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- ItemOptimisation of fine RCA content in mortar mixture based on the long-term fracture and fatigue tests(Elsevier, 2025-05-06) Miarka, Petr; Šimonová, Hana; Kucharczyková, Barbara; Seitl, Stanislav; Poletanovic, Bojan; Merta, IldikoThis paper presents the results of an experimental study with a focus placed on the long-term mechanical-, fracture- and fatigue analysis of mortar, in which natural aggregates (NA) were partially substituted with fine recycled concrete aggregates (RCA). Long-term tests were done at 28, 145 and 255 days under natural aging conditions. Fracture and fatigue experimental analysis took place for tensile mode I, which was enriched by fracture tests performed under a combination of tensile and shear load – mixed-mode I/II loading conditions. In total, four mixtures (reference and three with fine RCA) were tested to examine the influence of the aggregate replacement on the fracture and fatigue properties of the material. The experimental results showed that 25% of replacement seems to be an optimum dosage of fine RCA, which improves both the fracture and fatigue properties of tested mixtures.
- ItemNon-linear digital twin-based performance and service life assessment(IA-FraMCoS, 2025-04-25) Strauss, Alfred; Taubling-Fruleux, Benjamin; Novák, Drahomír; Novák, Lukáš; Lehký, DavidThis work focuses on the load-bearing behavior of a specially reinforced existing pier of the Jauntal Bridge in Carinthia (DT Physical Model). This behavior is virtually simulated using a non-linear finite element model (DT Virtual Model). The aim is to draw conclusions about the constantly changing load conditions by observing the development of cracks and the geometric deformations (DT Monitoring, e.g., via orthographic and radar interferometry) and thus to make statements about the constantly fluctuating safety level and the fluctuating service life. Based on these findings, it should be possible to optimize the existing verification formats and the arrangement of the reinforcement measures, particularly the prestressing bars and the interaction between new and old concrete at the pier heads. Consequently, this would allow for a direct assessment of the constantly fluctuating loads and safety levels.
- ItemReliability 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, BenjaminMany 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.
- ItemGlobal Sensitivity Analysis and Surrogate Models for Evaluation of Limit States in Steel Truss Structures(North Atlantic University Union (NAUN), 2024-10-14) Kala, ZdeněkThis 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.
- ItemDetermination 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, StanislavThis 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.