Felix Candela designed and built many thin-shelled concrete roof structures, most during the 1950s and 60s in Mexico. His most sophisticated structures, and those that are pertinent to our analysis, are of the hyperbolic paraboloid (hypar) form. Using a finite element method that solves for large-scale optimization problems, one of Candela’s structures (Chapel Lomas de Cuernavaca, Capilla de Palmira) is modeled, meshed, and analyzed.
Candela stated that “of all the shapes we can give to the shell, the easiest and most practical to build is the hyperbolic paraboloid.” We can understand this shape best as a saddle (Figure 2a) in which there are a set of arches in one direction, and a set of cables, or inverted arches, in the other. The shape is defined by straight lines. The boundaries, or edges, of the hyperbolic paraboloid can be straight as shown in (Figure 2b), or curved as shown in Figure 2a. The edges in the latter case are developed by planes ‘cutting through’ the hypar surface. Candela used both straight edges and curved edges to create his designs. (http://www.princeton.edu)