## 3 Printing Information Model for Additive Manufacturing of Concrete Structures
### Verification of the Printing Information
#### 3.3.2 Competency Questions
Owing to PIM-O, it has been possible to verify the PIM model in terms of correctness, scope, and reasoning, satisfying the requirements in concrete printing and enhancing the semantic expressiveness of the PIM model. Furthermore, the purpose of the PIM model has been validated by testing if the PIM model is capable of describing process, geometry, and material input parameters as well as material-process interactions in the simulation of an exemplary concrete printing project with the help of the PIM tool. The PIM model, being a metamodel, has been instantiated into the PIM tool, which is capable of processing and updating BIM models. With the PIM tool, algorithms are implemented to facilitate the design and planning of concrete printing projects based on a single metamodel, improving geometry conformity, manufacturability, and performance. The PIM model has thus proven to be suitable to describe parameters and material-process interactions in concrete printing for simple components and has the potential to describe complex components. Figure 9: Simulation of the concrete printing process of a cylindrical tank. The PIM approach has been proposed as a semantic modeling approach that can be easily understood, extended, and implemented by practitioners and researchers in concrete printing while providing knowledge-based reasoning capabilities. The PIM approach has been developed by combining known practices used for building information modeling and for ontology development. Compared to FIM-based frameworks [23], the PIM approach has attempted to describe material-process interactions in concrete printing by describing the semantic relationships between process parameters (e.g., _TolpathData_) and material parameters (e.g., _TemporalBehavior_). Compared to existing ontologies developed for AM [20], the PIM approach has discretized the material properties of concrete into fresh-state properties, hardened-state properties, and temporal behavior, aiming to describe the semantics of the hardening process of concrete. Furthermore, the PIM approach has coupled BIM and AM concepts by aligning the PIM model with the IFC schema to describe geometry features and building components. As has been corroborated in this study, efficient solutions to enrich BIM models are software tools implemented as add-ons for BIM platforms that can interpret, process, and update the information contained in the BIM models. Here, the PIM model, as a metamodel for AM of concrete structures, has easily been instantiated into a software tool written for designing and planning concrete printing projects. The potential of coupling AM data modeling and BIM concepts has already been extensively discussed in the literature [4], as BIM models may serve as the basis for complete digital models for concrete printing, including process-related, material-related, and geometry-related information. By enhancing the capabilities of BIM concepts, BIM models may shift from a functional focus to a manufacturing focus [23], following the fabrication information modeling concept discussed above, to match the demands for geometry, material, and process representations in concrete printing. Practical applications of the PIM approach have been showcased with the PIM tool as an implementation example. Specifically, the PIM model can be used as a basis to develop software tools, such as BIM-based plug-ins, and to design databases to store the data collected and generated in concrete printing in an efficient manner. Data from heterogenous sources, such as BIM models and finite element models, can be easily aggregated using the PIM model for data integration by assigning and interpreting semantic information. Furthermore, once databases have been populated with sufficient data, the PIM model may support knowledge-based reasoning to infer ideal process parameters considering material-process interactions within concrete printing.