To improve the multi-functionality of a structure, a foldable or deployable structure with variable stiffness is needed. This article presents dual-stiffness structures with two stiffness states: a stiff state and a flexible state for a multi-mission capability. This dual-stiffness structure is based on a hybrid structure that combines rigid and flexible segments; when the rigid segments are rearranged, the bending motion of the compliant material is constrained by the rigid segments, which varies the stiffness of the structure. Instead of continuously changing the stiffness, the dual-stiffness structure abruptly changes the stiffness state with a simple reconfiguring mechanism. We developed two reconfiguring mechanisms: a sliding mechanism and a folding mechanism. Using a layering process, the dual-stiffness structure with a two-dimensional multi-layer design was manufactured. To verify the behavior of the structure, a simplified structure with no sliding mechanism was designed and simulated using a finite element method. The ratio of the length of a rigid segment to the length of a compliant segment determined the stiffness of the structure. This dual-stiffness structure with the reconfiguring mechanism can be effective for applications that require a big change in stiffness, such as for a deployable solar panel, or flexible display.

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-In a high-rise building, stack effect occurs through a vertical passage, such as stairwell or elevator shaft due to a difference in indoor-to-outdoor temperature in winter and summer. Since this stack effect leads to adverse effects in terms of residential environment, energy and disaster prevention, there is a need to come up with the measures to control the pressure difference caused by the stack effect. In a recent research, a circulation-type stack effect control device for performing air supply and exhaust using a blower and a vertical airduct has been proposed as a method for active and quantitative control of the stack effect. In this study, useful measures that can control the stack effect in the stairwell of a high-rise building were developed through field experiments in a situation where the stack effect occurs, and the feasibility of the proposed stack effect control technique was reviewed through a fullscale experiment in the actual building during the winter season.