Integrated cost and time models for measuring, valuing and controlling construction projects

A claim is a matter about which agreement has not been reached at a given point in time. Many claims arise out of changes, including variations, delays and disruptions. Traditional contractual cost and time models do not facilitate swift, systematic and equitable valuation of any but the simpler variations. Bill items (cost) and programme activities (time) are incompatible, so the inherent interdependency between cost and time is not modelled. As a result, dispute and conflict over claims are a common feature of construction activity. This thesis presents a rational yet simple cost and time modelling system which should help reduce the incidence of claims and fulfil the various estimating, planning, control and feedback functions. The system links cost and time effectively in a manner which should allow a wider range of changes (and change types) to be valued systematically, swiftly and fairly through the contract. A resource significant item (RSI) is one of a small number of items which together represent a consistent and significant proportion of the resource hours and costs on a construction project. A resource significant item is identified as any item in a bill of quantities which has a labour, plant or material resource value (cost or hours) which is greater than the mean labour, plant or material resource value for the bill. RSIs account for around 90% of the total value of work in a bill of quantities and 30% of the items. The philosophy of resource significance has been used to develop a set of standard integrated models for the measurement, valuation and control of cost and time on civil engineering projects. These models are called resource significant cost and time models (RSCTM) and have been developed for reinforced concrete bridges and roads (flexible construction). Each model consists of resource significant work packages. The cost or productivity of each work package is characterised by the resource cost or productivity for the work item with the largest quantity, provided that the item accounts for at least 70% of the total work package quantity. The resource significant cost and time models have been tested. They can predict the cost of a bridge with an accuracy of 4% Cv and the number of resource hours with an accuracy of 6% Cv. The cost and number of resource hours for roads is predicted to 3% Cv. The work packages in each model can be integrated with the activities on the programme using operational modelling. Operational modelling is a series of five charges expressing the major factors which affect cost and time on a construction project. The work packages in the RSCTM, the programme and operational modelling are collectively termed the Resource Significant Modelling System (RSMS). The RSMS has been used to simulate the valuation of the full cost and time effect of changes in civil engineering projects. It can value a greater proportion of changes swiftly, equitably and systematically than is currently achieved under traditional valuation systems incorporating the bill of quantities. This capability of the RSMS should lead to a drop in the frequency of claims involving considerable dispute and conflict on construction projects.