Cd

Compreesion ring (at crown)

Compreesion ring (at crown)

Tension ring (at springing)

Horizontal thrust

Dead loads

Fig. 42: Dome (body of revolution)

Tension ring (at springing)

Horizontal thrust

Dead loads

Fig. 42: Dome (body of revolution)

As with barrel vaults and arches, in domes we are always faced with the question: How is the thrust to be accommodated, reduced and taken down to the foundations?

At the Pantheon in Rome the designers employed various features to handle this problem. The weight of the dome decreases as it rises, which is achieved not only by reducing the cross-section but also by using lighter materials. The dimensions of the dome are such that the flow of forces starting from the crown remains within the cross-section of the dome. The extra wall height externally adds weight and hence allows the tensile forces to be accommodated in the wall. Likewise, a steel strap acting as a tension ring would also have been conceivable.

Pier Luigi Nervi's Palazetto dello Sport makes use of a complex dome: the concrete shell is reinforced with folds and is resolved into Y-shaped raking columns, which accommodate the thrust by extending the dome and beneath the apex of the Y have a vertical column to transfer the forces vertically into the ground. In the ground there is a circumferential reinforced concrete tension ring. This allowed Nervi to create an interior space completely free from any intervening vertical loadbearing elements.

Fig. 43: Dome with voids to reduce weight and consumption of materials (omission of superfluous material). This creates a grid of Fig. 45: An early example of construction with Roman concrete stiffening loadbearing ribs. In addition, lighter materials were employed further up the dome. Pantheon, Rome (I),118-125 AD (opus caementitium). Pantheon, Rome (I), 118-125 AD

Fig. 43: Dome with voids to reduce weight and consumption of materials (omission of superfluous material). This creates a grid of Fig. 45: An early example of construction with Roman concrete stiffening loadbearing ribs. In addition, lighter materials were employed further up the dome. Pantheon, Rome (I),118-125 AD (opus caementitium). Pantheon, Rome (I), 118-125 AD

Examples

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