Two-way slabs: Experimental investigation of load redistributions in steel fibre reinforced concrete

Abstract

2014): Two-way slabs: Experimental investigation of load redistributions in steel fibre reinforced concrete, Engineering Structures 80 (2014) pp. 61-74, http://dx. AbstractIn the design of two-way reinforced concrete slabs, e.g. using the strip or yield line design method, the possibility of redistributing the load between different loading directions is used. The main aim of the present study was to investigate how fibres affect the structural behaviour such as the possibility for redistribution, crack patterns and load-carrying capacity. The investigation was conducted by means of experiments on two-way octagonal slabs, simply supported on four edges, centrically loaded with a point load. The slabs spanned 2.2 m in both directions and the reinforcement amount was twice as large in one direction as in the other, in order to provoke uneven load distribution. Three slabs of each reinforcement configuration were produced and tested: conventionally reinforced slabs, steel fibre reinforced slabs and a combination of both reinforcement types. The reaction force on each supported edge was measured on five rollers per edge. A moderate fibre content (35 kg/m 3 ) of double hook-end steel fibres was used. The steel fibres affected the structural behaviour significantly by providing post-cracking ductility and by increasing the ultimate load-carrying capacity by approximately 20%. Most significant, the steel fibres influenced the load redistribution in such a way that more load could be transferred to supports in the weaker direction after cracking. Further, more evenly distributed support reactions were obtained in the slabs containing both reinforcement types compared to the case when only conventional reinforcement was used. The slabs reinforced by steel fibres alone did not experience any bending hardening; however, a considerable post-cracking ductility was observed. Furthermore, the work presented in this paper will provide results suitable for use in benchmarking numerical and analytical modelling methods for steel fibre reinforced concrete, as the experimental programme also included extensive testing of material properties.

Internal force distribution in RC slabs subjected to punching shear

“…However, for slabs PT32 and AM 04, the load rotation curves along both x and y directions are slightly dissimilar because of the different layout of reinforcement or column geometry in both directions. This observation was also consistent with the results from the two-way slab experiments by Fall et al [31].…”

Development of modelling strategies for two-way RC slabs

“…Fall et al carried out a series of tests on two-way slabs, which have been reported in [19]; in this section only a brief description of the experiments is made. The geometry and test set-up were designed so that a flexural failure occurred.…”

“…Furthermore, the influence of different modelling choices on the analysis results has been investigated. The load-carrying capacity, load-deflection response, crack patterns and reaction force distribution from FE analysis of a two-way slab under a concentrated load has been compared to corresponding experimental data from Fall et al [19]. The influence of the following modelling choices has been investigated: geometrical nonlinearity, element properties, material models for concrete, reinforcement (including interaction between reinforcement and concrete), and stiffness of supports.…”

Two-Way Flexural Behavior of Donut-Type Voided Slabs

“…Only diagonal cracks propagate along the yield line, as occurred in the solid and TF-D-S-P.P slabs. In contrast, in a slab with an asymmetrical rebar arrangement, the cracks propagate perpendicular to the weak direction (Sagaseta et al 2011;Matešan et al 2012;Fall et al 2014). The legs of the merged-type fixing device increase the tensile reinforcement ratio by 0.40%, creating a strong direction and a weak direction, relative to one another.…”

“…Previous studies (Sagaseta et al 2011;Matešan et al 2012;Fall et al 2014) that conducted two-way bending tests used a pointed load at the center of the slab. However, with a pointed load, an unexpected punching shear failure could occur because of the concentration of shear stress around the loading point.…”