Experimental Study on Tensile Performance of Steel Pipe Grouting Sleeve Connections

Literature Overview

This paper by Chen Haibin, Wu Liwei, and Su Youpo from North China University of Science and Technology, published in World Information on Earthquake Engineering (2016, Vol. 32, No. 2, pp. 18-24), presents a systematic experimental investigation on the axial tensile performance of full-scale steel pipe concrete column grouting sleeve connections. The study was supported by multiple National Natural Science Foundation grants and addresses a critical junction in prefabricated structural systems. The research examined 27 full-scale test specimens under axial tension, analyzing the effects of grout strength and connection length on ultimate bearing capacity and bond strength.

Core Technical Findings

The experimental results reveal clear trends in the mechanical behavior of grouting sleeve connections. As grout strength increases, both the ultimate bearing capacity and the bond strength rise proportionally, which is consistent with the fundamental mechanics of adhesive interfaces. However, the relationship between connection length and bond strength shows an inverse trend: as the connection length increases, the bond strength decreases even though the ultimate bearing capacity continues to grow. This phenomenon reflects the well-known stress concentration and uneven bond stress distribution along the bonded interface, where shorter connections experience higher average bond stress but shorter specimens fail at lower total loads.

The authors provided regression-based estimation formulas for bond strength at connection lengths of 60 mm, 80 mm, and 100 mm. These formulas offer practical design tools for engineers working on prefabricated structures and offshore platform pile connections.

Welding and Manufacturing Considerations

From a pipe fabrication and welding perspective, the grouting sleeve connection introduces several quality control challenges. The sleeve-to-pipe fit tolerance is critical: excessive clearance leads to voids and poor bond formation, while interference fits can cause stress concentrations at the sleeve entrance. The grout material itself must exhibit controlled rheological properties to ensure complete filling without air entrapment, particularly in vertical or inclined assemblies. In practice, the grouting process should be monitored through acoustic emission or pressure drop methods to verify complete fill.

The bond strength formulas derived in this study should be cross-referenced with actual grout material specifications. Commonly used grouts in China include epoxy-based and cementitious formulations with compressive strengths ranging from 40 MPa to 80 MPa. The connection length-to-diameter ratio also plays a role, and engineers should ensure that the sleeve diameter and wall thickness are adequate to resist the applied tensile loads without local buckling.

Engineering Practice Implications

This research is directly applicable to offshore platform pile splicing and prefabricated building column connections. In marine environments, the grout must additionally resist chloride-induced corrosion and sulfate attack, which may degrade bond performance over time. For long-term structural integrity, periodic ultrasonic testing of the bond interface is recommended. The study's regression formulas provide a baseline, but site-specific calibration using pull-out tests on representative coupons is advisable before full-scale deployment.

Study Insights

The inverse relationship between connection length and bond strength underscores the importance of optimizing sleeve geometry rather than simply increasing connection length. An excessively long connection may mask localized bond failures while providing diminishing returns in efficiency. Engineers should aim for a balanced design where the connection length is sufficient to develop the required load transfer without creating unnecessary material costs or construction complexity.