Design of Beams Theory | Structural Design
* Plastic neutral axis divides the cross section into two equal areas. * When plastic hinge is formed at all fibres at the section all fibres are having yield stress, with opposite nature on either side of N–A Zp = , for rectangular sections. * The sections are classified as class 1 (plastic), class 2 (compact) and class (3 semi-compact) classification of various sections into class 1 to class 3 may be found in Table 2 of IS 800–2007. Design procedure 1. Select a trial section assuming it is going to be plastic section. 2. Find the class to which it belongs. 3. Check for bending strength, shear strength and deflection. Revise the section if necessary. Bending strength If , two cases (a) If V £ 0 .6 Vd Md = bb fy × for simply supported beams = for cantilever beam where bb = 1.0 for plastic and compact sections = for semi-compact sections (b) If V > 0.6 Vd (i) Plastic or compact sections Mdv = where b = Md = Plastic design moment of the whole section Mfd = plastic design st...