Artificial reefs are being implemented around the world for their multi-functions including coastal protection and environmental improvement. To better understand the hydrodynamic and morphodynamic roles of an artificial reef (AR) in beach protection, a series of experiments were conducted in a 50 m-long wave flume configured with a 1:10 sloping beach and a model AR (1.8 m long × 0.3 m high) with 0.2 m submergence depth. Five regular and five irregular wave conditions were generated on two types of beach profiles (with/without model AR) to study the cross-shore hydrodynamic and morphological evolution process. The influences of AR on the processes are concluded as follows: (1) AR significantly decreases the incident wave energy, and its dissipation effect differs for higher and lower harmonics under irregular wave climates; (2) AR changes the cross-shore patterns of hydrodynamic factors (significant wave height, wave skewness and asymmetry, and undertow), leading to the movement of shoaling and breaking zones; (3) the beach evolution is characterized by a sandbar and a scarp which respectively sit at a higher and lower location on the profile with AR than natural beach without AR; (4) the cross-shore morphological features indicate that AR can lead to beach state transformation toward reflective state; (5) the scarp retreat process can be described by a model where the scarp location depends linearly on the natural exponential of time with the fitting parameters determined by wave run-up reduced by AR. This study demonstrates cross-shore effects of AR as a beach protection structure that changes wave dynamics in surf and swash zone, reduces offshore sediment transport, and induces different morphological features.
Hydraulic design is automatically inherent in hydraulic engineering courses, conventional teaching of the Waterway Engineering Design course tends to have limitations such as low participation, poor interactivity, disconnection between theoretical and experimental training, and restriction of experimental design by time and space. To address these needs, a virtual simulation cloud system of Waterway Engineering Design is developed based on outcome-based education. Taking real engineering projects as prototypes, this system adopts virtual reality technology and cloud platform to simulate the scene structure and instrument function with high precision. The multi-model, integrational teaching expands the experimental content, enhances the interactivity of the design process, and provides a high-quality, immersive online learning experience for students. Since its application, the Waterway Engineering Design Virtual Simulation Cloud System has received good feedback from both teachers and students. During the Covid-19 epidemic, it provided significant support for experiments and teaching of the Waterway Engineering Design course and became a pivotal supplement to the existing teaching system. The Waterway Engineering Design Virtual Simulation Cloud System adheres to the "student-centered" teaching principle, builds up students' ability for independent learning and engineering practice, and facilitates their personal development and training for excellent engineers.
Local scour is one of the key factors that cause the collapse of structures. To avoid structure failures and economic losses in water, it is usually essential to predict the equilibrium scour depth of the foundation. In this study, several design models which were presented to predict the equilibrium scour depth either under steady clear water conditions and combined waves and current conditions were recommended. These models from China, the United States and Norway were analyzed and compared through experiments. Moreover, flume tests for monopile foundation embedded in sand under different flow conditions were carried out to observe the process and gauge the maximum depth around the pile. Based on this study, for predicting the equilibrium scour depth around bridge piers, the computational results of three design methods are all conservative, as expected. For the foundation of offshore structures in marine environment, most of the predicted scour depths by design methods are different from field data; in particular, the mean relative error with these design methods proposed may reach up to 966.5%, which may lead to underestimation of the problem, overdesign and consequently high construction cost. To further improve the ability of the scour prediction in a marine environment, data from flume tests and some field data from a previous study were used to derive the major factors of scour. Based on the dimensional analysis method, a new model to estimate the equilibrium scour depth induced by either current or waves is proposed. The mean relative error of the new formula is 49.1%, and it gives more accurate scour depth predictions than the existing methods.
The parametric resonance of a frame structure may lead to a disastrous consequence. Structural engineers need a straightforward and practical method to calculate the large nonlinear parametric resonance responses of the frame structure for assessing structural safety. This paper reports on a new Vector Form Intrinsic Finite Element (VFIFE) method to analyse the nonlinear parametric resonance of planar beam structures. By taking into account the geometric stiffness effect of the internal axial force for the frame element, a relationship between internal nodal forces and deformation components is firstly established based on the VFIFE principle and the parametric resonance mechanism of frame structures. The VFIFE scheme is then developed to analyse the nonlinear parametric resonance of frame structures. To demonstrate the efficacy of this approach, a simply-supported beam is used as a numerical example, and the resulting VFIFE calculations are compared to the solutions obtained by current analytical methods. A parametric resonance test of the cantilever beam is conducted to verify the applicability of the VFIFE method. The numerical results show that this approach can overcome the limitations of existing analytical methods, well simulate the nonlinear phenomena of parametric resonances, and produce predictions that are consistent with experimental observations. The numerical stability boundary of parametric resonance agrees well with the experimental boundary. Possible causes of deviations between the numerical and experimental results are discussed. The proposed VFIFE method is a simple and effective means of analyzing the stability and nonlinear responses of parametric resonance of planar beam structures.
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