The article 'A computational model for short-range van der Waals interactions between beams and shells' written by A. Borković, M.H. Gfrerer, R.A. Sauer has been published in 'Computer Methods in Applied Mechanics and Engineering' by Elsevier.

Abstract
We consider potential-based interactions between beams (or fibers) and shells (or membranes) using a coarse-grained approach with focus on van der Waals attraction and steric repulsion. The involved 6D integral over volumes of a beam and a shell is split into a 5D analytical pre-integration over the beam’s cross section and a surrogate plate tangential to the closest point on the shell, and the remaining 1D numerical integration along the beam’s axis. This general inverse-power interaction potential is added to the potential energies of the Bernoulli–Euler beam and the Kirchhoff–Love shell. The total potential energy is spatially discretized using isogeometric finite elements, and the nonlinear weak form of quasi-static equilibrium is solved using the continuation method. We provide error estimates and convergence analysis, together with two intriguing numerical examples. The developed approach provides excellent balance between accuracy and efficiency for small separations.

Read the open access article here:

On Friday, 14 August 2026, at 2:00 PM Giao Vu gave her PhD defense, titled 'A Virtual Coda Wave Interferometry Laboratory for Damage Assessment in Reinforced Concrete Structures'.

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Dear Giao, congratulations on defending your PhD successfully! We wish you great success in your future ahead!

Abstract:
Concrete infrastructure ages long before it fails visibly. Detecting that deterioration early – while repairs are still cheap – is one of the central challenges in structural health monitoring. Coda Wave Interferometry (CWI) offers a promising solution by exploiting the late-arriving portion of ultrasonic measurements. Having travelled repeatedly through the material, these waves sample a far larger volume than conventional methods and are sensitive to microstructural change. Embedded ultrasonic sensors are inexpensive, making CWI an attractive basis for permanent monitoring systems. The obstacle is interpretation: a measured signal change tells us that something has happened inside the concrete, but not what, where, or how severe.

This thesis closes that gap with a virtual CWI laboratory. Meso-scale models simulate the cracking process and the ultrasonic waves travelling through it, linking a structure‘s internal state directly to its measured response. The framework was validated against real experiments from material specimens up to reinforced concrete beams, across varying mixtures, structural layouts, and sensor configurations.

The result is a quantitative map from velocity change to what engineers care about: crack width, reinforcement strain, stiffness degradation. The synthetic data then trained a transformer-based classifier which, after domain adaptation, predict damage states from real measurements with good accuracy.

Together, the framework provides scalable tool for designing sensor networks, generating validated training data, and translating monitoring signals into decisions.

'Measurements of Fiber and Load-rate Effects on Micro- and Macro-fracture of Ultra-High- Performance Concrete' is the title of the lecture given by Prof. Eric N. Landis (University of Maine, USA) on Friday, 14 August 2026.

Abstract:
Advances in 3D imaging have opened up different ways to observe the internal mechanisms that dictate how a material dissipates energy under extreme loading conditions. Specifically, quantitative analysis of such 3D images allow us to measure fracture and damage in new ways. In the study presented here, several new analysis techniques were applied to an ultra-high-performance concrete subjected to different loading rates. The cylindrical specimens were subjected to x-ray CT scans to create 3D images of the material‘s internal structure. Using a combination of digital volume correlation and discrete crack measurements we were able to break total damage down in macro-cracking and micro-cracking. Here the micro-cracking is defined as that due to the residual strain measured through DIC that is not visible as a macro-crack. While this definition is somewhat arbitrary and dependent on the resolution of the images, it allows us to quantify the effects of both loading rate and micro-structure on the distribution of cracking and damage in the material. Such quantitative information can be used to tune and validate computational models for these materials.

The Faculty of Civil and Environmental Engineering has nominated Lennart Stöttelder for the 2026 RUB Student Award in recognition of his outstanding thesis, 'Computationally Simple and Efficient Locking Alleviation in Isogeometric Thin Shells.' This prestigious prize is conferred annually by the Rectorate of Ruhr University Bochum.

The master thesis presents an improved version of the hybrid membrane-bending interpolation method of Sauer et al. (2024) for isogeometric thin shells. The proposed modifications reduce computational cost through reduced integration and a single-element formulation while preserving the locking-free behavior and accuracy of the original method. Extensive L2-error convergence studies demonstrate the superior performance of the proposed B2M1-formulation compared to classical isogeometric shell formulations.

We congratulate Lennart on his award.

The open access article with the title "A Survey of Interlayer Interaction Models for Graphene and Other 2D Materials in Advanced Materials Interfaces" written by Gourav Yadav, Shakti S. Gupta, Roger A. Sauer, is now published in "Advanced Materials Interfaces" by Wiley.

Abstract:
This work presents a survey of mechanical models describing van der Waals interactions between 2D materials, encompassing both continuous elastomer-like materials and discrete (crystalline) 2D materials such as graphene. These interactions give rise to a range of physical phenomena, including contact instabilities, Moiré patterns, surface reconstructions, and superlubricity. The underlying contact forces follow from the variation of an interfacial interaction potential. The presentation first discusses normal contact models, and then tangential contact models. Both atomistic and continuum approaches are considered. In addition, the influence of external loading and changes in length scale on the ground state configuration and frictional contact behavior are analyzed. A particular emphasis is placed on discussing strategies that reduce computational cost in multiscale modeling.