At present, elevated pile-cap structures are extensively utilized in deep-water bridges. However, studies on seismic wave-induced hydrodynamic forces acting on circular pile-caps remain limited. In this study, numerical models of a circular pile-cap and a deep-water pier with identical cross-sectional dimensions are established and validated. Subsequently, the generation mechanisms and characteristics of hydrodynamic forces on circular pile-caps are comprehensively analyzed. The results indicate that the hydrodynamic force calculation methods for deep-water piers cannot be applied to pile-caps because the hydrodynamic forces on pile-caps are significantly influenced by free surface waves and bottom free end effects. Additionally, both the inertial force and the wave force are important components of the hydrodynamic force on the pile-cap, especially when the seismic excitation frequency is lower, i.e., 0.20 Hz <= f <= 0.40 Hz. The bottom free end effects not only reduce the wave force but also diminish the inertial force in the hydrodynamic force on the pile-cap. The contribution ratios of the inertial force and the wave force to the hydrodynamic force are approximately not influenced by the seismic excitation amplitude, and are weakly influenced by the aspect ratio, but are significantly influenced by the seismic excitation frequency.

The characteristics and influencing factors of the tsunami bore force on the multi-box girder are experimentally studied for the first time by using breaking solitary waves to simulate the tsunami bore. The factors influencing tsunami bore force such as wave height a, water depth h, and clearance Z are investigated. It is found that the tsunami bore force time history curve can be divided into three stages, that is, the impinging stage, the fluctuation stage, and the quasi-stable stage. The horizontal and vertical tsunami bore force maxima (Fx+ and Fz+, respectively) occur in the impinging stage. The girder model is decomposed into panels, and the contribution of each panel of the multi-box girder to the tsunami bore force maxima is significantly different from that of the T-girder because of the difference in the geometric shape of the upstream panel. The contribution of the side panels of the multi-box girder to Fz+ is larger than that of the T-girder, because the horizontal projection area of the side panels of the multi-box girder is larger than that of the T-girder. And Fx+ generally decreases with clearance and increases with wave height. However, Fx+first increases and then remains stable as the wave height increases when the clearance is smaller (e.g. less than 0.04m). When h=0.64m and Z=0.02m, and the wave height increases from 0.12 m to 0.21 m, the increment of Fx+ is 221.76%, and Fz+ increases with wave height, but significantly decreases with clearance. When h=0.61m and a=0.15m, the clearance increases from 0.01m to 0.07m, and the reduction of Fz+ is 87.56%.

The water sloshing in aqueducts under seismic excitations is essentially a sloshing problem of water in liquid storage tanks. However, the present calculation method for the lateral natural frequency of water within U-shaped aqueducts is extremely complicated, inefficient, and only valid for the first lateral natural frequency calculation. Based on an existing calculation method derived from the Rayleigh quotient for the natural frequency of water in 2D (two-dimensional) containers with arbitrary shapes, a simplified calculation method for the lateral natural frequency of water within U-shaped aqueducts is proposed. The Taylor series, along with the β and Γ functions, is used to simplify the complex non-elementary integrals as algebraic expressions, making this calculation method convenient and efficient enough to calculate the first four lateral natural frequency of water in U-shaped aqueducts. Furthermore, a numerical model established by OpenFOAM-9 is employed to validate the accuracy of the proposed method. Validation shows the proposed calculation method is 9 times as precise as the method specified in Chinese code for the first lateral natural frequency calculation, and it can also calculate the second- to fourth-order lateral frequencies of the water in U-shaped aqueducts precisely. Results also show when water level inside the U-shaped aqueduct is beyond the semicircle part, aqueduct width significantly influences water natural frequency, whereas water depth has a minor impact.

In recent years, tuned liquid dampers (TLDs) have attracted significant research interest; however, overall progress has been limited due to insufficient understanding of the mechanisms governing sloshing-induced loads. In particular, it remains unclear whether the water in aqueducts—common water-diversion structures in many countries—can serve as an effective TLD. This study investigates the generation mechanisms of sloshing loads during the first-order transverse resonance of water in a U-shaped aqueduct using a two-dimensional (2D) numerical model. The results reveal that, at the equilibrium position, the free surface difference between the left and right walls, the horizontal force on the aqueduct, and the fluctuating component of the vertical force all reach their maxima, with energy predominantly stored as potential energy. At the maximum displacement position, the surface difference and horizontal force drop to zero, while the fluctuating vertical force attains its minimum and energy shifts primarily to kinetic form. At this stage, static pressure is governed solely by the vertical convective acceleration, whereas at equilibrium it is closely linked to both the free surface difference and vertical local acceleration of the water. This dynamic energy exchange generates vertical force oscillations even when the free surface appears nearly symmetric.

Many studies show that the hydrodynamic force on the unit height of the deep-water pier near free surface under earthquakes changes with excitation frequency, but no investigation has been conducted to uncover the change mechanism behind this phenomenon. Based on radiation wave theory, the hydrodynamic force is decomposed into the radiation wave force and the inertial force for the first time. It's found that the added mass coefficient of radiation wave force changes with excitation frequency, which is responsible for the change of hydrodynamic force with excitation frequency. When excitation frequency is smaller, the increment of the radiation wave force is larger than the decrease of the inertial force, resulting the increase of hydrodynamic force when getting closer to the free surface; when excitation frequency is larger, the increment of radiation wave force is ignorable and the decrease of inertial force is larger, resulting the decrease of hydrodynamic force when getting closer to the free surface. Further investigation in flow field reveals that when excitation frequency is smaller, the flow field near free surface is dominated by wave flow field; when excitation frequency is larger, the flow field is dominated by oscillating flow.

In recent years, tuned liquid dampers (TLDs) have emerged as a focal point of research due to their remarkable potential for structural vibration mitigation. Yet, progress in this field remains constrained by an incomplete understanding of the fundamental mechanisms governing sloshing-induced loads in liquid-filled containers. Aqueducts present a distinctive case, as the capacity of their contained water to function effectively as a TLD remains uncertain. To address this gap, the present study investigates the generation mechanisms of sloshing loads under non-resonant cases through a two-dimensional (2D) computational fluid dynamics (CFD) model developed in ANSYS Fluent. The incompressible Reynolds-Averaged Navier-Stokes (RANS) equations are solved, while the Volume of Fluid (VOF) method captures the evolution of the air-water interface. Turbulent flow behavior is modeled using the RNG k-s approach. The ensuing results reveal the dynamic characteristics of the horizontal force (Fh) and the fluctuating component of the vertical force (Fvf). Fh is predominantly governed by the inertia of the deep-water region and its phase varies coherently with the aqueduct's acceleration. With increasing excitation amplitude (A) and frequency (f ), the contribution of deep-water inertia to Fh intensifies markedly, accounting for 82.6-92.1% of the total horizontal load at an excitation amplitude of 0.15 m and frequencies of 1.0-1.6 Hz. The extreme values of F Fvf arise primarily from asymmetric static pressures induced by free-surface fluctuations, which are further amplified when wall gaps appear at large amplitudes (A >= 10 cm) and high frequencies (f >= 1.4 Hz). Unlike resonant cases dominated by free-surface resonance, non-resonant sloshing loads are principally driven by deep-water inertia and motion-induced surface asymmetry.

The pile group-pile cap structure is a key foundation form for deep-water bridges. However, current effective methods for calculating the earthquake-induced hydrodynamic forces on pile caps with arbitrary cross-sections remain insufficient. In this study, the hydrodynamic force is considered as the added mass, and the dynamic equilibrium equations of the isolated pile cap structure (IC model) and the pile group-pile cap structure (PC model) under earthquakes are established, respectively, based on the structural dynamics theory. Correspondingly, the relationships between the hydrodynamic added masses and the fundamental frequencies in the IC model and the PC model are derived, respectively. The fundamental frequencies of the IC model and the PC model are obtained by numerical models built with the ABAQUS (2019) finite element software, and then the added masses on the IC and PC models are calculated accurately. The calculation method proposed in this study avoids the complex fluid–structure interaction problem, which can be applied for the seismic design of deep-water bridge substructures in real practice.

Research on characteristics of tsunami forces acting on conical islands and acting on cylindrical structures placed on top of a conical island, as well as the generation mechanisms of the tsunami forces, is limited. The total tsunami force acting on conical islands and its generation mechanisms are studied in cases with different initial water depths and relative wave heights. The results indicate that the peak values of the positive and negative tsunami forces, which increase with both initial water depths and relative wave heights, have almost the same magnitude. The initial submerged state of the conical island does not change the variation trend of tsunami force peaks with relative wave height. Then the tsunami forces on the structures located at different positions on the conical island are compared and analyzed, and the results show that when the conical island is not submerged at the initial state, the front cylinder has the largest peak value; when the conical island is submerged at the initial stage, the rear cylinder has the largest peak value.

The hydrodynamic force generated by the interaction between deep-water pier and water under earthquake exerts a significant influence on the dynamic response of the pier. At present, there is a lack of characterization methods to measure the influence degree of pier-water interaction on the dynamic response of the deep-water pier. Based on the structural dynamics theory and considering the coupling effect of pier-water interaction, the dynamic equilibrium equations for the deep-water pier under earthquake are established, and the solutions are deduced and validated by the finite element simulation results. Then the comprehensive analysis of influence mechanism is conducted. Further, the displacement influence coefficients and internal force influence coefficients are proposed to evaluate the influence degree of hydrodynamic force on dynamic response of deep-water piers. Validation shows that the proposed coefficients have high accuracy, indicating the important application of the proposed coefficients in seismic design of deep-water piers in real practice.

The deep-water bridge would suffer more serious damage under earthquake than that standing in air. The larger blocking ratio has remarkable effect on the added mass coefficient, which deserves a further and comprehensive study. The generation mechanism of block effect is analyzed by using the numerical simulation software ANSYS Fluent. Results show that the recirculation zone with focus decreases the pressure on the rear surface of the cylinder, results in the peak value of the in-line force does not occur synchronously with the peak value of acceleration. Results also indicate that the change of the position and intensity of the recirculation zone with focus, as well as the change of the water flow around the cylinder surface, are the generation mechanism of the block effect, the block effect has a 10% influence on the hydrodynamic force. The added mass coefficient changing rule with blocking ratio is then discussed elaborately, and the modification approach to the present added mass coefficient calculation method is suggested. Finally the physical experiments are conducted to validate the modification approach, results shows the modification approach is accurate and can be used both in the further study and in real practice.

Flow around a round-ended caisson in the submerging process is investigated using the $k-\omega$k-omega SST turbulent model and the volume of fluid (VOF) method in the present study. Six types of vortex structures around the round-ended caisson are identified, i.e. the neck vortex in front of the cylinder near the free surface, the attached vortex below the free end surface, the tip vortex originating from the free end, the spanwise vortex on the side surface, the U-shaped vortex behind the cylinder and the trailing vortex in the wake. The influence of the free surface, free end and bottom boundary on vortexes are analysed. The physical generation mechanism of vorticity on the free end surface is discussed. Additionally, the drag coefficient increases with Fr when Fr < 1 and decreases with Fr when 1 <= Fr <= 1.8, and the run-up of the free surface increases with increasing Fr.

This study focuses on the hydrodynamic interaction between tsunami waves and bridge girder. Firstly, a series of tsunami waves were experimentally generated by dam-break waves under various initial water depths, the wave front profiles and their evolution were obtained accordingly. Then, experimental studies on hydrodynamic interaction between these tsunami waves and a plate-girder as well as a T-girder were carried out systematically, and the characteristics of the whole interaction process were analyzed successively. After that, the pressure time histories on the front side, back side, upper side and downward side of the bridge girder were obtained, and the obvious differences in pressure time histories at different positions were compared and analyzed in detail. Furthermore, the horizontal impact peak force, vertical impact peak force and impact peak moment on the two bridge girders, as well as the forces and moments in the quasi-stationary stage, ware presented, and their evolution with initial water depth, incoming wave height and girder elevation are revealed elaborately. Finally, based on the findings of this study and considering the variation of tsunami wave front profile and girder elevation, the calculation formulas for the impact peak forces and moment, as well as the forces and moment in the quasi-stationary stage, are proposed for the plate-girder and T-girder, and related coefficients are suggested from the experimental results of this study. This study could deepen the insight of the hydrodynamic interaction between tsunami waves and bridge girders, and provides a new rapid calculation method for the forces and moment on plate-girder and T-girder.

Based on a comprehensive analysis of the advantages and disadvantages of existing tsunami resistant fairings for bridge girders, two novel types of fairings are proposed: the upper arc fairings (UA- alpha) and the lower arc fairings (LA- alpha). In addition, the exceedance impulse of horizontal force is suggested as a new indicator for evaluating tsunami resistant capability of fairings. In numerical simulations, comparative analysis is conducted among the upper arc fairings (UA- alpha), lower arc fairings (LA- alpha), and existing L-shape fairings (L- W ) to evaluate their tsunami resistance capabilities. Results show that the UA- 120 and L-1.00H H are the best among the upper arc fairings (UA- alpha) and L-shape fairings (L- W ), respectively. The differences between tsunami resistance capability of the lower arc fairings (LA- alpha) are inapparent, and LA- 60 demonstrating relatively superior performance. Physical experiments further indicate that the UA-120 and L- 0.50H H fairings can averagely reduce the exceedance impulse of horizontal force 76.88% and 76.24% respectively. And the LA-60 fairing can averagely reduce the exceedance impulse of horizontal force 45.08%.

During the submerging process of multi-box girder attacked by flood, the air entrapped in chambers escapes continuously, which changes the vertical component of flood force on multi-box girder remarkably. ANSYS Fluent software is employed to simulate air escape and pressure change in chambers of multi-box girder during the submerging process. Results show that when submergence ratio is small, the air in chamber is forced out from the bottom of the chamber after water rushes into the chamber, and then enters the next chamber and finally escapes from the downstream chamber; when submergence ratio is large, the air in chamber is drawn into water or vortex rushing into the chamber, and then escapes from the chamber directly. It is also found that the pressure difference in chambers is positive at the instant when the chamber is closed by flood, and gradually decreases to a negative value with the increase of submerging ratio. The decrease of the pressure difference is mainly caused by air escape and the main vortex at the bottom of girder. The fluctuation of the pressure difference is mainly caused by the periodical vortex shedding at the bottom of the girder.

基于广州洛溪大桥拓宽工程现场监测数据,对旋挖钻孔时临近隧道结构的变形进行分析,以研究旋挖钻孔成桩技术对临近地铁隧道结构的影响.该工程中,当桥梁桩基距离地铁盾构边线超过7 m时,采用旋挖钻机成孔施工方法;当桩基与地铁盾构边线的距离减小至约3.0 m时,采用旋挖钻机与全套管全回转钻机联合成孔施工方法.现场监测结果表明,桩基施工过程中,地铁隧道监测点平行于隧道中轴线方向的累计位移最大值为2.41 mm,垂直于隧道中轴线方向的累计位移最大值为1.94 mm,垂直于地面方向的累计位移最大值为2.02 mm,均在合理范围内.地铁左、右轨道差异沉降值存在超过2 mm但小于3 mm的现象,道床平顺度也存在个别监测值超过2 mm/10 m但小于3 mm/10 m的现象.本工程旋挖钻孔施工方法对地铁隧道变形影响较小,但左右轨道差异沉降与道床平顺度应该受到重点监测.

Comprehensive and intensive understanding to the failure process and failure mechanism of girder bridges is extremely crucial for anti-tsunami design of coastal bridges. The scaled down model of the multi-box girder bridge was manufactured and physical experiments were conducted in the dam-break flume to investigate the failure mode and failure mechanism. Results show that the superstructure can fail in three modes: HM (horizontal movement), HMR (horizontal movement with rotation) and HMRD (horizontal movement with rotation and dropping). And the two variables, namely the exceedance duration and the exceedance impulse, are proposed to analyze the possible failure mode and failure mechanism of the superstructure. The analysis conclusions obtained by the proposed method agree with the failure modes observed in the physical experiments. It is found that transverse horizontal movement of the superstructure always takes precedence over rotation and flow upward. With the increase of incoming tsunami bore height, the risk of failure increases; with the increase of the initial downstream water depth, the exceedance duration and exceedance impulse of horizontal force decreases firstly and then increases, the exceedance duration and exceedance impulse of vertical force and overturning moment increase.

This paper focuses on the hydrodynamic interaction between dam-break waves and circular pier. Firstly, a series of dam-break waves under dry-bed and wet-bed conditions were conducted, the evolution of wave front profiles are obtained experimentally. Then, experimental studies on hydrodynamic interaction between these dam-break waves and a circular pier were carried out systematically. After that, the pressures and their vertical distributions on the front, back and lateral side of the circular pier are obtained and analyzed in detail. In which, sudden rise of pressures on the front side, obviously oscillatory pressures on the back side, and negative pressures on the lateral side are observed. Furthermore, the forces and moments on the circular pier are presented, and their charac-teristics are explored. Among which, the maximum force and moment occur in the impulse stage when there are fluctuations upstream of the wave front, otherwise they occur in the quasi-stationary stage. In addition, the corresponding dimensionless coefficients are obtained and their evolutions are revealed elaborately. Finally, the calculation formulas for maximum force and moment on circular pier, considering the variation of wave front profile, are proposed, and related coefficients are suggested. This study could provide reference for the improvement of calculation method.

翻转课堂将知识的传授过程放在课前由学生通过自主学习来完成,将知识的内化过程放在课堂上通过教师组织学生开展多样的互动性、参与性学习来完成,是更加符合学生认知规律的教学方法.为了阐释翻转课堂的理论精髓,文章深入分析了翻转课堂相比于传统课堂教学的优势及其实施范围与程度两个重要问题;为了充分发挥翻转课堂的优势,项目组对课前、课中、课后的关键教学环节的设置目的、设计方法及实施注意事项进行了深入剖析,为成功开展翻转课堂教学提供了理论依据和实操方法.

Pounding tuned mass damper (PTMD), an improved passive damping device based on the traditional tuned mass damper (TMD), dissipates vibration energy by pounding when the main structure vibrates fiercely and dissipates vibration energy in a traditional TMD mode when the main structure vibrates slightly. PTMD has been demonstrated to be effective and robust to reduce vibration of the main structure in air and in still water in previous studies. However few studies focus on PTMD damping performance to the vortex-induced vibration of the main structure in water flow. This study proposed a new form PTMD with double L-shaped cantilever beams and streamlined mass blocks, and also designed the test model to validate the damping performance of the PTMD. Results show the test model works well both in air and in water flow, and the new form PTMD can reduce vibration of the main structure when the main structure vibrates in air. The new form PTMD is demonstrated to be effective and robust to reduce vibration when the main structure vibrated by vortex shedding in water flow. Furthermore, comparison reveals that the new form of PTMD has better damping performance when working in water flow than in air.