Shear capacity of slabs and slab strips loaded close to the support

In reinforced concrete one-way slabs, two limit states related to shear need to be checked: beam shear over an effective width at the support and punching shear on a perimeter around the load. Current code provisions are based on shear tests on heavily reinforced slender beams under point loads. The question remains if these procedures are valid for wide beams and slabs under point loads close to the support. To evaluate the shear capacity of reinforced concrete slabs and the associated effective width, a series of experiments is carried out on eight continuous one-way slabs and twelve continuous slab strips loaded close to the simple and continuous supports. Test results are compared to current code provisions and methods to calculate the shear capacity from the literature. The influence of the shear span to depth ratio, the size of the loading plate and the overall width of the specimen are discussed. From these results follows that the behavior in shear of slabs and beams is not identical. The effective slab width, used for calculating the beam shear capacity, is recommended to be based on load spreading under 45° from the far side of the loading plate towards the support.