Seismic Performance of Steel Tube Concrete Frame with Diagonally Stiffened Thin Steel Plate Shear Wall

Literature Overview

The paper by Wang Xiantie, Liu Lida, Gao Yajing, Ma Yusu, and Zhou Qinghan, published in the Journal of Xi'an University of Architecture and Technology (2015, Vol. 47, No. 4, pp. 503-510), presents experimental research on the seismic behavior of square steel tube concrete (STC) frame structures incorporating thin steel plate shear walls with diagonal cross stiffeners. Funded by the National Natural Science Foundation of China (Grant 51108369), the Shaanxi Provincial Young Science and Technology Star Project, and the Ministry of Housing and Urban-Rural Development Science and Technology Project, this study addresses a critical issue in modern seismic-resistant structural engineering: how to enhance the lateral load-resisting capacity of steel tube concrete frames through innovative shear wall design.

Core Technical Approach

Two single-bay, two-story specimens at a 1:3 scale were subjected to low-cycle reversed loading tests. The experimental program compared two configurations: (1) STC frame with diagonally stiffened thin steel plate shear wall (cross diagonal stiffeners), and (2) STC frame with unstiffened thin steel plate shear wall. The test objectives encompassed obtaining hysteresis curves, skeleton curves, characteristic loads and displacements, and quantitative seismic performance indicators including ductility, energy dissipation capacity, load-bearing capacity, and stiffness degradation.

Key Experimental Findings

The study demonstrated that diagonal cross stiffeners significantly improved both the strength and stiffness of the thin steel plate shear wall while effectively restraining out-of-plane deformation. This is particularly important because thin steel plate shear walls, while offering material efficiency, are inherently susceptible to local buckling under cyclic loading. The cross stiffener configuration creates a triangulated load path that converts membrane stresses into more stable compression and tension fields.

Technical Insights and Engineering Implications

From a steel pipe manufacturing and structural engineering perspective, several observations merit attention. First, the square steel tube concrete vertical edge members play a crucial role in ensuring the full performance realization of the thin steel plate shear wall. This implies that the connection quality between the steel tube columns and the steel plate wall—typically achieved through high-strength bolts or welded connections—must be carefully controlled. In practice, this means that the welding processes used at these critical junctions (likely GTAW or FCAW for structural steel) must produce full-penetration welds with acceptable HAZ properties to prevent premature failure at the connection interface.

The stiffener arrangement described in this study—diagonal cross configuration—aligns with the concept of forming a truss-like mechanism within the shear wall panel. From a fabrication standpoint, the stiffeners are typically flat steel bars welded to the steel plate surface. The welding quality at these stiffener-to-plate joints directly influences the effectiveness of out-of-plane restraint. In industrial practice, fillet welds with a leg size of at least 6 mm are commonly specified for stiffener attachments on shear wall panels.

The finding that the STC vertical edge members guarantee full performance development of the shear wall has direct implications for the design of steel tube concrete columns. The concrete infill within the steel tubes provides confinement and axial load capacity, while the steel tube itself contributes to shear resistance and torsional rigidity. The composite action between the steel tube and concrete is essential for maintaining the integrity of the shear wall boundary conditions throughout the seismic loading cycle.

Connection to Steel Pipe and Welding Practice

For engineers involved in steel pipe fabrication, this research highlights the importance of maintaining dimensional accuracy and surface quality in square steel tubes used for structural framing. Any ovality or out-of-squareness in the tubes can affect the fit-up of shear wall connections and the overall alignment of the frame. Furthermore, the residual stresses introduced during the welding of stiffeners and connections must be considered in the design of seismic-resistant details, as these stresses can reduce the effective yield strength and promote premature local buckling under cyclic loading.

Summary

This study provides valuable experimental evidence that diagonally stiffened thin steel plate shear walls, when integrated with steel tube concrete frames, offer superior seismic performance compared to unstiffened configurations. The key engineering takeaway is that the synergistic interaction between the stiffeners, the steel plate, and the concrete-filled steel tube edge members creates a robust lateral force-resisting system. For practitioners in steel pipe manufacturing and structural welding, the implications center on maintaining high fabrication quality, ensuring proper weld integrity at stiffener and connection interfaces, and understanding how residual stress distributions influence the cyclic behavior of the composite system.