LIMITATIONS OF USE

Some local conditions can limit the benefits of building with arches, vaults, and cupolas.

• Rejection by the inhabitants for cultural reasons

• High cost of labor

• High cost of suitable building materials

• Use in earthquake areas requires special care

• Lack of building norms

The technology must be adjusted to a given context, and the techniques must be mastered to warrant the advantages of using arches, vaults, and cupolas.

SPATIAL CONSIDERATIONS

The curved forms generated by arches, vaults, and cupolas define free variable heights that increase with the span and the rise. Depending on requirements, one should first determine the curvature of the element and the height of its spring-point. The ability to move between one space and another also makes it important to take account of the ability to open out between the interior and the exterior of a vault or of a cupola. One can distinguish between open, semiopen, and closed types.

Подпись: FIGURE 8 Three vault shapes. Building systems using arch, vault, and cupola structures can range from the simplest to the most complex. The main distinction to be made is between modules that are inde­pendent from one another (whether con­nected or not) and sophisticated systems that respect very precise geometrical traces. The sophisticated systems get an optimum use of the material and perform very well from the point of view of costs. On the other hand, their replicability can be tricky, since a high degree of precision at the laying out stage is required. As a general rule, the more the shapes of the vaults or the cupolas are visible, the cheaper the building. Certain models per­mit a simple and inexpensive transition to slo­ped roofs, as shown in Figure 8.