Czech Academy of Sciences, Institute of Theoretical and Applied Mechanics

Abstract This study investigates the materials and construction techniques employed in the Baroque stucco decorations of the ground-floor halls at Kroměříž Château, executed by Baldassarre Fontana and his workshop. The material composition of sixteen samples was analysed using optical microscopy, SEM-EDS, XRD, thermal analysis, and acid dissolution. The results revealed the deliberate use of high-purity calcitic lime, sourced from Devonian limestone near Přerov and gypsum from the Ketř-Opava basin. Two mortar types were identified: a lime-gypsum-sand core modelling mortar and a lime-rich finishing stucco mortar, reflecting layered application techniques. The presence of crushed marble in certain decorations suggests recipe changes and indicates a multi-phase construction process possibly extending beyond Fontana’s supervision. Surface finishes were initially limited to white limewash, later overpainted with layers containing zinc white pigments. The findings highlight 17th-century stucco practices, provide a foundation for further conservation and historical research, and establish a benchmark for Central-European Baroque stucco studies.

In this work, an in-situ study of phase transitions in low-carbon steel is presented. The phase changes were monitored by the transmission energy dispersive X-ray diffraction technique during the heating, annealing and quenching cycle of the sample under standard laboratory conditions. During energy dispersive X-ray diffraction, the sample volume was transmitted with a pencil beam generated by a standard polychromatic X-ray tube without any spectral filtering. Two-dimensional polychromatic diffraction images were acquired by a Timepix3 pixelated detector. This detector is capable of achieving a throughput of up to 38Mhits/s in continuous stream mode using USB 3.0 interface. For each detected photon, its position is known with an accuracy of 55µm in the detector plane and its energy with a resolution of 4keV at 60keV. The recorded polychromatic data is then recomputed to get the equivalent monochromatic XRD pattern that would be produced using a monochromatic X-ray source. Thanks to the 90kV voltage potential of the X-ray tube, the polychromatic pencil beam was able to pass through a highly attenuating sample made of 1.5 thick steel sheet. In addition, by utilizing the entire X-ray spectrum, the pencil beam has a sufficiently high brilliance to obtain XRD patterns rapidly enough to investigate relatively fast processes with temporal resolution of 10s. It made to possible to analyze the phase transitions in a polycrystalline sample during its temperature treatment under standard laboratory conditions.

Abstract Replacing limestone aggregates with lightweight ones, such as pumice, results in more sustainable concrete. However, cracking at early ages poses a significant concern for its structural use. In this work, we use X-ray computed tomography to study cylindrical lightweight concrete specimens before and after uniaxial compression to enhance our understanding of how pumice affects the development of tension cracks in the concrete matrix. The results show smaller particles and those with a higher aspect ratio break less. Whilst there’s no proof that the orientation of the particles affects breakage, there are indications that the internal porosity of the particles is highly anisotropic, and its orientation with respect to the loading direction will determine whether the pumice will break or not.

Abstract While the positive effect of trees on thermal comfort is well‐established, particularly in urban street canyons, their impact on air quality remains questionable, especially in the case of pollutants emitted by heavy traffic at the pedestrian level. Complex microscale models of an urban boundary layer with a high spatial resolution (down to 1 m) enable a deeper understanding of most processes at street‐level scale and can simulate selected variables related to air quality and bio‐meteorology with high precision and fidelity. In this study, scenarios with different percentages of tree coverage of two streets were simulated under different atmospheric stratifications to investigate the problem. Real geography and quasi‐real meteorology were used as a background. Results of the Parallelized Large‐eddy Simulation Model (PALM) model simulations, which utilised a large‐eddy simulation (LES) core, showed the spatio‐temporal variability of the thermal comfort and dust concentration at the pedestrian level. The findings indicate that the effect of trees on the local microclimate is crucial and complex and cannot be omitted during the planning of urban mitigation measures. The study demonstrates a notable improvement in thermal comfort, with a significant decrease in the thermal index in shaded areas beneath trees during the hottest part of the day, as well as a cooling effect of urban greenery just after sunset. However, the analysis also revealed a significant downside: in narrower streets, concentrations increased by more than 100% compared with tree‐free scenarios. The slowdown and vertical shift of the primary vortex within the street caused by the trees can mostly explain the changes in pollution dispersion. This indicates a potential trade‐off between thermal comfort and air quality in densely built urban environments.

Abstract Nature has long served as a source of inspiration for the development of new materials, with foam‐like structures in citrus fruits such as oranges and pomelos serving as examples of efficient energy dissipation. Inspired by the internal structure of citrus fruit, soft conductive silicone foams are fabricated. The foams are made from a polydimethylsiloxane (PDMS) by mold casting using sugar templates. Addition of silicone oil and carbon black to the silicone allows creation of extremely soft foams that serve as resistive sensor. Completed by a pneumatic radial compression actuator (PRCA) surrounding the foams like a ring in analogy to citrus fruit peel, smart tunable dampers with sensing capabilities are demonstrated. The foams are evaluated for their electrical and mechanical properties alone as well as in conjunction with the PRCA. When pressurized, the PRCA radially compresses the smart foams, allowing to tune their stiffness and thus damping properties. Tunability of this system is evaluated by means of ball drop tests with respect to damping as well as the sensor performance regarding its sensitivity and stability. Overall, the study provides valuable insights into the behavior of conductive silicone foams and their potential as cushioning and impact sensing material.

<p>Climate change accelerates the degradation of the built environment, affecting material integrity and structural performance. With global projections anticipating intensified climate patterns, there is a pressing need for reliable risk assessment methods and climate-tailored, resilience-building measures. This paper presents an ongoing project, investigating the impact of climate change on key engineering infrastructure using wind tunnel simulations. The aim is to identify critical resilience parameters, damage functions and risk indicators. Activities include field measurements and observations, and laboratory work in the climatic tunnel to investigate climate phenomena and the response of building materials and structures. Results will contribute to the definition of upgraded safety evaluation methodologies and guide future research on technical recommendations and user-oriented strategies addressing engineering, economic, and social aspects.</p>