Life-Cycle Cost Analysis Of Construction Project Basing On Concrete Durability

The Reinforced Concrete (RC) structure is the main structural type in construction engineering all over the world. In most countries, nevertheless, the RC structures, especially civil infrastructure facilities in severe environmental conditions, are found to be suffering from deterioration of structural performance and degradation of safety, due to the deficiency of concrete durability. Many construction projects failed much earlier than their expected service life, or failed to accomplish their expected functions, some of them must be repaired frequently, and some of them collapsed during use, thus, it has become a matter of serious concern about vast economic loss and unfavorable social impacts. Therefore, the construction project must be appraised about its safety and cost in lifetime basing on considering the concrete durability.Construction projects are charaterized by the extremely importance of safety issues, and the degree of structural safety has crucial influences on the economic indices of the project, so the life cycle cost analysis (LCCA) of construction project can not depart from the safety problems, especially the deterioration of structural safety performance caused by the concrete durability. For construction project, the LCCA is not merely a matter of economics, is in close relationship with the structural performance including the behaviors of safety and maintenance. The ultimate aim of construction project is maximal expected benefit or the minimal life cycle cost (LCC) under the constraint of structural safety reliability.The main research works in this dissertation are as below:1. The concept and meanings of the LCCA of construction project are defined and discussed. The lifetime of a construction project is divided into five periods including planning period, design period, construction period, working and maintenance period, and abolition period. The influences of the five periods on the LCC are discussed respectively.2. The basic theories, content and methods in common use of the LCCA ofconstruction project are summarized, and the extension and content of costs and benefits are analysed and discussed, and the selection issues of the important parameters such as the study period, the discount rate and the price, are analysed. The meaning and the elementary evaluation methods of the project working life are fully studied.3. The problems of concrete durability, mainly including the concrete carbonation, reinforcement corrosion, freeze-thaw destruction and alkali-aggregate reaction are discussed. The techniques and management ways to improve the RC durability are specially worked over.4. Based on the introduction of the theory of structural reliability and the selection of structural safety indices, the uncertainty during the analysis of structural reliability is investigated. The structural reliabilities at different stages and its meaning are defined, and the time-variant reliability and the analysis method of existing structures are studied.5. The standard of limit state and its selection methods, the grade division and the evaluation of the RC durability are discussed, and the assessment principles and prediction methods of service life of the RC structures are studied. The methods and procedures of the assessment and prediction are illustrated based on a case.6. The basic methods of the LCCA of construction projects are investigated. The way of the determination and selection of the optimum initial reliability of RC structures, the relationship between the initial construction cost and the initial structural reliability, and the constraints of maintenance and abolition of structures are analysed. The methods of analysis and computation of the loss because of structural failure are researched into. The coefficient of the deficiency of working performance is proposed, and taking advantage of it, the expected economical loss due to performance deficiency and the profit of maintenance are analysed and estimated.7. The principles, methods and thoughts of durability design of construction projects are probed into, and the systematic framework of LCCA of construction project is established. Especially, the train of thought, the methods and the procedures of LCCA about new construction projects, civil infrastructure facilities and existing construction projects are deeply studied. The levels of the initial structural reliabilityand design durability, and the strategy of maintenance of a new construction project are analysed in detail. The systematic methods of LCCA of construction project are proposed, and the methods and procedures of the assessment and prediction of structure reliability in lifetime are studied in detail, and the Bayesian method is introduced to improve the level of the assessment and prediction of structural performance, and the test expenditures is also discussed briefly.8. Illustrated by a RC bridge under marine environment, the main methods and procedures of LCCA of construction project basing on concrete durability were disserted in the aspects of technology, economics and management.9. In the finality, the problems requiring further studied are discussed.The main innovations in the dissertation are as below:(1) Established the systematical framework of Life-Cycle Cost Analysis (LCCA) of construction projects basing on concrete durability.(2) Systematically researched into the level of the initial structural reliability, the strategy of maintenance and their economical influences on the construction projects and the relevant methods.(3) Proposed the systematic reliability appraisal methods of construction projects in lifetime.