Council on Tall Buildings and Urban Habitat
 

BSB Prefabricated Construction Method, Changsha
BSB Prefabricated Construction Method was recognized as an Innovation Award Winner in the 2013 CTBUH Awards Program.
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“You can see the mechanical engineering that permeates through this comprehensive innovation; as a group they have great potential for further development and innovation.”
- David Scott, Juror, Laing O’Rourke

Location
Changsha
Completion
2012
Height
100 m (328 ft)
Stories
30
Primary Use
Hotel

Owner/Developer
BROAD Group
Design Architect
BROAD Group

Structural Engineer
Beijing University of Technology; BROAD Group
MEP
BROAD Group
Project Manager
BROAD Group
Contractor
BROAD Group
Tall building designers have used prefabrication techniques on discrete elements for years, but never before has an entire prefabricated building system been developed to this degree. It is both a structural and mechanical engineering response to the demands of a rapidly urbanizing world. Integrating a bolted assembly technique with triple glazing, automatic blinds and air filtration systems, the BSB Method is a clear and innovative way of fundamentally rethinking tall building construction, and holds great promise for the future.

Tall building construction has always been a time-consuming enterprise, and it amplifies the widely acknowledged contribution of the building industry to landfill-bound waste. It is also a significant challenge to limit the energy consumption of massive buildings once constructed.
In observation of this challenge, BROAD Group devised the Broad Sustainable Building (BSB) technology, a prefabricated construction method that adopts modular design technology to vastly reduce the waste associated with construction. The aim of this process is to lower energy consumption, reduce environmental pollution, and save energy resources. The ultimate benefit will be the industrialization of the construction industry. BSB makes use of fabricated, diagonally braced joint steel frame structures, which offer resistance to earthquakes of a magnitude of 9 on the Richter scale, are 90 percent factory assembled, and produce buildings that contribute only one percent of the construction waste of a comparable conventionally built structure. From a structural perspective, the BSB system distributes stresses evenly and supports a high bearing capacity. The diagonally braced reinforced joint steel frame structure system consists of a main board, columns, and diagonal bracing.
Figure 1. Seismic test model of modular structural system Figure 2. Interior view of modular structural component
Construction members are factory made. The floor slab is made up of a concrete-filled, profiled steel sheet, which is affixed to steel beams – this creates a “board” module. Columns support the board; diagonal bracing is set between beams and columns. Heavy construction members are joined by high-strength bolts on-site. This approach helps to achieve the purpose of easy installation, easy disassembly, and easy maintenance, while still ensuring strength.
Figure 3. Recently completed modular components
The BSB project has changed the construction mode from an extensive construction process into a lean, sustainable production line. Only ten percent of construction time is on-site; the rest is inside the controlled conditions of a factory. Unlike conventional construction sites, in the factory there is virtually no risk of fire, no water or dust infiltration, no noxious odors, and no construction waste. Not only is environmental pollution reduced; the quality of construction, increase in productivity, and lowered cost of construction has significant implications for the future of building tall. On-site, workers lift boards, tighten bolts, and conduct painting. No sawing or welding is required, reducing the time spent, and noise and traffic disruption to neighboring communities. Beyond the improvements granted to basic structural erection, the BSB system employs more than 30 energy-saving technologies in interior and exterior assemblies. While three centimeters of thermal insulation is standard in China, BSB uses 20 centimeter panels and four-paned windows.
Figure 4. Placing completed modular components on-site
The mechanical systems are also pre-assembled at BROAD Group’s facilities. The heat-recovery fresh air system exchanges heat between outdoor fresh air and indoor exhaust air, recovering between 70 and 90 percent of the expended energy, providing extremely high indoor air quality.
The air filtration system is also prebuilt in the factory and optimized for areas with poor air quality, such as China’s urban regions. The initial stage of the system uses typical coarse filters that collect the largest particles. The second stage uses the Broad-specific electrostatic cleaner. Remaining particulates are removed in stage three by a HEPA filter. The final filtration efficiency can be as high as 99 percent. In a residential application, each room is equipped with a monitor that can check particulates, formaldehyde, and CO2 levels at any time, while comparing with outdoor conditions.

The process has been successfully implemented through the construction of the T30 Hotel, a 30-story, prefabricated hotel building in Xiangyin, Hunan Province. This construction project caught the world’s attention through the distribution of a YouTube video depicting its construction in just 15 days. BROAD Group has even higher ambitions for the technology: it has proposed to build the world’s next tallest building (at 838 meters) using the BSB Method in just nine months.
Figure 5. Exterior view of T30 Hotel
Related Links
CTBUH Skyscraper Center Profile:
T30 Hotel

BSB Prefabricated Construction Method was recognized as an Innovation Award Winner in the 2013 CTBUH Awards Program.

Download BSB Prefabricated Construction Method 2013 CTBUH Awards Book section
2013 CTBUH Awards Book
The CTBUH would like to thank BROAD Group for their assistance with this article.
Photography © BROAD Group