İnşaat Proje Süresi Tahmininde Referans Sınıf Tahmin Yöntemi

Öz

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

Öz

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.

Anahtar Kelimeler

• Construction,Project management,Estimating,Scheduling

Kaynakça

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