Abstract

PERDUH, M  and  STRASHEIM, J A v B. Finite element analyses of the structural behaviour of pylons supporting an inclined coal conveyor. J. S. Afr. Inst. Civ. Eng. [online]. 2015, vol.57, n.3, pp.44-56. ISSN 2309-8775.  http://dx.doi.org/10.17159/2309-8775/2015/V57N3A6.

As part of the coal conveyance system at Medupi Power Station, an inclined coal conveyor will transport coal from the stockyard to the coal transfer tower, and from there to the boilers. The conveyor is supported by concrete columns (pylons), in turn supporting the steel gantries on which the conveyor is located. The pylons can be considered as cantilever columns during the construction stage, while in the final operational stage with the steel gantries positioned in-between the pylons, a frame system will be formed. The gantries are connected to the pylons with custom-designed sliding joints, which allow limited movement of the gantries in the longitudinal direction of the conveyor. This paper describes how various finite element analyses of the structural behaviour of the pylons and the overall structure of the inclined coal conveyor were undertaken to assess wind and seismic actions. It focuses on modelling the behaviour of the concrete pylons during the construction period, a comparison between finite element models (FEMs) with different complexities and the implications of simplifying the FEMs. It will be shown that the simplified beam element models provide adequate modelling of the structural behaviour for this kind of structure. The modelling of non-linear connections between elements for static and dynamic conditions was also investigated, as well as the influence of the sliding joints between the pylons and the gantries on the overall behaviour of the structure. It will be shown that the overall behaviour of the structure can be highly influenced by the action of the sliding mechanism and that the force distribution between the structural members can differ significantly. Recommendations on how to approach the modelling of this type of structure are made. It is concluded that the simplified model can be used to capture the behaviour of the structure, as well as the complex sliding joint mechanism, which has a major influence on the performance of the structure and the force distribution in the structural system.

Keywords : inclined coal conveyor; Medupi; sliding joint; finite element analysis; force distribution; concrete pylon; steel gantry; simplified model.

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