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04.14: Transfer of axial loads in penstocks: Load carrying behaviour with and without thrust rings
Author(s) -
Ecker Alexander,
Unterweger Harald
Publication year - 2017
Publication title -
ce/papers
Language(s) - English
Resource type - Journals
ISSN - 2509-7075
DOI - 10.1002/cepa.134
Subject(s) - thrust , penstock , transfer (computing) , structural engineering , engineering , computer science , mechanical engineering , parallel computing
The transfer of axial loads in penstocks to the surrounding concrete and further into the rock was studied within a recently finished research‐project. The traditional way is to use thrust rings for the axial anchorage of penstocks in hydropower‐plants. A new idea is to transfer the axial loads without thrust rings, only considering friction between the steel pipe and the concrete. This approach is only applicable for the combination of axial loads and internal water pressure. The Austrian company TIWAG carried out measurements in a part of a newly built penstock without using thrust rings to determine the strains and displacements due to axial loads and internal pressure. The aim was to identify the behaviour due to the axial loads in the pipe and also the friction coefficient between the steel pipe and the concrete, based on additional numerical analyses. This paper gives an overview of the measurements and the comparison with the accompanying Finite‐Element‐Analysis. After that in a numerical‐parameter‐study the pipe thickness, the modulus of subgrade reaction of the rock and the friction coefficient between the steel pipe and concrete was varied to get an overview of the behaviour. Within this numerical‐parameter‐study also the load carrying behaviour with additional thrust rings, considering also their axial flexibility, was compared. Finally a design model for the distribution of the longitudinal stresses in the pipe and for the displacements at the end of the embedded pipe was developed, as a result of the parameter study. This design model is easy to handle and gives very accurate results for the displacements and the longitudinal stresses of the penstock without thrust rings under axial loads and internal pressure.