Ústav stavební mechaniky

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Reliability assessment of historical reinforced concrete bridge piers based on nonlinear fracture mechanics modeling and safety formats
(IA-FraMCoS, 2025-04-25) Novák, Drahomír; Novák, Lukáš; Lehký, David; Strauss, Alfred; Taubling-Fruleux, Benjamin
Many existing concrete structures have been fulfilling their purpose for several decades, but they may no longer meet current structural safety standards due to various factors. This fact highlights the urgent need for innovative solutions to ensure the durability and performance of these structures under increasing load and changing environment. Statistical study has to be included to consider uncertainties, also safety formats approaches can be utilized. The aim of this research is to show how a procedure for quality control and safety assessment of 100 m high concrete piers was developed based on non-linear finite element analysis and digital twin technology considering uncertainties involved. Piers are parts of Jauntal bridge, a 60-year-old, 450 m long railway bridge that has been equipped with a new bridge deck. The purpose of the study was to investigate structural safety, serviceability, durability, and remaining service life of the bearing socket and pier systems equipped with a new confinement concept. The research uses a reliability-based approach utilizing advanced probabilistic methods, based on reliability index determination and efficient safety format approaches. Standard ECoV and Eigen ECoV methods were employed for an estimation of mean values and standard deviations for all steps of the finite element analysis, assuming two limit cases of probability distribution of resistance – Gaussian and Lognormal. The stochastic model contains only the 4 most significant random variables of the computational model representing the material characteristics of the concrete pier.
Global Sensitivity Analysis and Surrogate Models for Evaluation of Limit States in Steel Truss Structures
(North Atlantic University Union (NAUN), 2024-10-14) Kala, Zdeněk
This article presents the global sensitivity analysis of the serviceability limit state of a steel truss using Monte Carlo simulations. The focus is on the probabilistic assessment of deflection, with failure probability defined as the likelihood of exceeding the deflection limit. Deflection is computed using the beam finite element method. A surrogate model is introduced to reduce computational costs. By integrating the surrogate and original models, significant CPU cost reductions are achieved. Furthermore, classical Sobol sensitivity analysis is used to examine the model outputs and analyze the significance of member loading and stiffness on the deflection. This study advances the use of surrogate models in global sensitivity analysis, enhancing computational efficiency and the understanding of interactions between input variables in the reliability assessment of steel truss structures.
Determination of the geometric parameters of the defects based on the tomographically obtained data and their influence on the fatigue behavior of the S960 with laser cladded protective layers
(Gruppo Italiano Frattura, 2024-10-11) Doubek, Pavel; Kumpová, Ivana; Malíková, Lucie; Al Khazali, Mohammad Sami; Seitl, Stanislav
This article deals with identifying defects of layered high strength steel materials with the help of tomography measurement. Test samples were made of S960 High Strength Steel to which layers of either aluminium bronze, hardchrome, cobalt alloy or stainless steel were applied by a laser cladding technology. The experimental campaign included a study of morphometric parameters of internal defects in and near the bi-material interface region using X-ray micro-tomography and their potential influence on the fatigue behavior during a three-point bending test.
Hybrid Geopolymer Composites Based on Fly Ash Reinforced with Glass and Flax Fibers
(MDPI, 2024-10-26) Šimonová, Hana; Bazan, Patrycja; Kucharczyková, Barbara; Kocáb, Dalibor; Lach, Michal; Dariusz, Mierzwiński; Setlak, Kinga; Nykiel, Marek; Nosal, Przemysław; Korniejenko, Kinga
This article’s aim is to analyze physical, mechanical, and fracture properties as well as the thermal investigation of geopolymer composites reinforced with flax, glass fiber, and also the hybrid combination of fibers. Two types of matrices were considered as composites matrices. The first composition was based on fly ash and river sand. The second matrix composition contained fly ash and glass spheres. The content of reinforcement was 1% by mass. Compressive strength and three-point bending fracture tests were performed. The values of fracture toughness and fracture energy were determined. The resonance method was used to verify the dynamic characteristics, such as the dynamic modulus of elasticity and the dynamic Poisson ratio. The results show that single-type fibers in composites based on fly ash and glass spheres did not affect compressive strength. However, introducing hybrid reinforcement increased compressive strength by about 10% compared to the reference specimens. Flax fibers and hybrid reinforcement ensured higher fracture toughness and energy. The results also revealed great potential for glass sphere application to geopolymer materials in terms of fracture mechanics and thermal properties. Despite the lower strength properties in relation to geopolymers based on sand aggregate, applying reinforced fibers into the composite with glass spheres enhanced the compressive strength compared to other materials. Materials modified with glass spheres have a thermal conductivity twice as low as that of materials containing river sand.
Short fatigue crack behavior under various level of mixed-mode
(IOS Press, 2024-10-18) Malíková, Lucie; Miarka, Petr; Seitl, Stanislav
In this work, results of a numerical parametric analysis are presented in order to compare them with experimentally observed concrete cone failure features. Such a kind of failure is typical for cast-in steel anchors embedded in concrete substrates. Thus, numerical simulations via finite element method have been performed in order to investigate basic fracture parameters for specimens with a short fatigue crack and stress distribution for specimens without any crack. Several parameters were varied and their effect on the stress intensity factors or distribution of stress tensor components around the anchor corner were studied and discussed. Slight differences between the average angle typical for concrete cone failure observed experimentally and numerical results were found out and thus, more complex numerical simulations shall be recommended.

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