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Modeling Vertical Gravity Gradients Using Geodetic and Geological Data
No full textThe vertical gravity gradient, defined as the change in gravity with height, is a crucial physical quantity that plays an essential role in various geodetic and geophysical modelling and data processing applications. It is also significant in the processing of gravity measurements, as gravity acceleration measured by an instrument must be reduced from the sensor level to a stabilized reference point. Typically, the normal vertical gravity gradient (308.6 μGal/m) is used, representing a generally accepted average value. However, the actual values of the vertical gravity gradient values can vary considerably.
Our research has modelled the vertical gravity gradient using normal gravity fields, digital terrain models, and density models of the Earth’s surface without taking into account gravity anomalies on the geoid or the physical Earth’s surface. The chosen approach falls into the category of “forward modelling methods”. The gravitational effect of the topographic masses was modelled by summing the topographic masses between the ellipsoid and the geoid and those between the geoid and the Earth’s physical surface, using a rectangular prism as the fundamental body. Notably, in the modelling process, we did not use any data on the Earth’s gravity field (e.g., anomaly field), but only topographic data (DTM) and surface topographic mass density data (DDM). Instead of the usual circular boundary, we used a square boundary for the study area, avoiding edge problems and improving computational efficiency. In addition, the theoretical equations used in the modelling process can be applied regardless of the geographical location and altitude of the analyzed point.
We utilized various available input data, combining digital terrain models and surface density models, including a constant average topographic mass density of 2670 kg/m³. Several global density models exist, created in different time periods that are used in geodesy and geophysics for gravity field modelling. However, using or creating regional or local density models that provide significantly more detailed data is reasonable. For this purpose, we have also created a 2D density model of surface topographic masses for the entire test area of Slovenia.
We also tested different calculation distances around the analyzed points, thereby modifying zone divisions. By combining different input data, we created various models (54 in total), which were then used for comparative analysis, result evaluation and impact assessment.
Using this approach, we conducted vertical gravity gradient modelling at 44 reference points, which were divided into test area 1 (13 points) and test area 2 (31 points). The subdivision was based on the availability of different input data. We performed vertical gravity gradient measurements using a relative gravimeter at all 44 points before modelling. This enabled a direct comparison of the modelled and measured vertical gravity gradient values. The modelling error, defined as the difference between the measured and modelled values, was calculated and analyzed. Based on the deviations between measured and modelled values, we performed analyses and statistical evaluations of the results. Consequently, we derived an optimal model and criteria for selecting data in modelling vertical gravity gradients
Soil-Structure Interaction Effect on Seismic Response of Mid-Rise RC Buildings
No full textIt has long been considered that dynamic soil-structure interaction (DSSI) has a beneficial effect on the seismic response of structures. This assumption stems from the idea that taking into account DSSI increases the overall structural flexibility, thereby reducing seismic forces. However, this rationale oversimplifies the complex and highly coupled behavior of soil-structure systems. Consequently, DSSI was often neglected in practice, with structural design based on fixed-base models.
To identify conditions under which DSSI effects become critical, this study investigates the seismic response of mid-rise RC shear wall buildings through parametric analysis of key structural parameters. Four building types were modelled using the finite element method, considering both fixed-base and DSSI conditions. DSSI effects were accounted for through impedance functions of the soil, calculated for three different soil types, representing stiff, medium, and soft ground. Response spectrum analyses based on substructuring approach were carried out for all models using spectra derived from three recorded ground records and one design response spectrum. The seismic performance of all building models was evaluated in terms of base shear and roof displacement.
The results reveal that conventional assumptions regarding DSSI do not always hold. Although DSSI consistently leads to longer vibration periods, it does not necessarily result in reduced base shear. In several cases, especially for stiffer models founded on soft soils, base shear increased compared to the fixed-base models. In contrast, effects of DSSI on more flexible models were negligible. Roof displacements generally increased when DSSI was considered, particularly for stiff models on soft soils. These findings suggest that while DSSI can have beneficial effects in certain configurations, it may also amplify critical response parameters in others
Static and Dynamic Determination of Stiffness Properties of CLT Panels
No full textCross laminated timber (CLT) is becoming increasingly popular in contemporary buildings due to simple production techniques, high level of prefabrication, high strength-to-weight ratio and good insulating capabilities. Mechanical properties of CLT can be obtained either by experimental testing on full-scale elements or by computational methods based on geometric data and material properties of constituent boards. Design of CLT panels is mostly governed by serviceability limit states (limits for vibrations and deflections), making stiffness properties very important. This paper presents dynamic and static experimental testing of three identical samples of CLT panels with the aim of determining stiffness properties. Dynamic (modal) testing included excitation of transverse vibrations of CLT panels using an impact hammer. Vibration response was analysed using operational modal analysis (OMA) technique. Analytical model for predicting the fundamental frequency was used to calculate bending stiffness of panels. Static four-point bending test was then performed on same CLT panels and global bending stiffness was determined based on load-deflection curves. The results showed that value of static bending stiffness is greater than dynamic bending stiffness with a difference of only 3% on average. Modal testing can be a reliable option for measuring bending stiffness of CLT panels due to its
non-destructive nature and short testing time
First look inside the gravity field of Montenegro
No full textThis study is the first dedicated investigation of Montenegro’s gravity field. Using 1301 gravimetric points, 44 height anomalies, and the selected Global Geopotential Models, gravity anomalies were determined across the territory. Free Air anomalies range from −124.74 to 32.29 mGal, and Bouguer anomalies from −151.14 to −29.56 mGal. The quasigeoid shape was recovered, with height anomaly differences of −6 cm to 13 cm compared to GPS levelling. Despite the irregularity in data, a preliminary geoid model has been determined. The findings emphasize the need for more detailed gravity data within Montenegro and neighbouring countries to enhance the model's reliability
Pasoš za renoviranje zgrada u cilju dostizanja nulte emisije gasova do 2050. godine – studija slučaja višeporodične stambene zgrade u Srbiji
No full textTransformacija fonda zgrada ka nultoj emisiji gasova do 2050. godine jedan je od ključnih ciljeva Evropskog zelenog dogovora i nove EPBD direktive. Zgrade, kao najveći potrošači energije, zahtevaju sistemsku i dubinsku obnovu. Pasoš za renoviranje zgrada (Building Renovation Passport – BRP) uveden je kao alat koji omogućava fazni i strateški pristup unapređenju energetske efikasnosti i dekarbonizaciji izgrađenog okruženja. Ovaj rad prikazuje metodologiju razvoja BRP-a kroz studiju slučaja tipične višeporodične stambene zgrade iz 1980-ih u urbanom delu Srbije. Renoviranje je podeljeno u tri faze: poboljšanje omotača zgrade, optimizacija tehničkih sistema i integracija obnovljivih izvora energije. Kroz analizu troškova, koristi i prepreka, rad pokazuje kako BRP može doprineti postepenoj i održivoj obnovi, omogućavajući vlasnicima dugoročno planiranje i informisano donošenje odluka u pravcu zgrada bez emisija
Decoupling Nexus Interlinkages: Strategies for Urban Resilience
No full textClimate change is increasingly driving the frequency and intensity of extreme events, which
significantly impact human societies' wellbeing and resilience. This situation is worsened by population growth, urbanization, and changes in land use, which often heighten the
vulnerability and exposure of human systems. Additionally, the complexity of modern human
systems, characterized by the interconnectedness of critical entities, makes urban areas
particularly prone to domino effects triggered by a single initial shock.
This study aims to understand and assess the Nexus effects of extreme events related to
climate and other natural hazards, such as earthquakes, volcanoes, and tsunamis. It considers
an extended Water-Energy-Food Nexus schema, incorporating Ecosystems, Climate, Soil,
Transportation, Land Use, Health, and Information and Communication Technologies.
The analysis synthesizes practical case studies of extreme events that have occurred over
the last few decades, primarily in Europe. It examines the implications across three
timescales: short-term, mid-term, and long-term. The study employs a modified Nexus
oriented literature review approach, analyzing nine different types of extreme events:
droughts, earthquakes, floods, heatwaves, landslides, tornadoes, tsunamis, volcanoes, and
wildfires. At least three case studies are analyzed for each type of extreme event.
For each case study, the Nexus tree approach is applied. The synthesis of the Nexus trees
for each extreme event will create the Nexus signature of that specific event. Based on these
signatures, an inventory of recommendations for decoupling the nexus interlinkages will be
developed. These recommendations will be categorized into operational, tactical, and strategic
levels, corresponding to the three impact horizons. Special focus will be given to the
implementation of Nature-based Solutions.
The ultimate goal of the NEXUSNET taskforce is to provide tangible tools and capacity to
enhance urban resilience against climate change-induced and other extreme events
Structural analysis and geometric patterns of the Romanesque portals in medieval Serbia: the case study of Studenica
No full textThis paper presents structural analysis and geometric properties of Romanesque portals in Serbian medieval churches, built under patronage of the Nemanjić dynasty (12th–14th centuries). Using geometric analysis, 3D modeling and stress simulations in SolidWorks, the study aims to deepen understanding of structural behavior of portal's elements, related to the portal's architectural design - geometric shaping, constraints and proportioning. This research contributes to cultural heritage preservation by examining the way geometry influences the stability and longevity of the portals of medieval structures
The model for grain wheat yield prediction at highspatial resolution based on physical-geographicalproperties and satellite vegetation indices
No full textPrecision agriculture is promising approach for improving agricul-tural production, especially nowadays when the population is rap-idly increasing. For that, crop yield estimation provides valuableinformation. The main research focus was to predict within-fieldgrain yield and detect its drivers. The Random Forest regressionmodel on data from diverse sources at the 10-meter spatial reso-lution was developed. The study was conducted in the Vojvodinaregion (Serbia) for eight wheat-planted fields, having precise grainyield data. Open-source data including 15 vegetation indices (VIs)was calculated from Sentinel-2 satellite bands, physical-geograph-ical features obtained from the digital elevation model and soilproperties. The model succeeded in predicting the wheat grainyield with the RMSE of 0.66 t/ha (average yield of 0.09 t/ha) andthe best predictors were VIs considering chlorophyll and moisturecontent in plants, while physical-geographical properties man-aged to explain within-field variability. This methodology can beapplied to other crops (maize, soybean)
RCF Irregularities on the Rail Head – Guidelines for Maintenance
No full textThe focus of the paper is on defining clear guidelines for the identifi-cation, monitoring, and management of these phenomena with the goal of ex-tending the service life of both railway infrastructure and rolling stock, while also improving the overall efficiency of the maintenance system. The manage-ment of rail defects is approached as an integral part of both track superstruc-ture and substructure maintenance systems. Modern non-destructive testing methods are recommended for rail inspection, including ultrasonic and eddy current techniques, which allow for the detection of internal and surface flaws without damaging the material. Control of defect development involves the use of grinding, rail head reprofiling, lubrication on curved track sections, and time-ly rail replacement in cases where the risk of fracture becomes critical. Special attention is given to dangerous combinations of multiple fatigue-related defects, which can significantly increase the risk of sudden failure. The paper contrib-utes to the advancement of predictive and preventive maintenance strategies in modern railway systems
Seismic Perfomance of RC Frame Buildings with Decoupled Infills
No full textDecoupled infills have been recently proposed to improve the seismic performance of infilled RC frame buildings. In this paper, the so-called INODIS system, developed at the RWTH Aachen University, is investigated. The INODIS system exploits soft elastomeric material to decouple masonry infills from the surrounding frame, while withstanding OOP loads through a suitable mechanism. A typical 6-storey RC frame building equipped with, alternatively, traditional and decoupled infills is examined through Nonlinear response-time history analyses, considering IP/OOP interaction for the infills. The results of this study clearly confirm the good seismic performance and significant damage reduction achievable with decoupled infills