Zhuojin Pipe Fitting Co., LtdShip Collision Test and Simulation of Sand-Filled Steel Pipe Pile Cofferdam
Literature Overview
This 2024 paper by Fang Hai, Ju Wei, Zhu Lu, Zhang Xinchen, and Yao Pengfei, published in China Journal of Highway and Transport, presents a novel ship collision protection system using steel pipe pile cofferdams filled with sand particles. The research combines scaled model testing (1:25 scale) with nonlinear finite element simulation to evaluate the collision energy absorption capacity of this innovative system. The study is particularly relevant to bridge engineering and steel pipe structural applications where ship impact protection is required.
Core Technical Content
The proposed protection system utilizes steel pipe piles arranged as a cofferdam around bridge piers, with the internal space filled with sand particles as an energy-dissipating material. This represents a permanent-temporary combined design approach that can serve as both construction cofferdam and permanent collision protection.
| Test and Simulation Parameter | Value / Result |
|---|---|
| Scale ratio | 1:25 |
| Peak collision force error (test vs. FEM) | Less than 10% |
| Impact depth error (test vs. FEM) | Less than 5% |
| Impact depth reduction rate (with protection) | 34.25% |
| Peak force reduction for 200,000 t vessel at 3.97 m/s | 38.11% |
| Number of collision scenarios analyzed | 4 groups |
The finite element model was validated against the scaled test results, demonstrating excellent agreement in both peak force and impact depth predictions. This validation is critical for extrapolating the results to full-scale engineering applications.
Steel Pipe Engineering Analysis
From a steel pipe manufacturing and welding perspective, this system presents several important technical considerations:
- Steel pipe pile specifications: The steel pipe piles used as cofferdam elements must meet stringent requirements for impact resistance. The material should exhibit good low-temperature ductility and fracture toughness, as impact loading can induce brittle fracture in susceptible steels. Recommended grades include API 5L X65/X70 or equivalent, with Charpy V-notch impact energy requirements at service temperature.
- Welding of cofferdam connections: The connections between steel pipe piles and the cofferdam framework are critical load paths during collision. These welded joints must be designed and executed to prevent brittle fracture under high-strain-rate loading. Friction stir welding (FSW) or submerged arc welding (SAW) with appropriate preheat and interpass temperature control would be preferred processes.
- Sand particle confinement: The interaction between the sand particles and the steel pipe pile walls creates a complex pressure distribution. The steel pipe must resist localized bearing pressure from the sand without local buckling, which requires appropriate wall thickness design.
Quality Control and Defect Analysis
For the steel pipe piles in this application, the following quality control measures are essential:
| Defect Type | Detection Method | Acceptance Criteria | Impact on Collision Performance |
|---|---|---|---|
| Longitudinal seam defects | UT (ultrasonic testing) | Per ASME V, Level 2 | Reduced wall thickness at seam, potential crack initiation |
| Surface cracks | MT (magnetic particle testing) | Zero tolerance | Stress concentration, fracture propagation |
| Wall thickness variation | UT thickness measurement | Within ±10% of nominal | Uneven stress distribution under impact |
| Residual stress | X-ray diffraction / hole drilling | Below 0.5σ_y | Risk of stress corrosion cracking |
| Hydrogen-induced cracking | Delayed crack observation | None after 48h | Sudden fracture under impact loading |
Engineering Practice Integration
The practical application of this system requires careful consideration of the following factors:
- The sand fill material must be properly compacted to ensure uniform density, as voids or loose zones can lead to asymmetric load distribution on the steel pipe piles.
- The steel pipe piles should be protected against corrosion in the marine environment, either through coating systems or cathodic protection.
- Periodic inspection of the steel pipe pile integrity is essential, particularly after collision events or during typhoon seasons.
The numerical simulation approach demonstrated in this paper provides a powerful tool for optimizing the steel pipe pile layout, spacing, and wall thickness for different vessel sizes and impact scenarios. Engineers can use parametric studies to balance cost-effectiveness with collision protection performance.
Study Insights and Conclusions
This research demonstrates the effectiveness of sand-filled steel pipe pile cofferdams as ship collision protection systems. The combination of scaled testing and validated finite element simulation provides reliable design data for full-scale applications. For steel pipe engineers, the key insight is that the collision protection performance depends not only on the structural design but also on the material properties and fabrication quality of the steel pipe piles. The system offers a dual-purpose solution that reduces overall project costs by combining temporary construction cofferdam with permanent collision protection. Future research should investigate the long-term durability of the system under cyclic marine environmental loading and the effect of sand degradation on collision protection capacity over time.