İnşaat Proje Süresi Tahmininde Referans Sınıf Tahmin Yöntemi

Projelerde yaşanan süresel gecikmeler, pek çok ülkede inşaat sektörünü ve diğer sektörleri etkileyen küresel bir sorundur. Süresel gecikmelerin planlama ve bütçeleme üzerindeki etkisi, ilgili tüm paydaşlar için ciddi ve çözülmesi zor olmaktadır. Bu çalışmanın amacı, geçmişte tamamlanan benzer projelerin gerçekleşen sürelerine dayalı olarak, kamu binası projelerinin süresel tahminlerinin güvenilirliğini analiz etmektir. Bu amaçla Türkiye'de tamamlanan 643 kamu inşaat projesinin verileri temin edilmiştir. Proje verileri; sözleşme süreleri, fiili gerçekleşme süreleri ve toplam inşaat alanlarından oluşmaktadır. Bu verilere dayalı olarak güvenilir ve gerçekçi proje süresi tahminleri üretmenin mümkün olup olmayacağını irdelemek için Referans Sınıf Tahmin (RST) yöntemi önerilmiş ve kullanılmıştır. RST, kabul edilebilir risklerin farklı seviyeleri için değişik referans sınıflarının fiili proje sürelerini gerçekçi bir şekilde tahmin edebilen bir yaklaşımdır. Sonuç olarak; Türkiye'de gerçekleştirilen kamu inşaat projelerinin sözleşme süresi öngörülerinin genellikle iyimser veya olması gerekenden düşük olduğu belirlenmiştir. Doğru ve gerçekçi tahminler üretmek adına, en yüksek ortalama inşaat alanına sahip olan devlet binalarının, öngörülen proje süreleri üzerinden nispeten daha düşük yükseltme değerlerine sahip oldukları tespit edilmiştir. RST yöntemi, önceki çalışmalarda proje süresinden ziyade yapım maliyetini tahmin etmek için yaygın bir şekilde kullanılmıştır. Bu çalışmada ise RST yönteminin bina projelerinin süresel tahmininde kullanılabilirliği esas alınmıştır.

Anahtar Kelimeler:

Yapı, Proje yönetimi, Tahminleme, İş programı

Reference Class Forecasting Method in Predicting Construction Project Duration

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.

Keywords:

Construction, Project management, Estimating, Scheduling,

PDF

___

[1] Laptalı, E., Bouchlaghem, N. M., Wild, S. 1996. An Integrated Computer Model of Time and Cost Optimisation. 12th Annual ARCOM Conference, 11-13 September, Sheffield Hallam University, UK, 133-139.
[2] Owolabi, J.D., Amusan, L.M., Oloke, C.O., Olusanya, O., Tunji- Olayeni, P., Owolabi, D., Peter, J., Omuh, I. 2014. Causes and Effect of Delay on Project Construction Delivery Time. International Journal of Education and Research, 2(4), 197-208.
[3] Faridi, A.S., El-Sayegh, S.M. 2006. Significant Factors Causing Delay in the UAE Construction Industry. Construction Management and Economics, 24(11), 1167-1176.
[4] Sambasivan, M., Soon, Y.W. 2007. Causes and Effects of Delays in Malaysian Construction Industry. International Journal of Project Management, 25(5), 517-526.
[5] Fugar, F.D.K., Agyakwah-Baah, A.B. 2010. Delays in Building Construction Projects in Ghana. Australasian Journal of Construction Economics and Building, 10(1/2), 103-116.
[6] Couto, J.P., Teixeira, J.C. 2007. The Evaluation of the Delays in the Portuguese Construction. CIB World Building Congress `Construction for Development`, 14-18 May, Cape Town, South Africa, 292-301.
[7] Ng, T., Mak, M.M.Y., Skitmore, M., Lam, K.C., Varnam, M. 2001. The Predictive Ability of Bromilow’s Time–Cost Model. Construction Management and Economics, 19(2), 165-173.
[8] Zujo, V., Diana, C.P., Vejzovic, A.B. 2010. Contracted Price Overrun as Contracted Construction Time Overrun Function. Technical Gazette, 17(1), 23-29.
[9] Construction Sector Report. 2016. The Turkish Employers Association of Construction Industries (INTES). http://intes.org.tr/ti/779/0/Insaat-Sektor-Raporu-(Temmuz---2016).php (Access date: 20.09.2017).
[10] Moret, Y., Einstein, H.H. 2016. Construction Cost and Duration Uncertainty Model: Application to High-Speed Rail Line Project. Journal of Construction Engineering and Management, ASCE, 142(10), 05016010.
[11] Flyvbjerg, B., Hon, C.K., Fok, W.H. 2016. Reference Class Forecasting for Hong Kong’s Major Roadworks Projects. Proceedings of the Institution of Civil Engineers - Civil Engineering, 169(6), 17-24.
[12] Batselier, J., Vanhoucke, M. 2016. Practical Application and Empirical Evaluation of Reference Class Forecasting for Project Management. Project Management Journal, 47(5), 36-51.
[13] Arditi, D., Akan, G.T., Gurdamar, S. 1985. Reasons for Delays in Public Projects in Turkey. Construction Management and Economics, 3(2), 171-181.
[14] Erdis, E. 2013. The Effect of Current Public Procurement Law on Duration and Cost of Construction Projects in Turkey. Journal of Civil Engineering and Management, 19(1), 121–135.
[15] Sweis, G., Sweis, R., Abu Hammad, A., Shboul, A. 2008. Delays in Construction Projects: The Case of Jordan. International Journal of Project Management, 26(6), 665-674.
[16] Abd El-Razek, M.E., Bassioni, H.A, Mobarak, A.M. 2008. Causes of Delays in Building Construction Projects in Egypt. Journal of Construction Engineering and Management, ASCE, 134(11), 31-841.
[17] Vandevoorde, S., Vanhoucke, M. 2006. A Comparison of Different Project Duration Forecasting Methods Using Earned Value Metrics. International Journal of Project Management, 24(4), 289-302.
[18] Bromilow, F.J. 1969. Contract Time Performance: Expectations and the Reality. Building Forum, 1(3), 70-80.
[19] Bromilow, F.J. 1974. Measurement and Scheduling of Construction Time and Cost Performance in the Building Industry. The Chartered Builder, 10(9), 79-82.
[20] Odabasi, E. 2009. Models for estimating construction duration: An application for selected buildings on the METU campus. MSc thesis, Middle East Technical University, Ankara, Turkey.
[21] Dursun, O., Stoy, C. 2011. Time-Cost Relationship of Building Projects: Statistical Adequacy of Categorization with Respect to Project Location. Construction Management and Economics, 29(1), 97-106.
[22] Ogunsemi, D.R., Jagboro, G.O. 2006. Time-Cost Model for Building Projects in Nigeria. Construction Management and Economics, 24(3), 253–258.
[23] Walker, D.H.T. 1994. An investigation into the factors that determine building construction time performance. PhD dissertation, Royal Melbourne Institute of Technology, Melbourne, Australia.
[24] Love, P.E.D., Tse, R.Y.C., Edwards, D.J. 2005. Time-Cost Relationships in Australian Building Construction Projects. Journal of Construction Engineering and Management, ASCE, 131(2), 187-194.
[25] Stoy, C., Pollalis, S., Schalcher, H. 2007. Early Estimation of Building Construction Speed in Germany. International Journal of Project Management, 25(3), 283–289.
[26] Dursun, O., Stoy, C. 2012. Determinants of Construction Duration for Building Projects in Germany. Engineering, Construction and Architectural Management, 19(4), 444-468.
[27] Guerrero, M.A., Villacampa, Y., Montoyo, A. 2014. Modeling Construction Time in Spanish Building Projects. International Journal of Project Management, 32(5), 861–873.
[28] Gab-Allah, A.A., Ibrahim, A.H., Hagras, O.A. 2015. Predicting the Construction Duration of Building Projects Using Artificial Neural Networks. International Journal of Applied Management Science, 7(2), 123-141.
[29] Leu, S.S., Liu, C.M. 2016. Using Principal Component Analysis with a Back-Propagation Neural Network to Predict Industrial Building Construction Duration. Journal of Marine Science and Technology-Taiwan, 24(2), 82-90.
[30] Jarkas, A.M. 2016. Predicting Contract Duration for Building Construction: Is Bromilow’s Time-Cost Model a Panacea? Journal of Management in Engineering, ASCE, 32(1), 05015004.
[31] Vahdani, B., Mousavib, S.M., Mousakhanic, M., Hashemid, H. 2016. Time Prediction Using a Neuro-Fuzzy Model for Projects in the Construction Industry. Journal of Optimization in Industrial Engineering, 9(19), 97-103.
[32] Jin, R.Z., Han, S., Hyun, C.T., Cha, Y. 2016. Application of Case-Based Reasoning for Estimating Preliminary Duration of Building Projects. Journal of Construction Engineering and Management, ASCE, 142(2), 04015082.
[33] Flyvbjerg, B. 2004. Procedures for Dealing with Optimism Bias in Transport Planning, Guidance Document in association with COWI. Report nr. 58924, The British Department for Transport, UK.
[34] Flyvbjerg, B., Holm, M.K.S., Buhl, S.L. 2005. How (In)accurate are Demand Forecasts in Public Works Projects? The Case of Transportation. Journal of the American Planning Association, 71(2), 131-146.
[35] Flyvbjerg, B. 2007. Eliminating Bias Through Reference Class Forecasting and Good Governance. Report nr. 17, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
[36] Salling, K.B., Leleur, S. 2012. Modelling of Transport Project Uncertainties: Feasibility Risk Assessment and Scenario Analysis. European Journal of Transport and Infrastructure Research (EJTIR), 12(1), 21-38.
[37] Eythorsdottir, E.O. 2012. Reference class forecasting method used in Icelandic transportation infrastructure projects. MSc thesis, Reykjavík University, Reykjavík, Iceland.
[38] Kahneman, D. 2002. Maps of Bounded Rationality: A perspective on intuitive judgment and choice. Prize Lecture, The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, Princeton University, USA.
[39] Kahneman, D. 1994. New Challenges to the Rationality Assumption. Journal of Institutional and Theoretical Economics, 150(1), 18-36.
[40] Kahneman, D., Frederick, S. 2002. Representativeness Revisited: Attribute Substitution in Intuitive Judgment, in T. Gilovich, D. Griffin, and D. Kahneman, 2002 eds., Heuristics and biases: The Psychology of Intuitive Judgment, Cambridge University Press, NY, US, 49–81.
[41] Flyvbjerg, B. 2006. From Nobel Prize to Project Management: Getting Risks Right. Project Management Journal, 37(3), 5-15.
[42] De Reyck, B., Grushka-Cockayne, Y., Fragkos, I., Harrison, J., Read, D. 2015. Optimism Bias Study Recommended Adjustments to Optimism Bias Uplifts: Final Report. Department for Transport, UK.
[43] Flyvbjerg, B. 2005. Design by Deception: The Politics of Megaproject Approval. Harvard Design Magazine, 50-59.