Bond behavior between multi-strand tendons and surrounding grout: Interface equivalent modeling method

An interface equivalent modeling method is proposed in this study to describe the bond behavior between multi-strand tendons and surrounding grout. The interface equivalent principle is firstly proposed to determine the effective bond interface between tendons and grout considering the effects of the quantity, the arrangement and the space of strands. Then, the maximum bond stress of the multi-strand tendons provided by the interface is derived and incorporated into the existing bond stress-slip relationship to characterize the bond of multi-strand tendons. Subsequently, a pull-out numerical model incorporating the considered effects is developed to predict pullout forces-slip response for tendons. Finally, a direct pull-out test on three strands tendons is designed to verify the interface equivalent modeling method by comparing with the numerical and experimental results. The proposed method is also validated against previous experiment on seven strand tendons. Results indicate that the proposed interface equivalent modeling method can reasonably predict the bond behavior between multi-strand tendons and surrounding grout. The applicability and feasibility of the proposed equivalent modeling method is also investigated.