Anti-Prism Based Folded Plate Forms

What is an anti-prism based form?

Anti-prism based forms are among the bidirectional folded forms of folded plates. The folding pattern we achieve this form through is called Yoshimura, or Diamond pattern which is formed of obtuse angled isosceles triangles. These forms are unable to create flat surfaces due to their geometry and their cross sections are cylindrical.

Connecting the Plates

Among the stability factors of folded plates, dihedral angle of plates and hinges between them have great importance. A dihedral angle of 90 degrees seems to work the best in terms of stability and the ideal range of angle is 70 to 110 degrees. As for the hinges, their mechanics affect stability greatly as well as their axes. Bending moments are also transferred between plates, so the strength of hinges becomes crucial in resisting these forces. Axes of hinges are also critical, especially since Yoshimura pattern allows hinges in one of the two connections between plates. In order to achieve greater spans and enhance the axial property of hinges, we changed the isosceles triangles of Yoshimura pattern into isosceles trapezoids.

Reactions to Loads

Main structural property of folded plate structures is the transfer of load through inclined surfaces. In longitudinal direction inclined planes act like beams while in short direction folds act like rigid supports. The loads need to be transferred to the ground through either vertical support elements or other adjacent plates. In anti-prismatic folded structures, this occurs through adjacent plates. Since the top plates have lesser opportunities to transfer their loads vertically, maximum vertical displacement occurs at the top. Among many folded plate structures, anti-prismatic forms have the lowest amount of displacement. Among the reasons we have the deviation of central line from funicular curve. This deviation created by the magnitude of moments in anti- prismatic forms is closest to the smooth shell funicular curve, which means more stiffness in a plate structure.

 

Tensegrity

Tensegrity Systems

Tensegrity structure idea is based on the interaction of isolated components which are discontinuous elements in compression and continuous pre stressed tensile cables in tension. All elements are constantly in tension or compression so the structure works independently without any external force so tensegrity is always pre stressed. The interaction forms an integrated whole structure also It causes to have stable volume in space and rigidity in the structure. Tensegrity provides more minimal and lightweight qualities for the structural system.

Materials and Tension

The behaviour of discontinuous elements tends to buckling under a load. These elements are compressed and tendency is losing its straight shape. Also, the behaviour of the same elements is tension in the same direction without any load and It tends to be straight shape. That’s why, preferences of material is so crucial for tensegrity structure. The material must resist for buckling situation and It should be durable for traction forces. In the recent years main preference is using steel bars or struts for discontinuous elements.

Mini Explanations

• Pre-stresses of the continious tensile cables provides stability to integrated whole construct.
• Tip of the each struts should have at least 3 cables.
• The struts are arranged in non-touching manner.