The second alternative was a vertical pivot design. It was chosen for the initial casting because of its simplicity and elegance. These sketches illustrate the variety of ideas generated in the initial design stage. The alternatives were generated in response to various issues that surfaced during discussions. These sketches led to the development of two alternative designs.
Geometry offers the most expedient means for reducing weight.
The first design is a thin plane of concrete with a thickened edge to carry the load and accept hinge and lock hardware. Cross bracing could be introduced to pro-vide protection against sh ear stress. The design includes a frame that allows the door to close solidly. The second alternative chosen for development is a pivoting door which thickens at the pivot point and tapers at each end to minimum thickness. Hardware is minimal.