SCAD model of solid finite elements: calculation of reinforced concrete waffle slabs

Introduction. Current requirements for structural engineering oblige designers to use structures capable of resisting progressive collapse. Such structures include multiribbed reinforced concrete waffle slabs. Spatial systems are multiple indeterminate, their calculation is carried out in software systems based on the finite element method. Models of ribbed structures can be developed from different types of finite elements. The forces determined by different models can vary significantly, which is confirmed by the examples available in the literature.Aim. To detect a simple and accurate finite element model for computer-aided calculating the ribbed reinforced concrete waffle slab.Materials and methods. The study was carried out by comparing the bending moments obtained analytically and in the SCAD software by the finite element method for beams in waffle slabs of 12.0 × 18.0 m in plan with caissons of 1.5 × 2.25 m. The bar model consisting of a T-beam-and-girder construction and a solid model of bulk finite elements are calculated.Results. The bending moments, calculated both analytically and using a solid model, have similar values. The maximum deviations of the computer calculation from the analytical method are from -3.2 to +2.6 %. The maximum deviations of the values of bending moments obtained when comparing the solid model with the bar model are from -9.2 to +4.0 %.Conclusion. The finite element model, which is based on solving the volumetric problem of the elastic theory, is an effective verification model for studying complex systems; however, it is time-consuming and difficult for data analysis. A solid model can be recommended for studying individual structures or their critical zones.