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Concrete dams in cold regions are designed to resist static loads from the ice sheet forming on the reservoir. Current guidelines suggest design ice loads of 50-250 kN/m based solely on geographical location, overlooking site-specific conditions. For many dams, this constitutes a considerable part of the total horizontal load and could theoretically cause problems with stability, especially for lower dams. However, the knowledge about the actual magnitude of ice loads remains limited, and no stability failure initiated by ice loads has been reported. This paper presents results from ice load measurements using a 1 X 3 m2 load panel installed at two dams in Sweden. The results from ice load measurements are presented alongside external factors such as water level, ambient temperatures, precipitation, and ice thickness, offering a more comprehensive understanding of the variables affecting ice loads on concrete dams., QC 20241211, Forecasting of ice-loads on concrete dams

Dammhaverier är mycket ovanliga och därför är kunskapen om brottförloppet vid ett potentiellt dammbrott begränsad. Uppstår brottet utan förvarning, eller finns tidiga tecken på allvarliga problem? Hur utvecklas brottsbräschen under brottförloppet? Detta är frågor som blivit än mer aktuella efter tre internationella dammhaverier under 2023. För att söka svar har en serie skalmodellförsök utförts där haverier av betongdammar simuleras. En viktig parameter vid säkerhetsbedömningen av en betongdamm består i att utvärdera dess stabilitet. Förenklat görs dettag enom att jämföra om dammkroppens vikt är tillräcklig för att stå emot lasten från vattnets tryck. Traditionellt beaktas enbart en mindre del av en betongdamm när dess stabilitet utvärderas men de nya försöken indikerar att det vore eftersträvansvärt att undersöka hela dammen samtidigt eftersom lasten fördelas mellan konstruktionsdelarna. Många betongdammars tillstånd övervakas idag genom automatiska mätningarav till exempel vattenstånd, förskjutningar och grundvattentryck. Dock finns det ingen standardiserad metod för att definiera larmgränser,vilket detta projekt syftar till att utveckla i framtiden., QC 20240118

Med syfte att frigöra attraktiv markyta för ny bebyggelse finns det imånga svenska städer idag ett önskemål att förtäta den befintliga stadsmiljön. En sådan åtgärd kan dock resultera i minskade avstånd mellan byggnader och transportled, vilket kan medföra ökade krav med hänsyn till bland annat explosioner. För att skapa en optimal helhetslösning för sådana olycksscenarion behöver de tre delområdena riskhantering, explosionslast och strukturrespons samordnas på ett korrekt sätt. I dagens explosionshantering finns dock betydande brister bland både riskanalytiker och konstruktörer, något som ofta beror på otillräcklig kommunikation och kunskap., QC 20240122

The piano key (PK) weir is a cost-effective structure for flood discharge. Its typical layout comprises a rectangularly cranked crest in planform with up- and downstream overhangs. With the intention to enhance its hydraulic efficiency, the conventional weir is improved. The sloping floor of each key is modified with a downward semi-circle in the cross-section; each overhanging apex is thus assigned an elliptical crest. Thus, the developed crest length of the resulting weir becomes considerably extended. Experiments are performed to compare the hydraulic behaviors of the improved weir with a reference one. The models are 3D-printed to attain high manufacture precision. For the model dimensions chosen in the study, the developed crest is similar to 36% longer. The study demonstrates that the improvements in geometry lead to appreciably enhanced flow discharge capacity. Within the hydraulic range examined, the augment in flow discharge varies within a range from 30% to 53%. In terms of both discharge capacity and flow patterns, the improved weir clearly outperforms the conventional one. The elliptical overhang apexes noticeably extend the developed crest length. The streamlined upstream overhang without singularity and the lowered inlet key floor reduce the entrance energy loss and improve the inflow to the inlet key and the flow over the crest. The lowered floor also gives rise to extra water volume, which administers to the flow motion towards the crest. For the outlet key, its lowered floor facilitates the outflow and alleviates the liableness of local submergence at high discharges. If the footprint for spillway construction is limited or the increase in the reservoir water stage must be controlled, the use of a more effective PK weir for flood discharge has significant engineering implications., QC 20231222

Steel fibre reinforced shotcrete (sprayed concrete) is a vital factor for achieving long technical lifespan and safe performance for the support of hard rock tunnels. A large number of fibres must cross areas with large tensile stresses for the shotcrete to be efficient. Computed tomography (CT) is a laboratory testing technology based on X-ray scanning followed by digital image detection to visualize the material interior. This is here used in a mesoscale approach for investigation of in situ cored shotcrete samples containing full size fibres and aggregates. For investigating the occurrence and orientation of steel fibres in shotcrete this method is much more efficient than the traditionally used electron microscopy studies of sawn thin slices, which is time consuming, costly, destroys the samples and provide limited information. The newly developed method provide a complete and detailed description of the fibre orientation within a cored shotcrete sample., Part of ISBN 9781003348030QC 20231023

Large volumes of steel fibre reinforced shotcrete (sprayed concrete) and steel bolts are commonly used to support tunnels in hard rock. This generates a high CO2-footprint which must be reduced in order to decelerate the continuously increasing average temperature worldwide caused by the emissions of greenhouse gases. Thus, alternative design methods and the possibility to use other materials than steel are currently investigated. Work is ongoing on testing the load-bearing capacity of shotcrete reinforced with fibres of steel, basalt and synthetic materials. This also includes a comparison between tests using Round Determinate Panels (RDP) and four-point bending of beams. Moreover, the practical use of RDP testing as a quality control methodology is also investigated in situ. Here, the goal is to identify several shotcrete mixes suitable for use in tunnelling so that the right material and fibre volume can be used in the right place., QC 20231023

Although the failure of a concrete dam is a complex and highly dynamic process, the current safety assessments of concrete gravity and buttress dams rely on a simplified 2D stability analysis, which neglects the load redistribution due to 3D monolith interactions and the valley shape. In addition, the estimation of breach parameters in concrete dams is based on assumptions rather than analyses, and better prediction methods are needed. Model tests have been conducted to increase the understanding of the failure behavior of concrete dams. A scale model buttress dam, with a scale of 1:15, consisting of 5 monoliths that were 1.2 m in height and 4 m in width, was constructed and loaded to failure using water pressure. The model dam had detachable abutment supports and shear keys to permit variations in the 3D behavior. The results showed that the shear transfer was large between the monoliths and that the failure of a single dam monolith is unlikely. A greater lateral restraint gives not only a higher failure load but also a better indication of impending failure. These findings suggest that the entire dam, including its boundary conditions, should be considered during a stability assessment. The results also suggest that the common assumption in dam safety codes that a single monolith fails during flooding analysis is not conservative. The dataset obtained provides a foundation for the future development of dam-monitoring alarm limits and for predictive models of dam-breaching processes., QC 20231017

Dam failures may have catastrophic consequences, including the release of largeamounts of water, significant property damage, and loss of life. However, safety assessments ofconcrete gravity and buttress dams often rely on simplified methods that do not consider the interactionbetween monoliths, the shape of the foundation or the presence of stiff abutments. Numericalmodeling can be a valuable tool for analyzing the stability of these dams, but it can bedifficult to validate these models due to a lack of documented dam failures. This paper presentsthe results of a numerical study examining the ability of dynamic finite element analyses to simulatedam failures. The study used the results from a series of physical model tests as a case studyfor validation. It was found that the numerical model was able to accurately reproduce the failuremode and breach development observed in the physical model tests and capture the effect of theloading rate on the failure mode and time for the failure to develop. Simulations were also performedin prototype scale to verify that the model tests were representative of a real dam failure.Further research is needed to determine the reliability of the numerical models under differentloading conditions and in realistic geological settings. However, these findings suggest that numericalmodeling can be a valuable tool for analyzing the stability of concrete gravity and buttressdams and predicting the development of failures., QC 20231017

Fibre-reinforced shotcrete (sprayed concrete) is one of the major components in the support system for tunnels in hard rock. Several empirical design methodologies have been developed over the years due to the complexity and many uncertainties involved in rock support design. Therefore, this paper aims to highlight how the choice of design methodology and fibre type impacts the structural capacity of the lining and the emission of greenhouse gases (GHG). The paper starts with a review of different design methods. Then, an experimental campaign is presented in which the structural performance of shotcrete reinforced with various dosages of fibres made of steel, synthetic and basalt was compared. A case study is presented in which the permanent rock support is designed based on the presented design methods. Here, only the structural requirements were considered, and suitable dosages of fibres were selected based on the experimental results. The emission of GHG was calculated for all design options based on environmental product declarations for each fibre type. The result in this paper indicates that synthetic fibres have the greatest potential to lower the emissions of GHG in the design phase. Moreover, the choice of design method has a significant impact on the required dosage of fibres., QC 20230307

In recent decades, many cities have become densely populated due to increased urbanization, and the transportation infrastructure system has been heavily used. The downtime of important parts of the infrastructure, such as tunnels and bridges, seriously affects the transportation system’s efficiency. For this reason, a safe and reliable infrastructure network is necessary for the economic growth and functionality of cities. At the same time, the infrastructure is ageing in many countries, and continuous inspection and maintenance are necessary. Nowadays, detailed inspections of large infrastructure are almost exclusively performed by inspectors on site, which is both time-consuming and subject to human errors. However, the recent technological advancements in computer vision, artificial intelligence (AI), and robotics have opened up the possibilities of automated inspections. Today, semiautomatic systems such as drones and other mobile mapping systems are available to collect data and reconstruct 3D digital models of infrastructure. This significantly decreases the downtime of the infrastructure, but both damage detection and assessments of the structural condition are still manually performed, with a high impact on the efficiency and accuracy of the procedure. Ongoing research has shown that deep-learning methods, especially convolutional neural networks (CNNs) combined with other image processing techniques, can automatically detect cracks on concrete surfaces and measure their metrics (e.g., length and width). However, these techniques are still under investigation. Additionally, to use these data for automatically assessing the structure, a clear link between the metrics of the cracks and the structural condition must be established. This paper presents a review of the damage of tunnel concrete lining that is detectable with optical instruments. Thereafter, state-of-the-art autonomous tunnel inspection methods are presented with a focus on innovative mobile mapp, QC 20230426, TACK -Tunnel Automatic CracK Detection

In the present paper, the walls of a concrete frame used for over-decking in a road tunnel were first designed using the relevant design provisions. The response of the wall was then analysed using non-linear finite element analysis, and the results of the finite element analysis were compared to what was predicted using the design guidelines. Additionally, simulations of the blast load resulting from gas leakage during transportation were conducted as a separate study. The results from two vapour clouds containing gases of hydrogen and propane were compared., Part of ISBN 978-1-003-34803-0QC 20231127

Steel fibre reinforced shotcrete (sprayed concrete) is a vital factor for achieving long technical lifespan and safe performance for the support of hard rock tunnels. A large number of fibres must cross areas with large tensile stresses for the shotcrete to be efficient.Computed tomography (CT) is a laboratory testing technology based on X-ray scanning followedby digital image detection to visualize the material interior. This is here used ina mesoscale approach for investigation of in situ cored shotcrete samples containing full sizefibres and aggregates. For investigating the occurrence and orientation of steel fibres in shotcretethis method is much more efficient than the traditionally used electron microscopy studiesof sawn thin slices, which is time consuming, costly, destroys the samples and providelimited information. The newly developed method provide a complete and detailed descriptionof the fibre orientation within a cored shotcrete sample., Part of proceedings ISBN 978-1-003-34803-0QC 20230825

Traditionally, the evaluation of changes in construction projects focuses on implications for cost and time. Analysis of impact on the configuration and subsequent end-user functionality is less analysed. Healthcare constructions have complex configurations and the functionality is imperative for patient care. There are problems with the deliveries in healthcare construction projects not fulfilling end-user functionality. Control of configuration changes reduces the risk for deviations from intended functionality. This study establishes the information required to obtain control and the availability in healthcare construction projects. A framework based on a literature review describes the information that is required to control configuration changes. In a case study of thirteen healthcare reconstruction projects, the available informationabout changes was compared with the framework. Management of changes was deficient in all the cases. In the investigated project logs, the implications of the configuration changes were significantly underestimated. Object models data provided detailed information about the impact of changes on the configuration, but this possibility was not used. There was no available information about requests to change the configuration, consequence analyses or implementation decisions. This study fills a research gap by adding the configuration perspective to change management in construction projects., QC 20221003

The structural behaviour of fibre reinforced shotcrete (sprayed concrete) as support in hard rock tunnels are complex and depends on the interaction between shotcrete, bolts and rock. It is here studied how variations in shotcrete thickness and bond strength affect the behaviour of this type of rock support system. Numerical models are used to simulate bond failure, shotcrete cracking and pull-out of grouted rock bolts. It is shown that local variations in shotcrete thickness affects possible shrinkage crack patterns and when subjected to the load from a loose block, the force is transferred to the surrounding rock through bond stresses distributed over a narrow band in the shotcrete. Moreover, it is shown how the structural capacity with respect to bond failure depends on the shotcrete thickness., QC 20220919

Hospitals are complex buildings and design solutions should fulfil functionalities to enable accurate diagnosis, treatment, and care. However, scientific results are seldom the basis for the design solution choices. Magnetic resonance imaging facilities require concrete structures fulfilling high requirements on vibration isolation to ensure diagnostic accuracy. The aim of the studies was to compare evidence from the literature to the chosen solutions in eight newly designed magnetic resonance imaging facilities. The conclusions are that there is insufficient scientific evidence for which structural configurations fulfil vibration requirements of MRI facilities, while those found were only partially implemented in recent designs., QC 20221003

Due to the construction of dams and sluices, habitat fragmentation of riverine species is an issue of concern in hydropower projects. An artificial fishway aims to restore flow connectivity and facilitate migration. As an alternative to the conventional layout with straight walls, labyrinth layouts are introduced, consisting of either triangular, trapezoidal, or rectangular weirs. Three-dimensional CFD simulations are performed to examine their influences on the fishway hydraulics. The labyrinth layouts exhibit an appreciable three-dimensional flow structure in a pool, featuring flow fluctuations in both cross- and along-channel directions, which is indicative of the potential for multiple species with distinct swimming preferences. The streamwise reduction in mean flow velocity is correlated with the Froude number, with the labyrinth weirs leading to a somewhat lower reduction than the conventional one. The dimensionless pool water depth declines with specific flow discharge. The turbulence kinetic energy is the lowest in the triangular layout and the vorticity in the conventional one. Among the labyrinth layouts, the differences in volumetric power dissipation are small. An equation is developed for dissipation estimation. All the labyrinth layouts generate higher energy loss than the conventional one. With optional weir configurations, the findings provide reference for engineering design., QC 20220315

In the assessment of concrete dams in cold climate, it is common that the theoretical stability becomes insufficient for load cases that include ice loads. However, the magnitude and return period of these ice loads have a high degree of uncertainty. This study estimates the magnitude of ice loads on eight concrete dam monoliths using measurements of their displacement from 29 winters. In the displacement signals, events are identified and assumed to be caused solely by ice loads. The observed displacement during an event is interpreted as an ice load using a load-displacement relationship derived from FE simulations of each dam. These simulations show that ice loads of the magnitudes given in design guidelines and recorded in previous measurements would significantly affect the structural response of the studied dams. However, only small traces of ice loads can be found in the observed responses of the studied dams. The estimated ice loads are significantly lower than the ice loads recorded in traditional ice load measurements. These results indicate that the average magnitude of ice load on an entire monolith is significantly lower than the measured local pressures. This would imply that ice loads may be a smaller concern regarding dam safety than previously believed., QC 20220318

In this dataset, data from experimental testing of fibre-reinforced shotcrete is presented. The dataset contains five different fibres made of steel (Dramix 3D, Dramix 4D and Dramix5D), synthetic (BarChip R54) and basalt (MiniBar). Preparation of specimens and testing were performed by Vattenfall R&D in Älvkarleby, Sweden. This first version of the dataset contains the results for shotcrete specimens prepared through casting. The same shotcrete mix was used for all specimens, and three different dosages were used for each of the fibres except for Dramix 5D, for which only two dosages were tested. The dataset contains the shotcrete mix and standard output for the test of compressive strength according to EN 12390-3, residual flexural strength according to EN 14488-3 and energy absorption according to ASTM C1550. This dataset can be used to study how the structural toughness of fibre-reinforced shotcrete is affected by the dosage of fibre. Moreover, the data can be used to compare the structural performance of fibres of different materials. The data also provide a foundation to select a reasonable dosage of fibres to fulfil the structural requirements put on shotcrete in the design phase., QC 20230404

Fibre-reinforced shotcrete is the most common support method for hard rock tunnels in the Nordic countries. The design of shotcrete is often based on empirical methods or simplified analytical equations, which neglect variations in mechanical properties and shotcrete thickness. Data collected from the field shows that significant variations in shotcrete thickness and bond strength should be expected during tunnel construction. However, how this affects the structural behaviour and capacity of the shotcrete lining is unknown. Moreover, the design philosophy for shotcrete assumes that the primary failure modes of shotcrete, i.e. bond and flexural failure, can be treated separately. This was derived based on observations of experiments in a laboratory environment. Therefore, the focus of a finalized doctoral project was to develop a numerical framework to simulate the structural behaviour of fibre-reinforced shotcrete in interaction with hard rock and rock bolts. The effect of variations in shotcrete thickness and bond strength was studied through numerical simulations to increase the understanding of its effect on the failure load of the lining. The results indicate that the most important parameter is the mean value of the shotcrete thickness and bond strength around a narrow perimeter of the block., QC 20230307

Impact loads in previous research showed to induce brittle responses of statically flexure-critical reinforced concrete (RC) beams designed for ductility. The impact load may produce flexural shear damage modes similar to that observed during quasi-static loads and local shear damage under the impact zone. The occurrence of shear damage modes during impact tests has been investigated extensively, but their effect on the residual quasi-static and dynamic capacity is not fully understood. For this aim, an initial high-velocity impact test initiated severe shear damage to RC beams. The beams were then tested quasi-statically and by sequential impact testing using the same setup as the initial tests. The results indicate a flexure-dominated response during sequential impact tests for beams containing extreme shear reinforcement amounts, favouring the energy-absorption capacity. Significant shear and flexural damage occurred for beams with less shear reinforcement, indicating a hybrid response that varied throughout the tests. The tests for the residual quasi-static capacity indicated severe consequences from initial local shear damage on the capacity, as shown by the brittle response of the beam with the most shear reinforcement. However, wide initial flexural cracks instead showed a favourable effect, as there was an indication of transfer from brittle to ductile failure. For beams showing both global and local shear damage, it was concluded that global shear damage modes were critical for the residual static and dynamic shear capacity., QC 20221215

Världen står inför en enorm utmaning där utsläppen av växthusgaser måste minskas för att bromsa den ständigt ökande globala medeltemperaturen. Samtidigt har en lång urbaniseringstrend lett till att transportinfrastrukturen i många tätbefolkade städer måste byggas ut för att bibehålla ett fungerande transportnät. I många fall är tunnlar det mest fördelaktiga alternativet eftersom de inte stör den befintliga stadsbilden. För att minska klimatpåverkan från byggandet av nya tunnlar har Trafikverket initierat ett forskningsprojekt som ska undersöka potentialen för alternativa fibrer och detta drivs av avdelningen för Betongbyggnad på KTH., QC 20221227

The numerical simulations presented in the present paper were on beam models geometrically identical to the beams previously tested in a shock tunnel but now provided with increased shear reinforcement consisting of vertical stirrups. The tested beam failed in brittle flexural shear during the blast loading in the tunnel. The results from the numerical investigation showed that brittle shear failures of beams subjected to blast loads may be prevented by dense shear reinforcement. The guideline for impulse loaded structure showed to underestimate the dynamic shear capacity as it is not dependent on the actual transverse reinforcement amount. This is however considered in the model used for determining the static shear capacity, meaning that further work developing a similar model fit to impulse loading is advised. To realize this development a new test series is proposed., QC 20230621