Novel composite beam element with bond-slip for nonlinear finite-element analyses of steel/FRP-reinforced concrete beams

A new one-dimensional two-node layered composite beam element that accounts for the bond-slip between reinforcing bars and surrounding concrete is presented for nonlinear analysis of steel/fiber-reinforced polymer (FRP) concrete beams. A layered approach is used not only to represent the nonlinear material property accurately but also to model the bond-slip effect between the reinforcing bars and the concrete. In addition to the typical transverse displacement and rotation at the two nodes of the beam element, additional nodal degrees of freedom are introduced to represent the axial displacements of the reinforcements to account for bond-slip effect. Timoshenko's beam functions are employed for the displacement shape functions, and shear locking is avoided naturally. The element is validated against numerical examples and demonstrated to be accurate and computationally efficient for the analysis of steel/FRP-reinforced concrete beams with bond-slip.