A dome is a structural element of architecture that resembles the hollow upper half of a sphere. Dome structures made of various materials have a long architectural lineage extending into prehistory. Dome

Ribbed domes, one of the earliest forms, are still very popular because of the popular because of the possibility of prefabrication. They consist of a number of identical radial solid or trussed (latticed ribs) interconnected at the crown and supported in an adequate way at the foundation. RIBBED DOMES

This type of roof is not economical because sot does not incorporate the advantages of structural interaction of latitudinal intermediate rings. Depending on the base diameter of the dome, there may be eight to seventy-two intersecting braced ribs. They are usually of constant depth. BRACED RIB DOMES

Solid-rib domes are similar to b raced arch domes in spatial arrangement, except that ;-  The meridional ribs are composed of shallower solid-web sections, rolled, built, up, boxed, or even diamond box shaped.  The meridional space system is additionally integrated by intermediate rings between the upper compression ring and the lower peripheral ring. SOLID RIB DOMES

 All the ribs generally terminate at the upper compression ring instead of some being carried through. Because it presents a neat appearance form underneath, considerable dead load and cost may be saved by dispensing with the ceiling, having straight ribs. The ribs can be made from timber, steel, concrete or aluminum.

In practice the rigidity of the connection of all the ribs at the apex depends upon the method of construction. If the connections are welded, the apex joint is fully rigid, introducing fixing moments which make the analysis of these domes very tedious. Many attempts have been made in practice to unbolt all the ribs together in such a way as to avoid the rigid connections. This was done by the introduction of a hinge, allowing free rotation in certain directions, it is also advisable to pin the ends of the ribs at their foundation. PRACTICAL CONSIDERATIONS OF SOLOD RIBBED DOMES

It is to be noted that a ribbed dome, even if the ribs are pin- connected at the ground, but fixed rigidly at the apex can resist a perfectly general system of loading. But if the huge is introduced at the top also, the dome will be able to resist only the loads applied in the vertical planes and passing through the neutral axis of the ribs. Thus in practice, it is usually assumed that the lateral loads are resisted by the roofing skin, and that the applied external loads are radial.

The connection details of a timber ribbed dome are shown in figure, This type of timber dome can be used to cover spans of over 90m and can be covered with wood wool slabs. Smaller, lighter ribbed domes may be constructed with laminated ribs covered with plywood or layers of tongued and grooved boarding. Often, in addition to the roof covering stiffening the structure, the three-pinned domes have diagonal members connecting two adjacent ribs together. The three pinned ribbed domes can be prefabricated and speedily erected on site using little scaffolding.

Erection of ribbed structural member may be accomplished very quickly by using a crane to position in place. The dome too may supported as additional ribs added by a crane, by gin pole or inflated compressed dome structure balloons the individual ribs then becomes self supported after the intermediate rings have been added the assembly processes is completed by riveting or bolting or welding.

SUBMITTED BY S K C VARTHI(060130), B.Arch; VIII Sem, JNA & FAU