Numerical Study of Concrete Beams with 3D Printed Strain-Hardening Cementitious Composites (SHCC) (2024-09)¶

Three-dimensional (3D) concrete printing technology is revolutionizing the construction industry, offering significantly improved productivity, cost-effectiveness, and design flexibility[1-3] Among the construction materials for 3D concrete printing, Strain-Hardening Cementitious Composites (SHCC) could be particularly promising due to their superior tensile and flexural properties[4, 5]. Despite these advantages, comprehensive numerical simulations of 3D-printed SHCC structures are still limited. Numerical simulation could provide a detailed, cost-effective, and comprehensive analysis solution for structural analysis, effectively managing complex geometries and material properties, which facilitates improved design and optimization. This study addresses this gap by exploring the flexural behavior of 3D-printed SHCC beams utilizing finite element analysis. Three-dimensional finite element models were developed using ABAQUS software to analyze the flexural behavior of 3D printed SHCC beams during four-point bending tests. The study varied two main parameters: the number of printed layers and the material properties of the SHCC, including elastic modulus, tensile ductility, ultimate tensile strength, and compressive strength. These parameters were systematically altered to observe their impact on the flexural behavior of the beams. The Mohr-Coulomb and Concrete Damaged Plasticity (CDP) models were applied to represent the elastic and plastic behaviors under flexural loads, respectively. Within the CDP framework, specific tailored tensile and compressive models for SHCC materials were employed. Interaction between SHCC layers in the 3D-printed beams was modeled using both surface-to-surface contact (two separatable surfaces that can transmit forces) and tie constraints (bind two surfaces together) as interaction modes. Additionally, loadings were applied in two directions to these layered SHCC beams to replicate various types of stresses encountered by 3D-printed structures, as shown in Fig. 1. The important findings of this study can be summarized as follows: 1. The flexural strength of 3D printed Engineered Cementitious Composite (ECC) beams is slightly higher with tie constraints than with surface-to-surface contact. 2. As the number of printed layers in layered ECC beams increases, there is a slight decrease in both flexural strength and normalized deflection capacity. 3. In addition to influencing flexural stiffness, the elastic modulus of ECC positively correlates with the flexural strength under loading conditions. 4. The tensile ductility and ultimate tensile strength of ECC show a linear relationship with both the flexural strength and deflection capacity of the beams, indicating a consistent pattern in how these properties interact. This research highlights the complexities and potential of using SHCC in 3D printed structures. The findings not only aid in optimizing structural designs but also pave the way for future investigations into more nuanced aspects of 3D printing in civil engineering. Continued advancements in numerical modeling methods including the improvement of contact model, comparative study with discrete element methods (DEM) simulation will be essential in better understanding material heterogeneity and improving simulation reliability. These steps are critical in advancing numerical modeling methods and fully leveraging the capabilities of this promising 3D concrete printing technology.