改进固定工期大中型工程的完工成本估算

传统挣值管理框架内的完工成本估算模型，不能很好适用于工期目标固定的大中型工程。首先，在项目前锋期（t₀），提出利用进度挣值方法（ES）估算完工工期T₂，以及对于固定工期（T₀）需要压缩的工期（ΔT=T₂-T₀）。然后，采用指数函数模拟时间-费用分阶段凸成本曲线，估算压缩工期的成本。在此基础上，结合Gompertz生长模型（GGM）估算未压缩时的完工成本，提出固定工期大中型工程的完工成本的估算模型。最后，以某机场工程子项目作为案例，分别利用传统挣值法的四种基本估算方法与改进后的挣值管理完工估算方法，对项目完工成本进行估算。横向对比结果发现，改进后的挣值管理完工估算方法具有相对较优性。本研究的成本估算模型改进了传统挣值法对完工成本估算的预测能力，对于进度为主要目标的中国大中型工程具有较强的实践指导意义。

Improving Cost Estimate at Completion of the Duration-fixed Mega Construction Project

The existing cost estimation models within the Earned Value Management (EVM) framework can not be well applied to mega construction projects (MCPs) with fixed duration.Firstly, the estimated total time (T₂) for all authorized work was estimated using earned schedule-based method, and the compressed duration was calculated by ΔT=T₂-T₀ at time t₀.Secondly,the Convex-exponential Time-cost function was used to estimate duration compressed cost (DCC), and the Gompertz Growth Model (GGM) was used to estimate the uncompressed EAC. On this basis, the estimation model for estimate at completion (EAC) of MCPs with fixed duration was proposed.Finally, taking the subproject of an airport project as a case, four basic estimation methods of traditional EVM and the improved estimation method were used to estimate its EAC respectively, and development trend of estimated deviations and their reasons for EACs of each model was systematically analyzed. The comparison results showed that the improved estimation method is more suitable for MCPs with fixed duration. The cost estimation model of this study improves the forecasting ability of traditional methods to estimate EAC within EVM framework, which is of practical significance to guide the MCPs with tight schedule in China.