Abstract: Orthotropic steel deck (OSD) are widely used in steel bridges because of their many advantages, but the structures and stresses of OSD are complex and sensitive to fatigue. Based on the model test, the structural fatigue analysis of OSD is carried out by using the extended finite element method (XFEM) to understand and reveal the causes of fatigue detail cracks and the generation and propagation of fatigue cracks at the welding ends of diaphragms, U-ribs, and diaphragms, which are the main structural fatigue details of the deck. The results show that: the fatigue crack at the diaphragm opening is not caused by a single factor, but the horizontal relative displacement is the root-cause of the fatigue crack; the contribution of out-of-plane displacement to the fatigue crack is more significant than that of vertical displacement or in-plane stress, which often leads to the initiation and propagation of the fatigue crack; the crack-propagation direction is perpendicular to the contour of principal stress, and the crack propagates into the plate along the high-stress area in the horizontal direction, which is in accordance with the basic theory of crack propagation. The research methods can provide technical support for the design of similar structures.

Abstract: In an effort to find more cost-effective and proactive ways to keep bridges in good condition, the use of instrumented vehicles has gained great interest in the last decade. Two bridge components that can wear rapidly are the bearings and the road surface. However, past research on drive-by monitoring has placed focus mostly on detecting losses of bending stiffness in the bridge deck, while assuming ideal support conditions that may differ from real cases significantly, and ignoring the characterization of the road profile. Even further, the need for specialized vehicles equipped with high-tech instrumentation, low speeds, or very good road profiles has been a major obstacle preventing its practical implementation. This paper investigates the use of axle accelerations from an ordinary two-axle vehicle crossing the bridge to quantify the rotational stiffness of the supports and the height of the road irregularities while overcoming the limitations exposed above. In contrast to previous research where the response of the contact point has been derived from other vehicular locations based on complex differential equations of motion, transfer functions are employed here. The key advantage of transfer functions is their simple algebraic form that can be easily calibrated on the field. The road profile is then obtained by subtracting the displacement of the bridge under each axle from the displacement of the contact point. There is one prediction of the road profile per axle but only a unique value of rotational stiffness at each support that will yield the same prediction by both axles. The algorithm is successfully tested with a half-car traveling at 5, 10, 15, and 20 m/s, over a 15-m bridge beam model with ISO road classes “A,” “B,” and “C,” for boundary conditions ranging from simply supported to fixed. The solution's robustness to modeling inaccuracies and noisy data is also investigated.

Abstract: In recent years, there has been an increasing interest in renewable energies in view of the fact that fossil fuels are the leading cause of catastrophic environmental consequences. Ocean wave energy is a renewable energy source that is particularly prevalent in coastal areas. Since many countries have tremendous potential to extract this type of energy, a number of researchers have sought to determine certain effective factors on wave converters’ performance, with a primary emphasis on ambient factors. In this study, we used metaheuristic optimization methods to investigate the effects of geometric factors on the performance of an Oscillating Surge Wave Energy Converter (OSWEC), in addition to the effects of hydrodynamic parameters. To do so, we used CATIA software to model different geometries which were then inserted into a numerical model developed in Flow3D software. A Ribed-surface design of the converter’s flap is also introduced in this study to maximize wave-converter interaction. Besides, a Bi-level Hill Climbing Multi-Verse Optimization (HCMVO) method was also developed for this application. The results showed that the converter performs better with greater wave heights, flap freeboard heights, and shorter wave periods. Additionally, the added ribs led to more wave-converter interaction and better performance, while the distance between the flap and flume bed negatively impacted the performance. Finally, tracking the changes in the five-dimensional objective function revealed the optimum value for each parameter in all scenarios. This is achieved by the newly developed optimization algorithm, which is much faster than other existing cutting-edge metaheuristic approaches.

Abstract: Abstract This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters.

Abstract: Presentation slides commonly use visual patterns for structural navigation, such as titles, dividers, and build slides. However, screen readers do not capture such intention, making it time-consuming and less accessible for blind and visually impaired (BVI) users to linearly consume slides with repeated content. We present Slide Gestalt, an automatic approach that identifies the hierarchical structure in a slide deck. Slide Gestalt computes the visual and textual correspondences between slides to generate hierarchical groupings. Readers can navigate the slide deck from the higher-level section overview to the lower-level description of a slide group or individual elements interactively with our UI. We derived side consumption and authoring practices from interviews with BVI readers and sighted creators and an analysis of 100 decks. We performed our pipeline with 50 real-world slide decks and a large dataset. Feedback from eight BVI participants showed that Slide Gestalt helped navigate a slide deck by anchoring content more efficiently, compared to using accessible slides.

Abstract: Vortex-induced vibrations (VIVs) remain a key issue for slotted box girders. To clarify the influence of additional structural elements on the aerodynamic characteristics of a double-slotted box girder for highway and railway hybrid bridges, wind tunnel tests involving the pressure distribution, VIV responses, and wake measurements were performed. The wind pressures and vortex-shedding frequency characteristics of a bridge were compared under different additional structural element combinations of balustrades, wind barriers on highways and railway deck surfaces, maintenance rails, and so on. The results indicated that the maintenance rails had a limited influence on VIV characteristics and distributed pressures of the double-slotted box girder. However, owing to the stronger disturbance of the wind barriers and balustrades on the highway deck surface, unsteady shear flow separating from the wind barrier top acts on the middle and leeward girders, resulting in large-amplitude torsional VIVs to generate considerable excitation forces. Moreover, because wind flow across the slotted parts interacted with the girder and additional structural elements, stronger torque forces were generated. Consequently, correlation and contribution were enlarged, which corresponded to large-amplitude torsional VIVs. This provides a reasonable explanation for the considerable influence of wind barriers on highway decks on torsional VIVs. Moreover, with regard to the double-slotted box girder [especially the upper surface of the windward girder, upper and lower surfaces of the leeward girder, and windward gap of the three girders (Regions II to IV, VI, and X to XI, respectively)], the distributed wind pressures acting on the characteristic parts of bridge decks further contributed to the generation of torsional VIVs.

Abstract: Traditional aerodynamic measures with fixed geometric shapes make it difficult to relieve the wind-induced vibration issues under the continuous expansion of bridge spans. Active aerodynamic control measures would be an alternative way to improve the wind vibration performance of long-span bridges. In this study, a bridge flutter control method based on active flaps was proposed, and the main girder-active flap-suspended aeroelastic model was designed to study the control effect. A pair of active flaps was installed on both sides of the box girder near the lateral fairings, and the movement signal of the main girder was detected using internal sensors. The two flaps move relative to the deck according to the preset equations of motion. This improved the flutter stability of the system with high effectiveness compared to traditional passive aerodynamic measures. By adjusting the gain coefficient in the motion function of the flaps and the phase difference between the flaps and the deck, the changing characteristics of the critical flutter wind speed were revealed with a deeper understanding of the relationship between the phase differences and gain coefficient of the active flaps and main girder. Studies have shown that the flutter performance of the deck-flap system is significantly affected by the phase difference and gain coefficient on both sides of the aerodynamic flap. The control law of the windward flap is relatively stable, but the control effect of the leeward flap is greatly affected by the movement of the windward flap.