Steel structures represent one of the three primary structural systems used in prefabricated buildings. They offer numerous advantages, including excellent seismic performance, high construction quality, straightforward manufacturing, rapid assembly, and environmental sustainability. In February 2016, the Central Committee of the Communist Party of China and the State Council issued the “Several Opinions on Further Strengthening the Management of Urban Planning and Construction” (Zhongfa [2016] No. 6). This document advocates for the advancement of new construction methods, actively promoting prefabricated buildings and steadily encouraging the development of steel structure buildings.
This article presents a case study of a commercial real estate network project in Shenyang. It primarily focuses on the technical innovations and applications of a new prefabricated steel structure enclosure system, analyzing both its cost-effectiveness and technical advantages. The steel structure prefabricated construction system features full assembly, completely dry construction, and all-season applicability. The building area cost index is approximately 1500 yuan per square meter, which is slightly higher than traditional reinforced concrete structural systems but remains more economical than prefabricated reinforced concrete buildings.
The standardized construction system for prefabricated steel structures builds upon traditional steel structural systems by employing standardized design principles. This approach integrates the four major subsystems of prefabricated buildings — structural framework, enclosure, equipment and piping, and interior finishes — through universal parts and components, adding complete decoration to form a novel prefabricated steel structure building system.
Key standardized components include box-shaped steel columns and H-shaped steel beams forming the main structure, prefabricated steel stairs, GRC floor panels, and GRC insulated integrated roof panels. The exterior protection system uses GRC insulation-integrated exterior wall panels, while interior partitions are constructed with GRC interior wall panels.
Project Overview: This commercial network project employs a comprehensive prefabricated steel structure. Prefabricated building manufacturers were engaged during the design phase to provide technical support, ensuring the integrated design and construction strategy of prefabricated buildings is fully realized.
Leveraging BIM technology and considering the manufacturing characteristics of prefabricated components, the project designs standardized components and connection nodes, especially for steel-framed lightweight floor panels, roof panels, and wall panel systems. This approach not only satisfies design requirements but also significantly reduces the variety of panel types and node configurations, simplifying construction and cutting project costs.
(Project construction site)
① Technology Application
The new prefabricated steel structure enclosure system demonstrates the following technical applications:
1. Steel Structure as the Primary Structural Form of Prefabricated Buildings
The project’s main body adopts prefabricated steel structures with green building characteristics. The design features bolted connection nodes, known for being lightweight, fast to assemble, reliable, and cost-efficient. The steel structure system closely integrates with the enclosure system, such as the commonly used steel column plus external wall panel configuration.
2. Information Management Platform Utilizing BIM Technology
Under the EPC model, a professional team supports detailed design coordination during the design phase through scheme planning, BIM guidance, and XSTEEL modeling. The procurement phase involves joint design and construction, establishing a standardized sampling process that controls the design, detailing, and production cycle within one month.
3. Prefabricated Decoration in Accordance with Relevant Policies and Standards
The enclosure system adopts a new dry-construction decoration method. Components are pre-fabricated in factories and assembled on site by industrial workers, ensuring high quality, fast installation, and zero pollution. The project uses integrated exterior wall and roof panels that combine decoration and structure, delivering superior quality and appearance compared to traditional methods, while maintaining controllable costs.
4. Integrated Insulation for Roof and Wall Panels
Insulation for roof and exterior wall panels is formed in one process, moving most production to factory settings. This reduces on-site disruptions and supports environmental protection efforts. The panels use eco-friendly raw materials, undergo strict factory testing, and are suitable for both indoor and outdoor applications.
5. Construction Efficiency
The prefabricated steel structure allows a construction speed of about 5 days per floor, improving efficiency by over 60% compared to concrete structure projects.
② Innovation Highlights
The new prefabricated steel structure enclosure system features the following technical innovations:
1. New Prefabricated Steel Structure Main System:
- Standardization: Modular design with advanced processing for the main structure, finishes, and components.
- Prefabricated Construction: Achieves 100% dry assembly through the steel structure prefabricated system.
- Integration and Efficiency: Utilizes standardized design and dry assembly to enable seamless process integration and maximize efficiency.
2. New Prefabricated Steel Structure Enclosure System:
(1) Lightweight
The lightweight steel-framed concrete slab weighs less than 800 kg/m³, approximately 30% of traditional concrete. This reduces steel use by around 35 kg/m² due to the slab’s lightness.
(2) High Load-Bearing Capacity
Using a composite structure of a light steel frame and high-strength inorganic lightweight core material, the slab maintains the load-bearing and safety characteristics of traditional reinforced concrete slabs. It supports uniform loads and has strong concentrated load capacity, making it an ideal alternative to conventional concrete roof panels and floor slabs.
(3) Excellent Durability
Careful selection of materials and construction methods yields a product lifespan of up to 50 years. The inorganic core offers stability, anti-aging properties, and durability comparable to concrete. Steel wire diameters are at least 3 mm with a protective layer thickness of 20 mm or more, and moisture absorption is below 0.1%.
(4) Integrated Insulation Panels
The panels provide outstanding insulation with a low thermal conductivity and overall heat transfer coefficient around 0.1 W/㎡·K, meeting energy-saving standards for high-altitude regions. Roof and exterior wall panels incorporate insulation layers whose joints are sealed on-site to satisfy insulation, fire prevention, and energy requirements. Subsequent leveling and waterproofing layers on the roof and walls follow conventional building methods.
(5) Superior Sound Insulation
Testing shows indoor noise levels without doors range from 42 to 55 decibels. With doors and windows installed, noise levels fall between 40 and 50 decibels. These results comply with the “Urban Area Noise Standard of the People’s Republic of China,” which limits daytime noise to 50 decibels and nighttime noise to 45 decibels. They also meet the “Residential Building Code” (GB50368-2005), which requires noise prevention measures in residential design and construction, with an allowable noise level of 50 dB during the day and 40 dB at night for bedrooms and living rooms with windows closed.
(6) High Seismic Performance
Steel skeleton panels are lightweight, enhancing earthquake resistance. With well-designed seismic nodes, they meet seismic fortification intensity requirements of 8 degrees. Additionally, the lightweight metal panels cause minimal secondary damage during earthquakes, making them ideal for buildings in seismic zones.
(7) Energy Efficiency and Environmental Protection
The steel skeleton board primarily uses natural inorganic materials that do not emit toxic substances. Its breathability contributes to a healthy and comfortable indoor environment.
(8) Ease of Use
Installation of steel-framed lightweight floor, roof, and wall panels is fast and involves fewer construction steps, significantly shortening the schedule. Panels can be customized in shape and size to accommodate openings and other requirements. They also provide practical solutions for installing skylights, ventilation equipment, lightning protection systems, and secondary finishes.
(9) Dry Winter Construction, Unaffected by Weather
All steel components and panels are fully prefabricated in factories and assembled on-site in sequence. The use of new external wall panel connection nodes greatly improves construction efficiency, shortens timelines, and ensures construction proceeds smoothly regardless of season.
(10) Low Maintenance
Steel-framed lightweight panels require no special maintenance during normal use and have low operating costs. Local damage can be repaired on-site, and individual panels can be replaced without impacting the overall structure.
③ Cost Analysis
Our company conducted a cost estimate for the steel structure prefabricated construction system used in this project. The construction area cost index is approximately 1500 yuan per square meter. This quotation covers manufacturing, transportation, and installation of the main steel frame, as well as GRC roof panels, floor panels, exterior wall panels with insulation, and panel jointing. It excludes block interior walls, exterior walls, facades, and architectural features.
The cost breakdown is as follows (note that costs may vary for projects outside the city):
The main structure costs approximately 1146 yuan per square meter, covering steel columns, beams, prefabricated steel stairs, GRC floor panels, as well as materials, processing, transportation, and installation of GRC insulation-integrated roof panels.
The enclosure structure costs about 367 yuan per square meter, including materials, processing, transportation, and installation of GRC insulation-integrated exterior wall panels.
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