Zhuojin Pipe Fitting Co., LtdShaking Table Test Study on Steel Tube Concrete Inclined Column Conversion Structure in a Super High-Rise Building
Literature Overview
This paper by Yang Chun, Wu Hongwei, Mo Tingwei, Cai Jian, Wu Yi, Zuo Zhiliang, Chen Qingjun, and Pan Guangbin, published in Journal of Southwest Jiaotong University (2021, Vol. 56, No. 3, pp. 517–525), presents the results of a 1:35 scale model shaking table test on a super high-rise building featuring a steel tube concrete (STC) inclined column conversion structure. The building's tower is supported by two STC mega-frame columns, with an inclined column conversion system at floors 7–11. The study investigates the dynamic response, failure modes, and seismic performance of this structural system, with numerical analysis performed using PERFORM-3D software.
Core Technical Findings
Structural Configuration
The building under study employs a dual structural system: the tower portion is supported by two STC mega-frame columns that span multiple floors, and the transition between the tower and the supporting structure is achieved through an inclined column conversion system at floors 7–11. This configuration is typical of super high-rise buildings where architectural requirements necessitate a change in the structural system at different levels.
Dynamic Response Characteristics
The shaking table test revealed several important dynamic characteristics:
| Response Parameter | Key Finding | Engineering Significance |
|---|---|---|
| Natural periods | Consistent with numerical predictions | Validates analytical models |
| Inter-story drift angles | Generally within 1/100 limit at near-rare earthquake level | Structural safety is maintained |
| Torsional response | Significant torsion due to asymmetric layout | Torsional stiffness is inadequate |
| Failure mode | Torsional failure of tower portion at 470 cm/s² PGA | Capacity is reached at near-rare earthquake |
| Conversion zone | No damage observed in any test case | Conversion structure has adequate capacity |
The peak table acceleration of 470 cm/s² corresponds to a near-rare earthquake scenario. At this level, the tower portion experienced torsional failure, but the inter-story drift angles at most floors still satisfied the elastic-plastic drift limit of 1/100. The conversion zone, including the STC mega-frame columns and inclined columns, remained in the elastic range throughout all test cases, indicating that the conversion structure has substantial reserve capacity.
Numerical Validation
The PERFORM-3D nonlinear elastic-plastic analysis results showed good agreement with the shaking table test results, confirming the reliability of the analytical model. This agreement is important for the prediction of full-scale building behavior under seismic loading.
Engineering Practice Implications
The findings from this study have several important implications for the seismic design of super high-rise buildings with STC conversion structures:
- Torsional control is paramount: The asymmetric structural layout leads to significant torsional effects, which can govern the seismic performance even when the vertical load-bearing capacity is adequate. Engineers should pay close attention to torsional stiffness and consider measures such as increasing the torsional stiffness of the tower portion or improving the symmetry of the structural layout.
- Conversion structure capacity: The fact that the conversion zone remained elastic under near-rare earthquake loading indicates that the STC inclined columns and mega-frame columns have adequate capacity. However, this does not mean that the conversion structure is immune to damage under extreme events. Further investigation of the behavior under beyond-capacity loading is warranted.
- Performance-based design: The study demonstrates the value of performance-based seismic design for complex structural systems. The combination of shaking table testing and nonlinear numerical analysis provides a comprehensive understanding of the building's seismic behavior that cannot be obtained from code-based design alone.
Key Questions and Reflections
One significant question is whether the torsional failure observed in the tower portion could be mitigated by structural modifications. Options include increasing the torsional stiffness of the floor diaphragms, adding bracing elements, or modifying the layout to improve symmetry. The cost-effectiveness of these measures should be evaluated in the context of the overall structural design.
Another consideration is the scale effect. The 1:35 scale model may not fully capture the behavior of the full-scale structure, particularly regarding the concrete-steel interaction and the bond between the steel tube and the concrete core. The numerical model, calibrated against the test results, provides a reasonable prediction of full-scale behavior, but uncertainties remain.
Study Insights and Conclusions
This shaking table test study provides valuable experimental data on the seismic performance of STC inclined column conversion structures in super high-rise buildings. The key finding that the conversion zone maintains elastic behavior under near-rare earthquake loading is encouraging for the safety of such structures. However, the significant torsional response highlights the need for careful attention to torsional control in the design of asymmetric structural layouts. The good agreement between numerical analysis and test results validates the analytical approach for predicting the seismic behavior of complex STC structures. Engineers designing similar structures should consider performance-based design methods and incorporate torsional control measures to ensure adequate seismic performance.