The Theme Pavilion designed by soma architecture from Vienna, Austria, is one of the central buildings of the Expo 2012 in Yeosu, South Korea. The main entrance and the side overlooking the expo site are characterized by a moving media façade, which draws attention on the Expo‘s theme The Living Ocean and Coast.
The basis for the development of the biomimetic façade was the analysis of natural movement principles found in the flora world. The use of glass-fiber reinforced plastics (GRP), which combine high tensile strength with low bending stiffness, allo- wed large reversible elastic deformations and thus enabled a completely new interpretation of convertible structures.
During the preliminary design phase various technical approaches were investigated, taking aspects of aesthetical and ar- chitectural influences on the kinetic media façade into consideration. The result of this process is a solution which perfectly reflects the competition idea of creating a seamless surface of 108 lamellas which changes its form through soft movements with a conceptually simple logic motion.
a) Large-scale, biomimetic deformation with minimal kinematics
A compressive stress is applied at the upper and lower ends of each lamella by actuators which causes an elastic bending deformation of the segments - the façade opens. The façade is adaptable both to necessary light conditions as well as to structural-physical conditions. Furthermore, by operating a special pre-programmed choreography, the kinematic facade acts as a moving focal-point for visitors to the Expo.
To transfer the choreography into a motion sequence of the lamellas, all 216 servo motors have to be activated and con- trolled by the coordinating control unit. Each actuator, a servomotor driving a ball screw spindel, is synchronized, whereupon sensors continuously check the lamella’s status and report appropriate data back to the server via a BUS-system. Upper and lower motors often work with opposite power requirements (driving – braking). Therefore generated energy can be fed back into the local system to save energy.
In order to use the lamellas as a media facade, they LED are positioned in a 10cm grid. Additional LED light strips fitted along the inside edges emphasize the deformation processes.
b) Adaptive pretension of the lamella against wind loads
To stabilize the flexible lamellas during typhonn loads, they are closed against each other. The soft edge of each lamella is stretched by means of actuators and the façade’s curvature is pressed against the rigid edge of the neighboring lamella. The applied pre-tension is gradually adjusted according to the wind load.
The adaptive adjustment has two advantages: Firstly, the strong pre-tension of the lamellas is only short-term and thereby reduces the material stress which positively influences their durability. Secondly, the overall performance of all simultane- ously active drives is reduced to 80kW. Thus, in normal operation all lamellas, and during the pre-tension process up to 13 lamellas, can all be moved simultaneously.