Keywords: nonlinear analysis, bond-slip, tension-stiffening, boundary spring element, cracking behaviour, anchorage slip, rotating crack model, anchorage slip, biaxial stress.

The post-cracking behaviour of reinforced concrete (RC) structures depends on many influencing factors, the concrete crack, bond-slip effect and tension-stiffening effect. Shear wall structures especially experience a combination of axial and horizontal forces, given that the bond-slip effect dominantly occurs. Furthermore, making an analysis by considering the bond-slip effect is challenging because modelling the entire structure through a double node leads to an increase in the number of element nodes and the degrees of freedom.

When a RC shear wall is subjected to a gradually increased horizontal force, the cracking behaviour in the structure will be initiated at the bottom face of the RC wall, while accompanying the slip which causes delamination of the structure from the foundation and leads to rigid body motion. In particular, the occurrence of slip can be assumed as the total slip along the reinforcing bar embedded in the concrete matrix of the shear wall if the anchorage slip induced from the portion of the reinforcing bar sufficiently anchored into the foundation is relatively small.

In order to demonstrate the validity of the model introduced, the response of an anchored reinforcing bar subject to monotonic pull-out at one end is studied. The use of the numerical model makes it possible to construct a relationship between the steel stress and bond-slip at the loaded end. Moreover, on the basis of experimental data, a regression formula is introduced.

The perfect bond assumption case overestimates the structural response of the RC beam compared to the result considering the bond-slip. Therefore, the bond-slip effect must be taken into account to reach a numerical result that agrees fairly well with the experimental result.

In this paper, a numerical boundary spring element which can simulate the bond-slip effect without taking double nodes along the steel element over the entire domain of the RC beam and shear wall is introduced. Unlike the classical bond-link and bond-zone element which have the restrictions in the numerical modeling such as a reinforcing bar of a concrete element and a double node to represent the relative slip between reinforcing steel and concrete, the proposed model which does not take the double nodes can yield significant savings in the number of nodes needed to account for the effect of bond-slip, particularly, in three dimensional finite element analysis of RC structures.

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