Seismic Performance of Steel Tube Concrete Frame with Integrated Prefabricated Infill Walls

Literature Overview

The research by Zhou Zhongyi, Xu Zhiling, Tian Lizhu, Wang Tao, Li Yong, and Feng Aidong (2011), published in Journal of Harbin Institute of Technology, Vol. 53, No. 4, pp. 89-95, presents a full-scale low-cycle reversed loading test on a two-span, two-story steel tube concrete (SRC) column frame with integrated prefabricated infill walls. The study was conducted at the Key Laboratory of Earthquake Engineering and Engineering Vibration (Institute of Engineering Mechanics, China Earthquake Administration) and funded by multiple institutional grants. The primary objective was to verify the reliability of a flexible connection system between prefabricated infill wall panels and the SRC frame, thereby eliminating the adverse effects of infill walls on the seismic performance of the frame.

Structural Configuration and Connection Design

The key innovation in this study is the structural configuration that preserves the inherent advantages of SRC frames—high deformation capacity and excellent ductility—while incorporating prefabricated infill walls for architectural and functional purposes. The design employs two critical measures:

Gap provision: A deliberate gap is left between the SRC columns and the infill wall panels, preventing rigid contact that would transfer excessive lateral forces to the brittle wall panels.
Flexible connection: A flexible connection system is used between the infill wall panels and the steel beams, allowing relative displacement while maintaining overall structural integrity.

This configuration represents a significant departure from conventional infill wall design, where rigid connections between walls and frames often lead to premature wall failure and a reduction in the frame's ductility.

Test Results and Performance Indicators

Performance Indicator	Test Result	Engineering Significance
Hysteresis curve shape	Full and stable	High energy dissipation capacity
Ultimate drift angle	1/41	Exceeds typical code requirements
Post-peak load stability	Stable residual capacity	Good safety reserve
Wall panel damage onset	Delayed	Flexible connection effectively shields walls
Frame deformation capacity	Fully mobilized	SRC advantages preserved

The test demonstrated that even at a drift angle of 1/41, the overall structure maintained stable load-bearing capacity. This drift level significantly exceeds the typical 1/50 to 1/200 drift limits specified in seismic design codes for non-collapse performance, indicating substantial safety margins.

Engineering Practice Integration

For steel pipe and fitting engineers involved in the design and fabrication of SRC frames, this study provides critical guidance on the interface design between structural frames and architectural infill systems. The flexible connection concept must be carefully detailed at the fabrication stage, as the connection hardware (sliding bearings, elastomeric pads, or mechanical linkages) must be precisely manufactured and installed to function as intended during seismic events.

The study also highlights an important quality control consideration: the gap between the SRC column and the infill wall must be maintained throughout construction and service life. Any accidental closure of this gap—whether through construction debris, thermal expansion, or differential settlement—would fundamentally alter the load path and potentially trigger brittle failure modes. Engineers should incorporate construction tolerances and long-term serviceability requirements into the gap dimensioning.

Key Reflections and Implications

The successful demonstration of this system validates a design philosophy that steel pipe engineers should adopt: structural systems should be designed with clear load paths and defined deformation mechanisms, rather than relying on composite action between dissimilar materials. The SRC frame and the infill wall system are fundamentally different structural elements with different material properties, deformation capacities, and failure modes. By using flexible connections and deliberate gaps, the design ensures that each element performs its intended function without imposing unwanted demands on the other.

From a welding and fabrication standpoint, the SRC columns require high-quality welding of the steel tubes to the concrete encasement reinforcement, and the connection details between the steel beams and the flexible connection hardware must be designed for cyclic loading. Engineers should pay particular attention to the weld quality at these connection nodes, as cyclic loading can initiate fatigue cracks that may propagate during a seismic event. The use of full-penetration welds with proper pre-qualification procedures, in accordance with standards such as AWS D1.1 or ISO 3834, is essential for ensuring the long-term reliability of these connections.