Mesoscale Analysis of RC Anchorage Performance in Multidirectional Reinforcement Using a Three-Dimensional Discrete Model

To investigate anchorage performance in a multidirectional arrangement of reinforcement bars, simulations are carried out using a three-dimensional discrete model, specifically the three-dimensional rigid-body-spring model (3D RBSM). In 3D RBSM, a material is partitioned into an assemblage of rigid bodies interconnected along their contact boundaries through discrete springs. In this study, for example, RC is meshed into rigid bodies with a size of 1-2 cm, where the opening, closing, and sliding of cracks can be modeled by the deformation or transmission of internal forces between two rigid bodies through the use of nonlinear springs along their contact boundaries. Simulations are conducted, one with the number of transverse reinforcement bars as a parameter and another varying the clear space between column reinforcement and embedded reinforcement in a congested joint. The results of these simulations are evaluated through comparison with experimental data; good agreement is observed with respect to anchorage capacity, crack pattern, and failure mode. The simulation results indicate the concrete strength is reduced if the reinforcement spacing between the column reinforcement and the embedded reinforcement is very close because of a nonhomogeneous behavior of concrete, where in the previous experiment large voids around reinforcing bars were observed. Simulations also suggest that the propagation of local cracks depends on the arrangement of reinforcing bars. This research shows how mesoscale analysis using the 3D RBSM can be a useful technique to consider the effect of a multidirectional arrangement of reinforcing steel that results in a complex stress and strain state due to the 3D bond transfer mechanism. It can be used for the design of a reinforcement arrangement in congested areas that is not addressed by the design code. As a result, a rational reinforcement arrangement can be designed on a case-by-case basis. (C) 2017 American Society of Civil Engineers.