Accounting the Influence of the Flanges Width when Calculating the Console Beams of the Ribbed Slab

Ribbed slabs are widespread due to the lack of concrete in the tensile zone, where the tensile forces are fully taken up by the reinforcement. According to modern standards, the beams of such a slab in the supporting zones under the action of negative moments are calculated as rectangular ones without taking into account the influence of the plate in the tensile zone. This method was developed in the 1940s of the XX century and is used in modern standards to this day. The slab, which is part of the bridging, does not take part in the calculation of such a cross-section, since it is in the tensile zone. However, it is not quite correct to completely disregard the work of the flange, because the plate reinforcement in the support section of the beam is tensile and with the appearance of cracks in the flange will be included in the work and take the bending support moment. Failure to consider the slab reinforcement can lead to overreinforcement. This effect will be especially noticeable in slabs with beams limited in height and slabs of considerable thickness (more than 100 mm). The paper proposes a calculation method for beams of T-section taking into account the influence of slab reinforcement. The comparative analysis of the calculation of the existing monolithic ribbed console slab section both according to the modern norms and the proposed methodology has been carried out. The dependences of some parameters on the ratio of the plate thickness to the beam height in the calculation according to the proposed methodology, taking into account the influence of the plate reinforcement are also considered. Relevant conclusions are made, which show that taking into account the influence of the stretched slab reinforcement in the calculation of console slab beams has a significant impact on the carrying capacity, stiffness and cracking resistance of the beam.