TY - JOUR A1 - Robens-Radermacher, Annika A1 - Schmidt, Wolfram A1 - Unger, Jörg F. A1 - Mezhov, Alexander T1 - Characterization of temperature influence on the structural build-up of 3D printed concrete N2 - 3D concrete printing technologies enhance design freedom while reducing material use and costs without the need for formwork. Thereby, structural build-up is the key property governing stability and early strength evolution of 3D printed concrete after placement. Structural build-up is influenced by various factors, i.e., environmental conditions such as temperature. In this paper, the influence of ambient temperature on structural build-up was investigated through experimental and numerical approaches. Three experimental setups (small amplitude oscillatory shear, constant shear rate, and small amplitude oscillatory extensional tests) were applied to materials of increasing complexity under varying temperature conditions. A common modeling framework based on the maturity approach was developed to capture the time and temperature evolution. A stochastic framework was employed to estimate the unknown model parameters using experimental data. Experimental results demonstrate a significant temperature influence on structural build-up, consistent across all test setups and materials. The calibrated models successfully predict the structural build-up under different temperatures, confirming the applicability of the maturity approach to rheological parameters at early age. Furthermore, the stochastic parameter estimation allows a correct quantification of the uncertainties, enhancing model reliability. The comparison of two time evolution formulations indicates that a model with an additional linear stage is required for predicting the increase of the storage moduli ( $${G}{\prime}$$ G ′ , $${E}{\prime}$$ E ′ ). In conclusion, the study demonstrates that temperature significantly affects the structural build-up, and that the proposed modeling approach allows to predict this behavior. KW - Structural build-up KW - 3D concrete printing KW - Rheology KW - Temperature influence KW - Modeling KW - Green intelligent building PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654138 DO - https://doi.org/10.1617/s11527-025-02931-3 SN - 1359-5997 VL - 59 IS - 2 SP - 1 EP - 20 PB - Springer Science and Business Media LLC AN - OPUS4-65413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosenbusch, Sjard Mathis A1 - Diercks, Philipp A1 - Kindrachuk, Vitaliy A1 - Unger, Jörg F. T1 - Integrating custom constitutive models into FEniCSx: A versatile approach and case studies N2 - The development and integration of user-defined constitutive relationships into finite element (FE) tools using standardized interfaces play a pivotal role in advancing the capabilities of FE solvers for structural mechanics applications. While commercial FE solvers like Abaqus and Ansys have designed their interfaces to provide custom stresses, tangents, and updated history variables, the open-source solver FEniCSx remains efficient only when the constitutive update has an analytical representation. This restricts the application of FEniCSx for non-linear structural mechanics. Since FEniCSx has become a powerful and popular open-source tool for solving partial differential equations, particularly due to its automatic computation of Hessians, we aim to develop a generalized interface to enhance its capability for constitutive modeling. This approach will address complex constitutive equations that require iterative solutions at the quadrature point level. Specific implementation challenges, such as using return-mapping procedures, can then be managed commonly. The provided interface for custom constitutive models offers a versatile way to implement them in various languages, including C++, Python, Rust, and Fortran. Finally, with UMATs for viscoplastic models as an example, we demonstrate how existing user subroutines can be incorporated into the interface and utilized within the FEniCSx framework. KW - Finite element method KW - Constitutive models KW - FEniCSx KW - UMAT KW - Rust KW - Python KW - C++ PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-630439 DO - https://doi.org/10.1016/j.advengsoft.2025.103922 SN - 0965-9978 VL - 206 SP - 1 EP - 11 PB - Elsevier CY - Amsterdam AN - OPUS4-63043 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jafari, Abbas A1 - Vlachas, K. A1 - Chatzi, E. A1 - Unger, Jörg F. T1 - A Bayesian framework for constitutive model identification via use of full field measurements, with application to heterogeneous materials N2 - In this paper, we present a Bayesian framework for the identification of the parameters of nonlinear constitutive material laws using full-field displacement measurements. The concept of force-based Finite Element Model Updating (FEMU-F) is employed, which relies on the availability of measurable quantities such as displacements and external forces. The proposed approach particularly unfolds the advantage of FEMU-F, as opposed to the conventional FEMU, by directly incorporating information from full-field measured displacements into the model. This feature is well-suited for heterogeneous materials with softening, where the localization zone depends on the random microstructure. Besides, to account for uncertainties in the measured displacements, we treat displacements as additional unknown variables to be identified, alongside the constitutive parameters. A variational Bayesian scheme is then employed to identify these unknowns via approximate posteriors under the assumption of multivariate normal distributions. An optimization problem is then formulated and solved iteratively, aiming to minimize the discrepancy between true and approximate posteriors. The benefit of the proposed approach lies in the stochastic nature of the formulation, which allows to tackle uncertainties related to model parameters and measurement noise. We verify the efficacy of our proposed framework on two simulated examples using gradient damage model with a path-dependent nonlinear constitutive law. Based on a nonlocal equivalent strain norm, this constitutive model can simulate a localized damage zone representing softening and cracking. The first example illustrates an application of the FEMU-F approach to cracked structures including sensitivity studies related to measurement noise and parameters of the prior distributions. In this example, the variational Bayesian solver demonstrates a sizable advantage in terms of computational efficiency compared to a traditional least-square optimizer. The second example demonstrates a sub-domain analysis to tackle challenges associated with limited domain knowledge such as uncertain boundary conditions. KW - Constitutive model identification KW - Full-field measurements KW - Variational Bayes KW - Force-based finite element model updating KW - FEMU-F PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-615476 DO - https://doi.org/10.1016/j.cma.2024.117489 SN - 1879-2138 VL - 433 IS - Part A SP - 1 EP - 32 PB - Elsevier B.V. AN - OPUS4-61547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bos, Freek A1 - Menna, Constantino A1 - Robens-Radermacher, Annika A1 - Wolfs, Rob A1 - Roussel, Nicolas A1 - Lombois-Burger, Hélène A1 - Baz, Bilal A1 - Weger, Daniel A1 - Nematollahi, Behzad A1 - Santhanam, Manu A1 - Zhang, Yamei A1 - Bhattacherjee, Shantanu A1 - Jia, Zijian A1 - Chen, Yu A1 - Mechtcherine, Viktor T1 - Mechanical properties of 3D printed concrete: a RILEM TC 304-ADC interlaboratory study — approach and main results N2 - To show compliance to structural engineering codes and implement quality control measures, it is critical to obtain reliable mechanical properties of the materials in question. For conventional cast and precast concrete, the experimental procedures and relationships between mechanical properties, the material composition, and the production methods are globally known, but for 3D concrete printing (3DCP), these relations have not yet been established. Previous studies have shown little consistency in results, and the underlying experimental methods have not been established broadly. There is an urgent need to address these issues as the application of 3DCP in practice projects is growing rapidly. Therefore, RILEM TC 304-ADC: Assessment of Additively Manufactured Concrete Materials and Structures has set up a large interlaboratory study into the mechanical properties of 3D printed concrete. This paper presents key elements of the experimental approach detailed in the Study Plan and the supporting considerations. Furthermore, it reports on the response, consisting of 34 contributions from 30 laboratories, detailing global coverage, properties of the applied mixture designs and characteristics of the printing facilities that have been used. Subsequently, some fundamental results from compression, flexural, and E-modulus testing are presented and—considering cast specimens as a reference—discussed. On average, a reduction in strength was found in compression and E-modulus (all tested orientations). For flexure, on the other hand, an increase was found in two testing orientations, while a decrease was observed in the third orientation. Importantly, even though the applied experimental methods were found to be reasonably appropriate to obtain the required data, the differences found between individual contributions are significant and sometimes non-consistent, suggesting that testing on specific material-facility combinations is necessary to reliably determine the mechanical properties of objects produced from them. Furthermore, a theoretical framework needs to be developed to further explain the variations that were observed. Extensive analyses of all acquired data are out of the scope of this contribution, but presented in two associated papers, whereas a third presents the data management approach used to process the approximately 5,000 test results. KW - 3D printed concrete KW - 3DCP KW - Mechanical properties KW - Interlaboratory study PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634631 DO - https://doi.org/10.1617/s11527-025-02686-x VL - 58 IS - 5 SP - 1 EP - 29 PB - Springer Nature AN - OPUS4-63463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Robens-Radermacher, Annika A1 - Kujath, Cezary A1 - Bos, Freek A1 - Mechtcherine, Viktor A1 - Unger, Jörg F. T1 - Mechanical properties of 3D printed concrete: a RILEM TC 304-ADC interlaboratory study-Design and implementation of a database system for querying, sharing, and analyzing experimental data N2 - Interlaboratory studies are essential for implementing standardized test methods for new innovative materials or technologies such as 3D concrete printing, certifying reference materials, and validating methods. They provide the basis for recommendations and design standards. Typically, the collected data are used only for one study and are published in paper form, without open access to the raw data files. However, preserving the collected data and analysis procedures in a shareable and reusable way leads to advantages for further usage. New data with the same structure can be added or the data can be analyzed by a new analysis procedure generating new knowledge. Additionally, resources are saved by avoiding the repetition of the same measurements. In line with the recent digitalization trend in material science and engineering, a database for the interlaboratory study on mechanical properties of 3D printed concrete conducted in RILEM Technical Committee 304-ADC is established. The challenges and experiences from defining the data structure, uploading the data, and using the database for evaluations are discussed. The openBIS software is used to create and fill the database, while an export method to an SQLite format is developed and discussed to generate a shareable and reusable database. With the exported database, querying the data is possible independently of a particular data management system. Additionally, examples of data processing with reusable workflows automating the analysis procedure are demonstrated. KW - Data management KW - Interlaboratory study KW - 3D concrete printing KW - Database KW - Reusability PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634627 DO - https://doi.org/10.1617/s11527-025-02650-9 SN - 1871-6873 VL - 58 IS - 184 SP - 1 EP - 37 PB - Springer Nature AN - OPUS4-63462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wolfs, Rob A1 - Versteegen, Jelle A1 - Santhanam, Manu A1 - Bhattacherjee, Shantanu A1 - Bos, Freek A1 - Robens-Radermacher, Annika A1 - Muthukrishnan, Shravan A1 - Menna, Costantino A1 - Ozturk, Onur A1 - Ozyurt, Nilufer A1 - Roupec, Josef A1 - Richter, Christiane A1 - Jungwirth, Jörg A1 - Miranda, Luiza A1 - Ammann, Rebecca A1 - Caron, Jean-François A1 - de Bono, Victor A1 - Monte, Renate A1 - Navarrete, Iván A1 - Eugenin, Claudia A1 - Lombois‑Burger, Hélène A1 - Baz, Bilal A1 - Sinka, Maris A1 - Sapata, Alise A1 - Harbouz, Ilhame A1 - Zhang, Yamei A1 - Jia, Zijian A1 - Kruger, Jacques A1 - Mostert, Jean‑Pierre A1 - Šter, Katarina A1 - Šajna, Aljoša A1 - Kaci, Abdelhak A1 - Rahal, Said A1 - Snguanyat, Chalermwut A1 - Arunothayan, Arun A1 - Zhao, Zengfeng A1 - Mai, Inka A1 - Rasehorn, Inken Jette A1 - Böhler, David A1 - Freund, Niklas A1 - Lowke, Dirk A1 - Neef, Tobias A1 - Taubert, Markus A1 - Auer, Daniel A1 - Hechtl, C. Maximilian A1 - Dahlenburg, Maximilian A1 - Esposito, Laura A1 - Buswell, Richard A1 - Kolawole, John A1 - Isa, Muhammad Nura A1 - Liu, Xingzi A1 - Wang, Zhendi A1 - Subramaniam, Kolluru A1 - Mechtcherine, Viktor T1 - Mechanical properties of 3D printed concrete: a RILEM TC 304-ADC interlaboratory study — flexural and tensile strength N2 - This paper discusses the flexural and tensile strength properties of 3D printed concrete, based on the results of a RILEM TC 304-ADC interlaboratory study on mechanical properties. These properties are determined using different testing techniques, including 3- and 4-point flexural tests, splitting tests, and uniaxial tension tests, on specimens extracted from large 3D printed elements in accordance with a prescribed study plan. The relationship between compressive and flexural or tensile strengths, cast or printed samples, different types of tests, and different loading orientations, are analysed to understand the influence of 3D printing. As expected, the strength can reduce significantly when the main tensile stress is acting perpendicular to the interface between layers. The role of deviations from the standard study procedure, in terms of the time interval between the placing of subsequent layers, or the adoption of a different curing strategy, are also assessed. While the increased time interval significantly impacts the strength in the critical direction, the use of variable curing conditions does not seem to have a clear-cut effect on the strength ratios of the printed to cast specimens. Additionally, the paper looks at the variability in the results for the printed specimens, in order to emphasize the need for multiple replicates for obtaining a proper result. An extensive insight into the aspects affecting the variability is presented in the paper. Finally, with the limited dataset available for specimens tested at a larger scale, it is difficult to arrive at a clear understanding of the role of specimen size (i.e., greater number of layers). KW - 3D concrete printing KW - Digital fabrication KW - Flexural strength KW - Tensile strength KW - Interlayer bond strength PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634655 DO - https://doi.org/10.1617/s11527-025-02687-w SN - 1871-6873 VL - 58 IS - 5 SP - 1 EP - 33 PB - Springer Nature AN - OPUS4-63465 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mechtcherine, Viktor A1 - Muthukrishnan, Shravan A1 - Robens-Radermacher, Annika A1 - Wolfs, Rob A1 - Versteege, Jelle A1 - Menna, Costantino A1 - Ozturk, Onur A1 - Ozyurt, Nilufer A1 - Roupec, Josef A1 - Richter, Christiane A1 - Jungwirth, Jörg A1 - Miranda, Luiza A1 - Ammann, Rebecca A1 - Caron, Jean‑François A1 - de Bono, Victor A1 - Monte, Renate A1 - Navarrete, Iván A1 - Eugenin, Claudia A1 - Lombois‑Burger, Hélène A1 - Baz, Bilal A1 - Sinka, Maris A1 - Sapata, Alise A1 - Harbouz, Ilhame A1 - Zhang, Yamei A1 - Jia, Zijian A1 - Kruger, Jacques A1 - Mostert, Jean‑Pierre A1 - Štefančič, Mateja A1 - Hanžič, Lucija A1 - Kaci, Abdelhak A1 - Rahal, Said A1 - Santhanam, Manu A1 - Bhattacherjee, Shantanu A1 - Snguanyat, Chalermwut A1 - Arunothayan, Arun A1 - Zhao, Zengfeng A1 - Mai, Inka A1 - Rasehorn, Inken Jette A1 - Böhler, David A1 - Freund, Niklas A1 - Lowke, Dirk A1 - Neef, Tobias A1 - Taubert, Markus A1 - Auer, Daniel A1 - Hechtl, C. Maximilian A1 - Dahlenburg, Maximilian A1 - Esposito, Laura A1 - Buswell, Richard A1 - Kolawole, John A1 - Isa, Muhammad Nura A1 - Liu, Xingzi A1 - Wang, Zhendi A1 - Subramaniam, Kolluru A1 - Bos, Freek T1 - Mechanical properties of 3D printed concrete: a RILEM 304-ADC interlaboratory study – compressive strength and modulus of elasticity N2 - Traditional construction techniques, such as in-situ casting and pre-cast concrete methods, have well-established testing protocols for assessing compressive strength and modulus of elasticity, including specific procedures for sample preparation and curing. In contrast, 3D concrete printing currently lacks standardized testing protocols, potentially contributing to the inconsistent results reported in previous studies. To address this issue, RILEM TC 304-ADC initiated a comprehensive interlaboratory study on the mechanical properties of 3D printed concrete. This study involves 30 laboratories worldwide, contributing 34 sets of data, with some laboratories testing more than one mix design. The compressive strength and modulus of elasticity were determined under three distinct conditions: Default, where each laboratory printed according to their standard procedure followed by water bath curing; Deviation 1, which involved creating a cold joint by increasing the time interval between printing layers; and Deviation 2, where the standard printing process was used, but the specimens were cured under conditions different from water bath. Some tests were conducted at two different scales based on specimen size—“mortar-scale” and “concrete-scale”—to investigate the size effect on compressive strength. Since the mix design remained identical for both scales, the only variable was the specimen size. This paper reports on the findings from the interlaboratory study, followed by a detailed investigation into the influencing parameters such as extraction location, cold joints, number of interlayers, and curing conditions on the mechanical properties of the printed concrete. As this study includes results from laboratories worldwide, its contribution to the development of relevant standardized testing protocols is critical. KW - Additive manufacturing KW - Digital fabrication KW - Hardened concrete KW - Compressive strength KW - Young's modulus PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634672 DO - https://doi.org/10.1617/s11527-025-02688-9 SN - 1871-6873 VL - 58 IS - 5 SP - 1 EP - 30 PB - Springer Nature AN - OPUS4-63467 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bekemeier, Simon A1 - Caldeira Rêgo, C. R. A1 - Mai, H. L. A1 - Sikia, Ujjal A1 - Waseda, O. A1 - Apel, M. A1 - Arendt, F. A1 - Aschemann, A. A1 - Bayerlein, Bernd A1 - Courant, R. A1 - Dziwis, G. A1 - Fuchs, F. A1 - Giese, U. A1 - Junghanns, K. A1 - Kamal, M. A1 - Koschmieder, L. A1 - Leineweber, S. A1 - Luger, M. A1 - Lukas, M. A1 - Maas, J. A1 - Mertens, J. A1 - Mieller, Björn A1 - Overmeyer, L. A1 - Pirch, N. A1 - Reimann, J. A1 - Schröck, S. A1 - Schulze, P. A1 - Schuster, J. A1 - Seidel, A. A1 - Shchyglo, O. A1 - Sierka, M. A1 - Silze, F. A1 - Stier, S. A1 - Tegeler, M. A1 - Unger, Jörg F. A1 - Weber, M. A1 - Hickel, Tilmann A1 - Schaarschmidt, J. T1 - Advancing Digital Transformation in Material Science: The Role of Workflows Within the MaterialDigital Initiative N2 - The MaterialDigital initiative represents a major driver toward the digitalization of material science. Next to providing a prototypical infrastructure required for building a shared data space and working on semantic interoperability of data, a core focus area of the Platform MaterialDigital (PMD) is the utilization of workflows to encapsulate data processing and simulation steps in accordance with findable, accessible, interoperable, and reusable principles. In collaboration with the funded projects of the initiative, the workflow working group strives to establish shared standards, enhancing the interoperability and reusability of scientific data processing steps. Central to this effort is the Workflow Store, a pivotal tool for disseminating workflows with the community, facilitating the exchange and replication of scientific methodologies. This article discusses the inherent challenges of adapting workflow concepts, providing the perspective on developing and using workflows in the respective domain of the various funded projects. Additionally, it introduces the Workflow Store’s role within the initiative and outlines a future roadmap for the PMD workflow group, aiming to further refine and expand the role of scientific workflows as a means to advance digital transformation and foster collaborative research within material science. KW - Digitalisation KW - FAIR principles KW - MaterialDigital KW - Scientific workflows KW - Semantic interoperability PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624088 DO - https://doi.org/10.1002/adem.202402149 SN - 1527-2648 IS - 2402149 SP - 1 EP - 25 PB - Wiley-VCH GmbH AN - OPUS4-62408 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strobl, Dominic A1 - Unger, Jörg F. A1 - Ghnatios, C. A1 - Robens-Radermacher, Annika T1 - PGD in thermal transient problems with a moving heat source: A sensitivity study on factors affecting accuracy and efficiency N2 - Thermal transient problems, essential for modeling applications like welding and additive metal manufacturing, are characterized by a dynamic evolution of temperature. Accurately simulating these phenomena is often computationally expensive, thus limiting their applications, for example for model parameter estimation or online process control. Model order reduction, a solution to preserve the accuracy while reducing the computation time, is explored. This article addresses challenges in developing reduced order models using the proper generalized decomposition (PGD) for transient thermal problems with a specific treatment of the moving heat source within the reduced model. Factors affecting accuracy, convergence, and computational cost, such as discretization methods (finite element and finite difference), a dimensionless formulation, the size of the heat source, and the inclusion of material parameters as additional PGD variables are examined across progressively complex examples. The results demonstrate the influence of these factors on the PGD model’s performance and emphasize the importance of their consideration when implementing such models. For thermal example, it is demonstrated that a PGD model with a finite difference discretization in time, a dimensionless representation, a mapping for a moving heat source, and a spatial domain non-separation yields the best approximation to the full order model. KW - Additive manufacturing KW - Mapping for unseparable load KW - Model order reduction (MOR) KW - Thermal transient problem KW - Sensitivity analysis KW - Proper generalized decomposition (PGD) PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598001 DO - https://doi.org/10.1002/eng2.12887 VL - 6 IS - 11 SP - 1 EP - 22 PB - John Wiley & Sons Ltd. CY - Berlin AN - OPUS4-59800 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agrawal, A. A1 - Tamsen, E. A1 - Unger, Jörg F. A1 - Koutsourelakis, P-S T1 - From concrete mixture to structural design—a holistic optimization procedure in the presence of uncertainties N2 - We propose a systematic design approach for the precast concrete industry to promote sustainable construction practices. By employing a holistic optimization procedure, we combine the concrete mixture design and structural simulations in a joint, forward workflow that we ultimately seek to invert. In this manner, new mixtures beyond standard ranges can be considered. Any design effort should account for the presence of uncertainties which can be aleatoric or epistemic as when data are used to calibrate physical models or identify models that fill missing links in the workflow. Inverting the causal relations established poses several challenges especially when these involve physicsbased models which more often than not, do not provide derivatives/sensitivities or when design constraints are present. To this end, we advocate Variational Optimization, with proposed extensions and appropriately chosen heuristics to overcome the aforementioned challenges. The proposed approach to treat the design process as a workflow, learn the missing links from data/models, and finally perform global optimization using the workflow is transferable to several other materials, structural, and mechanical problems. In the present work, the efficacy of the method is exemplarily illustrated using the design of a precast concrete beam with the objective to minimize the global warming potential while satisfying a number of constraints associated with its load-bearing capacity after 28 days according to the Eurocode, the demolding time as computed by a complex nonlinear finite element model, and the maximum temperature during the hydration. KW - Black-box optimization under uncertainty KW - Mix design KW - Performance oriented design KW - Precast concrete KW - Probabilistic machine learning KW - Sustainable material design PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-615443 DO - https://doi.org/10.1017/dce.2024.18 VL - 5 IS - e20 SP - 1 EP - 32 PB - Cambridge University Press CY - England AN - OPUS4-61544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -