The research paper titled "Mechanics of longitudinal joints in segmental tunnel linings: A semi-analytical approach" has been witten by Zhen Liu, Xian Liu, Abdullah Alsahly, Yong Yuan, and Günther Meschke.
It is now published in "Tunnelling and Underground Space Technology" by Elsevier.

Abstract:
To meet basic structural serviceability and durability requirements throughout the life of tunnels, the design and evaluation of segmental tunnel linings requires accurate structural models. Considering that segmentation introduces non-trivial kinematics to the lining system, it is important to properly evaluate the moment-rotation relationship for longitudinal joints. In this study, a nonlinear semi-analytical model is proposed to assess the mechanical behavior of the longitudinal joint, taking into account the nonlinear behavior of the concrete in the vicinity of the joint and the contact deformation induced by the roughness of the contact surface. Through the proposed model, the moment-rotation relationship of the joint and the stress distribution in the vicinity of the joint are obtained simultaneously without the need for highly resolved finite element analyses. It is demonstrated how the proposed model can be applied to parametric analysis of joint configurations and to predict tensile stresses that may cause spalling and splitting cracks. The performance of segmental joints is systematically investigated, revealing a more accurate distribution of the contact pressure and the deformations and the stress field within the joint influence zone. To fully consider the influence of the joint, the effective joint rotation angle is defined to consider the additional rotational flexibility resulting from the joint-induced deformations, which attributes to the contact deformation and the disturbed stress field within the joint influence zone. Since the joint rotation angle calculated based on the classical rigid plate assumption (nominal joint rotation angle) tends to overestimate the effective joint rotation angle, a correction factor relating the nominal and the effective joint rotation angles is proposed for practical applications.

The full paper is providing a 50 days' free access and is avialable until June 24, 2025: Personalized Share Link/a>
or is available via

"A finite strain model for fiber angle plasticity of textile fabrics based on isogeometric shell finite elements" by Thang X. Duong and Roger A. Sauer has been published in "Journal of the Mechanics and Physics of Solids" Volume 200, July 2025, 106158 by Elsevier.

Abstract:
This work presents a shear elastoplasticity model for textile fabrics within the theoretical framework of anisotropic Kirchhoff–Love shells with bending of embedded fibers proposed by Duong et al. (2023). The plasticity model aims at capturing the rotational inter-ply frictional sliding between fiber families in textile composites undergoing large deformation. Such effects are usually dominant in dry textile fabrics such as woven and non-crimp fabrics. The model explicitly uses relative angles between fiber families as strain measures for the kinematics. The plasticity model is formulated directly with surface invariants without resorting to thickness integration. Motivated by experimental observations from the picture frame test, a yield function is proposed with isotropic hardening and a simple evolution equation. A classical return mapping algorithm is employed to solve the elastoplastic problem within the isogeometric finite shell element formulation of Duong et al. (2022). The verification of the implementation is facilitated by the analytical solution for the picture frame test. The proposed plasticity model is calibrated from the picture frame test and is then validated by the bias extension test, considering available experimental data for different samples from the literature. Good agreement between model prediction and experimental data is obtained. Finally, the applicability of the elastoplasticity model to 3D shell problems is demonstrated.

The open access article is available here:

A new publication titled "A Multiscale Model for Predicting the Young’s Modulus and the Thermal-Expansion Coefficient of Concrete at High Temperatures” by Simon Peters, Giao Vu, Günther Meschke has been released in the journal Construction and Building Materials by Elsevier.

Abstract:
A semi-analytical micromechanical model is proposed to predict the evolution of the Young’s modulus and thermal-expansion coefficient of concrete at elevated temperatures, considering three scales of observation, namely cement paste, mortar and concrete. After validation with various experimental data sets, the model quantifies different sources of damage to concrete at elevated temperatures, indicating that the chemical decomposition of cement paste has a minor influence on the evolution of the Young’s modulus, while the thermal degradation of the aggregate plays a major role. At higher temperatures, cracking is the main mechanism driving the reduction of the Young’s modulus of the investigated concretes.

With regard to the thermal-expansion coefficient evaluated at multiple scales, load-induced thermal strains highly effect the homogenized total strains at the mortar level. Moreover, it is demonstrated that the dehydration degree of C-S-H increases proportionally with the measured load-induced thermal strains.

You can read the full paper as open access publication here:

On Monday, 28. April 2025 at 1PM, the doctoral defense of Stefanie Schoen took place. The title of her dissertation was: Reliability analysis and design of RC and SFRC structures considering Polymorphic Uncertainties.


Dear Stefanie, congratulations on your successful defense! We wish you all the best as you take on further achievements.

Abstract:
Ensuring structural safety requires a precise understanding of uncertainties in material properties, environmental conditions, and modeling assumptions. This dissertation advances the design of reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) structures by integrating polymorphic uncertainties – combining aleatory and epistemic uncertainties – into a reliability-based framework. While aleatory uncertainties account for inherent randomness, such as material heterogeneity, epistemic uncertainties stem from limited knowledge, including variations in fiber orientation.

Building on semi-probabilistic safety concepts, this study employs probabilistic methods to quantify failure probabilities across ultimate and serviceability limit states. However, accurately estimating low failure probabilities requires a large number of realizations, making finite element simulations computationally prohibitive. To overcome this challenge, reliability analysis is combined with a Transformer-based model for uncertainty quantification.

Finally, reliability-based design optimization reveals that while steel fibers can partially replace conventional reinforcement, their greatest value lies in complementing its – substantially reducing crack width sensitivity to stochastic loads and enhancing durability. Hence, this thesis underscores the importance of integrating uncertainties and the strategic use of steel fibers in the sustainable and durable design of concrete structures.

For further information please check:

Every year at the IA-FraMCoS, young researchers under 40 who are the first author of their paper have the chance to be awarded with the Young Researcher Best Paper Award.

This year, Koussay Daadouch and Vladislav Gudžulić from the Institute for Structural Mechanics received an Honorable Mention for their papers:

A Mesh Adaptation Algorithm to Reduce Mesh Bias in 2D And 3D Crack Propagation Analysis Using Cohesive Zone Models
Authors: Koussay Daadouch, Vladislav Gudžulić, Günther Meschke

Computational Analysis of Size Effect and Failure Modes In Reinforced Concrete Beams
Authors: Vladislav Gudžulić, Günther Meschke

Both papers are available as open access papers on the conference website https://framcos12.conf.tuwien.ac.at/programme/awards/ .

We all congratulate them both on their success!