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In our scheme, the profile stiffness can be used as an active factor in the form-finding process. The real stiffness - a profile stiffness of a practical profile that can be used in the bearing structure - is useful to explore the structural behaviour of elastic grids under geometric constraints. Besides, if the grid lengths are pre-determined, the real stiffness is helpful to solve a grid pattern in accordance with these pre-determined grid lengths.

If minimising the bending strain energy is a more critical issue than maintaining grid lengths, the fictitious stiffness - a profile stiffness that is designed on purpose and is only used in the form-finding stage - is used, which is defined by multiplying the bending and torsional stiffness by a weighted factor lager than one and keeping the axial stiffness unchanged. The fictitious stiffness enables the grids to have a larger range of strained lengths, which is helpful to reduce curvatures of the bending elements. Besides, this character can be utilised to generate smoothly curved grid patterns with various grid lengths.