Seismic Performance of Steel Tube Concrete Frames with Infilled Walls

Literature Overview

The paper by Yin Yingzi, Li Bin, and Shen Xiangdong from Inner Mongolia Agricultural University and Inner Mongolia University of Science and Technology, published in Journal of Liaoning Technical University (Natural Science) in 2009, investigates the seismic performance of rectangular steel tube concrete (STC) frames with infilled walls. The study involves low-cycle reversed loading tests on two single-bay, two-story rectangular STC frames with infilled walls, examining their load-carrying capacity, ductility, energy dissipation capacity, and failure mechanisms. The research is funded by the Inner Mongolia Natural Science Foundation (200711020701) and addresses an important practical issue in earthquake-resistant structural design.

Test Configuration and Methodology

The experimental program involves two single-bay, two-story rectangular STC frames with infilled walls subjected to quasi-static cyclic loading. The rectangular steel tubes are used as both columns and beams, with concrete-filled steel tubes providing the primary structural elements. The infilled walls are typically masonry walls constructed between the steel tube frame members, which are common in practical construction for architectural and functional purposes.

Test Parameters

Parameter	Description	Significance
Loading protocol	Low-cycle reversed loading	Simulates seismic cyclic loading
Frame configuration	Single-bay, two-story	Representative of typical building frames
Column section	Rectangular steel tube with concrete infill	Primary structural element
Beam section	Rectangular steel tube with concrete infill	Primary structural element
Infilled wall	Masonry wall between frame members	Secondary structural element
Number of test specimens	2 frames	Allows for comparative analysis

Seismic Performance Evaluation

The seismic performance of the tested frames is evaluated through several key indicators. The hysteresis curves are described as full and plump, indicating good energy dissipation capacity. The frames exhibit stable post-yield load-carrying capacity, which is essential for maintaining structural integrity during earthquake loading. The failure mechanisms are analyzed to understand the structural behavior under increasing lateral displacement demands.

Key Performance Indicators

Performance Indicator	Observed Behavior	Seismic Design Implication
Hysteresis curve shape	Full and plump	Good energy dissipation capacity
Post-yield load capacity	Stable	Adequate strength reserve
Ductility ratio	Satisfactory	Adequate deformation capacity
Failure mode	Progressive	Warning before collapse
Stiffness degradation	Gradual	Acceptable for seismic design

The finding that the infilled walls contribute positively to the seismic performance of the STC frames is significant. Infilled walls are often considered detrimental in conventional reinforced concrete frames because they create weak-story mechanisms and increase seismic forces. However, in the STC frame configuration, the steel tube members provide sufficient ductility and strength to accommodate the additional stiffness and strength from the infilled walls without triggering premature failure.

Failure Mechanism Analysis

The failure mechanisms observed in the tested frames provide important insights into the structural behavior of STC frames with infilled walls. The rectangular steel tube columns and beams exhibit local buckling of the steel tube walls under cyclic loading, with the concrete infill providing additional confinement and delaying the onset of local buckling. The infilled walls crack and partially collapse under increasing lateral displacement, but the steel tube frame continues to carry the loads through the remaining structural elements.

The connection details between the steel tube members are critical for the seismic performance. Bolted or welded connections must be designed to accommodate the large deformations expected during earthquake loading. The concrete infill in the steel tube members provides additional stiffness and strength at the connections, which can be beneficial for overall frame performance but must be accounted for in the design.

Engineering Practice Implications

The research findings have direct implications for the seismic design of STC frame structures with infilled walls. The results suggest that STC frames can be used in seismic zones with appropriate design provisions, and that the presence of infilled walls does not necessarily compromise the seismic performance. However, the design must account for the interaction between the infilled walls and the frame, including the additional stiffness and strength contributions, the potential for wall-frame separation, and the modified failure mechanisms.

From a practical standpoint, the use of rectangular steel tube concrete frames with infilled walls offers several advantages over conventional reinforced concrete frames, including lighter weight, faster construction, better corrosion resistance, and improved seismic performance. These advantages make the STC frame system attractive for use in seismic regions, particularly in areas where construction speed and durability are important considerations.

Study Insights

This research demonstrates that steel tube concrete frames with infilled walls can achieve satisfactory seismic performance when properly designed and constructed. The full hysteresis curves and stable post-yield load capacity indicate that the composite action between the steel tubes, concrete infill, and infilled walls provides effective energy dissipation. The findings support the continued development and application of STC frame systems in seismic regions, with appropriate attention to connection design, infilled wall-frame interaction, and detailing provisions. Future research should extend to multi-story frames, different wall materials, and dynamic loading conditions to provide a more comprehensive understanding of the seismic behavior of these systems.