Zhuojin Pipe Fitting Co., LtdSeismic Performance of Prefabricated Double-Skin Steel Tube Concrete Frame with Beam-End Connected Steel Plate Shear Wall
Literature Overview
This paper by Zhao Junhai, Hu Yi, and Zhang Dongfang, published in the China Civil Engineering Journal in 2020 (Vol. 53, No. 5, pp. 78-88), presents a novel prefabricated structural system combining double-skin steel tube concrete (DSTC) frames with beam-end connected steel plate shear walls (BSW). The system incorporates prefabricated beam-column connections, prefabricated column-column splices, and prefabricated frame-to-shear wall connections, all achievable through full bolted assembly. Three 1:2 scale model specimens were tested under quasi-static loading to evaluate the seismic performance of this innovative system.
Core Technical Content
The proposed structural system addresses two major challenges in modern construction: the need for seismic resilience in tall buildings and the demand for prefabricated construction efficiency. The double-skin steel tube concrete column provides exceptional axial load capacity, ductility, and fire resistance due to the composite action between the inner and outer steel tubes and the concrete core. The steel plate shear wall, connected to the frame at the beam ends, provides lateral resistance and energy dissipation capacity.
Prefabricated Connection Technologies
The system incorporates three types of prefabricated connections:
- Prefabricated beam-column connections: Designed to achieve moment-resisting behavior through bolted connections with appropriate shear and moment transfer mechanisms.
- Prefabricated column-column splices: Bolted splices that maintain structural continuity while allowing field assembly of column segments.
- Prefabricated frame-to-shear wall connections: Beam-end connections that transfer both shear and moment between the frame and the BSW, ensuring composite action during seismic loading.
All connections are designed for full bolted assembly, eliminating the need for on-site welding, which significantly reduces construction time, improves quality control, and enhances construction safety.
Experimental Results
Three 1:2 scale model specimens were subjected to quasi-static low-cycle reversed loading. The key findings are summarized below:
| Performance Parameter | Result | Assessment |
|---|---|---|
| Maximum inter-story drift angle | Exceeds 4% | Excellent ductility |
| Displacement ductility coefficient | Exceeds 4 | Satisfies seismic design requirements |
| Failure mode | BSW buckling followed by tearing at frame connection, then frame plastic hinging | Progressive and predictable |
| BSW contribution | Provides first line of seismic defense | Effective energy dissipation |
| Frame contribution | Provides second line of defense | Redundancy ensured |
The failure sequence is particularly noteworthy. The BSW buckles first, forming a distinct tension band, then tears at the connection to the frame, and finally the frame forms plastic hinges at the beam-column joints and column base. This progressive failure sequence is ideal for seismic design because it provides multiple lines of defense and ensures that the structure degrades gracefully rather than collapsing suddenly.
Analysis of BSW Contribution
The study demonstrates that the BSW effectively improves the bearing capacity, stiffness, and ductility of the frame structure, and the improvement is approximately linear with the number of BSWs. This linear relationship is valuable for design optimization — engineers can predict the performance improvement by simply counting the number of BSWs installed. The BSW acts as the first line of defense, absorbing energy through buckling and plastic deformation before the frame itself reaches its plastic limit.
The prefabricated connection between the BSW and the frame was found to be reliable throughout the entire loading process, ensuring composite action between the BSW and the frame. This is critical because if the connection fails prematurely, the BSW cannot contribute effectively and the frame must resist the full lateral load alone.
Engineering Practice Implications
For engineers considering this system for practical application, several factors merit attention. The double-skin steel tube concrete column requires careful attention to the manufacturing and assembly of the inner and outer tubes. The gap between the tubes must be maintained consistently to ensure proper concrete filling and composite action. During column-column splicing, the alignment of the inner and outer tubes must be precisely controlled to avoid eccentricity that could compromise the structural performance.
The bolted connections require careful detailing. The bolt grade, hole tolerance, and connection geometry must be designed to achieve the required moment and shear capacity. Field assembly of bolted connections is generally more forgiving than welding, but the quality of bolt installation — including torque control and bolt straightness — must be rigorously inspected. Non-destructive testing of bolted connections, such as visual inspection and torque verification, should be part of the quality control plan.
The prefabricated construction approach aligns well with modern construction trends toward faster, cleaner, and more predictable construction schedules. However, the transportation and handling of prefabricated components must be carefully planned to avoid damage to connection details.
Study Insights and Reflections
This research represents a significant advancement in prefabricated seismic-resistant structural systems. The integration of DSTC columns with BSWs and fully bolted prefabricated connections addresses the dual goals of seismic safety and construction efficiency. The experimental results demonstrating drift angles exceeding 4% and ductility coefficients exceeding 4 are encouraging and meet or exceed the requirements of most seismic design codes.
From a welding and fabrication perspective, although the system emphasizes bolted connections, the manufacturing of the DSTC columns and BSW panels still involves significant welding. The welding of the outer and inner steel tubes, the welding of connection plates to the tubes, and the welding of BSW panels to their edge stiffeners all require careful attention to weld quality. Weld procedures should be qualified in accordance with relevant standards, and welders should be certified for the specific welding processes used. The heat-affected zone properties of the steel tubes, particularly if high-strength steel grades are used, must be verified to ensure adequate ductility in the welded regions.
The progressive failure sequence observed in the tests — BSW first, then frame — is the desired behavior for seismic design. Engineers should ensure that this failure sequence is maintained through proper detailing of the connections. If the BSW-to-frame connections are over-designed, the BSW may not buckle first, and the frame may be subjected to higher lateral loads than anticipated. Conversely, if the connections are under-designed, the BSW may separate from the frame prematurely, negating its contribution. The optimal design achieves a balance where the BSW yields and buckles before the frame reaches its plastic limit.
This system has significant potential for application in tall buildings in seismic regions, particularly where prefabricated construction is desired to reduce construction time and improve quality control. The experimental data and analytical framework presented in this paper provide a solid foundation for the development of design guidelines and code provisions for this structural system.