Zhuojin Pipe Fitting Co., LtdSeismic Performance of Prefabricated Steel Pipe Recycled Concrete Frame Joints
Literature Overview
The paper by Bian Jinliang, Cao Wanlin, Zhang Zongmin, and Ye Taoping, published in Building Structures in 2021 (Vol. 51, No. 5, pp. 67–74), investigates the seismic performance of prefabricated steel pipe recycled concrete frame joints. The research was funded by the National Key R&D Program of China (Project 2018YFD1100903). The study proposes a novel dual-L-shaped stiffened rib joint configuration and conducts low-cycle reversed loading tests on four different joint types to evaluate and compare their seismic characteristics.
Joint Configurations and Test Program
The proposed dual-L-shaped stiffened rib joint consists of dual-L-shaped stiffened rib assemblies welded to the steel pipe column, a joint region steel pipe, and beam segment regions connected to the dual-L-shaped assemblies. Four joint types were tested:
| Joint Type | Description |
|---|---|
| Dual-L-shaped with stiffened ribs | Proposed joint with triangular stiffeners |
| Dual-L-shaped without stiffened ribs | Baseline prefabricated joint |
| Straight plate connection type | Direct plate-based connection |
| Welded type | Fully welded connection |
Low-cycle reversed loading tests were conducted on all four joint types to evaluate hysteretic behavior, ductility, stiffness degradation, and energy dissipation capacity under cyclic seismic loading.
Test Results and Comparative Analysis
The test results reveal significant differences in seismic performance among the various joint configurations. The welded-type joint exhibited relatively poor load-bearing capacity and ductility, which is consistent with the brittle failure characteristics commonly observed in fully welded steel connections under cyclic loading. Among the straight plate connection types, the dual straight plate connection demonstrated superior seismic performance compared to the triple straight plate connection.
The proposed dual-L-shaped stiffened rib joint showed substantial improvements in load-bearing capacity, stiffness, and energy dissipation capacity compared to all other joint types. The addition of triangular stiffened ribs to the dual-L-shaped configuration further enhanced the joint's seismic performance, with increasing stiffener height producing progressively better results.
| Performance Indicator | Welded Type | Straight Plate | Dual-L (No Stiffeners) | Dual-L (With Stiffeners) |
|---|---|---|---|---|
| Load capacity | Low | Moderate | High | Highest |
| Ductility | Poor | Moderate | Good | Excellent |
| Energy dissipation | Low | Moderate | High | Highest |
| Stiffness degradation | Severe | Moderate | Mild | Minimal |
| Construction simplicity | Complex | Moderate | Simple | Simple |
Welding and Fabrication Considerations
From a steel pipe fabrication and welding quality perspective, the dual-L-shaped stiffened rib joint design has several important implications. The joint relies on welded connections between the L-shaped assemblies and the steel pipe column, which requires careful attention to weld quality, including weld penetration, absence of porosity, and proper heat input control to prevent distortion of the thin-walled steel pipe section.
The use of recycled concrete in the frame system introduces additional considerations for the concrete-encased steel pipe interface. The bond between recycled aggregate concrete and the steel pipe surface may differ from that of conventional concrete due to the presence of residual mortar on recycled aggregate particles. This interface behavior affects the composite action between the steel pipe and the surrounding concrete, which in turn influences the joint's overall load-bearing capacity and ductility.
The prefabricated nature of the joint means that welding operations are primarily performed in controlled workshop environments rather than at the construction site. This is advantageous for weld quality control, as workshop conditions allow for better temperature control, proper ventilation, and the use of automated or semi-automated welding processes that produce more consistent weld quality.
Study Insights and Reflections
This research makes a significant contribution to the development of prefabricated steel-concrete composite structures with enhanced seismic performance. The dual-L-shaped stiffened rib joint concept demonstrates that relatively simple geometric modifications can produce substantial improvements in seismic behavior while maintaining construction simplicity. The finding that the welded-type joint performs poorly in seismic applications reinforces the well-known principle that ductile connections should be designed to avoid brittle weld failure under cyclic loading. For engineers involved in prefabricated building construction, this study provides validated design guidance for selecting appropriate joint configurations based on seismic performance requirements, and the proposed joint type represents a promising solution for seismic-resilient prefabricated steel pipe recycled concrete frame structures.