China Zun Tower / KPF / Beijing

China Zun Tower 

• Architects:  TFP Farrells, Kohn Pedersen Fox Associates, Beijing Institute of Architectural Design, CITIC General Institute of Architectural Design & Research Co., Ltd.
• Location:  Beijing, China
• Client:  CITIC HEYE Investment Co., Ltd.
• Structural Engineer:  ARUP, Beijing Institute of Architectural Design
• Structural Material:  Composite (Core: Concrete Encased Steel; Columns: Concrete Filled Steel; Floor Spanning: Steel)
• Building Type:  Headquarters, Supertall
• Size:  437,000 m2 / 4,703,828 ft2  
• Height:  528 m / 1,765 ft  
• Project Dates:  2012-2018
• Energy Label:  LEED-CS Gold Precertification, China Certificate of Green Building Label-Three Star  
• MEP Engineer:  WSP, Beijing Institute of Architectural Design
• Main Contractor:  China Construction Third Engineering Bureau Co., Ltd.  
• Cost Consultant:  China Construction Jingcheng Project Consultants, WT Partnership
• Energy Concept:  Azbil Control Solutions
• Facade Consultant:  ALT Limited
• Fire Consultant:  ARUP
• LEED Consultant:  EMSI
• Lighting Consultant:  Brandston Partnership Inc.
• Vertical Transportation:  WSP
• Wind Consultant:  RWDI, China Academy of Building Research
• Elevator Consultant:  KONE

CITIC Tower (China Zun)

CITIC Headquarters: A Finely Crafted-Vessel in the New CBD Core.

Located at the core of Beijing's new 30-hectare central business district, CITIC Tower is the tallest building and a new icon of the capital. CITIC Tower will be the flagship building of Beijing's comprehensively planned 30-hectare central business district core.

The tower's gently rising and curving form resembles an ancient Chinese ceremonial vessel, called the "ZUN." The design concept is that of a transforming shell that gradually bends to create a dramatic form. This concept is also applied to other key elements of the tower, including the entrances, ground floor lobby, and observation deck. At the base, the tower thrusts into the ground with massive corner supports, while the exterior shell is gently lifted up and stretched forward at the four sides. The design physically extends the lobby outward, forming dynamic drop-off spaces. At the top, the exterior envelope becomes more transparent at the observation deck and allows more visibility to the inner trumpet-shaped business center, which lights up at night, forming a beacon that will be visible throughout the city.

Compared to a typically straight or tapering supertall tower form, the concave tower profile offers more valuable prime-floor spaces and ample space for window washing, as well as other support systems, at the top of the tower. While the large poses significant structural challenges, the larger base provides an opportunity for structural balance, formal contrast and preferred core-to-perimeter distances.

In a city with the highest seismic fortification requirement of the major cities in China, the structural system was particularly sensitive to adjustments in the complex form of the building. Architects and engineers utilized parametric modeling to greatly expedite the design and coordination process to ensure that the design achieved both an iconic form and a solid structural system.

Overall Tower Design - 

The tower contains 350,000 square meters of Gross Floor Area spread over 108 floors above the grade. While the tower profile is curved, its floor plates are square with rounded corners. Combined with a square core, leasable interior office space is optimized. Below grade, there are seven floors totaling 87,000 square meters, primarily accommodating lower-floor office elevator lobbies, a bank, retail, building management, and parking spaces.

Exterior Envelope Design -

The tower envelope is divided into 128 panels per floor, with continuous vertical panel divisions. The vertical are grouped into alternating major and minor ribs. Continuous window washing tracks are housed in the middle of the major ribs, while LED lighting strips are embedded into the sides of the minor ribs. The vertical ribs helps to mitigate the complexity of the curtain wall. At the top of the tower, the major ribs extent the full height of the business center dining floor and the observation deck at levels 105 and 106. The minor ribs terminate at level 104 and are replaced by a tensioned cable system with horizontal glass fin bracing, affording a wider exterior view.

Structural Design -

Beijing has the highest seismic fortification requirement of China's major cities (PGA=0.20g for a 475 year return period). The structural system of a tower with such a height must find a proper balance between stiffness and ductility. The China Zun Tower has a narrow 'neck' and an enlarged 'head,' which contrasts with most high-rise buildings, that reduce width s height increases. The potential adverse effect of the additional mass located at the top was considered carefully in the structural design.

Conclusion -

China Zun Tower to achieve the following quantities: utilizing high operation efficiency, providing advanced and easy access, maximizing the floor usage, and maximizing the floor efficiency; minimizing the travel times and walking distance, applying reliable and safe technologies for high operation efficiencies and low maintains costs; providing comfortable working space in human scale and ecological atmosphere, exploiting sustainable design and green energy uses; applying reasonable cost control not only in construction but also in future maintenance and operation.