In this study, a numerical approach is developed for simulating the rate‐dependent behaviors of concrete without mesh sensitivity. The rheological units (e.g., dashpot) are integrated with the six directional springs in the rigid‐body spring network (RBSN) elements to reflect the rate‐dependent behavior of concrete. Previously, the viscoplastic damage model was associated with the elemental degrees of freedom. However, in the present approach, a viscoelastic constitutive law is newly defined for the normal direction as a function of the strain rate, from which the internal forces can be updated from the regularized elemental stresses. Such improvements are validated through the numerical simulations of the direct tensile test and spalling test using the modified split‐Hopkinson pressure bar (SHPB). The simulated results show consistent structural responses without mesh dependence on the strain rate. In addition, the influences of the softening curve shapes on the crack localizations are examined. It is shown that the rheological parameters can be optimized and determined for consistent applications through virtual experiments. The proposed numerical approach enables the mesh construction procedure without concerning the mesh‐size sensitivity due to the strain rate, and various applications are expected for the simulations of detailed numerical models of concrete materials and structures under high loading rates.

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To date, FRCCs (Fiber Reinforced Cementitious Composites) have been used with many different applications in various industries. However, the construction field has adopted this system relatively late compared to other industries. As this field shows an increasing need for FRCCs, research in this area has also expanded rapidly. Recently, various cutting-edge technologies have been integrated with the manufacturing of matrices and fibers to develop higher-performance FRCCs. However, the technologies involved in the current stage are usually focused on the development of material properties, the performances of matrix and fibers, and interfaces between matrix and fibers. Among the newly developed technologies, 3D printing has increased in popularity and has been favored over others. Many different applications are currently attempting to utilize 3D printing techniques to enhance performance in an innovative approach to the field of construction. Applications of 3D printing in this field have been developed for new materials and methodologies to print structures directly. In this study, reinforcements, including rebars and fibers, are printed using a 3D printer to make high-performing FRCCs and RC (Reinforced Concrete). In particular, when making FRCCs, fibers are usually mixed with the cement-based matrix during the process. In this method, the distribution of fibers is impossible to control because of the random nature of the fibers' positions. This study focuses on how fibers and reinforcement can be printed in a controlled manner. If the suggested new fiber and reinforcement printing process can be developed, mixing problems such as clumping, poor distribution, and difficulties during mixing will easily be solved with printed fibers and reinforcement using the SIFCON (Slurry Infiltrated Fiber Concrete) process.

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