Zhuojin Pipe Fitting Co., LtdSeismic Performance Testing of Steel Tube Recycled Concrete Frames
Literature Overview
The 2016 paper by Meng Ercong, Wu Xiaoping, Yang Zhen, and Su Yisheng, published in the Journal of Guangxi University (Natural Science Edition), investigates the seismic performance of steel tube recycled concrete (STRC) frame structures from a structural-level perspective. Funded by the National Natural Science Foundation of China (Grant No. 51468003) and other institutional grants, the study addresses the growing need for sustainable construction materials in seismic-prone regions. The research is particularly significant given the increasing availability of recycled aggregate from demolished concrete structures and the imperative to reduce construction waste while maintaining structural safety.
Experimental Design and Test Methodology
Two full-scale single-bay, single-story frames were designed and fabricated with 100% recycled aggregate replacement in both the square steel tube recycled concrete columns and the reinforced recycled concrete beams. The beam section height was selected as the primary variable parameter to investigate its influence on seismic performance. Low-cycle reversed loading tests were conducted to simulate earthquake-induced cyclic loading, following established protocols for structural seismic testing.
| Specimen Parameter | Specimen 1 | Specimen 2 |
|---|---|---|
| Column type | Square steel tube recycled concrete | Square steel tube recycled concrete |
| Beam type | Reinforced recycled concrete | Reinforced recycled concrete |
| Recycled aggregate replacement | 100% | 100% |
| Beam section height | Lower (baseline) | Higher (increased) |
| Test method | Low-cycle reversed loading | Low-cycle reversed loading |
The test setup incorporated appropriate boundary conditions to simulate realistic frame behavior, with the columns fixed at the base and the beams loaded at the mid-span. Instrumentation included strain gauges, displacement transducers, and load cells to capture the complete load-displacement response and local deformation characteristics.
Key Experimental Results
The hysteresis curves of both specimens exhibited full, spindle-shaped loops, indicating good energy dissipation capacity. The equivalent viscous damping coefficient at failure (h_eu) exceeded 0.22 for both specimens, demonstrating that the STRC frames possess satisfactory energy dissipation performance comparable to conventional reinforced concrete frames. The story drift angle at failure was approximately 1/39, indicating good collapse resistance and ductility.
The influence of beam section height on seismic performance revealed a nuanced relationship. Increasing the beam section height improved the load-bearing capacity and initial elastic stiffness but reduced the ductility coefficient. More importantly, the effect on energy dissipation capacity was non-monotonic: before the peak load, increasing beam section height enhanced energy dissipation, but after the peak load, it reduced energy dissipation. The residual stiffness after peak load was relatively insensitive to beam section height changes.
| Performance Indicator | Lower Beam Height | Higher Beam Height | Interpretation |
|---|---|---|---|
| Peak load capacity | Lower | Higher | Greater cross-section provides more strength |
| Initial elastic stiffness | Lower | Higher | Greater section modulus |
| Ductility coefficient | Higher | Lower | Larger section reduces deformation capacity |
| Energy dissipation (pre-peak) | Lower | Higher | Greater stiffness increases energy per cycle |
| Energy dissipation (post-peak) | Higher | Lower | Greater ductility compensates for lower stiffness |
| Equivalent viscous damping (failure) | >0.22 | >0.22 | Both satisfactory |
| Story drift angle at failure | ~1/39 | ~1/39 | Comparable collapse resistance |
Engineering Practice Implications
The study provides valuable guidance for the design of STRC frame structures in seismic regions. The finding that 100% recycled aggregate replacement does not significantly compromise seismic performance is encouraging for sustainable construction practices. However, the non-monotonic relationship between beam section height and energy dissipation capacity suggests that designers must carefully optimize beam dimensions rather than simply maximizing section size for seismic resistance.
From a materials engineering perspective, the use of recycled aggregate introduces additional considerations regarding material quality variability, aggregate particle shape, and bonding characteristics with cement paste. The study's results suggest that these factors do not prevent the achievement of satisfactory seismic performance, but engineers should ensure proper quality control of recycled aggregate to maintain consistent material properties. The square steel tube columns provide confinement to the recycled concrete, which is particularly beneficial for compensating for any reduced concrete strength due to recycled aggregate use.
Study Insights and Outlook
This research makes a meaningful contribution to the field of sustainable structural engineering by demonstrating that recycled concrete can be effectively used in seismic-resistant frame structures without significant performance degradation. The structural-level testing approach provides more realistic insights than component-level tests, as it captures the interaction between columns, beams, and joints under cyclic loading. The nuanced findings regarding the influence of beam section height on energy dissipation capacity highlight the importance of balanced design optimization rather than simple strength maximization. As the construction industry increasingly adopts recycled materials to address environmental sustainability goals, this study provides experimental evidence supporting the seismic viability of recycled concrete in structural applications, which is essential for gaining acceptance from design professionals, building codes, and stakeholders in the construction supply chain.