{"id":20178,"date":"2026-01-28T16:08:47","date_gmt":"2026-01-28T15:08:47","guid":{"rendered":"https:\/\/www.darda.de\/?page_id=20178"},"modified":"2026-01-28T16:08:47","modified_gmt":"2026-01-28T15:08:47","slug":"section-modulus","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/section-modulus","title":{"rendered":"Section modulus"},"content":{"rendered":"
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The section modulus is a central parameter in structural mechanics. It describes a cross-section\u2019s ability to resist a bending moment or a torsional moment. It is especially important for planning deconstruction steps, separation cuts, and splitting operations because it directly influences the expected stresses and thus crack and fracture behavior. In concrete demolition and deconstruction<\/a>, during building gutting, in rock excavation and tunnel construction, or in natural stone extraction, understanding the section modulus helps plan measures in a controlled way\u2014for example when applying concrete pulverizers or when using rock and concrete splitters<\/a> from Darda GmbH.<\/p>\n

Definition: What is meant by section modulus<\/h2>\n

The section modulus is a geometric property of a cross-section. It links the external action (moment) with the resulting stress at the extreme fiber. For bending: \u03c3 = M \/ W, where \u03c3 is the bending stress, M the bending moment, and W the (linear) section modulus. It is determined from the second moment of area I and the distance to the extreme fiber c: W = I \/ c. Unit: m\u00b3. For torsion of circular cross-sections, the polar section modulus Wp is used; there, \u03c4 = Mt \/ Wp, with \u03c4 as shear stress and Mt as torsional moment. The section modulus is thus a measure of a cross-section\u2019s \u201cbending or torsional robustness\u201d\u2014the larger W or Wp, the lower the stresses for the same moment.<\/p>\n

Physical principles and variables<\/h2>\n

Bending stress increases proportionally with the bending moment and inversely with the section modulus. The second moment of area I (unit m\u2074) describes the area distribution about the neutral axis; dividing by the extreme fiber distance c yields the section modulus W. For plates, beams, pipes, or sections, not only the material but above all the geometry<\/em> is decisive: greater section depth and a suitable shape significantly increase I and thus W. Notches, openings, slot cuts, and holes reduce W\u2014often more than the removed area would suggest. In deconstruction practice, this geometry effect is deliberately used to induce controlled breaking of components and to reduce the required tool forces.<\/p>\n

Cross-section shapes and typical section moduli<\/h2>\n

For simple cross-section shapes, closed-form approximations exist. Key examples:<\/p>\n