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

Many braced dome geometries exist but only three will be mentioned herein. These are the:Schwedler dome which consists of polygonal rings interconnected by meridional members as shown inFigure FIGURE 12.19(a). A feature of this dome is that it can be analysed as a statically determinatestructure.Lamella dome developed by Dr Kiewitt and shown in FIGURE 12.19 (b). A feature of this dome is that itresults in an even stress distribution throughout and handles large concentrated loads efficiently.Geodesic dome developed by Buckminster Fuller and shown in FIGURE 12.19 (c). A feature of this dome isits suitability to construction situations requiring point supports. This is opposed to the previously mentioneddomes, both of which require continuous edge supports.Ribbed domes consist of arches or ribs constituting the meridians intersecting at the crown and eitherpinned at the base or connected to a horizontal base ring. Horizontal rings (hoops) are also required inconjunction with bracing elements as shown in FIGURE 12.19 (a).FIGURE 12.19: Shows some different dome geometries12.18 Dome Design - Structural ActionThe ribbed dome develops its load carrying capacity for symmetrical loads, through the meridionals actingas funicular arches, i.e with no bending only compression and the rings restraining the arches bydeveloping hoop stresses. The hoop stresses may be compressive only for shallow domes andcompressive and tensile for high rise domes.Load transfer in thin shell domes is almost entirely due to membrane action, i.e. by in-plane direct andshear forces. Hence, the three active forces on a thin shell element are N x , N y and N xy as shown in FIGURE12.20 (a). The term thin is relative since there is no doubt an eggshell fits this category but equally, an89mm thick shell spanning 75.6m in Germany, does so as well.175