Triangular finite element model

The effect of **torsional stiffness of beams** was studied parametrically as a percentage οf full elastic torsional stiffness of beams (100%, 10%, 1%).

Ιn the case of full elastic torsional stiffness, both side beams are stressed by high torsion, caused by the moments on the supports of the main joists~~ ~~sitting on those beams.

Member model

For 10% the torsion of the two beams is of moderate intensity.

Member model

For 1% both beams are practically not stressed by torsion.

Triangular finite element model

Similar results obtained from both models (members, two-dimensional finite elements).

Triangular finite element model

For 10%, the torsion of the two beams is of moderate intensity.

Triangular finite element model

For 1% the torsion of the two beams is lower but not zero.

In conclusion, the assumption of the members for modelling structural frames and the approach of independent functionality of slabs are both acceptable and, under certain circumstances, form an adequately reliable solution. In finite element analysis, the common assumptions adopted for slab supports are: zero torsional stiffness, pinned supports on beams and columns, and monolithic supports on walls. Regardless of the calculation method, the minimum structural provisions of the regulations regarding the minimum (secondary, negative) reinforcement of slabs should be followed diligently.