The risk level having the best option, on-time was determined for each test project. These acceptable risk distributions of the duration overruns of the test projects are shown in Table 7 and the results obtained are evaluated in Fig. 4 which shows that the average duration overruns based on the planned duration without applying uplifts are 10.22%, 30.43%, 81.67% and 30.20% whilst the average duration overruns after applying uplifts on the contract duration are -3.69%, -10.42%, 38.68% and 0.93% from RC-1 to RC-4 respectively
Summary
The competitive nature of the construction industry exerts pressure on contractors to keep project duration and cost as low as possible [1]. Project delay is a global problem affecting the construction industry but the overall economy of countries [3,4]. Experience from construction in other developing and transition countries has indicated serious problems as consequences of delay of projects on the economy [8]. In Gaziantep, an 18classroom school project was completed in 2005 in 420 days, in contrast to its contract duration of 179 days. This represents a 135% delay from the original plan. The differences between contract and actual durations were established by categorizing the types of the building projects as; educational, health service, government and security for use in RCF application
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