Norman Foster is known for his modern, energy-saving designs and innovative use of modern materials and advanced technology. Foster Partners, a team led by Norman Foster, believe in making the design sustainable as well as connect the users to natural daylight with high – tech materials. Khan Shatyr Entertainment Center is one such project, which is designed for the extreme climatic conditions, and at the same time serves as an example of neo-futuristic style architecture that creates an impact of emphasis in the skyline of Kazakhstan’s capital, Astana.
The tent-like structure gained recognition as the world’s tallest tensile structure, which rises 150 meters above the ground. This seven-storied structure which is 200 × 195 meters long covering an area of 100,000 square meters, houses leisure centers like boating river, an urban-scale park, mini-golf, swimming pool, and sandy beach, as well as shopping centers, restaurants, and cinemas, becoming a platform for cultural and social gathering for the people of Astana. It also acts as a space where people visit for relaxation from the extreme climate of Astana all year round.
The comfortable climate in extreme winters and summers is very well achieved by Foster + Partners, by using ETFE sheets over a network of steel cables that sits on a 90-meter high tubular steel tripod in the center, weighing 70 tons, which continues upwards to form a single mast until 150 meters. ETFE, i.e., Ethylene-tetra-fluoro-ethylene, is majorly used in the space industries. This material is used as a cushion in the Entertainment Center which is light-weight in nature and helps maintain a comfortable environment inside the structure. The material is also good for insulation.
The sustainable design approach provides a comfortable temperature between 15 degrees Celsius to 30 degrees Celsius inside the structure by creating the stack effect. The warm air is transferred from the shopping area planned inside the circumference of the base – to the central area – and then to the car park; thus reducing the energy consumption of the building and the fresh air load.
Creating a giant and free space with minimal support was the concept for the Entertainment Center which also led to the tent-like form of the structure. The one-sided pulled cone shape is also achieved by adjusting the interior spaces, giving it an identity of the Entertainment Center. This form tackles the harsh climate of the region, and also allows natural light to diffuse and flood in the interior spaces on each floor. This form also creates wavy terrace levels giving the users a flowy movement, and the sense of an entertainment hub, both physically as well as visually. Different kinds of plants border every floor and space, allowing the users to connect with the outside world of nature that is not seen around the region of Khan Shatyr Entertainment Centre.
The temperatures in Astana can be as high as +35 degrees Celsius in summers and can be as low as -35 degrees Celsius in winters. In winters, the three-layered ETFE cushions become cold due to the warm air that hits the colder surface, which immediately cools down and drops, creating an internal wind inside the building. This also stops the ice to form on the ETFE cladding. These cushions are 3.5× 30 meters and are light and economical material that can be recycled and do not degrade due to the harsh ultra-violet rays and environmental pollution. The large length of the ETFE cushions was planned to reduce their numbers and also for faster construction. These cushions also do not pose any threat to the ozone layer. ETFE cushions are non-stick, due to which, the dirt on the outside can be self-removed by rains. The swimming pool area of the Entertainment Center has a secondary ETFE cladding that avoids condensation on the main outer tent. It also leads to a warm environment in the swimming pool area all year. The ETFE cushions have only 1% of the weight of the glass.
The structure sits on a concrete base of the size of 200×195 meters. The network of steel cables meets on a ring 90 meters above the base level over the tripod. The radial steel cables that go with the form of the structure are pre-stressed against another set of cables – hoop cables, arranged perpendicularly, which together forms an anticlastic surface. This network of cables acts as tension elements which allow the entire structure to move due to the forces of wind and snow. This movement is in very small amounts. The high pre-stress of the cable forces is used in the tent that controls the deflection over the longest cable span. Also, the ETFE cushions are flexible enough to accept a large deflection of the network of cables. But, as the frames are rigid, the ETFE cushions are placed in a staggered manner.
This iconic structure creates an example of the use of advanced building material concerning the climatic condition of the region, and the form that serves the purpose of the space, altogether considering the impact on the skyline of Astana.