Graphene oxide (GO) has been widely used as an additive due to its numerous unique properties. In this study, the compressive strength, flexural strength and elasticity modulus of concrete containing 0.02 wt%, 0.05 wt % and 0.08 wt % GO, and its dry shrinkage performance have been experimentally investigated. After the sample preparation, apparatus for compression test and flexural test were used to test the relevant properties of concrete containing GO. The dial indicators were used to measure the shrinkage of samples. The results indicate that GO can considerably improve the compressive strength, flexural strength, and elasticity modulus of concrete at the concrete age of 28 days by 4.04–12.65%, 3.8–7.38%, and 3.92–10.97%, respectively, which are substantially smaller than the increment at the age of 3 d by 5.02–21.51%, 4.25–13.06%, and 6.07–27.45% under a water-cement ratio of 0.35. It was also found that GO can increase the shrinkage strain of concrete. For example, at the age of 60 days, 0.02 wt%, 0.05 wt% and 0.08 wt% GO can increase the shrinkage strain of ordinary concrete by 1.99%, 5.79% and 7.45% respectively under a water-cement ratio of 0.49. The study has advanced our understanding on mechanical and shrinkage behavior of concrete containing GO.

In this study, the shrinkage and creep of concrete containing graphene oxide (GO) nanosheets were experimentally and theoretically investigated. Experiments for the shrinkage and creep of concrete with 0.02% and 0.08% GO nanosheets by the weight of cement and common concrete were carried out. Subsequently, the influence of GO nanosheets on the shrinkage and creep of concrete was analyzed and discussed. A modified model was developed to accurately predict the shrinkage and creep of concrete containing GO nanosheets after models for predicting shrinkage and creep of common concrete were compared and the influential factors and application scope were determined. Results indicate that: (1) GO nanosheets can increase the shrinkage strain and reduce the creep coefficient of concrete, and (2) a modified ACI209 (92) model can accurately predict the shrinkage and creep of concrete containing GO nanosheets. Factors considering concrete strength can be introduced in the model to improve the model accuracy.

Wind tunnel tests have become one of the most effective ways to evaluate aerodynamics and aeroelasticity in bluff bodies. This paper has firstly overviewed the development of conventional wind tunnel test techniques, including high frequency base balance technique, static synchronous multi-pressure sensing system test technique and aeroelastic test, and summarized their advantages and shortcomings. Subsequently, two advanced test approaches, a forced vibration test technique and hybrid aeroelastic- force balance wind tunnel test technique have been comprehensively reviewed. Then the characteristics and calculation procedure of the conventional and advanced wind tunnel test techniques were discussed and summarized. The results indicated that the conventional wind tunnel test techniques ignored the effect of structural oscillation on the measured aerodynamics as the test model is rigid. A forced vibration test can include that effect. Unfortunately, a test model in a forced vibration test cannot respond like a structure in the real world; it only includes the effect of structural oscillation on the surrounding flow and cannot consider the feedback from the surrounding flow to the oscillation test model. A hybrid aeroelastic-pressure/force balance test technique that can observe unsteady aerodynamics of a test model during its aeroelastic oscillation completely takes the effect of structural oscillation into consideration and is, therefore, effective in evaluation of aerodynamics and aeroelasticity in bluff bodies. This paper has not only advanced our understanding for aerodynamics and aeroelasticity in bluff bodies, but also provided a new perspective for advanced wind tunnel test techniques that can be used for fundamental studies and engineering applications.

Existing research on interference effects predominantly focuses on rigid structures. However, studies based on rigid models tend to overlook the feedback of structural motions on the flow field, thus failing to capture the intrinsic dynamics of the interference effect induced by wind-induced structural vibrations. This paper provides a comprehensive analysis of the fluid–structure interaction mechanisms considering interference effects involving two parallel square prisms, employing large-eddy simulation (LES). Various factors, including wind speed, arrangement, and vibration amplitude, are meticulously considered in the analysis. The study utilized three-dimensional LES simulations, incorporating the narrowband synthesis random flow generator method for inlet turbulence generation and adjusted through the “feedback” approach to ensure accuracy and efficiency. The research highlighted different structural arrangements exhibited distinct interference effects, and the end effect of the structure could substantially modify the flow pattern at various heights. In the tandem arrangements, the study observed several flow phenomena, including early reattachment, attenuation of the end effect, premature formation of roll structures, increased turbulence in the flow field due to vibration, resulting in wider second leading-edge separation, and a fragmented wake flow on the downstream structure. For side-by-side arrangements, the “acceleration effect” was identified and found to be further intensified by structural vibrations. The vibration of the interfering structure was noted to cause changes in vortex shedding frequencies and alterations in the wake flow pattern. In addition, vibration would enhance the interference effect but increasing amplitude and wind speed might diminish the interference effect. Overall, this study offers valuable insight into the intricate interplay of factors influencing the aerodynamics of parallel structures across diverse arrangements and under varying conditions.

In this study, flow behaviors and vortex morphology around the sloping terrain that is covered by an atmospheric boundary layer are investigated using a combination of numerical and experimental methods. An array of wind tunnel experiments and high-fidelity large eddies simulations have been conducted, considering different slope angles θ = 90°, 45°, 26.5°, and 18.2°. Systematic analysis of turbulence phenomena pertaining to the flow field's topography-driven distortions and accelerations was performed quantitatively via time-averaged velocity field, terrain-induced turbulence intensity, velocity spectrum, and acceleration ratio. Two recirculation zones, one originating from the upstream boundary layer's gradual separation bubble (GSB) and the other from the forced separation bubble (FSB) behind the downstream sharp leading-edge, were confirmed by detailed visualization of the flow field. An acceleration zone of considerable magnitude is also observed, connecting the GSB and FSB. Subsequently, a new vortex structure—the parallel ribbon vortex (PRV)—was disclosed. The PRVs originate from the disordered turbulence structures inside the GSB, spiraling into coherent structures. The accelerated mainstream up the step then stretches and elongates the coherence structures into ribbon-like vortices parallel to the mainstream, completing the formation process. Finally, the PRVs transport fluid up the step before encountering the strong spanwise vortices and dissipating thereafter. The investigation into the slope flow characteristics and turbulence structure conducted in this study has the potential to enhance the prediction of wind characteristics and wind load specifications in mountainous regions.

This work proposes a novel reduced-order model that integrates proper orthogonal decomposition (POD) and high-order dynamic mode decomposition (HODMD) to explore the dominant aerodynamic modes and interference mechanisms of three-dimensional finite-length tandem square cylinders. By leveraging POD to extract spatially dominant mode characteristics and integrating HODMD's amplitude-dominant modes to identify those significantly contributing to interference effects, results demonstrate that the POD-HODMD model can be effectively applied to the study of interference effects in three-dimensional finite-length tandem square cylinders, providing a robust method for reduced-order analysis of complex flow field data. The interference effects significantly influence the aerodynamic characteristics of the structures within the vortex shedding frequency bandwidth, and various structural spacings modify the positions of shear layer separation and reattachment, as well as their combined effects with the inter-structural flow field on the pressure distribution patterns on each surface of the structures. The interference effects on the flow field patterns vary across different frequency ranges. Low-frequency modes reshape gap vortex distributions and velocity orientations at structural ends, while high-frequency modes modify gap vortex distributions at the mid-span plane and wake continuity of the disturbed structure. The vortex shedding mode causes separation and wake vortices to become fuller and larger in scale. This technology not only provides a systematic method for analyzing aerodynamic and flow field characteristics for tandem structures but also deepens insight into the intricate dance of fluid–structure interactions within such configurations.