|Author:||Wong, Lai-wah Clement|
|Title:||A methodology for tunnel availability assessment|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Tunnels -- Design and construction -- Evaluation
Tunnels -- Design and construction -- Safety measures
|Department:||Department of Electrical Engineering|
|Pages:||xx, 179 leaves : ill. (some col.) ; 30 cm|
|Abstract:||The reliability and maintainability of tunnel infrastructure and systems are crucial factors for ensuring safety of tunnel operation. Unsafe conditions will cause closure of a tunnel. Efforts to improve availability of a tunnel often increase the tunnel's construction cost. Due to complexity of tunnel systems, it is difficult to compare different tunnel designs, and trade-off analyses to strike a balance between target availability and construction cost of a tunnel design are seldom performed. Furthermore, evaluating availability of a large-scale tunnel that includes civil, electrical, mechanical and electronic systems is a difficult task. This thesis presents a methodology for performing such assessments, featuring the use of the Markov Model. The methodology involves application of Failure Mode, Effect and Criticality Analysis (FMECA), State Space Diagram construction, formulation of State Space Equations, and development of Transitional Matrices. It also involves transformation of Multi-State Models into 2-State Models (each comprises an 'up' state and a 'down' state) through the use of the Frequency and Duration Method for determining the failure and repair rates, as well as the Mean-Time-Between-Failures (MTBF) of the entire tunnel. By using the proposed bottom-up approach, a MTBF tree linking the availability measures of individual equipment with those of sub-systems, and ultimately the whole tunnel can be developed. The tunnel availability measures obtained by this analysis can be used in making comparisons between different tunnel designs so as to determine the value for money of various options. Furthermore, weaknesses in a tunnel design can be identified in the analysis. This way, huge sums of construction costs can be saved without compromising availability of the tunnel. The information obtained from this method can also be used to evaluate adequacy, security and maintainability of a tunnel. The methodology can also be used to evaluate designs of other complex systems such as power generation or petrochemical processing plants. A worked example in the Western Harbour Tunnel, Hong Kong demonstrating the application of the proposed methodology along with identification of areas for improvement is also presented in this thesis.|
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