Zhuojin Pipe Fitting Co., LtdComparative Test on Seismic Performance of Rectangular Steel Tube Concrete Frame Structures with and without Infill Walls
Literature Overview
This paper by Wen Yang, Guan Lipai, and Cai Meifeng, published in the Journal of Shenyang Jianzhu University (Natural Science) (2014, Vol. 30, No. 1, pp. 34-40), presents a comparative experimental study on the seismic performance of rectangular steel tube concrete (RCHS) frame structures with and without infill walls. The research was supported by the National Natural Science Foundation of China (Grant 51068021) and the Inner Mongolia Natural Science Foundation (Grant 2013MS0715). The authors conducted low-cycle reversed loading tests on RCHS frame specimens, with the column steel ratio as the comparative analysis parameter. The results show that the frame with infill walls has significantly higher load-bearing capacity than the frame without infill walls, and both configurations meet the ductility requirements for seismic design.
Core Technical Content
Test Specimen Configuration
The experimental program involved constructing RCHS frame specimens with and without infill walls, and subjecting them to low-cycle reversed loading to simulate seismic conditions. The column steel ratio was used as the comparative analysis parameter, which allows for a systematic evaluation of the influence of the steel-to-concrete ratio on the seismic performance of the frame.
| Test Parameter | Description | Comparison |
|---|---|---|
| Column steel ratio | Ratio of steel cross-sectional area to total cross-sectional area | Varied across specimens |
| Infill wall presence | With and without infill walls | Primary comparative variable |
| Loading protocol | Low-cycle reversed loading | Simulates seismic cyclic loading |
| Vertical load | Constant axial load on columns | Simulates gravity load |
| Ductility coefficient | Ratio of ultimate displacement to yield displacement | Key performance metric |
Seismic Performance Results
The experimental results reveal several important findings regarding the seismic performance of RCHS frames:
- Load-bearing capacity: The frame with infill walls has significantly higher load-bearing capacity than the frame without infill walls. The infill wall provides additional stiffness and strength to the frame, enhancing its resistance to lateral loads.
- Ductility: The frame without infill walls has a ductility coefficient ranging from 5.56 to 6.80, which meets the seismic design requirement. The frame with infill walls has a ductility coefficient ranging from 4.07 to 4.27, which is slightly lower but still meets the requirement of a ductility coefficient greater than 4.0 for ductile frames.
- Failure behavior: The frame with infill walls exhibits a more gradual failure process, even though its deformation capacity is slightly lower than that of the frame without infill walls.
Technical Analysis and Process Interpretation
Role of Infill Walls in Seismic Performance
The infill wall plays a dual role in the seismic performance of RCHS frames. On one hand, it provides additional stiffness and strength, which increases the load-bearing capacity of the frame. On the other hand, it can reduce the ductility of the frame by restricting the lateral deformation of the frame members. The experimental results show that this trade-off is acceptable, as the ductility of the frame with infill walls still meets the seismic design requirement.
Influence of Column Steel Ratio
The column steel ratio is a critical parameter that affects the seismic performance of RCHS frames. A higher steel ratio generally provides greater strength and stiffness, but it can also reduce the ductility by making the column more brittle. The experimental results provide guidance on the optimal steel ratio for achieving a balance between strength and ductility in RCHS frame structures.
| Column Steel Ratio | Load-Bearing Capacity | Ductility Coefficient | Seismic Performance |
|---|---|---|---|
| Lower ratio | Lower | Higher | More ductile but less strong |
| Higher ratio | Higher | Lower | Stronger but less ductile |
| Optimal ratio | Balanced | Balanced | Best overall seismic performance |
Integration with Engineering Practice
Design Recommendations for RCHS Frame Structures
Based on the experimental findings, the following design recommendations are made for RCHS frame structures:
- Utilize the beneficial effect of infill walls to enhance the load-bearing capacity of the frame, while ensuring that the ductility requirement is met.
- Select an optimal column steel ratio that provides a balance between strength and ductility, based on the specific seismic design requirements.
- Design the infill wall connections to the frame members to ensure proper force transfer and prevent premature failure of the infill wall.
- Implement quality control measures for the fabrication and installation of the rectangular steel tubes, including dimensional inspection, material certification, and weld quality control.
- Consider the interaction between the infill wall and the frame members in the structural analysis, using appropriate analytical models that capture the composite behavior.
Quality Control for Rectangular Steel Tube Fabrication
The fabrication quality of rectangular steel tubes is critical to the seismic performance of RCHS frame structures. The following quality control measures are recommended:
- Dimensional inspection to verify tube dimensions, including width, height, wall thickness, and corner radius
- Material certification to verify mechanical properties, including yield strength, tensile strength, and elongation
- Weld quality control including visual inspection, magnetic particle testing (MT), and ultrasonic testing (UT) of all welds
- Hydrostatic testing to ensure structural integrity and detect any internal defects
- Surface quality inspection to ensure smooth, defect-free surfaces for proper concrete infill bonding
Key Questions and Reflections
An important question arising from this research is the long-term behavior of the infill wall under repeated seismic events, considering factors such as cracking, deterioration, and loss of composite action. Another question concerns the interaction between the infill wall and the frame members under large lateral displacements, which may lead to unexpected failure modes. The study also raises questions about the applicability of the findings to different building heights and seismic design categories.
Study Insights and Implications
This literature provides valuable experimental data and design guidance for RCHS frame structures with and without infill walls. The finding that the frame with infill walls has significantly higher load-bearing capacity while still meeting the ductility requirement is a significant contribution to the field of seismic structural engineering. For steel pipe manufacturers, this research highlights the importance of producing high-quality rectangular steel tubes with accurate dimensional properties and appropriate material properties, as these directly influence the seismic performance of the frame. The overall contribution of this study to the field of seismic structural engineering is significant, providing both experimental data and practical design recommendations that can be directly applied in future projects to enhance the seismic safety of RCHS frame structures. The practical implication is clear: engineers should fully leverage the beneficial effects of infill walls in the seismic design of RCHS frames, while ensuring that the ductility requirement is met through appropriate design and quality control measures.