Stiffness Modification of a RC Beam (Simplified Method)
Comparison of FEM modeling approaches for reinforced concrete slab-beam systems
A simplified method of stiffness modification of a reinforced concrete beam allows to model beams integrated in a slab surface (plane) and take into account the real geometry of the slab-beam system. This is a simplified method for elastic analysis that does not take into account the effective width of a T-beam (for example, as in Eurocode 2 Section 5.3.2.1 [1]).
A comparative analysis is shown in the article "Inżynierski problem komputerowego modelowania pracy żelbetowej płyty dwuprzęsłowej z uwzględnieniem sprężystej podatności belki" by Dr inż. Paweł Kossakowski [2]. Additionally, a more advanced method was described by Sofistik T-beam philosophy [3].
A comparison between different design models for a RC beam with dimensions (b×h) 40×60 cm integrated in a RC slab with thickness of 20 cm is shown below.
| Case | 3D View | Moments in the Slab |
|---|---|---|
| No stiffness modification, no offsets |  |  |
| Stiffness modification (simplified method) |  |  |
| Beam modelled with offsets |  |  |
| Beam modelled as a panel |  |  |
| Line support |  |  |
[1] Eurocode 2: Design of concrete structures — Part 1-1: General rules and rules for buildings
[2] Paweł Kossakowski. "Uwzględnienie wpływu sprężystej podatności belek w numerycznym modelowaniu stropów żelbetowych". Politechnika Świętokrzyska, 2014
[3] Sofistik AG T-beam philosophy: https://youtu.be/GoT1f0aGdgs