Steel fibres effects on the flexural cracking behaviour of reinforced high strength concrete beams with particular reference to the major design codes crack width models

Abstract

In the present experimental work, 28 reinforced concrete beams were manufactured and tested in bending under 2 concentrated loads. The beams, which were made in high strength concrete and in ordinary concrete for comparison purposes, had different quantities of fibres, with two aspect ratios. During the testing, a special attention was given to the monitoring of flexural cracking in terms of width, spacing and length, using a digital camera and Gom-Aramis software for the analysis of the recorded images. The measured crack widths were compared with theoretical values predicted by three major universal design codes for reinforced concrete, namely the American ACI 318, the British Standard 8110, the Eurocode 2, and by the technical document of Rilem TC 162-TDF. In the present experimental work, an amendment of the Rilem model, taking into consideration the three important parameters, namely the quantity of fibres, their orientation factor and their aspect ratio, is proposed. The predicted values of the crack width obtained by the modified Rilem model were compared with the test values and assessed against other experimental data on fibre-reinforced concrete beams taken from the literature. The results show that the modified Rilem model is fairly reliable in predicting the crack width of fibre-reinforced concrete.

Keywords:

• Steel fibre-reinforced concrete
• flexural cracking
• tensile strength
• crack spacing
• crack
• bridging
• crack width
• stiffness