Kadzielnia Amphitheatre

Description

In the historic place called Kadzielnia, located in the Polish city Kielce, the new amphitheatre with a membrane roof over the audience and the stage has been erected. The structure consist of a permanent roof over the scene and a retractable roof over the audience.
The area of the retractable membrane roof is about 2700m2 and of the permanent membrane roof 1500m2. The membrane roof over the audience is used only in the summer. The permanent roof over the scene must withstand a 1.8kN/m2 snow load. The span of the main cable over the scene is 35m and over the audience 55m. The rigid structure consists of two sets of columns (one behind the stage and one behind the audience), and a pendulum frame in the middle. The pendulum frame, with a span of 35m is stabilized by main cables.
The pendulum frame is foreseen as a garage for the folded membrane, which is stored during the winter. The technical solutions of the retractable roof were inspired by the retractable roofs at Fortress Kufstein designed by Alfred Rein Ingenieure and by these of the Frankfurt Stadium and Warsaw National Stadium designed by Schlaich Bergermann und Partner. Unique in the Kadzielnia amphitheatre structure is that the retractable roof is not built on a closed system. The edge cable of the retractable membrane deflects inwards during the process of folding and tensioning of the membrane. In order to enable large horizontal deflections of the edge cable, a special double hinge rotary head, connecting the cable to the column, was introduced.

Technical aspects - driving system
The mechanism of the roof tensioning consists of three main assemblies:
• cable winches
• hydraulic system
• automatic and calibration systems
The cable winch is installed on a column, where the main roof cables are installed as well. The winch frame is mounted on the rotary head of the column, therefore the position of the winch is adjusted to the changing direction (during tensioning of the roof) of the main cable. The unit of the servomotors is located on the winch frame and is responsible for: tensioning the cable unfolding the membrane (1), gripping the first membrane pulling trolley (2), final membrane tensioning (3) and locking the membrane in a final position (4). After the final locking of the membrane, all mechanical, hydraulic and controlling devices may be set off. In this stage the membrane is finally locked and preserved. The roof tensioning unit is controlled with an automatic system. The system is doubled and consists of the fixed desktop, installed on a control box and a movable radio desktop, enabling the supervision of the process from every section of the amphitheater. The controlling system enables permanent supervision of all mechanical and hydraulic devices as well as the supervision of devices installed individually on each particular column. The possibility of permanent supervision is very helpful during the membrane calibration.

Description of the environmental conditions