Shells can be defined as curved structures capable of transmitting loads in more than two directions to supports.

Loads applied to shell surfaces are carried to the ground by the development of compressive, tensile, and shear stresses acting in the in-plane direction of the surface.

Constructions of spherical domes by using inflated membranes as forms have proven to be a viable solution to many problems.

The largest shells constructed are now less than 300 feet in diameter.

For very large spans, a grid constructed with pans is necessary so that the dome will be stiff enough and still weigh less than a uniform depth.

A vault may be defined as a single barrel shell, supported on its side by walls or columns.

Shells and folded plates are different than stacked units and frames.

The thin diaphragm forming the shell is created uniformly rather than being assembled in discrete pieces.

Most shell and plate building enclosures are constructed from reinforced concrete

A shell arch has a longitudinal cross section of a barrel shell or a folded plate, but is a circular arch or other shape in profile.

There is less concrete

in the roof than in the floor system, and the reinforcing will be minimum.

Dome shells have emerged due to a new concept in building design.

These structures have the

potential for significant markets in commercial and many other small residential and industrial applications.

The structures utilize superior material technology

Curved shell roofs can provide large uninterrupted space in many building types.

The arrangement consists of :

external and internal layers of glass reinforced cement (GRC)

the strong stiff layers

with a lightweight polyurethane core forming the separation medium required to develop the sandwich action.

Construction of the domes involves a three stage processes:

(a )Completed Slab, )b( Inflatable former, )c( Completed domeshell

As the diameter of the domes increases, the stresses rise

Barrel shells of materials such as wood, steel and plastics are often found.

Reinforced concrete is by far the most common material

Edge beams serve to:

to stiffen the shell edge

to act together with the shell in carrying stresses

The design for king Abdullah Stadium in Jeddah. The shell design is remarkable. The building of this giant stadium will begin by the end of this year.