Explore the vast range of titles available.

The technique of air-deck charge has been applied in open-pit blasting for a long time. However, the effects of axial air deck in borehole on blast-induced ground vibrations have not been well investigated. In this study, the influences of axial air deck on blast-induced peak particle velocities (PPVs) are investigated based on field tests and numerical simulations. Five blasting tests with the ratios of top axial air deck (i.e., defined as the air-deck volume in borehole divided by the borehole volume) of 0/16, 1/16, 2/16, 3/16 and 4/16 are implemented in an open-pit mine. PPVs and their attenuation trends corresponding to different air-deck ratios are analyzed and discussed. The test results show increasing air-deck ratios can decrease near-field ground vibrations to some extent. In addition, numerical models with single borehole are built and validated with blasting test results. The influences of air-deck positions, air-deck ratios and air-deck numbers in single borehole on near-field ground PPVs are investigated with the calibrated numerical models. It is found that near-field ground PPVs induced by the top air-deck charge are lower than those induced by the bottom and middle air-deck charges when the air-deck ratio is the same. Meanwhile, the variation of air-deck ratios located at the top of borehole has a greater influence on near-field ground PPVs than that located at the middle and bottom of borehole. With the increase of the number of air-deck layers in one borehole, near-field ground PPVs induced by the top air-deck charge increase, while those induced by the middle and bottom air-deck charges decrease.

This paper describes the main characteristics of CNRM‐CM6‐1, the fully coupled atmosphere‐ocean general circulation model of sixth generation jointly developed by Centre National de Recherches Météorologiques (CNRM) and Cerfacs for the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6). The paper provides a description of each component of CNRM‐CM6‐1, including the coupling method and the new online output software. We emphasize where model's components have been updated with respect to the former model version, CNRM‐CM5.1. In particular, we highlight major improvements in the representation of atmospheric and land processes. A particular attention has also been devoted to mass and energy conservation in the simulated climate system to limit long‐term drifts. The climate simulated by CNRM‐CM6‐1 is then evaluated using CMIP6 historical and Diagnostic, Evaluation and Characterization of Klima (DECK) experiments in comparison with CMIP5 CNRM‐CM5.1 equivalent experiments. Overall, the mean surface biases are of similar magnitude but with different spatial patterns. Deep ocean biases are generally reduced, whereas sea ice is too thin in the Arctic. Although the simulated climate variability remains roughly consistent with CNRM‐CM5.1, its sensitivity to rising CO2 has increased: the equilibrium climate sensitivity is 4.9 K, which is now close to the upper bound of the range estimated from CMIP5 models. Key Points Description of CNRM‐CM6‐1 model components, their coupling, and tuning procedures are described Historical simulations and DECK experiments are assessed Preindustrial simulation is stable and mean climate and variability in historical runs is realistic

The mathematical model of vortex-induced vibrations (VIV) on long-span bridges is important to predict nonlinear structural responses. Such models can be divided into two categories: wake-oscillator and single-degree-of-freedom (SDOF) models. The SDOF model is widely used for wind-induced vibration calculations. However, the traditional SDOF model based on the standard van der Pol oscillator cannot simulate VIVs with multistability. In this study, a newly generalized van der Pol model is proposed to incorporate the limit-cycle oscillation (LCO) with multiple amplitudes, and the nonlinear damping is expressed by polynomial expansion. Next, the multiple LCO amplitudes can be determined from the energy evolution formula derived from the averaging method. Similarly, the evolution of the vibration amplitude during the transient response is also derived by the same method. Subsequently, nonlinear parameter identification methods based on constraint optimization are derived according to both the LCO amplitude and transient responses. In the last part of this study, the “energy map” is proposed to present the energy extracted from the fluid–structure interaction with different wind speeds and vibration amplitudes, and it is constructed by the parameters identified in the lock-in range of VIV. The “energy map” can provide a complete picture of the evolution of the energy of VIVs on bridge decks.

Wind tunnel tests or computational fluid dynamics (CFD) simulations of the aeroelastic model of a bridge deck section are currently used to make sure that significant vortex-induced vibration (VIV) of a long-span bridge will not occur after the bridge is put into operation. However, significant VIV still occurred in several long-span bridges in operation, indicating that the currently used wind tunnel tests and CFD simulations have some drawbacks or uncertainties. This study aims at establishing a digital twin by interacting CFD simulation with wind tunnel test for accurately and efficiently predicting the VIV response of a bridge deck. The measurement information of VIV of the deck section is collected from the wind tunnel test and fused with the CFD simulation. The optimisation for reducing uncertainties existing in wind tunnel test and CFD simulation is then carried out to make the CFD simulation as a digital twin. The digital twin is finally used to investigate the blockage effect of wind tunnel test and give an accurate and efficient prediction of VIV of the bridge deck. The flat closed-box steel deck section used in the Xiangshan Harbor cable-stayed bridge is selected as a case study. The results from the case study show that the digital twin can be established and used for an accurate and efficient prediction of VIV of the bridge deck section.

Nonlinear self-excited forces pose a significant role in wind-induced aeroelasticity of long-span bridges, predominantly characterized by the flutter derivatives. As in other works already in the literature, the flutter derivatives are extended here to the nonlinear case by introducing amplitude dependence. At that point, accurately describing the nonlinearity of aerodynamic damping as a function of amplitude, etc., is crucial for the precise identification of flutter derivatives, while the nonlinearity of amplitude-dependent structural damping should also be considered. Therefore, this study aims to develop a time-domain method, that simultaneously accounts for the structural and aerodynamic nonlinearities in calculating the wind-induce responses of a double-deck truss girder. First, wind tunnel tests were performed to measure the time histories of displacement responses for the section model accounting for various damping ratio levels, from which the corresponding structural and aerodynamic damping was extracted. Next, the generalized Van der Pol oscillator (GVPO) model was employed to characterize the nonlinear structural and aerodynamic damping, and the accuracy was validated by comparing the computed displacement histories by the GVPO model with the experimental results. Subsequently, the nonlinear flutter derivatives at lower damping level are determined, with the nonlinear characteristics captured through the GVPO model. Finally, both the heaving and torsional responses at higher damping levels are predicted using the nonlinear flutter derivatives identified from the responses measured at lower damping levels, and the predicted results align with the experimental results. The time-domain method developed in this study incorporates both the aeroelastic and structural nonlinearities.

We introduce the concept of deck transformations within the category of developable complexes of groups. Drawing inspiration from classical covering theory for topological spaces, we propose an alternative construction of the universal development of a developable complex of groups, formulated in terms of equivalence classes of paths. This framework allows us to provide a natural characterization of the group of deck transformations.

The fatigue problem of orthotropic steel bridge decks of urban rail transit steel bridges has gradually become one of the hot research topics. And it is also a key problem that restricts the further development of rail transit steel bridges. In this paper, the orthotropic steel bridge deck structure of a long-span urban rail transit cable-stayed bridge is studied. Based on the segmental finite element model and full-scale model, the fatigue details of the joint weld between an orthotropic steel bridge deck and U-rib were studied theoretically and experimentally. The theoretical model of the segment is analyzed to obtain the hot spot stress characteristics. On this basis, the full-scale model fatigue test and the fatigue performance evaluation are completed based on the S-N curve. The results show that the fatigue performance of the bridge deck and U-rib joints of the orthotropic steel bridge deck structure model meets the design requirements and has a certain safety reserve. The joint fatigue details of the bridge deck, the U-rib joint weld, and the diaphragm plate are the sensitive areas that are most likely to occur fatigue failure first and need to be paid attention to in the later bridge maintenance and inspection.

We study poker hand rankings in the partially generalised setting of a deck with \\(r\\) ranks, rather than the typical 13 ranks. We provide the hand rankings for all \\(r\\) and observe some interesting phenomena such as the smallest \\(r\\) such that flushes rank below one-pair hands. Perhaps surprisingly, as \\(r\\) grows without bound, the hand ranking is not stable until \\(r=761\\) (a 3044 card deck). We consider showdown frequency, which is the frequency that a given type of hand is declared by a player at showdown, and make note of counterintuitive instances in which a hand with lower absolute frequency than some other hand nonetheless has a higher showdown frequency. This can be interpreted as a form of Gadbois paradox but in the typical setting of poker without wild cards. Conveniently, the standard deck with 13 ranks turns out to be the smallest deck that avoids a discrepancy between absolute frequency and showdown frequency for all hand types other than having a high card.

Orthotropic steel decks (OSDs) are commonly used in the construction of bridges due to their load-bearing capabilities. However, they are prone to fatigue damage over time due to the cyclic loads from vehicles. Therefore, the early structural health monitoring of fatigue damage in OSDs is crucial for ensuring bridge safety. Moreover, Lamb waves, as elastic waves propagating in OSD plate-like structures, are characterized by their long propagation distances and minimal attenuation. This paper introduces a method of emitting high-energy ultrasonic waves onto the OSD surface to capture the nonlinear Lamb waves formed, thereby calculating the nonlinear parameters. These parameters are then correlated with the fatigue damage endured, forming a damage index (DI) for monitoring the fatigue life of OSDs. Experimental results indicate that as fatigue damage increases, the nonlinear parameters exhibit a significant initial increase followed by a decrease. The behavior is distinct from the characteristic parameters of linear ultrasound (velocity and energy), which also exhibit changes but to a relatively smaller extent. The proposed DI and fatigue life based on nonlinear parameters can be fitted with a Gaussian curve, with the R-squared value of the fitting curve being close to 1. Additionally, this paper discusses the influence of rib welds within the OSDs on the DI, whereby as fatigue damage increases, it enlarges the value of the nonlinear parameters without altering their trend. The proposed method provides a more effective approach for monitoring early fatigue damage in OSDs.

The MLG (Main Landing Gear) bay pressure desk in civil aircraft, located in the center fuselage section, is subjected to complex multi-load scenarios and significantly impacts flight safety, rendering its design highly challenging. This paper details a design methodology for pressure deck structures. Based on structural load analysis, the methodology proposes a fundamental structural arrangement for the pressure deck, analyzes critical design considerations for primary structural components, and provides computational equations for key dimensional parameters. This approach resolves the complexity of multi-load conditions for the pressure deck, streamlines the structure manufacturing process, enables rapid and accurate calculation of critical dimensions, and offers substantial guiding significance for future aircraft structural design.