Reliability-Based Structural Design of Concrete Pipes
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TECHNICAL ARTICLE—PEER-REVIEWED
Reliability-Based Structural Design of Concrete Pipes Huu D. Tran
Submitted: 29 July 2014 / Published online: 5 November 2014 Ó ASM International 2014
Abstract Concrete pipes are widely used for transferring water in urban infrastructure facilities. The current design standard of concrete pipes in Australia is based on the deterministic indirect-design method. However, there is uncertainty in pipe performance during service life due to assumed design parameters, installation error, changed operational environments, and pipe deterioration. This study aims to assess the reliability of structural performance of concrete pipes at the design stage. The reliability assessment is based on the use of Markov chain theory for modeling pipe deterioration during service life and coefficient of variation for representing uncertainty in design, installation, and operational parameters. The results of a case study show that increasing pipe strength from class 2 as per current design to class 3 as per reliability assessment can significantly reduce the likelihood of structural failure during service life and delay inspection and structural rehabilitation by 10 years. There is a difference in structural deterioration between pipe cohorts, which should be taken into account for reliability-based design. Keywords Concrete pipes Design Reliability Markov model Pipe deterioration
Introduction Concrete pipes are widely used for urban drainage pipes including stormwater pipes, sewers, and road culverts. Since drainage pipes are often buried under road or nature H. D. Tran (&) School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, Australia e-mail: [email protected]
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strip in urban cities, their design must ensure structural safety. There are currently two approaches for structural design of concrete pipes [1]. The first approach is called indirect-design method, in which the total static and dynamic load on pipes must be smaller than the loadbearing capacity of pipes. The structural load-bearing capacity is tested using a crushing test or three-edge bearing test. The second approach is recently adopted and is called direct-design method. In this approach, soil stress around pipes and performance of pipe material relating to bending failure, shear failure, excessive crack width, and loss of concrete cover are considered [2, 3]. The indirect-design method is widely used and is specified in Australian Standard (AS 3725-2007) as design for installation of buried concrete pipe. Erdogmus et al. [1] compared two approaches and concluded that the directdesign method can provide more accurate analysis of pipe stress because it accounts for actual soil–pipe interaction and behavior of pipe. However, Erdogmus et al. [1] accepted that designers will continue to use indirect-design method due to its simplicity and proven performance. Drainage pipes are design for expected service life of 80–100 years. Design parameters (e.g., static and dynamic load), installation error,
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