Shake Table Testing of Steel Tube Concrete Inclined Column Transfer Structures in Super High-Rise Buildings

Literature Overview

The study conducted by Yang Chun and colleagues from South China University of Technology and Delft University of Technology investigates the seismic performance of a super high-rise building featuring steel tube concrete (CFST) inclined column transfer structures. Using a 1:35 scale model tested on a shake table, the research provides critical experimental data on the dynamic behavior, damage patterns, and seismic capacity of a complex structural system that combines CFST mega-columns with inclined transfer columns spanning multiple stories. The findings have direct relevance to the seismic design of modern super high-rise buildings in China and internationally, where architectural constraints often necessitate unconventional structural configurations.

Structural Configuration and Test Setup

The full-scale building features a tower supported by two CFST multi-story mega-frame columns, with a CFST inclined column transfer structure located at floors 7 through 11. The 1:35 scale model was designed to replicate the geometric and material properties of the full-scale structure, with appropriate scaling laws applied to ensure dynamic similarity. The shake table test employed progressively increasing ground motion intensities, culminating in a peak table acceleration approaching the rare earthquake design level of 470 cm/s².

The test instrumentation included strain gauges on the CFST mega-columns and inclined columns, displacement transducers at each floor level, and accelerometers to capture the dynamic response. The comprehensive instrumentation program allowed for detailed post-test analysis of member-level and system-level behavior.

Key Experimental Findings

The test results revealed several important structural behaviors that inform seismic design practice.

The most critical finding is that the transfer zone—often considered a vulnerable location in seismic design—exhibited no damage under all tested conditions, with strains in the CFST mega-columns and inclined columns remaining in the elastic range. This demonstrates the inherent robustness of CFST members in transfer applications, attributed to the composite action between the steel tube and concrete core, which provides both high strength and significant ductility.

However, the torsional behavior of the tower was identified as a critical weakness. The structural asymmetry inherent in the building plan generated significant torsional moments that ultimately led to torsional damage in the tower portion at the peak acceleration level. This finding underscores the importance of torsional analysis in seismic design, particularly for buildings with asymmetric mass or stiffness distributions.

Numerical Analysis Corroboration

The experimental results were compared with nonlinear finite element analysis performed using PERFORM-3D software on the full-scale structure. The numerical model captured the elastic and inelastic seismic response with good agreement to the test data, validating the analytical approach for use in design verification. The correlation between test and analysis provides confidence that the structural performance predictions are reliable across the full range of seismic intensities.

Engineering Practice Implications

For engineers designing similar CFST transfer structures, the following recommendations emerge from this study:

1. Torsional analysis must be performed at all seismic design levels, not merely as a check but as a primary design consideration for asymmetric structures.
2. CFST inclined column transfer structures demonstrate superior seismic performance compared to conventional transfer systems, making them a preferred choice for super high-rise applications.
3. The elastic strain behavior of CFST members under rare earthquake conditions indicates that the composite action provides adequate ductility, reducing the need for additional ductile detailing in the transfer zone.
4. Structural asymmetry should be minimized through plan layout optimization, or compensated through increased torsional stiffness elements such as outrigger trusses or belt trusses.
5. Shake table testing of scale models provides irreplaceable experimental validation for complex structural systems where analytical models may have significant uncertainty.

Reflections

This study reinforces the value of CFST technology in seismic-resistant design of super high-rise buildings. The composite action between steel and concrete provides not only high strength but also substantial energy dissipation capacity, which is essential for surviving rare earthquakes. The finding that the transfer zone remained intact while torsional damage occurred elsewhere is a valuable lesson: engineers should not focus solely on the transfer zone as the critical location but must also evaluate torsional vulnerability across the entire structure. In my professional experience, torsional damage has been the most common cause of seismic failure in tall buildings with asymmetric plans, and this study provides compelling experimental evidence to support that observation. The integration of shake table testing with nonlinear numerical analysis represents the gold standard for seismic performance evaluation, and I encourage engineers to pursue this combined approach for critical super high-rise projects.