The phoenix-shaped Beijing Daxing International Airport has become a new iconic building in the Chinese capital.
Designed by Zaha Hadid Architects, ADP Ingénierie and Beijing Institute of Architectural Design (BIAD), the terminal building has a total GFA of over 700,000m² and is designed to have a maximum capacity of 100 million passengers every year, relieving pressure on the Beijing Capital International Airport.
The new airport is also designed to be a super transportation hub for Beijing – beneath the terminal building there will be three underground railway stations with a total area of 200,000m² for five railway lines to allow easy transfer for passengers to various means of transportation.
In realising this second international airport for Beijing, Arup was appointed as the fire engineering consultant by the Beijing Institute of Architectural Design, and later to carry out peer review and value engineering for the steel roof structure by the Beijing New Airport Construction Headquarters.
100mannual passengers maximum capacity
170,000+steel members for the signature rooftop
While the flowing, interconnected form of the terminal building creates a stunning piece of architecture, it poses huge design challenges in terms of fire safety, which is further complicated by the transportation hub underneath with interconnected spaces treated as a single massive fire compartment.
Arup’s fire engineers took a performance-based design approach and adopted a series of fire protection strategies, including smoke curtains, fire shutters and fire separation bands to prevent the spread of fire and smoke from one fire control zone to another, replacing traditional solid walls that affect passenger circulation. High risk areas are fully contained with fire resistant construction. We also took advantage of the large atrium in the Central zone to control the smoke by buoyancy and dilution.
A smart egress strategy
Emergency egress presents another major design challenge due to the terminal’s vast size and the large number of occupants. The escape distance to outside is over 200m for most parts of the Central zone, whereas in a standard building this escape distance should be within 75m. A total of 29 egress stairs are thus provided in the Central zone to shorten the travel distance on various floors and help divert passenger flow to prevent bottlenecks.
Concerning the risk posed by baggage handling rooms on arrivals hall during evacuation, Arup proposed a smart egress strategy for the public space in the Central zone by providing different egress routes based on the fire location.
Optimising the roof structure
The roof of the terminal building is a large-span and complex hyperboloid steel grid structure covering over 350,000m² and containing more than 170,000 steel members. It is supported by giant C-shape columns seamlessly connecting with the roof curvature.
Arup engineers, with the help of in-house developed software, studied the structural configuration, loading, vertical support system reactions and the structural deflection and displacement. A total of 420 load combinations were considered and 38 different cross section sizes were employed in the superstructure. Our analysis revealed that there was room for design optimisation.
With extensive experience in longspan steel structures and structural design optimisation, Arup proposed various strategies for the different zones of the terminal to improve the roof truss patterns and reduce unnecessary structural depth and member sizing.
Efficiency is the key
Although the design of the steel roof had already been reviewed by several local design institutes prior to the peer review, Arup’s comprehensive optimisation strategies helped the project to achieve further reduction in steel tonnage, resulting in significant cost saving and reduction in carbon emission.
By realising the integration of the transportation hub and the terminal building – instead of placing them at separate locations – Arup’s solution will help to save over 1.6 million hours for nearly 30 million passengers every year.