An-Najah Staff

Cost and time models have been developed for road and bridge projects using resource significance analysis, which is in turn based on the 80/20 rule. The work packages in these models are designed to relate to site operations. They serve as the basis for measurement, estimating, planning, valuation and control in civil engineering projects. For defined categories of work, a standard set of work packages have been developed which consistently contribute about 90% of a project's resource costs and hours. The resource significant cost and time models for bridges and roads predict cost to an accuracy of 4% Cv and 3% Cv respectively. The resource hours for a project can be predicted to an accuracy of 6% Cv for bridges and 3% Cv for roads. The bridge model contains 26 work packages and the road model contains 22 work packages. Coarser models have also been developed for situations where the road or bridge is only part of an overall project, with only a small loss of accuracy.

Recent research has demonstrated the feasibility of identifying, within any category of project, a small number of cost significant work packages whose value represent a consistently high proportion of the total bill value. Using the allied principle of quantity significance, it proved possible to build simple models, which could predict both the cost and the duration of a project. In the course of that work, a surprisingly linear relationship between value and quantity was noted. This paper reports the background to and consequences of that finding. Quantity-significant work packages are formed by aggregating those items within a trade for which a linear regression of value against quantity yields a correlation coefficient greater than 0.99 and an intercept insignificantly different from zero. The price of packages formed in this way can be determined simply by applying to all the items within the package the rate associated with the largest quantity, the so-called “characteristic item”. Application of the concepts of quantity-significance and characteristic items is expected to lead to simpler estimating and more effective control procedures, because there is no longer any need to allocate cost and resources to each individual item contributing to a work package.

أثبتت الأبحاث الحديثة إمكانية تحديد عدد من الرزم الأكثر أهمية في أي مشروع والتي تمثل قيمتها نسبة ثابتة من التكلفة الكلية للمشروع. أن استخدام نظرية الكميات المميزة أثبت إمكانية عمل نماذج بسيطة تمكن من تقدير الكلفة والفترة الزمنية للمشروع، وقد لوحظ أن هناك علاقة خطية مدهشة بين التكلفة والكمية. يقدم هذا البحث خلفية أثر هذه النتائج . لقد جمعت الرزم الأكثر تميزًا من عدة مشاريع ومعامل الارتباط ما بين الكمية والتكلفة كان بنسبة تزيد على ٩٩ % ، كما يمكن تحديد أسعار الرزم بضرب سعر الوحدة الأكثر كمية بالكميات الكلية للرزم. إن استخدام هذه الطريقة يمكن من حساب الكلفة ويسهل مراقبة المشروع دون الحاجة لتوزيع الموارد على كل بند من بنود الاتفاقية.