Fundamental Investigations on the Performance of Micro Steel Fibres in Ultra-High-Performance Concrete under Monotonic and Cyclic Tensile Loading

Jan-Paul Lanwer,Martin Empelmann

doi:10.3390/app11209377

Abstract

Ultra-high-performance fibre-reinforced concrete (UHPFRC) can preferably be used for lean and thin-walled structures due to its very high compressive strength. Based on the adverse relation between the increased load bearing capacities and the condensed dead weight of UHPFRC-structures, the impact of live loads in the design gets bigger and, in case of traffic loads, the effects of a cyclic loading have to be considered in more detail. In this context, this study investigated the material behaviour of UHPFRC, especially the tensile fatigue behaviour of high-strength micro steel fibres and the bond behaviour between those fibres and plain UHPC. The test programme included once tensile tests of high-strength micro steel fibres under monotonic and cyclic loading. Based on the test results, an S/N-curve was set up with the characteristic values. Furthermore, the test programme included pullout tests of fibre groups with different embedded lengths and orientations under monotonic and cyclic loading. It was observed that some fibres rupture under certain test configurations like the angle of orientation and the load amplitude.

Highlights

Ultra-high-performance concrete (UHPC) offers enormous possibilities in relation to thin-walled, light, and filigree concrete constructions
Besides the pure addition of steel fibres and in regard to the aforementioned ecological aspects, the design and the performance of micro steel fibres in ultra-high-performance fibre-reinforced concrete (UHPFRC) under monotonic and cyclic tensile loading is of great importance
High-strength micro steel fibres embedded in UHPC provide a ductile failure mode under monotonic loading

Summary

Introduction

Ultra-high-performance concrete (UHPC) offers enormous possibilities in relation to thin-walled, light, and filigree concrete constructions. High-strength micro steel fibres embedded in UHPC provide a ductile failure mode under monotonic loading. Makita [12], Graybeal [6], Lappa [13], and Bornemann [14] observed continuous fibre pullout but under cyclic tensile loading. These observations rest upon UHPFRC-specimens with a 3-D fibre orientation and not upon pullout tests. The bond stress between the fibre and UHPC must have been so high that fatigue failure of the steel fibre material occurred un-der the cyclic loading.

Fibre Design Philosophy

Investigation Strategy

Cyclic Loading

Findings

Monotonic Tensile Loading