Abstract
This paper presents a numerical investigation of a post-tensioned flat slab without conventional longitudinal reinforcement; only steel fibres were employed to ensure sufficient ductility and shear capacity of the slab. Results were taken from a reported experiment conducted on a full scale steel fibre-reinforced flat slab (0.38% fibre content) which was tested until failure, undergoing a ductile bending failure. A nonlinear finite element analysis was employed to study the experiment, including the ultimate state. A parametric study was performed using the numerical model to investigate the influence of the tensile behaviour of steel fibre-reinforced concrete (SFRC) on the structural response. The model proved to be relatively sensitive to changes in the tensile behaviour, but the differences were not prominent until entering the nonlinear area of the load-displacement curve. A constant curve with tensile stress equal to the residual tensile strength of the SFRC provided a robust numerical model and results on the conservative side. Including a peak stress with a multilinear tensile curve provided a less stable analysis but more accurate results. However, the model behaviour was stiffer than the experiment, providing too small deformations at failure. Nevertheless, the numerical model was able to display the ductile bending failure mode and moment redistribution.
Highlights
Concrete is one of the most important building materials in civil engineering, due to its simple production, its high compressive strength and versatility in form and application
The numerical model was capable of capturing the ductile bending behaviour of the slab and to display the correct failure mode, and the load-displacement curves corresponded well with the experiment
The contribution of the steel fibre was captured by the finite element model due to the implemented tensile behaviour of the steel-fibre reinforced concrete (SFRC), containing the residual tensile strength
Summary
Concrete is one of the most important building materials in civil engineering, due to its simple production, its high compressive strength and versatility in form and application. The main task of the fibres is to bridge cracks and transfer tensile stresses across cracks This leads to better crack control and smaller crack widths, in addition to increased flexural stiffness, which are desirable properties in the service limit state [1]. The residual tensile strength and other material properties of SFRC are dependent on the fibre content as well as the distribution and orientation of the fibre in the concrete. One important observation from these tests is that the residual tensile strength of SFRC varies considerably from small test beams to full scale structures. The reason for this is not yet fully understood and represents a major obstacle in making regulations for SFRC [15]. A parametric study has been conducted to obtain the optimal material parameters for modelling tensile behaviour of SFRC
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