Zhuojin Pipe Fitting Co., LtdExperimental Study on Bond-Slip Constitutive Relationship of Patterned Steel Tube Concrete
Literature Overview
This paper by Chen Lihua and colleagues from Hefei University of Technology, published in the Journal of Hefei University of Technology (Natural Science) in 2015, investigates the bond-slip behavior between patterned (corrugated) steel tubes and concrete. The research was supported by the Ministry of Housing and Urban-Rural Development Science and Technology Program (2013-k2-1). The study conducts push-out tests on nine specimens to develop a characteristic bond strength regression formula and a benchmark τ-Sf bond-slip constitutive model.
Core Technical Content and Experimental Design
The push-out test is the standard method for evaluating the bond performance between steel tubes and concrete infill. The experimental matrix considers two key variables:
| Variable | Levels Tested | Rationale |
|---|---|---|
| Pattern rib height | Multiple levels (low to high) | Primary factor influencing mechanical interlock |
| Concrete compressive strength | Multiple grades | Affects bond friction and chemical adhesion |
Bond-Slip Constitutive Model (τ-Sf Curve)
The proposed model divides the τ-Sf curve into three distinct stages:
| Stage | Description | Fitting Approach |
|---|---|---|
| Stage 1 (Elastic) | Linear relationship between bond stress and slip | Linear regression |
| Stage 2 (Plastic/Slip) | Rapid increase in slip with limited bond stress increase | Nonlinear curve fitting |
| Stage 3 (Residual) | Post-peak bond stress degradation and residual friction | Exponential or linear decay |
Key Experimental Findings
The research establishes that:
- Pattern rib height has a significant influence on characteristic bond strength — higher ribs provide greater mechanical interlock resistance.
- Concrete strength also affects bond strength, though the relationship is more complex than linear.
- The proposed τ-Sf constitutive model provides good agreement with experimental curves across all tested specimens.
Engineering Practice Implications
Patterned steel tubes represent an advanced CFST technology that enhances the bond between steel and concrete through mechanical interlock rather than relying solely on friction and chemical adhesion. From a steel pipe manufacturing perspective, producing patterned tubes requires specialized rolling or pressing equipment capable of forming consistent, controlled surface patterns without compromising the tube's structural integrity.
| Manufacturing Consideration | Technical Requirement | Quality Control Method |
|---|---|---|
| Pattern height uniformity | ±0.1 mm tolerance | Laser scanning or coordinate measurement |
| Pattern edge quality | No cracks or burrs at pattern transitions | Visual inspection + dye penetrant testing (PT) |
| Wall thickness after forming | Minimum wall thickness maintained | Ultrasonic thickness measurement (UT) |
| Material properties post-forming | No significant strength reduction | Tensile testing of formed specimens |
Key Insights and Reflections
The significance of this research extends beyond pure academic interest. In seismic design of CFST structures, the bond-slip behavior directly influences the energy dissipation capacity and ductility of the composite member. A well-characterized bond-slip model enables more accurate nonlinear finite element analysis, which is essential for performance-based design.
The finding that pattern rib height is the dominant factor suggests that designers can optimize the pattern geometry to achieve target bond strength levels while potentially using lower-grade concrete, resulting in cost savings. However, this optimization must be balanced against manufacturing constraints and the potential for pattern-induced stress concentrations that could affect the steel tube's local buckling resistance under compressive loading.