Bond-Slip Performance of Steel Tubular Composite Piles

To investigate the bond-slip performance of steel tubular composite (STC) piles with shear ring, drilling mud skin and anti-corrosion coating, a new bond-slip constitutive model of the STC piles was proposed assuming an exponential trend of adhesion stress along the length of interface. The correctness of the model was then verified using five push-out tests of STC piles conducted in construction of the Hong Kong-Zhuhai-Macao Bridge, among which two tests adopted pile samples with shear ring. Results showed that under the external load the theoretical predictions of the bond-slip displacement between steel tube and concrete and the stress of steel pipes were consistent with the experimental results. The relative slip displacement between steel tube and concrete was less than 0.2 mm when the failure of piles was induced by the bond-slip behavior. The adhesion stress between the steel tubes and concrete was reduced by drilling mud skin and anti-corrosion coating. The average bond strength of STC piles was increased by 50% because of the shear ring when the spacing of shear ring was 1D (where D is the diameter of the pile), while adverse effects of drilling mud skin and anti-corrosion coating would be ignored under this condition. In addition, the exponential relationship between adhesion stress and the length of interface was observed.