Compound flexion
Introduction
Compound bending is a type of stress on a beam or a mechanical prism subjected to bending moments with a non-zero component in the two principal directions in such a way that the direction of the neutral fiber does not coincide with any principal plane of inertia.[1] In a piece subjected to compound bending, the normal stress can be estimated by the Navier formula:
where:.
The previous equation can only be used if principal axes are being used for the second moments of area, if any axes that are not necessarily principal are used, the complete formula is:.
Where:.
It is also said that a section is in a state of deviated bending or skewed bending when the direction of the neutral fiber is not known a priori.[2] This situation is called compound bending when, in addition to the bending moment, it includes the concurrence of axial stress according to Eurocode 3.
In this case, an eccentricity of loads is caused that produces a bending moment (axiality due to eccentricity)[3] and the resistance of the section is lower than in the opposite case.[4].
References
- [1] ↑ Capítulo 6 Análisis de la sección en flexión. Hormigón Armado y pretensado (Concreto reforzado y preesforzado), edición del 2007. Enrique Hernández Montes et al. Deposito legal: GR-2975/2007 Edición electrónica.: http://www.ugr.es/~emontes/prensa/HormigonEstructural.pdf
- [2] ↑ Capítulo 17 Flexión esviada. Hormigón Armado, 14ª edición basada en la EHE. Ajustada a l Código Modelo y al Eurocódigo. Pedro Jiménez Montoya et al. ISBN 84-525-1825-x.
- [3] ↑ Definición de flexión esviada según Urbipedia [1].: http://www.urbipedia.org/index.php/Flexi%C3%B3n_Esviada
- [4] ↑ Apartado 6.2 de "Estructuras de Acero. Cálculo, norma básica y Eurocódigo, Argüelles et al., Editorial Bellisco, 1999. ISBN 84-930002-8-0.