Plenary lectures

prof. Chongmin Song

UNSW Sydney, Australia

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prof. Michael Beer

Leibniz Universitaet Hannover, Germany

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prof. Pol Spanos

Rice University, Houston, Texas, USA

A Scaled Boundary Finite Element Framework for Fully Automated Computational Engineering Analysis

Chongmin Song1

1University of New South Wales, Australia, c.song@unsw.edu.au

Abstract

With the rapid development of modern computer technology, computational analysis has become indispensable in tackling large-scale complex problems faced by modern engineering. The Finite Element Method (FEM) is arguably the most popular method, with many commercial software packages available. The FEM requires discretizing geometric models into simple-shaped elements, a process often involving extensive manual operations, making it time-consuming and error-prone. Additionally, new digital modeling technologies introduce a variety of geometric model formats, such as digital images, 3D-printing models, and point clouds, and pose new challenges for numerical simulations.

The Scaled Boundary Finite Element Method (SBFEM) [1], as a novel semi-analytical numerical method, aims to overcome some of the limitations of the traditional FEM. The SBFEM has emerged as a generalized finite element method with the following salient features:

  • Partition of unity and linear completeness are satisfied. SBFEM shape functions can accurately represent rigid body motions and constant strain states. With the addition of bubble functions, it is possible to achieve completeness to any order.
  • On the boundary, arbitrary high-order spectral elements can be applied, and different types of elements can be mixed as long as continuity on the boundary is maintained.
  • Standard numerical integration methods, such as Gaussian or Gauss-Lobatto-Legendre quadrature, can be applied on the boundary, similar to the FEM.
  • The shape functions of open elements contain singularities, which allows for accurate solution of singularities.
  • The method for applying boundary conditions is the same as that in FEM, making it a versatile numerical technique for various engineering analyses.
  • The difficulty in mesh generation is alleviated. A scaled boundary finite element is highly flexible in its shape and only requires the discretization of its boundary.
  • It is highly suitable for high-performance computing (HPC). When paired with an octree mesh, SBFEM significantly reduces memory requirements and is ideal for developing parallel algorithms.

This presentation summarizes our research towards developing a computational framework that fully automates the engineering analysis process directly from commonly used formats of digital geometric models. Our approach is underpinned by the scaled boundary finite element method, which enables us to incorporate an octree algorithm for automatic mesh generation across various formats such as digital images [2], STL models [3], point clouds [4] and traditional CAD models. Furthermore, the solution procedure is purposely designed for the scaled boundary finite element method to leverage modern computer hardware architectures for high-performance computing [5]. Numerical examples and demonstrations illustrate key features and the potential of the proposed framework for simulating complex 3D models, accounting for material and geometric nonlinearities, fractures, and contacts.

Scientific field: computational mechanics
Keywords: numerical method, scaled boundary finite element method, mesh generation, high-performance computing, image-based analysis


References:

  1. Song, C.: The Scaled Boundary Finite Element Method: Introduction to Theory and Implementation. John Wiley & Sons (2018)
  2. Saputra, A.A., Talebi, H., Tran, D., Birk, Cl, Song, C. Automatic image‐based stress analysis by the scaled boundary finite element method, “International Journal for Numerical Methods in Engineering” 2017, vol. 109, 697-738. doi.org/10.1002/nme.5304
  3. Liu, Y., Saputra, A.A., Wang, J., Tin-Loi, F., Song, C., Automatic polyhedral mesh generation and scaled boundary finite element analysis of STL models, “Computer Methods in Applied Mechanics and Engineering”, 2017, vol. 313, 106-132. doi.org/10.1016/j.cma.2016.09.038
  4. Zhang, J., Eisenträger, S., Zhan, Y., Saputra, A.A., Song, C., Direct point-cloud-based numerical analysis using octree meshes, “Computers & Structures”, 2023, vol. 289, 107175. doi.org/10.1016/j.compstruc.2023.107175
  5. Zhang, J., Ankit, A., Gravenkamp, H., Eisenträger, S., Song, C., A massively parallel explicit solver for elasto-dynamic problems exploiting octree meshes, “Computer Methods in Applied Mechanics and Engineering”, 2021, vol 380, 113811. doi.org/10.1016/j.cma.2021.113811
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Aleatory and epistemic uncertainties in engineering analysis

Michael Beer

Institute for Risk and Reliability, Leibniz Universität Hannover, Germany, beer@irz.uni-hannover.de

Department of Civil and Environmental Engineering, University of Liverpool, UK

International Joint Research Center for Engineering Reliability and Stochastic Mechanics (ERSM) & International Joint Research Center for Resilient Infrastructure (ICRI), Tongji University, China

Abstract

Analyzing engineering structures and systems we are challenged by complexity, nonlinearities and uncertainties, which call for highly efficient models and analysis technologies to provide realistic results at reasonable computational cost. An efficient and effective quantification of both aleatory and epistemic uncertainties is essential in this regard. To address aleatory uncertainties, a class of covariance models is discussed. It is shown that an optimal spectral representation can be derived to meet the key physics behind fluctuating engineering quantities and simultaneously to improve the efficiency of spectral stochastic analyses significantly. The discussion is the expanded to the consideration of epistemic uncertainties. It is highlighted that their appropriate consideration in an engineering analysis is a key requirement for proper design and operation of our structures and systems. The quantification of epistemic uncertainties is discussed elucidating the capabilities of the concepts. Clearly, the first consideration should be devoted to a probabilistic modelling, naturally through subjective probabilities, expressing some belief, which can be integrated into a fully probabilistic framework in a coherent manner with potent Bayesian approaches. While this pathway is already widely established and used, the potential of set-theoretical approaches and imprecise probabilities has only been utilized to some extent. Those approaches, however, attract increasing attention in cases when available information is not rich enough to meaningfully specify subjective probability distributions or when only bounding information on probabilistic models is available. They offer a complementing perspective providing additional insight for reliability assessment and decision-making. Their conceptual features facilitate a modelling at a reasonable level of detail and capturing the remaining epistemic uncertainty in a set-valued manner. This approach allows for an optimal balance between model detailedness and imprecision of results to still derive useful decisions. However, it is also associated with quite extensive numerical cost when applied in a crude way. To address this issue, a numerically efficient analysis technology is presented, which does not only resolve the additional burden of processing both aleatory and epistemic uncertainties, but also time-dependent reliability problems without the typical multiple repetition of the reliability analysis. Engineering examples show the practical applicability as well as the gain in using the proposed concepts.

 


Speaker Bio

Michael Beer is Professor and Head of the Institute for Risk and Reliability, Leibniz Universität Hannover, Germany. He is also part time Professor at the University of Liverpool and guest Professor at Tongji University and Beijing University of Science and Technology, China. He obtained a doctoral degree from Technical University Dresden, Germany, and worked for Rice University, National University of Singapore, and the University of Liverpool, UK. Dr. Beer’s research is focused on uncertainty quantification in engineering with emphasis on imprecise probabilities. Dr. Beer is Editor in Chief of the ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A Civil Engineering and Part B Mechanical Engineering. He is also Editor in Chief (joint) of the Encyclopedia of Earthquake Engineering, Associate Editor of Information Sciences, and Editorial Board Member of Engineering Structures and several other international journals. He has won several awards including the Alfredo Ang Award on Risk Analysis and Management of Civil Infrastructure of ASCE. Dr. Beer is the Chairman of the European Safety and Reliability Association (ESRA) and a Co-Chair of Risk and Resilience Measurements Committee (RRMC), Infrastructure Resilience Division (IRD), ASCE. He is serving on the Executive Board of the International Safety and Reliability Association (IASSAR), on the Executive Board of the European Association of Structural Dynamics (EASD), and on the Board of Directors of the International Association for Probabilistic Safety Assessment and Management (IAPSAM). He is a Fellow of the Alexander von Humboldt-Foundation and a Member of ASCE (EMI), ASME, CERRA, IACM and GACM.

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Prof. Chenfeng Li

Zienkiewicz Institute for Modelling, Data & AI, Swansea University, UK 

prof. George Stefanou

Aristotle University in Thessaloniki, Greece

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Prof. Nicholas Fantuzzi

University of Bologna, Italy

Random field modeling of the mechanical properties of heterogeneous materials based on their microstructure

George Stefanou1
1 Aristotle University of Thessaloniki, Greece, gstefanou@civil.auth.gr

This lecture presents a computational framework for the simulation of the mechanical properties of heterogeneous materials with random microstructure using random fields, which can serve as input for the response variability analysis of composite structures. Through high-resolution microstructure imaging techniques, such as SEM and CT, the spatial variability of the mechanical properties is quantified. By deriving random fields directly from these images, the proposed framework ensures accurate modeling that reflects real microstructures rather than relying on arbitrary assumptions of statistical distributions. Homogenization methods are used in conjunction with the moving window technique to compute mesoscale random fields, which are then employed for conducting macroscopic response analysis with the stochastic finite element method [1].

The proposed computational framework is illustrated through several applications that include [2,3]: the response variability of composite structures with random material property fields having uncertain parameters, the determination of the mechanical properties of graphene nanoplatelets (GNPs) containing random structural defects and the computation of random fields of bending stiffness properties based on real CT-image data of short fiber composites. An efficient random field computation approach is also proposed, which takes advantage of convolutional neural networks (CNNs) to make nearly instant random field predictions based on image data [4].

Scientific field: Computational mechanics
Keywords: heterogeneous material, microstructure, homogenization, mechanical properties, random fields, response variability


References:

  1. Stefanou G., Savvas D., Papadrakakis M., Stochastic finite element analysis of composite structures based on mesoscale random fields of material properties, Computer Methods in Applied Mechanics and Engineering, 2017, vol. 326, pp. 319-337, doi: 10.1016/j.cma.2017.08.002.
  2. Stefanou G., Savvas D., Gavallas P., Papaioannou I., The effect of random field parameter uncertainty on the response variability of composite structures, Composites Part C: Open Access, 2022, vol. 9, 100324, doi: 10.1016/j.jcomc.2022.100324.
  3. Gavallas P., Savvas D., Stefanou G., Mechanical properties of graphene nanoplatelets containing random structural defects, Mechanics of Materials, 2023, vol. 180, 104611, doi: 10.1016/j.mechmat.2023.104611.
  4. Gavallas P., Stefanou G., Savvas D., Mattrand C., Bourinet J.-M., CNN-based prediction of microstructure-derived random property fields of composite materials, Computer Methods in Applied Mechanics and Engineering, 2024, vol. 430, 117207, doi: 10.1016/j.cma.2024.117207.

Speaker Bio

George Stefanou is a Professor of Stochastic Methods in Structural Analysis and Dynamics of Structures at the Department of Civil Engineering of the Aristotle University of Thessaloniki, Greece. His research activity is mainly focused on the development and application of computer methods for stochastic finite element analysis of real-world structures, as well as on the multiscale modeling and uncertainty quantification of heterogeneous materials and structures. He has published over 130 articles in international refereed journals and conference proceedings. He is included in the Stanford list of top-cited scientists (2% or above) for the years 2019-2023. He is Secretary of the Greek Association of Computational Mechanics. He has co-organized several international scientific conferences and mini symposia. He is also Guest Editor of 4 journal special issues and member of the Scientific Committee of several international conferences.

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Marek ,

Marek

Over the past few decades algorithms using biologically inspired signal transformation – artificial neural networks (ANN) – have undergone a remarkable and exciting development path from simple algorithms for classification and approximation to deep learning-based procedures whose operation is almost indistinguishable from the assistance of an intelligent being. ANNs have found and continue to see their applications in various fields of civil engineering and mechanics, like composites, structural analysis, geotechnics, and others. In particular, ANNs are used as surrogates of calculations performed by finite element method (FEM) programs when solving inverse problems related to identification of model parameters or designing materials or structures. ANNs are also utilized as an element of constitutive descriptions of heterogeneous, anisotropic materials within the FEM procedure. Real and numerical experiments can serve as a source of ANN training data in these applications and many different learning strategies can be utilized to achieve the best modeling results. Classical ANN architectures, such as feed-forward networks (FFNN) and recurrent networks (RNN), as well as contemporary deep learning models, such as physics-informed neural networks (PINN) or transformer neural networks (TNN), are found to be suitable for engineering applications.

All contributions related to the use of ANNs in numerical modeling of engineering materials are welcome at this mini-symposium. Applications in soil mechanics and geotechnical engineering are especially welcome. The following subtopics will be considered in particular:

  • Back-calculation and solving inverse problems using ANNs;
  • Replacing FEM computations with ANN surrogate models;
  • Description of constitutive laws in FEM models using ANNs
  • Applications of deep learning algorithms in numerical modeling of engineering materials;
  • Site characterization and classification of soils using experimental data and ANNs;
  • Expert programs based on ANNs and data mining in engineering;
  • Other ANN applications related to the main topic.

Keywords: artificial neural networks; inverse analysis; back-calculation; surrogate models; constitutive modeling; deep learning; finite element method; soil mechanics; geotechnics; composite materials

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prof. Christian Hellmich

Technische Universitaet Wien, Austria

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prof. Alberto Corigliano

Politecnico di Milano, Italy

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prof. Jerzy Rojek

Institute of Fundamental Technological Research, Polish Academy of Science, Poland 

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Computing for mechanics and mechanics for computing

Authors: Alberto Corigliano, Andrea Manzoni, Luca Rosafalco, Matteo Torzoni
Affiliation: Politecnico di Milano, Italy
E-mail: alberto.corigliano@polimi.it, andrea1.manzoni@polimi.it, luca.rosafalco@polimi.it, matteo.torzoni@polimi.it

Science has always sought to interpret and understand reality through modelling and simulation. Before the advent of powerful computers, analytical approaches, cleverly combined with experimental observation and validation, were the main tools for scientific advancements. In the last century, computational methods have emerged as a driving force, allowing for increasingly realistic numerical simulations. In many engineering fields, numerical methods have become powerful tools for prediction and optimization. More recently, the integration of simulation with real-time acquisition of experimental data has opened the way for innovative practices in Structural Health Monitoring. As a result, numerical methods have become a close partner of experimental data, driving the rise of new digital twin concepts.

The extremely rapid advancements in Machine Learning and miniaturized sensors are today redefining the role of numerical methods. Numerical approaches can now be used to continuously learn from reality by cleverly combining information from experimental data and/or pre-acquired knowledge, possibly incorporating a priori physical principles. This learning process can drive a continuous optimization and/or adaptivity of materials and structures, enabling them to react dynamically to new stimuli coming from sensors.

New forms of computation can also emerge directly within physical objects. Artificial Neural Networks can be implemented, at least partially, through analog computing devices. In this case, the material or structure itself can function as a computing machine, as explored in Physical Reservoir Computing [1].

The lecture will explore recent trends and future prospects in numerical methods, drawing on the recent experiences of the speaker in structural optimization, structural health monitoring, deep and reinforcement learning [2]-[6] and trying to put in evidence the strict double link between mechanics and computation.

Scientific field: Computational mechanics

Keywords: Computer methods, model order reduction, optimization, machine learning, reinforcement learning, physical reservoir computing


References

  1. Kohei Nakajima, Ingo Fischer (eds). Reservoir computing. Theory, physical implementation and applications. Springer, 2021, ISBN: 978-981-13-1686-9.
  2. M. Torzoni, L. Rosafalco, A. Manzoni, S. Mariani, A. Corigliano, SHM under varying environmental conditions: An approach based on model order reduction and deep learning. Computers & Structures, 266, 106790, (2022).
  3. L. Rosafalco, J. M. De Ponti, L. Iorio, R. Ardito, A. Corigliano, Optimised graded metamaterials for mechanical energy confinement and amplification via reinforcement learning. European J. of Mechanics A/Solids, 99, 104947 (2023).
  4. L. Rosafalco, J. M. De Ponti, L. Iorio, R. V. Craster, R. Ardito, A. Corigliano. Reinforcement learning optimisation for graded metamaterial design using a physical‑based constraint on the state representation and action space. Scientific Reports, 13(1), 21836, (2023).
  5. G. Garayalde, M. Torzoni, M. Bruggi, A. Corigliano. Real-time topology optimization via learnable mappings. Int. J. Num. Meth. Engng. 125(15), e7502 (2024) doi: 10.1002/nme.7502
  6. G. Garayalde, L. Rosafalco, M. Torzoni, A. Corigliano. Mastering truss structure optimization with tree search. J. Mechanical Design, ASME, 2025, To appear.
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Multiscale and multiphysics modelling of powder metallurgy processes using the discrete element method

Author: Jerzy Rojek
Affiliation: Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland
Email: jrojek@ippt.pan.pl

Powder Metallurgy (PM) encompasses various technologies for the manufacturing of net-shape components from metallic or non-metallic powder mixtures. The present work aims at multiscale and multiphysics modelling of selected PM processes encompassing cold compaction, sintering, hot pressing, and electric current-activated sintering (ECAS). During the PM process, particulate materials are consolidated into a solid bulk material under mechanical, thermal, or combined mechanical and thermal action. In the latter case, thermal and mechanical phenomena are coupled. The ECAS technique, in which heating is produced by the Joule effect, involves the coupling of three physical fields: electrical, thermal, and mechanical. During PM processes, the material undergoes densification, which affects macroscopic properties. Changes in macroscopic properties during densification result from processes at microscopic levels. At the microscopic level, we observe particle rearrangement, plastic deformation, formation and growth of cohesive bonds, shrinkage and elimination of pores. The heterogeneity of the processed material has an effect on heat transfer. Similarly, the electric current flow is affected if it is employed in a PM process.

The design of PM processes is a complex engineering problem. Modelling and simulation can help in process design and a better understanding of the processes. Numerical models for different PM processes developed in the framework of the discrete element method (DEM) will be presented. In the DEM, materials are represented by a large assembly of spherical particles interacting with one another. It takes into account the particulate nature of powders in a simple way. It is a suitable tool for micromechanical modelling of PM processes. A standard DEM can be easily applied to cold powder compaction with low pressure [1]. A special interaction model is required for high-density compaction under high pressures. Similarly, special models are necessary for sintering. Sintering without or with pressure is used as a densification mechanism in many PM processes, such as free sintering, hot pressing (HP) or hot isostatic pressing (HIP). Sintering modelling in the presented research was based on the viscoelastic sintering model developed in [2]. Sintering is a process occurring at high temperatures. Therefore, the DEM, developed originally for mechanical effects in sintering, has been extended to heat conduction [3]. With the use of the electrical-thermal analogy, the thermal model has been adapted to model the flow of electric current [4]. Thus, the DEM formulation has all the ingredients for multiphysics modelling of the ECAS process, accounting for thermal, mechanical and thermal phenomena and two-way coupling within each pair out of them.

The DEM model of sintering was used in the multiscale framework as a model for microscopic modelling [4]. The DEM simulations provided data for the evaluation of macroscopic mechanical constitutive properties [4] and the effective thermal and electrical conductivities of the particulate material at different stages of sintering [5,6]. The DEM model of sintering has been validated using its own experimental results. Verification and validation results will illustrate the capabilities of the developed model.

Scientific field: computational mechanics

Keywords: powder metallurgy, modelling, multiscale, multiphysics, discrete element method

Acknowledgement: Research funded by NCN Poland, project no. 2019/35/B/ST8/03158.


References

  1. Rojek J., Nosewicz S., Jurczak K., Chmielewski M., Pietrzak K., Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure, “Comp. Particle Mechanics”, 2016, vol.3, pp.513–524, doi: 10.1007/s40571-015-0093-0.
  2. Nosewicz S., Rojek J., Pietrzak K., Chmielewski M., Viscoelastic discrete element model of powder sintering, “Powder Technology”, 2013, vol.246, pp.157–168, doi: 10.1016/j.powtec.2013.05.020.
  3. Rojek J., Kasztelan R., Tharmaraj R., Discrete element thermal conductance model for sintered particles, “Powder Technology”, 2022, vol.405, pp.117521-1–10, doi: 10.1016/j.powtec.2022.117521.
  4. Nosewicz A., Rojek J., Wawrzyk K., Kowalczyk P., Maciejewski G., Maździarz M., Multiscale modeling of pressure-assisted sintering, 2019, vol. 156, pp. 385–395, “Computational Materials Science”, doi: 10.1016/j.commatsci.2018.10.001.
  5. Nisar F., Rojek J., Nosewicz S., Kaszyca K., Chmielewski M., Evaluation of effective thermal conductivity of sintered porous materials using an improved discrete element model, “Powder Technology”, 2024, vol.437, pp.119546, doi: 10.1016/j.powtec.2024.119546.
  6. Nisar F., Rojek J., Nosewicz S., Szczepański J., Kaszyca K., Chmielewski M., Discrete element model for effective electrical conductivity of spark plasma sintered porous materials, “Comp. Particle Mechanics”, 2024, pp.1–11, doi: 10.1007/s40571-024-00773-4.
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Refinement of Hybrid Analyses Reveals Unexpected Load-Carrying Mechanisms of NATM- and TBM-Driven Tunnels

Christian Hellmich, Raphael Scharf, Ali Razgordanisharahi, Maximilian Sorgner, Bernd Moritz, Thomas Pilgerstorfer, Markus Brantner, Bernhard Pichler

Affiliations

1. TU Wien (Vienna University of Technology), Vienna, Austria

2. ÖBB Infrastruktur GmbH, Graz, Austria

3. Geoconsult, Puch bei Hallein, Austria

4. IGT-engineering, Salzburg, Austria

Contact Emails: christian.hellmich@tuwien.ac.at, raphael.scharf@tuwien.ac.at, ali.razgordanisharahi@tuwien.ac.at, bernhard.pichler@tuwien.ac.at

Abstract

In geotechnical engineering, the ground surrounding a tunnel opening is largely unknown. This makes precise and realistic mechanical modeling nearly impossible. Hence, accurately quantifying the forces acting on a tunnel shell is a formidable challenge. To address this, hybrid methods [1,4] have been proposed within the framework of the New Austrian Tunneling Method (NATM) [2]. These methods combine mechanical models for the aging viscoelastic tunnel shell, made of shotcrete, with geodetic measurement data [3] that provide displacement vectors at selected points on the inner tunnel surface. By increasingly refining interpolation strategies [1,4] of the point-specific displacements along the tunnel shell circumference, and applying the corresponding boundary conditions to a structural mechanical model of the shell, the utilization degree – a key indicator of the shell’s mechanical competence – can be quantified [1,4]. Recently [5] this approach has been substantially refined and extended in its application in two major ways:

First, rather than arbitrarily choosing displacement interpolation functions, the mathematical structure of the displacement fields was derived from viscoelastic shell theory [6]. This approach uses shell equilibrium conditions based on the principle of virtual power [7,8], along with a rate-type aging viscoelastic material law [9] in the Laplace-Carson space. This theory-based method allows for the translation of point-based displacement measurements into normal forces, bending moments, stresses, and ground pressure-related traction forces acting on the shell. When applying this refined concept to the top heading of the Stein tunnel [10], this tunnel shell was found to be highly flexible, even undergoing plastic moment deformation [11]. This behavior was rarely, if ever, observed in the context of NATM tunneling.

Secondly, a hybrid method for Tunnel Boring Machine (TBM)-driven segmental tunnels has been developed. Strains recorded at specific points from vibrating wire sensors placed at two reinforcement layers are first translated – using a viscoelastic model – into stresses [12]. These stresses are then integrated into bending moments and normal forces, which are subsequently interpolated along the shell circumference. This approach allows for (i) the assessment of mechanical competence of the longitudinal joints (the weakest portions of the tunnel shell), and (ii) through shell equilibrium conditions, the determination of ground pressure and shear traction at the shell-ground interface. When applied to construction lot KAT3 of the Koralm tunnel [13] in southern Austria, the tunnel shell, despite being segmental, behaves like a pseudo-monolithic structure. However, maximum bending moments are observed off the spring-line, indicating that ground-loosening forces are acting on the tunnel crown. This phenomenon may be linked to variations in the effectiveness of the grout bond between the tunnel shell and the surrounding ground.

Scientific field: Solid Mechanics

Keywords: Tunnel engineering, Viscoelasticity, Monitoring, Long-term assessment


References

  1. C. Hellmich, J. Macht, H. Mang. A hybrid method for determination of the level of utilization of shotcrete shells, Felsbau, 17(5), 422-425, 1999.
  2. H. Lauffer. The development of the NATM–a historical review, Geomechanics and Tunnelling, 3(6), 763-772, 2010.
  3. W. Schubert, A. Steindorfer, E. Button. Displacement monitoring in tunnels-an overview, Felsbau, 20(3), 7-15, 2002.
  4. M. Brandtner, B. Moritz, P. Schubert. On the challenge of evaluating stress in a shotcrete lining...
  5. C. Hellmich, B. Pichler, R. Heissenberger, B. Moritz. 150 years reliable railway tunnels– Extending the hybrid method...
  6. R. Scharf, B. Pichler, R. Heissenberger, B. Moritz, C. Hellmich, Data-driven analytical mechanics of aging viscoelastic shotcrete tunnel shells...
  7. P. Germain. The method of virtual power in continuum mechanics. Part 2: Microstructure. SIAM Journal on Applied Mathematics, 25(3), 556-575, 1973.
  8. R. Höller, M. Aminbaghai, L. Eberhardsteiner, J. Eberhardsteiner, R. Blab, B. Pichler, C. Hellmich. Rigorous amendment of Vlasov's theory for thin elastic plates on elastic Winkler foundations...
  9. S. Scheiner, C. Hellmich. Continuum microviscoelasticity model for aging basic creep of early-age concrete...
  10. J. Benedikt, H. Wagner, T. Herzeg. The St. Kanzian Chain of Tunnels–Tunnelling under very varied and extremely difficult conditions...
  11. R. Scharf, M. Brandtner, B. Moritz, B. Pichler, C. Hellmich, C. Refined hybrid structural analysis shows plastic flexibility enhancement in NATM tunnel shell...
  12. A. Razgordanisharahi, M. Sorgner, T. Pilgerstorfer, B. Moritz, C. Hellmich, B. Pichler, Realistic long-term stress levels in a deep segmented tunnel lining...
  13. B. Moritz, H. Wagner, K. Mussger, D. Handke, G. Harer. Criteria for the selection of tunnelling method through the example of the Koralm Tunnel...

BIO

Christian Hellmich is full professor at Technische Universität Wien (TUW, Vienna, Austria), directing there the Institute for Mechanics of Materials and Structures. At TUW, he received his (civil) engineering diploma (1995), his Dr.techn. (PhD, 1999), and his habilitation (2004). Being on leave from his academic position at TUW, he was Postdoctoral Fellow at M.I.T. from 2000 to 2002; and over the years, he has held several short-term visiting professorships in France, Italy, and Germany.

Together with collaborators across the globe, he has developed (micro)structural bio-chemomechanical models, in terms of theoretical foundations, computational realization, as well as experimental validation and developments for various biological and man-made systems; including bone and soft tissues, cement and concrete, wood and wood composites, rock and soil, brick, steel, rubber, graphene, DNA, as well as metal-, mineral-, polymer-, and glass-based biomaterials. These mathematical models are employed in concrete, tunnel, pipeline, and biomedical engineering.

Also trained as a violinist, he has been active at the crossroads of Science and Arts, from which he takes a broad cultural perspective on the nature of universities and their role in society. This is also reflected by his interdisciplinary work integrating engineers, physicists, chemists, biologists, and medical doctors.

Christian Hellmich has co-authored 185 peer-reviewed publications; and about the same amount of book chapters and proceedings papers; he has given more than 300 presentations at international conferences and universities, often as invited, keynote, or plenary speaker. He serves in editorial roles for several peer-reviewed journals, including Journal of Engineering Mechanics (ASCE), Mechanics of Materials, and AIP Applied Physics Reviews.

He has provided extensive reviewing and advisory service for various universities and science foundations, including his role as a panel member for the European Research Council (ERC). He has also served in the Engineering Mechanics Institute of the American Society of Civil Engineers (EMI-ASCE), in particular so in the Board of Governors and in various technical committees, as president of the International Association for Concrete Creep (IA-CONCREEP), as president of the Austrian Chapter of the European Society of Biomechanics (ESB), as symposium organizer for the Materials Research Society (MRS), and in the Board of Directors of the Young Academy of the Austrian Academy of Sciences (ÖAW).

His activities have been recognized through several national and international awards, such as the Kardinal Innitzer Advancement Award of the Archdiocese of Vienna (2004), the Science Recognition Award of the Region of Lower Austria (2005), the Zienkiewicz Award of the European Community on Computational Methods in Applied Sciences (ECCOMAS, 2008), an ERC grant (2010), and the Walter L. Huber Research Prize of ASCE (2012); moreover, he was named Fellow of EMI (2014), Fellow of the European Alliance of Medical and Biological Engineering & Sciences (EAMBES, 2019), corresponding member of ÖAW (2019), and Fellow of the Society of Engineering Science (SES, 2023).

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