Abstract:
A possible source of seismic failure in existing reinforced concrete structures is loss of anchorage in column reinforcement, along deficient lap splices with short lap length and inadequate transverse reinforcement conditions. Reliable modeling of the bond slip behavior and anchorage failures in such columns is important for performance assessment of existing buildings using nonlinear static and dynamic analysis methods. In this study, a novel analytical modeling approach is proposed, for simulating the lateral load – deformation response of reinforced concrete columns with deficient lap splices. The modeling approach involves implementing bond stress vs. slip springs in the formulation of a fiber-based macro model. Through this methodology, local bond-slip behavior associated with both pullout failure of reinforcing bars and formation of splitting cracks in concrete can be characterized. The proposed model directly considers the influence of bond slip deformations on the lateral load – displacement response of a column under reversed cyclic lateral loading, and successfully represents the distribution of bond stresses and slip deformations, due to either splitting or pullout anchorage failures, along the lap splice region. The model successfully represents the distribution of local bond slip deformations along the length of a reinforced concrete column, as opposed to conventional methods where bond slip deformations are assumed to be localized at prescribed locations. The flexible formulation of the model allows investigating the influence of using smooth reinforcing bars, presence of 180-degreee hooks, the strain penetration effects on the response of a column. Response predictions of the analytical model were validated against results of cyclic tests on lap-splice-deficient column specimens, and the model was found to consistently represent the experimental behavior, both at global and local response levels, with a reasonable level of accuracy. Additional correlation studies conducted between model predictions and test results in the literature further verified that the model can effectively reflect the global response characteristics and failure modes of various column configurations incorporating either deficient lap splices or anchorage-deficient continuous reinforcement. Overall, the modeling approach proposed in this study is believed to be a significant improvement, towards realistic consideration of bond slip deformations and anchorage failures on the seismic response and performance of reinforced concrete structures.
