The hyperbolic paraboloid takes the thinness of shell construction and applies it in a much more complex way. A hypar is essentially two parabolas that sit reflected and rotated along a common axis, or by a series of strait lines that are slid from one skew line to another. The hypar through the use reinforcing steel is capable of resisting the tensile forces of the edges of the parabola acting like a cable structure and transferring those into the compressive forces of the bottom.

St. Mary’s Cathedral, San Francisco California Architect Nervi

**la iglesia de La Milagrosa, Mexico City Architect Felix Candela**

Catalano House, Raleigh NC Architect Eduardo Catalano

The hyperbolic paraboloid is a series of parabolas strung together. This series however is a non-developable surface so the construction of it has to be precise. The two axial parabolas generate a surface curve that is both in compression and in tension. The use of reinforcing steel in the upward curvature of the parabola allows for the tensile forces to flow into first the neutral sag, or catenary then the thrust of the forces flow into the compression on the downward parabola.

Precedents

The Hyperbolic Paraboloid