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Abstract: Seepage during the first filling of a reservoir is a critical aspect for earth dams and embankments safety, which requires precise monitoring. The thermometric method has demonstrated significant potential for detecting seepage anomalies through continuous temperature measurements using optical fiber distributed temperature sensing (DTS). However, most previous research has primarily focused on thermal monitoring when seepage flow reached a steady-state condition, which highlights the need for more research on seepage and heat transfer in transient state, particularly in unsaturated soils during the reservoir’s first filling. This paper addresses the transient seepage flow and heat transfer during the first filling of a laboratory sand model. Temperature variations within the sand were recorded using an optical fiber DTS, while seepage progression was tracked through digital imaging at regular intervals, followed by image processing. A coupled hydrothermal numerical model was also developed to simulate transient seepage flow and heat transfer within the unsaturated and variably saturated sand. In numerical modeling, heat dispersion and the thermal conductivity of sand were investigated through parameter calibration. Results indicate that thermal monitoring using optical fiber DTS is an effective method for estimating the development of the phreatic line during the first filling of the reservoir. Numerical simulations further revealed that seepage velocity plays a key role in the heat transfer process during transient seepage. Additionally, the results highlight that heat dispersion significantly influences heat transfer, particularly during transient seepage flow, whereas the effect of thermal conductivity is relatively minor as seepage progresses.
Keywords: seepage, phreatic line, temperature, heat dispersion, optical fiber DTS
Published in DiRROS: 09.05.2025; Views: 578; Downloads: 343
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Abstract: This paper presents results of in-plane shear tests carried out at the ZAG laboratory in Ljubljana (Slovenia) on a RC frame with masonry infill made of clay blocks (KEBE OrthoBlock). The frame was loaded with constant vertical loads at the top of the columns and then by gradually increasing horizontal cyclic loads at the top beam level. Acquired forces and measured displacements allowed capturing hysteretic behavior for determination of dissipation energy. In addition, two Digital Image Correlation (DIC) systems, Aramis and the CivEng Vision, were used to visualize the behavior of the tested specimens, with an emphasis on computing locally required information about the behavior of highly deformable interfaces. Three types of specimens were tested in-plane: the reference specimen in form of plain RC frame, the reference specimen with constructed masonry infill without any strengthening and the specimen, previously damaged and then strengthened on both sides using glass mesh bonded to the infill and the RC frame using flexible adhesive made of polyurethane matrix (Glass Fiber Reinforced PolyUrethane - GFRPU system). The strengthening process, allowed the specimen to withstand additional cyclic loads, reaching a maximum drift of 3.6 % without serious damage disqualifying the structure from further exploitation. The GFRPU strengthening system was found to be highly effective in preventing infill collapse of damaged masonry infill wall during in-plane loading. Additionally, the results of extended thermal analysis of PU are presented as polymers are, in general, a material, poorly resistant to heat. However, the analyzed PU manifested stable properties up to 200 degrees Celsius, which makes this material promising in civil engineering applications at elevated temperatures.
Keywords: masonry blocks, damaged infill, fiber Reinforced PolyUrethane, external composite strengthening, in-plane shear, thermal tests, DIC measurements
Published in DiRROS: 14.08.2024; Views: 1098; Downloads: 712
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Abstract: Ultra-high-performance fiber-reinforced cement-based composite (UHPFRC) has been increasingly adopted for rehabilitation projects over the past two decades, proving itself as a reliable, cost-efficient and sustainable alternative against conventional methods. High compressive strength, low permeability and high ductility are some of the characteristics that render UHPFRC an excellent material for repairing existing aged infrastructure. UHPFRC is most commonly applied as a surface layer for strengthening and rehabilitating concrete structures such as bridge decks or building slabs. However, its implementation with steel structures has so far been limited. In this work, the UHPFRC strengthening of a steel bridge is investigated both in simulation as well as in the laboratory, by exploiting a real-world case study: the Buna Bridge. This Croatian riveted steel bridge, constructed in 1893, repaired in 1953, and decommissioned since 2010, was removed from its original location and transported to laboratory facilities for testing prior to and after rehabilitation via addition of UHPFRC slab. The testing campaign includes static and dynamic experiments featuring state-of-the-art monitoring systems such as embedded fiber optics, acoustic emission sensors and digital image correlation. The information obtained prior to rehabilitation serves for characterization of the actual condition of the structure and allows the design of the rehabilitation solution. The UHPFRC slab thickness was optimized to deliver optimal fatigue and ultimate capacity improvement at reasonable cost. Once the design was implemented, a second round of experiments was conducted in order to confirm the validity of the solution, with particular attention allocated to the interface between the steel substrate and the UHPFRC overlay, as the connection between both materials may result in a weak contact point. A detailed fatigue analysis, based on updated FEM models prior to and after strengthening, combined with the results of a reliability analysis prove the benefits of adoption of such a solution via the significant extension of the structural lifespan.
Keywords: bridge, steel, UHPFRC, structures
Published in DiRROS: 21.12.2023; Views: 1255; Downloads: 671
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