Mini-Symposia

Alberto Carpinteri (Shantou University, China)
Federico Accornero (Shantou University, China)

This mini-symposium aims at promoting recent advancements on high-performance concrete structures, with particular focus on the complex phenomena characterising the failure mechanisms of fibre-reinforced, hybrid-reinforced, FRP-bar reinforced, and prestressed concrete structures. These next-generation brittle-matrix composites can represent an effective solution to the main drawbacks related to conventional reinforced concrete in terms of durability and structural performances.

The idea of the mini-symposium is to provide a forum to discuss recent advancements in the above subjects, and to search for cutting-edge technical contributions.

Miroslav Vorechovsky (Brno University of Technology, Czech Republic)
Rostislav Chudoba (RWTH Aachen, Germany)

The mini-symposium aims to delve into both the experimental characterization and numerical modeling aspects of fatigue in concrete structures. We enthusiastically invite contributions that showcase data derived from rigorous laboratory experiments as well as real-world structural analyses. Papers that concentrate on the advancement of constitutive models and solvers specifically designed to address fatigue issues are particularly welcome. This includes, but is not limited to, finite element models, discrete models, and phase field models. Papers addressing the effect of stress configurations on fatigue and its microstructural origins are well suited. We also encourage submissions that explore stochastic fatigue, taking into account both the variability in material parameters and stochastic loading conditions. Furthermore, we are interested in coupled models that consider the impact of environmental conditions such as temperature and humidity, along with loading rate and dynamic effects, integrating damage, viscous effects, and plasticity. This minisymposium provides a platform for presenting cutting-edge research that contributes to our understanding and modeling of the fatigue behavior in concrete and fiber-reinforced concrete structures, with focus on prediction of fatigue lifetime.

Dimitrios G. Aggelis (Vrije Universiteit Brussel, Belgium)
Nathalie Godin (Laboratoire MATEIS, Institut National des Sciences Appliquées de Lyon (INSA), France)
Eric Landis (University of Maine,USA)

The mini-symposium on “Monitoring of fracture in heterogeneous media” focuses on innovative nondestructive techniques for assessing and monitoring structural integrity in diverse structural materials. This session explores the application of advanced methods, such as elastic waves and optical techniques, to detect and analyze fracture in a variety of materials. Participants will have the opportunity to delve into the latest developments in nondestructive evaluation methods that enable real-time monitoring of structural changes and fracture propagation. From traditional materials like concrete to emerging materials like composites, textile reinforced cement and 3D printed concrete, this session will showcase a range of applications and case studies highlighting the effectiveness of nondestructive techniques in fracture detection and characterization. Issues relating to lifetime prediction and modeling are also addressed. Researchers and practitioners in the broad field of materials science and engineering will benefit from the insights shared in this special session, gaining valuable knowledge on how to effectively apply nondestructive methods for fracture monitoring and structural health assessment in heterogeneous materials.

Marco Paggi (IMT School for Advanced Studies Lucca, Italy)
Laura Carreras Blasco (University of Girona, Spain)
Amirtham Rajagopal (IIT Hyderabad, India)
José Manuel Sena Cruz (University of Minho, Portugal)

The phase field approach is a mathematical technique used to simulate evolving discontinuities in continua. It is based on an additional partial differential equation which is coupled with the standard field equations of the fluid/solid continuum, greatly enhancing the tracking of the field transitions from the computational point of view.

The proposal of such an approach by Francfort and Marigo to simulate evolving displacement discontinuities in solids, which is a key problem of fracture mechanics, and the recovery of the Griffith theory in the limit of Gamma-convergence, has opened the way for a significant development of the method to make it a quantitative tool suitable for engineering technical applications. The aim of this mini-symposium is to bring together experts of theoretical, computational and experimental fracture mechanics to discuss limitations, challenges and perspectives of the phase field approach to fracture in relation to key open issues listed below.

• Fundamentals of the phase field method: from brittle to cohesive fracture.
• Comparison with benchmark tests in the lab for the technical assessment of the phase field approach to fracture for quasi-brittle materials.
• From the laboratory scale to the structural scale: how to exploit the phase field approach to fracture in relation to concrete materials and concrete structures.
• Competition between interface delamination and bulk fracture for civil applications (FRP strengthening, etc.).
• The phase field approach to fracture applied to masonry materials and masonry structures.
• Prediction of size-scale effects according to the phase field approach to fracture: limitations and challenges.
• The phase field approach to fracture for coupled problems: thermo-elasticity, corrosion and other chemico-mechanical problems.
• Fatigue and cyclic degradation phenomena simulated using the phase field approach to fracture.
• Computational methods and high performance computing strategies for large scale computations based on the phase field approach to fracture.

Matthias Neuner (University of Innsbruck, Austria)
Peter Gamnitzer (University of Innsbruck, Austria)
Günter Hofstetter (University of Innsbruck, Austria)

Many years of extensive research endeavors have led to advanced computational models to better understand and predict the complex nonlinear and time-dependent behavior of concrete. The models greatly enhance the capabilities to solve challenging engineering problems in various fields in concrete construction. Typical applications comprise but are not limited to numerical investigations of

• suitable measures to prevent potentially improper design of concrete structures, resulting in extensive cracking due to static, cyclic or dynamic loading,
• massive concrete structures due to hydration during construction,
• the effects of excessive loading of concrete structures or concrete components,
• the development of time-dependent stress changes in concrete structures due to creep and shrinkage, potentially resulting in cracking,
• the consequences of age-related deterioration of concrete structures on the structural integrity due to environmental effects, like freeze-thaw cycles or chemical reactions with the cement matrix or reinforcing steel,
• suitable rehabilitation and strengthening measures of concrete structures.

In this mini-symposium contributions involving the application of research-based computational models for numerical simulations of concrete structures and concrete components are welcome, which provide additional benefits beyond conventional models based on current building standards.

Branko Šavija (Delft University of Technology, the Netherlands)
Eric Landis (University of Maine, USA)
Hongzhi Zhang (Shandong University, China)
Yidong Gan (Huazhong University of Science and Technology, China)

Cementitious materials have a complex microstructure with heterogeneities on different length scales, from micro- to macro-scale. Their mechanical and time dependent behavior (including creep, shrinkage, and durability) is therefore a complex function of processes occurring at different length scales. The development of experimental techniques in recent years continues to enable us to understand the relationships between the material microstructure and their engineering performance. This includes (in-situ) nanoindentation and micromechanical testing, X-Ray computed tomography, non-destructive methods, but also the use of machine learning tools for data analysis.

This mini-symposium aims to bring together experts and researchers to discuss recent advances in small-scale experimental testing of mechanical, time-dependent, and durability behavior of cementitious materials. Topics of interest include, but are not limited to, the following:

• Nanoindentation
• X-ray computed tomography
• Image segmentation
• Advanced micro- and meso-scale experiments
• Model validation
• In-situ testing
• Machine learning for data analysis, prediction, and clustering

Jishen Qiu (Hong Kong University of Science and Technology, Hong Kong)
En-Hua Yang (Nanyang Technological University, Singapore)
Min Wu (Aarhus University, Denmark)

Concrete undergoes a variety of environmentally induced changes through its long service including cracking due to cement matrix expansion/shrinkage, cracking due to rebar corrosion, self-healing of cracks, etc. Despite the different driving forces, all these changes are essentially processes of adding (subtracting) minor amounts of substance to (from) critical micro-structures in concrete. For example, the expansion/shrinkage involves addition/removal of H2O molecule (absorption/desiccation); the rebar corrosion involves addition of O2 (oxidation); the autogenous healing involves addition of CO2 (carbonation).

Based on such generalization, analogies can be made between the microstructural evolutions in concrete and the repair/damage of structures—where columns/beams/joints are added to or subtracted from existing structures. Therefore, the environmental effect on the long-term concrete performance, which is now mainly studied by cement chemists and material scientists, can be greatly enhanced by researchers of mechanics and structures.

Topics: this mini-symposium is to share current works on how environmentally induced microstructural evolutions vary mechanical properties of concrete structures. While the focus is on the effect of environment on mechanical properties, the works on the effect of mechanical loading on environmental durability are also welcome.

The technical terms are broadly defined. The environmental effects will include but not be limited to humidity, temperature, pH, chloride, and CO2. The microstructural evolutions will include but not be limited to pore refinement, matrix cracking, interfacial cracking (rebar/aggregate/fiber-to-matrix), healing of cracks. The studied cement types will include mainstream Portland cement, pozzolanic cement, as well as the greener but volumetrically less stable cements including geopolymer, reactive magnesia, etc. Some exemplary topics are listed below for reference.

• Experimental/numerical/analytical methods to determine environmentally induced micro-structural evolutions and their effect on concrete properties
• Effect of self-healing on the mechanical recovery of cracked concrete
• Effect of chloride diffusion and rebar corrosion on the mechanical properties of reinforced concrete
• Effect of CO2 sequestration, elevated temperature, freezing temperature on the mechanical properties of concrete
• Combined environmental and mechanical loadings

Konstantinos Agathos (University of Exeter, UK)
Eleni Chatzi (ETH Zürich, Switzerland)
Savvas Triantafyllou (Technical University of Athens, Greece)

Accurate and robust simulation of evolving damage in complex materials and structures is an arduous and challenging task both from a physical and a computational standpoint. Recent advances in material modeling, fracture modeling, discretization approaches, and physics informed artificial intelligence have given rise to a wide ecosystem of methods that can significantly enhance the capacities of virtual simulation. This mini-symposium aims to provide a forum for idea exchange and knowledge dissemination vis-a-vis the latest developments in the field of computational fracture mechanics and damage modeling. Topics relevant to the Minisymposium include, but are not limited to, implementations and algorithmic solutions for:

• Discrete and diffuse fracture approaches and discretisation methods, for instance phase-field, XFEM/GFEM, etc.
• Inverse problems and data driven simulation.
• Methods to reduce computational expenses, including adaptivity, model order reduction, surrogates etc.
• Fracture across scales.

Contributions pertaining to the implementation of such methods on real-life applications, including high-strength concrete and brittle matrices reinforced with alloys under static and dynamic loading, are especially welcomed.

Christian La Borderie (Université de Pau et des Pays de l’Adour, France)
Hélène Carré (Université de Pau et des Pays de l’Adour, France)
Pierre Pimienta (CSTB – French Scientific and Technical Center for Buildings, France) 

Civil engineering structures must be able to withstand a fire, and this aspect has been studied for many years. Although concrete is reputed to be one of the most resilient construction material, it can be subject to instabilities in certain situations. These instabilities are linked to a complex interaction between mechanical, thermal, hydric and even chemical phenomena at different material and structural scales. Despite many years of study, the problem of spalling has not yet been fully elucidated, and some people refer to it as the “secret of spalling”.

The mini-symposium is dedicated to “concrete and concrete structures in fire”. We welcome any contribution that will help to lift the veil on the “secret of spalling”, whether in the field of experimentation, modeling or simulation, at the material or the structural scale.

Mohammed Alnaggar (Oak Ridge National Laboratory, USA)
Gianluca Cusatis (Northwestern University, USA)
Jan Elias (Brno University of Technology, Czech Republic)
Giovanni Di Luzio (Politecnico di Milano, Italy)
Enrico Masoero (Politecnico di Milano, Italy)
Gilles Pijaudier-Cabot (University of Pau and the Adour Region, France)
Jacek Tejchman (Gdańsk University of Technology, Poland)

Civil engineering heavily relies on the use of porous heterogeneous quasi-brittle materials, such as concrete, masonry, wood, and rocks, which play crucial roles in various structural applications. The performance and durability of these materials are influenced by a complex interplay of mechanical behavior, mass transport, heat transfer, and chemical reactions coupled with the occurrence of cracks at the scale of material heterogeneity.

Traditional material descriptions in civil engineering often rely on the assumption of continuity in displacements and other primary fields, making it challenging to accurately incorporate fracture mechanics, both at the structural scale and at the level of material heterogeneity. An alternative approach involves representing the material as a system of rigid bodies interconnected by cohesive contacts. These discrete models have been under development for several decades and today they offer an efficient means of representing multiscale and coupled multiphysics phenomena. They have demonstrated to supersede by far most of the other computational techniques for simulating heterogeneous quasi-brittle materials subject to fracture. They excel in applications where accurately capturing the internal structure of the material and understanding the interactions across different length scales are paramount.

This mini-symposium will provide a forum for international experts and researchers to present and discuss recent advances in discrete modeling.

Topics of interest include, but are not limited to:

• fracture, strain localization;
• multiscale;
• early-age behavior of cast and printed cementitious materials;
• coupled formulations for mass transport, shrinkage, creep, healing, chemical reactions or deterioration;
• hydraulic fracturing;
• theoretical and general advances in the field of discrete models.

Computational approaches of interest include, but are not limited to Lattice models, Rigid-body-spring networks, Lattice Discrete Particle Model (LDPM), Discrete Element Method (DEM), and Molecular Dynamics (DM).

Syed Yasir Alam (Ecole Centrale de Nantes, France)
Gilles Pijaudier-Cabot (Université de Pau et des Pays de l’Adour, France)

The interaction between transport and fracture in concrete are advanced phenomena of great practical relevance for the durability of civil engineering structures. These structures are facing major challenges such as climate change, energy harvesting and extended service life where the interplay between transport mechanisms and cracks has become a major issue in the design of concrete materials. These processes not only affect the overall structural performance but also significantly alter the local chemical and physical equilibrium resulting into damaging microstructural events such as crystallisation pressure, decalcification, pore pressure and increase in permeability. Considering the heterogeneous nature of the material and embracing a wide range of length scales from the atomistic level to the structural level, new approaches are constantly emerging to establish the coupling between cracking and transport mechanisms.

The objective of this mini-symposium is to share and discuss recent achievements in coupled transport fracture problem of cement based materials including experimental, theoretical and computational approaches. The topics of interest include, but are not limited to, the following:

• Advanced experimental characterization of transport processes, material degradation and structural failure under coupled loadings.
• Theoretical modelling and computational techniques from atomistic level to structural level for improved understanding and efficient prediction of coupled problems.
• Chemical degradation such as alkali silicate reaction, sulphate attack, acid attack, chloride ingress, carbonation, leaching or corrosion of reinforcement.
• Cracking due to combined climatic and mechanical actions such as creep, shrinkage, radiation, freeze-thaw, gas and moisture diffusion, fatigue and vibrations.
• Life-time and safety assessments of (reinforced concrete) structures subjected to combined climatic and mechanical actions.

Alfred Strauss (BOKU University, Austria
David Léhky (Brno University of Technology, Institute of Structural Mechanics, Czech Republic)
Drahomír Novák (Brno University of Technology, Institute of Structural Mechanics, Czech Republic)

In the last few years, there has been an increased societal and industrial demand for reliable assessment and design of structural systems that meet durability criteria for at least several decades. The life cycle characterisation of civil engineering structures in terms of anticipated service life remains a significant aspect of sustainability in the construction industry. This requires special attention to the definition of structural performance supported by experimental–computational characterization of mechanical fracture properties of the used materials based on fracture mechanics and inverse analysis. This is particularly relevant in the context of the recent development of new eco-efficient materials and adaptive manufacturing technologies.

This mini-symposium will present current trends in the use of reliability concepts and probabilistic nonlinear finite element modelling in the design and assessment of structures for performance and sustainability. The Mini-symposium will cover topics and case studies ranging from the development of new materials through advanced experimental–computational characterization of their properties, to the design and assessment of components/structures with respect to desired performance, safety, durability and sustainability throughout their life cycle.

Jing Yu (The University of Hong Kong, Hong Kong)
Botao Huang (Zhejiang University, China)
Qian Zhang (Florida A&M University-Florida State University, USA)
Iurie Curosu (Ruhr-Universität Bochum, Germany)

Since 1990’s, research on fracture of composites has led to the development of Engineered/Strain-Hardening Cementitious Composites (ECC/SHCC). The design approach is to achieve synergistic interactions between the matrix, fiber and matrix/fiber interface, to maximize the tensile performance while minimizing the dosage of short random fibers (generally less than 3% by volume). The ultimate tension strain of ECC/SHCC can reach 3-10%, which is hundreds of times that of ordinary (fiber-reinforced) concrete. Additionally, the crack width can be self-controlled (typically < 100 μm). Some full-scale structural applications have already appeared in Asia, Europe, and the United States, and the development of ECC/SHCC is still evolving.

This mini-symposia focuses on the recent development of ECC/SHCC. Contributions covering experimental, numerical, and theoretical aspects on ECC/SHCC are welcome.

Giovanna Xotta (University of Padova, Italy)
Ignacio Carol (UPC – Technical University of Catalonia, Spain)

Achieving a thorough comprehension and accurate modelling of the mechanisms behind concrete deterioration in real-world conditions, typically exposed to couple or even multiple aggressive conditions, suffering from the combined effects of mechanical load, physical attack, and chemical corrosion that operate at several length scales, remains an ongoing challenge and a widely discussed subject.

When exposed to increasing mechanical loads, cementitious materials initially develop distributed micro-cracks, some of which may eventually coalesce into localized macro-cracks. In addition to direct mechanical actions, concrete cracking is often caused by environmental processes or actions induced by flow/diffusion/reactivity/transport. This includes, for example, but is not limited to, cracking due to differential volume changes from durability-related phenomena such as drying shrinkage, sulphate attack, carbonation, alkali-silica reaction, freeze-thaw cycles and high temperatures.

A proper understanding and assessment of the various potential deterioration mechanisms, that can affect concrete and act simultaneously requires robust multi-physics models, where the level of coupling can vary substantially from case to case.

The highly heterogeneous nature of these materials also plays a key role in the crack-forming process, and micro- or meso-mechanical models, where heterogeneities are explicitly described, can greatly simplify the constitutive description, but at the same time provide a much more powerful tool for representing the behavior of materials in simple and complex scenarios, such as combinations of mechanical and diffusion-driven or coupled environmental actions. All this comes at the expense of increased computational effort, which in turn may require high-performance parallel computing.

This mini-symposium is intended to gather contributions on all those and related topics, including mainly numerical modelling, but also related experimental and theoretical studies. Classical models based on a continuum or a discrete approach, as well as more recent techniques such as XFEM, phase field, etc. are also welcome. This mini-symposium is dedicated to the memory of our esteemed friend and colleague Prof. Kaspar Willam, who, among other interests, devoted part of his research efforts to the topics proposed.

Tinh Quoc Bui (Duy Tan University, Vietnam)
Erkan Oterkus (University of Strathclyde, UK)
Gianluca Cusatis (Northwestern University, USA)
Nobuhiro Chijiwa (Tokyo Institute of Technology, Japan)
Yehui Bie (Peking University, China)
Erdogan Madenci (University of Arizona, USA)

Concretes and concrete structures are the backbone of many civil engineering applications and infrastructure systems. Understanding their failure mechanisms is essential and important, especially with the evolving demands of modern design and maintenance. In recent years, many computational approaches have been developed and demonstrated in different applications in a wide range of engineering fields, and they have now reached a high level of quality. This symposium aims at providing a comprehensive yet concise overview of the recent advances in fracture and damage modeling of these civil engineering materials and structures using advanced and modern computational approaches. We welcome (but are not limited to) the following approaches:

• Local and nonlocal damage models
• Peridynamics
• Phase field model for fracture
• Gradient-enhanced damage models
• Discrete and smeared damage approaches
• Machine learning based computational approaches for concrete and structures
• Enrichment-based discrete approaches
• Lattice discrete particle model

Amin Hariri-Ardebili (National Institute of Standards and Technology (NIST), USA)

Concrete structures, due to their inherently heterogeneous and multiphase nature, exhibit significant variability in mechanical, chemical, and physical properties. Understanding and accounting for this variability is essential for accurate reliability assessments and the development of robust design codes. This mini-symposium will focus on state-of-the-art probabilistic approaches and uncertainty quantification techniques in the context of concrete fracture mechanics, emphasizing the interpretation of probabilistic results through machine learning and artificial intelligence.

Concrete’s complex internal structure introduces multiple sources of uncertainty that must be captured in analytical and computational models. These models often consider spatial variability in material properties, transforming local irregularities into global structural responses. Critical to these studies is the probabilistic characterization of material strength and the impact of these variabilities on structural reliability. This session invites contributions that explore innovative methods for quantifying uncertainties and their implications on concrete fracture. Topics of interest include, but are not limited to:

• Probabilistic modeling of damage and failure mechanisms in concrete structures
• Size effects and statistical scaling in fracture mechanics
• Stochastic models for spatial variability in concrete properties
• Reliability assessment techniques for concrete structures under uncertainty
• Incorporation of variability in strength into design standards and codes
• Analysis of large-scale experimental databases using probabilistic methods
• Modeling of fatigue life and its uncertainty in concrete materials
• Advanced techniques for uncertainty quantification in fracture analysis
• Utilization of machine learning and AI for interpreting probabilistic outcomes
• Case studies demonstrating practical applications of probabilistic and uncertainty quantification methods in concrete fracture mechanics

By bringing together experts in probabilistic modeling, structural reliability, and machine learning, this mini-symposium aims to advance the understanding and practical application of uncertainty quantification in concrete fracture mechanics.