Zhuojin Pipe Fitting Co., LtdSquare Steel Tube Concrete Frame with Diagonal Cross-Stiffened Thin Steel Plate Shear Wall Under Cyclic Loading
Literature Overview
This paper, authored by Wang Xiantie and colleagues from Xi'an University of Architecture and Technology and Chongqing University, presents experimental results from low-cycle repeated loading tests on three 1/3-scale single-bay two-story square steel tube concrete (SRC) frames incorporating thin steel plate shear walls (SSPW). The research was supported by the National Natural Science Foundation of China (Project No. 51108369) and published in the Journal of Xi'an University of Architecture and Technology, Vol. 48, Issue 1, 2016. The study specifically investigates the influence of two beam-column connection types — through-bolt end-plate joints and internal diaphragm joints — on structural performance, and compares the seismic behavior of diagonally stiffened SSPW against unstiffened SSPW configurations.
Core Technical Findings
The experimental program examined three key variables: the type of beam-column connection, the presence or absence of diagonal cross-stiffeners on the steel plate shear wall, and the interaction between the SRC frame and the infill shear wall panel. The specimens were tested under quasi-static cyclic loading to simulate seismic demand conditions.
Failure Modes and Ductility Characteristics
The test specimens exhibited distinct failure patterns depending on the stiffening configuration. Unstiffened thin steel plate shear walls showed pronounced out-of-plane buckling with significant pinching in the hysteresis loops, indicating reduced energy dissipation efficiency under large drift demands. The diagonally stiffened configurations effectively constrained out-of-plane deformation of the steel plate, resulting in more stable hysteresis curves with reduced pinching and improved cumulative energy dissipation capacity.
The through-bolt end-plate connection demonstrated superior joint zone stiffness compared to the internal diaphragm connection. This increased stiffness delayed the onset of column wall bulging, which is a critical failure mode in SRC columns where the infilled concrete interacts with the steel tube under combined axial and bending demands. The vertical edge members of the SRC frame played an essential role in ensuring that the thin steel plate shear wall could fully develop its performance potential by providing adequate boundary constraints.
Key Performance Indicators
| Performance Indicator | Unstiffened SSPW | Diagonally Stiffened SSPW | Improvement |
|---|---|---|---|
| Initial lateral stiffness | Lower baseline | Significantly higher | Enhanced by cross-stiffeners |
| Peak load capacity | Moderate | Higher | Cross-stiffeners increase resistance |
| Hysteresis pinching | Severe | Mildly reduced | Stiffeners constrain buckling |
| Energy dissipation | Reduced by buckling | Stable and efficient | Improved loop fullness |
| Ductility ratio | Moderate | Comparable or improved | Stable post-buckling behavior |
| Stiffness degradation rate | Rapid | Gradual | Controlled deformation mechanism |
Connection Type Analysis
The through-bolt end-plate joint and the internal diaphragm joint represent two fundamentally different load transfer mechanisms. The through-bolt end-plate connection relies on high-strength bolt groups to transmit shear and moment through the end-plate weld to the column flange, creating a semi-rigid to rigid connection behavior depending on bolt pretension and plate thickness. The internal diaphragm connection transfers forces through an internal plate that is welded to the beam web and bolted or welded to the column interior, providing a more compact but potentially less ductile connection.
From a welding and fabrication perspective, the through-bolt end-plate connection requires careful attention to the weld quality between the end-plate and the beam flange/web, as these welds are subjected to high cyclic stresses. The bolted interface must maintain adequate clamping force throughout the loading history to prevent slip and ensure moment resistance. The internal diaphragm connection demands precise fit-up and full-penetration welds between the internal plate and column walls, which presents challenges for inspection and quality assurance in the field.
Engineering Practice Implications
The findings from this study have direct relevance to the design of mid-rise and high-rise SRC structures in seismic zones. The following practical recommendations emerge from the research:
- Diagonal cross-stiffeners should be incorporated in thin steel plate shear wall designs where the plate thickness-to-width ratio is less than 1/100, as out-of-plane buckling becomes the dominant failure mode in such configurations.
- The through-bolt end-plate connection is preferred when joint stiffness is critical to the overall lateral load-resisting system performance, particularly in moment-resisting frame configurations.
- Vertical edge members in SRC frames must be designed with adequate wall thickness and concrete strength to prevent premature bulging that would compromise the shear wall performance.
- The interaction between the frame and the shear wall infill must be carefully controlled; excessive restraint can lead to brittle failure, while insufficient restraint allows the steel plate to buckle prematurely.
Study Insights and Reflections
This research demonstrates that the combination of SRC frames with diagonally stiffened thin steel plate shear walls offers a compelling structural system for seismic applications. The synergy between the ductile SRC frame and the energy-dissipating steel plate shear wall creates a structure with high load-carrying capacity, adequate lateral stiffness, and good energy absorption characteristics. The cross-stiffeners act as discrete buckling constraints that partition the steel plate into smaller panels, raising the critical buckling stress and enabling the plate to sustain larger in-plane membrane stresses before failure.
From a fabrication and welding standpoint, the addition of cross-stiffeners introduces additional weld details that must be designed and inspected according to applicable standards such as GB 50661 or AWS D1.1. The stiffener-to-plate welds are typically fillet welds that must achieve adequate throat thickness to transfer the membrane forces. The joint between the stiffener and the plate edge requires careful preparation to avoid stress concentrations that could initiate fatigue cracks under cyclic loading.
The study also highlights the importance of boundary conditions in SSPW systems. The vertical edge members in the SRC frame provide the necessary confinement and boundary support that allows the steel plate to develop its full tensile and compressive membrane stresses. Without adequate edge restraint, the steel plate would exhibit excessive out-of-plane deformation and reduced effective width, leading to premature capacity loss.