For example, in addition to constraints on the minimum length of beams, we can also impose constraints on the maximum length.These constraints imitate the real-world difficulty of manufacturing and shipping long beams. (Due to state regulations on truck flatbeds, girders over 48 feet are not easily shipped in North America.) Other changes or additions we have made to the objective and constraint functions include: minimizing the total length of beams (rather than mass), preferentially using tensile members (cables) over compression members, and symmetry constraints, which couple the position of certain joints to each other in order to derive symmetric forms