One-way shear strength of circular voided reinforced concrete floor slabs

Abstract

Generally, voided reinforced concrete floor slabs in building structures have a lower shear strength compared with solid slabs owing to the reduction in their cross-sectional area. This study shows that the void shape and material of the void-shaper also influence the shear strength of voided slabs. To verify these assumptions, one-way shear tests were conducted for four test specimens. The first was a conventional solid slab and the others were voided slabs.The voids had toroidal or 'doughnut' shapes as well as non-doughnut shapes. The void-shaper was made of polypropylene plastic and glass-fibre-reinforced plastic. The test results showed that the shear strength of doughnuttype voided slabs was 73-78% of a solid slab and was superior to that of existing voided slabs. The shear crack angle changed with the void shape. A finite-element analysis was conducted to evaluate the influence of these parameters on the shear behaviour of the doughnut-type voided slab. Notation a shear span b v width of the void b w sum of smallest web thicknesses C Rd,c coefficient derived from tests D j diagonal length of the panel for measuring shear deformation d effective depth of the specimen d j depth of the panel for measuring shear deformation f ck specified compressive strength of concrete G shear modulus of elasticity H height of the slab h j width of the panel for measuring shear deformation k factor of size effect N number of doughnut-type void-shapers that are located in the shear crack region P cr measured load when first shear crack occurred R curvature radius of void edges V c nominal shear strength provided by concrete without shear reinforcement V HS shear strength of a doughnut-type void-shaper with varying materials V HS,Total sum of the shear strength of the doughnut-type void-shapers V n nominal shear strength of the voided slab without shear reinforcement V Rd,c nominal shear strength provided by concrete without shear reinforcement V u ultimate shear strength AE shear factor AE Doughnut shear factor of the doughnut-type voided slab ª 1 measurement of shear strain ª 2 measurement of shear strain ª s shear strain of the slab ª xy shear strain of the void-shaper ä 1 deformation of the panel in the diagonal direction ä 2 deformation of the panel in the diagonal direction å a strain of the void-shaper in the vertical direction å b strain of the void-shaper in the diagonal direction å c strain of the void-shaper in the horizontal direction Ł shear crack angle r tensile reinforcement ratio of the slab ô V shear stress of the void-shaper 336

An Innovative Method of Voided Reinforced Concrete One-Way Slabs Using Bundled Waste PET Bottled Tubes

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Bond Characteristics of a Deformed Steel Bar Embedded in Donut-Type Voided Slab

“…By applying the advantages of voided slabs, several voided slabs with various void shapes and details were developed, and many studies have been conducted to verify its structural performance in terms of the flexure, shear, and punching shear [3][4][5][6]. The donut-type voided slab is one of the developed voided slabs; Chung et al [7] proposed a donut-type void as the optimum shape for a void-shaper by conducting analytical studies in which various shapes of void were used as variables, and they also evaluated the structural performance of the voided slab in terms of the flexure, shear, and punching shear through empirical and analytical studies [8][9][10][11].…”

Punching Shear Design Method of Voided Slabs

“…However, in case of voided slab, the ratio between area of vertical section and a plane along with shear crack varies by the shape of void and shear crack angle. [4] As a result, the large fluctuation of 'ν u ' calculated with the vertical cross section area may appear in voided slabs. Therefore, the effective cross-section area ratio(α eff ) is used to calculate 'ν u ' for investigating the relationship between 'ν u ' and 'b 0 /d' in voided slab.…”