Linked Hybrid - An Open City Within A City
"The council of Tall Buildings and Urban Habitat (CTBUH) has recently awarded the Steven Holl Architects' Linked Hybrid Complex in Beijing as the 'CTBUH 2009 Best Tall Building Overall' selecting it from among various candidates from regions worldwide.
The CTBUH recognizes one outstanding tall building from each of four geographical regions: Americas, Asia and Australia, Europe, and Middle East and Africa annually. Recipients must possess seamless integration of architectural form, structure, and building systems, as well as exhibit sustainable design qualities working to preserve the quality of urban life and this year the honor goes to Steven Holl Architects' for their superb design of "Linked Hybrid Complex" in Beijing.
Commenting on the project during an award ceremony, CTBUH Awards Committee Chairman Mr. Gordon Gill stated, "This project is very rich in thought, both programmatically and architecturally. It presents an advances typology for dense urban living," whereas CTBUH Executive Director Antony Wood said, "This project 'Linked Hybrid' points the way forward for the intensified multi-use, multi-level connected cities of the future."
The 220,000 square-meter Linked Hybrid complex in Beijing, aims to counter the current urban developments in China by creating a twenty-first century porous urban space, inviting and open to the public from every side. A filmic urban experience of space; around, over and through multifaceted spatial layers, as well as the many passages through the project, makes the Linked Hybrid an "open city within a city." The project promotes interactive relations and encourages encounters in the public spaces that vary from commercial, residential, and educational to recreational; a three-dimensional public urban space.
|Location||: Beijing, China|
|Architect||: Steven Holl Architects|
|Client||: Modern Group|
|Floor area (square)||: 2383797sf/221462sm|
|Floor area (square) above||: 1753775sf/162931sm|
|Floor area (square) below||: 629635sf/58495sm|
|Building area (square)||: 2368060sf/220000sm|
|Structural Engineer||: Guy Nordenson and Associates: Derek Chan, Erik Nelson, Guy Nordenson, Claire Argow|
|Associate Structural Engineer||: Capital Engineering and China Academy of Building Research: Xiao Congzhen|
The ground level offers a number of open passages for all people (residents and visitors) to walk through. These passages include "micro-urbanisms" of small scale shops which also activate the urban space surrounding the large central reflecting pond. On the intermediate level of the lower buildings, public roof gardens offer tranquil green spaces, and at the top of the eight residential towers private roof gardens are connected to the penthouses.
All public functions on the ground level - including a restaurant, hotel, Montessori school, kindergarten, and cinema - have connections with the green spaces surrounding and penetrating the project. Elevators displace like a "jump cut" to another series of passages on higher levels. From the 18th floor a multi-functional series of skybridges with a swimming pool, a fitness room, a café, a gallery, etc., connects the eight residential towers and the hotel tower, and offers views over the unfolding city. Programmatically, this loop aspires to be semi-lattice-like rather than simplistically linear. Hope the public sky-loop and the base-loop will constantly generate random relationships; functioning as social condensers in a special experience of city life to both residents and visitors.
Focused on the experience of passage of the body through space, the towers are organized to take movement, timing and sequence into consideration. The point of view changes with a slight ramp up, a slow right turn. The encircled towers express a collective aspiration; rather than towers as isolated objects or private islands in an increasingly privatized city, the hope is for new "Z" dimension urban sectors that aspire to individuation in urban living while shaping public space.
Geo-thermal wells [660 at 100 meters deep] provide Linked Hybrid with cooling in summer and heating in winter, and make Linked Hybrid one of the largest green residential projects. The large urban space in the center of the project is activated by a greywater recycling pond with water lilies and grasses in which the cinematheque and the hotel appear to float. During winters the pool freezes to become an ice-skating rink. The cinematheque is not only a gathering venue but also a visual focus to the area. The cinematheque architecture floats on its reflection in the shallow pond, and projections on its facades indicate films playing within. The first floor of the building, with views over the landscape, is left open to the community. The polychrome of Chinese Buddhist architecture inspires a chromatic dimension. The undersides of the bridges and cantilevered portions are colored membranes that glow with projected nightlight and the window jambs have been colored by chance operations based on the 'Book of Changes' with colors found in ancient temples.
The project is a housing development for 622 apartments and a small hotel in eight interconnected towers. The towers are about 30m by 30m in plan with concrete flat slabs spanning between core and cross concrete shear walls and a perimeter concrete moment frame. The frame is a grid of uniform dimension interspersed with diagonal members. These diagonals occur on an adhoc basis where required for building cantilevers, overhangs and overall stiffness. Taking into consideration the substantial seismic demands of Beijing and the stringent code requirement of torsion, GNA undertook a number of design challenges: the core and cross concrete shear walls were used around the elevator shafts to provide a gravity load path for the long span flat plates and also substantial stiffness and resistance to seismic activity. Each of the seven bridges is isolated from the towers to minimize transfer from the bridge to the building tower.
The weight of the large cantilevers at the upper levels was decreased by using steel and concrete composite framing to cut down the self-weight. Lastly, systematic bracing members were added around the perimeter of the towers to increase torsional rigidity.
BridgesThe goal of the bridge structural design was to maximize transparency and create floating hallways of light, traversing 30 to 40 meters between the heavy concrete towers. In order to span the great distance required and also to achieve the utmost transparency, the bridges utilize a pair of parallel steel trusses (the truss being the most efficient form to resist flexure). A Pratt truss configuration was chosen to use thin tension only diagonal members and, in order to make the truss more elegant, the angle of the diagonals is variel, achieving a truss form with members oriented in such a fashion that the sizes of the diagonals have equal stresses, hence equal sizes. The connections between vertical and horizontal truss members were made rigid to form a complete three-dimensional rigid Vierendeel frame. This provides additional stiffness and redundancy to the bridge structure and allows for the removal of the center panel diagonal members.
The bridges are light and glass enclosed. In order to protect them from the effects of significant tower movement under an extreme seismic event, it was decided to isolate both sides of the bridges. The system selected was a "friction pendulum isolator" which is provided by Earthquake Protection Systems of California. The isolators are shaped with a radius to achieve a described period of vibration that will minimize the shear transfer by reducing the resonance. In an earthquake, the bridges will move up to 40cm relative to the buildings, sparing them, and the buildings, of the effects of lateral forces.