Effect of casting method and shear span-to-depth ratio on the behaviour of Ultra-High Performance Concrete cross arms for high voltage transmission lines

Abstract

This paper reports on a project that is in an area of high economic and technological importance to the hydro-power utilities. Currently, most high voltage transmission line poles and their cross arms are made either from wood or steel. As an emerging technology, the project addresses an important topic on the application of Ultra-High Performance Concrete (UHPC) cross arms, in high voltage transmission poles, as a competitive alternative in today’s market to replace the existing deteriorated wood and steel cross arms. The characteristic properties of UHPC cross arms make them the ultimate materials for the construction of thin members. Given all the advantages of UHPC concrete, and the market demand for a reliable and durable solution, it is expected that these UHPC cross arms are a repetitive application. Experimental test results of an investigation on the structural evaluation of prestressed UHPC C-channel cross arms are reported in this paper. The testing program was designed to corroborate the structural capacity of the UHPC cross arms under given loading scenarios according to specifications used by the hydro-power industries. Several tests were performed to examine the effect of steel-fibre orientation around the internal ordinary steel rebars on the flexural strength of UHPC cross arms using different casting types; and to evaluate the effect of varying the shear span-to-depth (or height) ratio on the flexural and shear capacity of the prestressed UHPC cross arms.