EWPAA Structural Plywood and LVL Design Manual - Engineered ...

The section modulus (Z) is:ZZ=Iy1=121= . ta6t(sin2)(asin ∝ ) .∝. sin ∝31h/ 2(12.3)For a uniform load p = (wa) kN/m, the maximum bending stress in an isotropic diaphragm is given by:12.5 ArchesIntroductionpL / 8σmax=Z2p . L / 8=2t . a sin ∝ / 626. w . a . L=28. t . a . sin ∝2σ 3 wLmax= .4 th2The arch and the portal frame are closely related and as such the arch can be rigid, two orthree hinged as shown in FIGURE 12.7 (a), (b) and (c). FIGURE 12.7 (d), (e), (f) show somevariations of the portal frame.(12.4)FIGURE 12.7: Basic arches and some portal derivativesThe arch provides a very versatile structural form fulfilling many structural roles in both two and threedimensional configurations, e.g. as a:• two dimensional idealisation of the singly curved cylindrical shell or barrel vault;• two dimensional idealisation of the doubly curved shell or dome;• two dimensional idealisation of saddle shells (hypars) in one direction;• a support for roofs of structures;• a support for bridge decks and in dam walls.FIGURE 12.8 shows examples of arches being utilised in a range of construction situations.163