OPTIMISATION OF A CONCRETE PIPE CULVERT BASED ON RELIABILITY

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7105-99-5 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 12, 635-642 pp, DOI: 10.5593/sgem2017/12/S02.081

ABSTRACT

Reliability of a concrete pipe culvert was tested under rail and embankment loads. In the finite element model soil-structure interaction and nonlinear behavior of the materials were taken into account. After a preliminary study three influential variables as random were selected for presented approach to probabilistic model, i.e. concrete strength, soil density and its modulus of elasticity. Because various concrete parameters can be easily derived from the compressive strength only this parameter was selected for concrete. The response surface method based on polynomial approximation was used to obtain reliability indexes. The key role in the paper plays modeling of plastic material behaviour for both the substrate and the pipe. The Coulomb-Mohr material model was used for soil, and Jefferson model with Kupfer - Gerstle failure criteria were used for concrete. The friction contact between the two bodies was modeled. Two states of failure were tested: concrete destruction and change of the pipe diameter. The first state was considered as an ultimate while the second one as a serviceability limit state. Both lead to similar failure modes of the culvert pipes. Simulations were performed for a wide spectrum of the random variables. They established an origin of optimisation task according to ISO2394:2015 reliability code, which can be important for an economical culvert design.

Keywords: culvert, reliability index, optimization, nonlinear FEM