Innovative Design of Asia’s Largest Hangar Roof (I)

When designing an ultra-large-span maintenance hangar roof in a site with extremely low height restrictions, this study introduces a novel “W” shaped inclined truss roof structure system. This paper details the design scheme and innovative features of the “W” shaped inclined truss roof structure system, based on the design practice of the Southern Airlines Hangar at Beijing Daxing International Airport. Despite the structural height being limited to just 11.5 meters, this system successfully achieves an ultra-large span of 222 meters, with a steel usage of only 170 kg/m², demonstrating significant results. The application of inclined trusses has altered the unidirectional load characteristics of ultra-large-span maintenance hangar roofs, enhancing the spatial load-carrying capacity of the roof and effectively reducing the burden on the door-side trusses, making the construction of large-span maintenance hangars in extremely low height restriction areas feasible.

The Hangar 1 is located on the west side of the airport’s second runway, oriented west to east, and consists of a hangar hall and attached buildings along the rear and side walls of the hangar hall. The hangar hall has a plan dimension of 405 meters by 100 meters, with the center of the roof structure’s lower chord elevated to 30 meters. The roof is supported on three sides in plan view, with the side facing the apron designed as an open space. An electrically operated sliding door, which supports both vertical and horizontal loads, is installed on the open edge of the door, with a clear height of 26 meters. The roof also features a suspended equipment system, radiant heating, fire sprinklers, and associated maintenance walkway systems. The attached building includes three floors above ground and one below. A gap between the hangar hall and the attached building creates a separate structural system.

Hangar 1 can accommodate the maintenance of five large wide-body aircraft simultaneously, with narrow-body aircraft maintenance positions arranged between two large wide-body aircraft positions. The span direction of the door opening is 405 meters, with only one ground-supporting column allowed, and the door opening spans 222 meters plus 183 meters, making it an ultra-large-span hangar. Upon completion, this hangar will be the largest single-unit maintenance hangar in Asia. In addition to the significant challenge of the 222-meter ultra-large span to existing engineering capabilities, Hangar 1 also faces stringent design conditions: the construction site’s airspace height restriction is 40 meters, and the center of the roof structure’s lower chord is 30 meters. After accounting for the height required for the roof enclosure system, the structural height of the hangar hall area is restricted to within 8.5 meters. By fully utilizing the 4-meter clear height difference between the hangar door and the hall, the height of the door-side truss structure can be increased to 11.5 meters (see Figure 2). Compared to the scale of the proposed hangar, the construction site is classified as an ultra-low height restriction area.

To address these challenges, the design team implemented innovative solutions, characterized as follows:

1. Mitigating Design Difficulties:  

The use of inclined trusses and linear trusses altered the load transfer paths, shortening the force transmission routes and significantly enhancing the efficiency of the structural system. The roof loads are effectively divided, reducing the burden on the door truss by over 80% and significantly lowering the required span-to-height ratio. Calculations indicate that the inclined trusses carry over 80% of the static loads and over 88% of the live loads, becoming the primary vertical load-bearing components. The “W” shaped inclined truss system effectively transforms the 222-meter ultra-large span into an equivalent of a 100-meter conventional span, greatly improving the efficiency of the structural load transfer.

2. Shortening Construction Time:  

Compared to traditional design schemes, the inclined truss design reduces the number of members and nodes by more than 10%, shortening the ground assembly time for the roof steel structure by over 10%. Additionally, the large space of 4.25 meters in height and not less than 12 meters in width formed between the linear trusses can be used as a logistics passage and space for ground construction machinery, reducing the difficulty of assembling the roof steel structure and enhancing assembly efficiency.