ANALYSIS
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Fig. 3.11 Buckling resistance moment—conservative approach.
Fig. 3.12 Plate girder.
In the rafter, a haunch at the eaves ensures that part remains elastic. The hinge forms near the ridge, and restraints to the top flange are provided by the purlins. Provisions for plastic design of portals are shown in Figure 3.14 detailed design is given in Section 4.2.
3.6 EXAMPLES 3.6.1 Ribbed dome structure (a) Specification A kiosk required for a park is to be hexagonal in plan on a 16 m diameter base, 3 m high at the eaves and 5 m at the crown (Figure 3.15). There are to be three braced bays with brick walls. The roof is felt on timber on purlins with ceiling. Deal load=1.0 kN/m2 on slope Imposed load=0.75 kN/m2 on plan Design using 3 No. three-pinned arches as shown in the figure, steel grade 50. For thickness <16 mm, py=355 N/mm2.