228 Romuald Tarczewski scarped).Fig.9 presents a comparison of shapes of cylindrical shells with variable rigidity.More sophisticated shapes can be achieved when rigidity is changing according to a parametric function. rigidity decreased in the center 442 rigidity increased in the center Fig.9.Comparison of shells with variable rigidity 4.2 Adaptable-Hardening Structure Variation of rigidity allows constructing a structure that actively adapts to external loadings.If the internal lever arm increases together with increasing external loadings-deformations increment slowly.Load-deformation relation in this case is an exponentially growing function.If the internal lever in the structure can be self adjusted in order to find position of equilibrium,then the structure reveals a "hardening"characteristic.In numerous situations this specific type of structures is more advantageous than any other,with a linear response.An example of hardening system is described in [7].Its application in pneumatic shells [8 is shown on Fig.10. air inflated cush●ns basic spring units Fig.10.Example of air-inflated hardening structure228 Romuald Tarczewski scarped). Fig. 9 presents a comparison of shapes of cylindrical shells with variable rigidity. More sophisticated shapes can be achieved when rigidity is changing according to a parametric function. Fig. 9. Comparison of shells with variable rigidity 4.2 Adaptable – Hardening Structure Variation of rigidity allows constructing a structure that actively adapts to external loadings. If the internal lever arm increases together with increasing external loadings – deformations increment slowly. Load–deformation relation in this case is an exponentially growing function. If the internal lever in the structure can be self adjusted in order to find position of equilibrium, then the structure reveals a “hardening”characteristic. In numerous situations this specific type of structures is more advantageous than any other, with a linear response. An example of hardening system is described in [7]. Its application in pneumatic shells [8] is shown on Fig. 10. Fig. 10. Example of air-inflated hardening structure