中文摘要：

工程变更、不利物质条件以及物价波动等工程项目履约风险是承包人工程项目履约有效性降低的主要动因。通过数理模型分析工程项目履约风险与履约有效性之间的关系,并试图找到字面履约与尽善履约关于履约有效性折减差异的数理表达方式,提出利用信任手段注入合同柔性和再谈判机制、促使履约风险再分担,激励承包人在字面履约有效性基础上尽力弥补折减差异,最终实现尽善履约。

英文摘要：

Performance risk in construction project,such as engineering changes,unfavorable conditions and price f luctuations,is the main cause of low performance effectiveness.The paper analyzes the relationship between performance risks and performance effectiveness based on mathematical model,then tries to find a mathematical expression describing the shading between perfunctory performance and consummate performance and proposes to introduce contract flexibility and renegotiation enhance based on trust theory and encourage reallocation of performance risks,motivates the contractor on the basis of effectiveness of perfunctory performance to make up for the shading differences,finally achieves consummate performance.