The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

[DOWNLOAD] Torsional section properties for concrete sections according to ACI 314

Written By: Lexatus - Nov• 16•13

Torsional properties 7 - Onorio

In this post, an Excel spreadsheet for the evaluation of the torsional section properties of concrete sections according to the ACI 318 is available. The sections are:

– rectangular near the edge;

– rectangular in interior position;

– L-shaped;

– inverted tee.

The design for torsion as per ACI 318 is based on a thin-walled tube, space truss analogy. A beam subjected to torsion is idealized as a thin-walled tube with the core concrete cross section in a solid beam neglected as shown below:

Torsional properties 5 - Onorio

Once a reinforced concrete beam has cracked in torsion, its torsional resistance is provided primarily by closed stirrups and longitudinal bars located near the surface of the member. In the thin-walled tube analogy, the resistance is assumed to be provided by the outer skin of the cross section roughly centered on the closed stirrups. Both hollow and solid sections are idealized as thin-walled tubes both before and after cracking.

Torsional properties 6 - Onorio

According to the ACI the fundamental properties are:

– Area enclosed by outside perimeter of concrete cross section;

– Outside perimeter of concrete cross section;

– Area enclosed by centerline of the outermost closed transverse torsional reinforcement;

– Perimeter of centerline of outermost closed transverse torsional reinforcement.

These properties are calculated for the types of sections discussed at the begin of the post, that are:


Torsional properties 1 - Onorio


Torsional properties 2 - Onorio


Torsional properties 3 - Onorio


Torsional properties 4 - Onorio

You can download the Excel spread sheet from here:

Download at just € 0.99



For any issues or questions, you can contact the author at:

Eng. Onorio Francesco Salvatore

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