Three-Dimensional Fiber-Based Models of Precast and Cast-in-Place Reinforced Concrete Columns

Reliable and robust numerical modeling of RC columns under lateral load is commonly performed using one-dimensional elements. Although the strain is assumed to vary linearly through the section, bond-slip and buckling of reinforcing bars at the joints/connections contribute substantially to the column response. This paper presents a three-dimensional (3-D) fiber-based model with explicit representation of the bond-slip that occurs at the column-footing interface for cast-in-place columns and at the interface between bars and mechanical couplers for precast columns with grouted sleeve (GS) connections. The model contains beam elements with fiber sections for concrete, beam elements for longitudinal steel bars and sleeves, and spring elements for interfacial bond-slip behavior. The novelty is that the model can be achieved using existing software implementations, retains the efficiency of fiber-based elements under cyclic loading, and parameters are calibrated based on component-level testing, unlike other resultant or hybrid models that require arbitrary backbone and cyclic property specification. An extensive experimental program was conducted to investigate the behavior of GS couplers and calibrate the bond-slip models. Four large-scale RC columns were then used to verify the proposed model by comparing the measured load-displacement, energy dissipation, curvature, and failure mode with the numerical responses.