Creation of a SCAD verification model for the design calculations of a reinforced-concrete waffle slab floor system

Introduction. Numerous researchers have examined issues associated with the analytical and computer-assisted design calculations for reinforced-concrete waffle slab systems. The obtained data indicate that forces in the beams can vary significantly depending on the created finite element model. Some models provide no means to correctly select beam reinforcement in the automatic mode of the selected analysis system.

Aim. To create a computer model of a waffle slab floor system, forces, reinforcement, and deflections in whose beams would be comparable to the data of analytical design calculations performed in accordance with regulatory requirements.

Materials and methods. According to the finite element method, the most accurate model comprises bar finite elements. The simplest analytical calculation can be performed for a square structure comprising square waffle slabs since it becomes easier to ascertain coefficients determining how the load is distributed on the beams. In this connection, the authors developed three bar finite-element models of a rectangular floor system measuring 9.0 х 9.0 m (square waffle slabs of 0.9 x 0.9 m) to be used in the procedure. The first model comprises bar finite elements having a T-section directly subjected to a load per unit length distributed from the coffers according to the triangle law. The second and third models differ from the first model in the way the load is applied to a flexible shell finite element having regular and chaotic partitions.

Results. The obtained results indicate that computer models accurately reflect the stress state of beams in the waffle slab floor system as compared to the analytical calculations. Bending moment deviations do not exceed +5 %.

Conclusions. The developed SCAD finite-element models enable reliable determination of forces, design calculations for the reinforced-concrete beams of the waffle slab floor system according to the ultimate and serviceability limit states, as well as comparison of the obtained data with analytical calculations performed in accordance with regulatory requirements. The proposed models can be used in verification calculations for floor system models comprising different types of finite elements (bar, plate, shell, and their combinations).

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