Experimental Study On Bond-Slip Behavior Of Large-diameter Steel Tubular Composite Pile

Steel tubular composite piles under the confinement effect of the steel tubular have many advantages such as the increasing of the strength of core concrete, lighter mass, better plasticity, fine resistance to impacting, fatigue and fire. The working performance of the steel tubular composite piles depends on the synergistic effects between the two materials of the steel tubular and the core concrete. So the bond-slip behaviors between the steel tubular and the core concrete have become the focus of the engineers recent years. By the model experimental verification, classical theoretical analysis and numerical analysis, this paper discuss the effect on the bond-slip behaviors and the integral rigidity of the pile from the drilling mud skin(thickness of0.1mm) and anticorrosion coating. The results are described as below:(1)The ultimate bond strength of the composite pile shows more between246and269KPa under the effect of the mud skin and anticorrosion;(2) The ratio of the flexural compression to the axial compression have a effect on the co-corporation performance of the steel tubular and the core concrete. The higher ratio makes the section of the pile much fit with the plane section assumption;(3) Through the comparative analysis, the bond strength decrease8%and4%separately due to the drilling mud skin and anticorrosion coating;(4) On the same load condition, the stress level of the steel tube with anticorrosion coating has increased comparing with the steel tube without anticorrosion coating while the steel level of the core concrete stay the same. The ultimate transverse displacement of the steel tube with anticorrosion coating is2%than the steel tube without anticorrosion coating. On the same condition, the ultimate transverse displacement of the steel tube with drilling mud skin increases3%than the steel tube without drilling mud skin;(5) In this test, the compressive stiffness and the flexural rigidity decrease4%and8%separately due to the drilling mud skin, and the drilling mud skin have little effect on the complex stiffness of the pile, within the limit;(6) In this test, the compressive stiffness and the flexural rigidity decrease4%and9%separately due to the anticorrosion coating, and the anticorrosion coating have little effect on the complex stiffness of the pile, within the limit;(7) The formula of the compressive stiffness and the flexural rigidity under the combination of the anticorrosion coating, the drilling mud skin and the shear ring is proposed; (8) The M-C penalty function is used to analyze the interface between the steel tube and the core concrete, and the small sliding formulation is adopted. The finite element results agree well with model test.μ the friction of the interface is0.3when there is only drilling mud skin.μ the friction of the interface is0.6when the anticorrosion coating exists, and μ the friction of the interface is0.6when the anticorrosion coating and the drilling mud skin exist.