Bridge Force Research Articles

Physical synthesis of six-string guitar plucks using the Udwadia-Kalaba modal formulation.

Extending the previous work done by the authors, this paper develops a time domain synthesis method for the classical guitar based on substructuring concepts and using the Udwadia-Kalaba modeling strategy. Adopting a modal description of the dynamics of the separate flexible subsystems in terms of their unconstrained modes and enforcing coupling constraint conditions for the assembly, the result is an explicit dynamical modal formulation for the coupled system that directly lends itself to time-stepping methods for simulation. The guitar model couples six strings through an experimentally based body model of an actual instrument, includes two string polarizations, and the string geometrical nonlinear effects, as well as the string/fret interaction as the instrument is played. Details are given for putting all the vibrating components together in a satisfying manner, and a specific strategy is explored to allow for a nonrigid fret using flexible-dissipative-inertial constraints. The reliability of the approach is demonstrated with simulation examples that confirm the features one would expect regarding the dynamical behavior of classical guitars. Finally, a pragmatic approach is made to calculate the radiated sound by convolution, combining the computed bridge force with a measured vibro-acoustic impulse response of the instrument, which proved to give satisfactory sounding results.

Fast and Optimized Calculation of the Cable Pretension Forces in Arch Bridges With Suspended Deck

This paper deals with an effective and fast approach to the optimization of the pretension forces in arched bridges with suspended deck, which makes use of the influence matrix method. The given cable-tensioning procedure leads to a linear system of equations with a reduced number of unknowns and can be effectively implemented within active control procedures that handle time-varying loading conditions. It achieves of a target bending moment distribution over the structure, which significantly mitigates the state of stress of the deck. Numerical results dealing with a Nielsen arch bridge illustrate the versatility of the proposed approach when dealing with different loading conditions

Dynamic tests and mechanical model for water-saturated soft coal with various particle gradations

Particle gradations significantly affects the dynamic response of water-saturated soft coal. To obtain the dynamic response of soft coal to various particle gradations, static and dynamic mechanical properties of water-saturated soft coal with different particle gradations were tested and compared. During these processes, the enhancement coefficient of the dynamic mechanical parameters to the corresponding static mechanical parameters was set as an index to describe the effect of non-uniformity coefficient Cu and median diameter d50. The results demonstrate that both the static and dynamic mechanical parameters of the water-saturated soft coal were affected by particle gradations. The enhancement coefficient was affected by both the d50 and Cu, which was microscopically attributed to effect of the d50 and Cu on the average dynamic liquid bridge force and scale dynamic rupture energy among the particles based on the microstructure and dynamic fracture evolution processes. In addition, the dimensionless scale rupture energy model among the water-bearing particles varied with the d50 and Cu were further established and applied to discuss the effect mechanism of particle gradations on the dynamic response of water-saturated soft coal. On this basis, the support measures of roadways in coal seam with different particle gradations were further discussed.

Experimental and Modeling Investigation of Liquid-Induced Agglomeration in a Gas–Solid Fluidized Bed with Liquid Spray

Particle agglomeration induced by liquid bridge force widely exists in industrial fluidization processes involving liquid spray. To understand the agglomeration mechanism, a cold-mode fluidized bed...

Experimental investigations on the influence of notch definition on the pullout performance of circumferentially notched z-pins

This paper presents the results of experimental investigations on the pullout properties of circumferentially notched z-pins in carbon-fiber/epoxy prepreg laminates with unidirectional (UD) and quasi-isotropic (QI) fiber orientation. Four different notch depths between 10 and 25 μm and three different notch distances between 100 and 300 μm were investigated to determine the influence of notches with rectangular shape incorporated at the pin surface on the characteristic z-pin bridging forces and the resulting pullout energies. At UD-laminates the highest increase of the maximum debonding force Pd and maximum friction force Pf could be determined with notched z-pins with a notch depth of 10 μm and a notch distance of 100 μm. This is also reflected in the specific pullout energy, which shows an increase of 40%, compared to samples with unnotched pins. For QI-laminates, the increases are higher and can be quantified with an increase in pullout energy of 55% at a notch depth of 15 μm. A variation of the notch distance at a constant notch depth of 20 μm shows linear dependencies of the pullout energy and achieves improvements of up to 29% for UD-laminates and 42% for QI-laminates at the highest notch distance of 300 μm.

An advanced vision-based deformation measurement method and application on a long-span cable-stayed bridge

An advanced vision-based method focusing on fast and accurate deformation measurement was developed. First, computing speed and sub-pixel matching accuracy were improved by modifying the feature extraction process and optimizing the elimination mechanism of random sample consensus. An impact vibration test on a beam was designed to verify this improvement. Second, a new displacement transformation equation that considers the location change of measuring points for oblique optical axis measurement was proposed, with its advantage verified through a specially designed translation test. Based on the above, software for synchronous multi-region tracing was developed and applied to monitor the mid-span deflection and multi-cable tensile force of the Su Tong Bridge, the second longest cable-stayed bridge in the world. The test results show the great application prospects of the proposed optical method for remote and non-target deformation measurement.

Two-fluid modeling of a wet spouted fluidized bed with wet restitution coefficient model

Hydrodynamics of wet fluidized beds is significantly affected by the liquid bridge force between solid particles. In this study, two-fluid modeling of wet fluidizations with wet restitution coefficient model was realized in Ansys Fluent® through its user-defined function portal. Wet restitution coefficient was calculated using the sub-model proposed by Davis et al. (Elastohydrodynamic rebound of spheres from coated surfaces, J. Fluid Mech., 2002, 468, 107–109.), which depends on liquid viscosity, liquid layer thickness, and impacting velocity. A spouted bed with central air nozzle at the bottom was chosen as the simulation system. The simulation was first validated against available experimental and CFD-DEM results. Then, effects of the liquid viscosity and liquid layer thickness on fluidization hydrodynamics and distributions of relevant quantities were investigated. The simulation results demonstrate that the effect of liquid viscosity is significant while the influence of liquid layer thickness can be ignored in the current study. Finally, some thoughts on future studies for two-fluid modeling of wet fluidizations with wet restitution coefficient model were discussed.

A DEM approach to study desiccation processes in slurry soils

Abstract A new DEM-based approach is proposed to study the desiccation of slurry soils. Distinctly to existing DEM approaches that only consider the solid phase, the proposed method explicitly models both phases, soil and water, using spherical particles to account for their volumetric portions. This new concept allows a close description of slurry soils mimicking actual experiment conditions and providing the capability of simulating suspended soil particles in water including their transformation to the semi-solid state as water evaporates during drying. Furthermore, the water loss can be now explicitly simulated by shrinking water particles, while the solid phase particles remain unchanged. To model the soil-water interaction during drying, an existing liquid bridge force model commonly used in DEM to deal with unsaturated soils is modified to extend its working range to tackle problems involving high water contents. The proposed approach is applied to simulate a desiccation experiment conducted on a Kaolin NY specimen. The results show that the new approach can qualitatively capture main factors controlling the formation and development of the soil curling behaviour observed in this experiment. This study suggests that the new approach can be a promising computational tool to provide insights into the transition behaviour of soils from the slurry to semi-solid states involving saturated and unsaturated soil conditions.

Stress wave in monosized bead string with various water contents

Wet granular materials exhibit unique physical and mechanical properties, especially in relation to wave propagation, which is quite different from dry granular materials. In this paper, by introducing the capillary bridge force into the discrete element method, the stress wave in mono-sized bead string with various water content has been studied. First the vibration of two particles with liquid bridge has been analyzed. The presence of the liquid bridge force causes the kinetic response of the particles to exhibit completely different properties than that of the dry particles. The equilibrium position is affected by both the physical properties of the particles and the liquid bridge properties. Then the wave propagation behaviors in a mono-sized bead string have been analyzed. According to whether the liquid bridge volume has an effect on granular motion, the whole process can be divided into two stages. Stage I, particles are physically contacted with each other directly. The influence of liquid bridge force is independent of the bridge volume. Stage II, particles start to oscillate back and forth at their equilibrium positions, the influence of the liquid bridge force becomes related to the bridge volume. The kinetic energy dissipation first decreases and then increases. A U-shaped trend appears throughout the dissipation process. In our work, the mechanical properties of wet granular materials are studied from two levels: particle vibration and wave propagation, which will provide theoretical guidance for the application of granular materials in aqueous environment.

Migration characteristics of droplet condensation on end surface of single-finger microgripper

Liquid droplet is a prerequisite for micro-robot based on liquid medium. The investigation of the migration characteristics of condensed droplets on the end surface of a single-finger microgripper is of significance for obtaining stable droplets. The principle of flexible operation for micro-components using droplet condensation is analyzed first. The liquid bridge force acting on a microsphere is derived. A growth model of condensed droplet on the tip of a single-finger microgripper is established, including single-droplet growth, droplet coalesce, droplet movement, and pining effect. Condensation process on the tip of single-finger microgripper with a diameter of 130－400 μm is observed experimentally. Small droplets are formed by directly growing with a big growth rate in the initial stage, then the droplet growth is determined by droplet coalesce. The experimental results show that a single droplet is formed on the end surface after direct growth and droplets coalesce. The maximum droplet volume of 5.5 nL appears on the tip of a single-finger actuator with a diameter of 400 μm under the conditions of surface temperature of –5 °C, room temperature of 24 °C and humidity of 37%. The stability of the formed droplets is dominated by temperature gradients and edge effects during growth process. The distribution of condensed droplets is asymmetric while the microgripper is placed on a cooling surface with temperature gradient. A big growth rate is shown in a low temperature range. A single asymmetric droplet with an offset of 13 μm with respect to the axis of the actuator is formed, which is caused by the temperature gradient. A stable contact angle of 112° is obtained on the end surface of a single-finger microgripper with a diameter of 137 μm because of edge effect using the ambient temperature of 24 °C and humidity of 42%. Condensed droplets located on the end surface of hydrophobic microgripper are more stable than the untreated microgripper. Compared with the droplet formation (0.3 nL) on an untreated microgripper with a diameter of 150 μm, a lager stable droplet of 0.4 nL is obtained on the end face of a small microgripper with a diameter of 130 μm because of the hydrophobic action. The validity of theoretical analysis is verified by experimental results. The experimental investigation of the migration characteristics of condensed droplets on the end surface of a single-finger microgripper shows that the droplet shape can be changed by adjusting the temperature gradient and hydrophilic/hydrophobic performance, which plays an important role in achieving a stable droplet on the end surface.

Bioinspired multifunctional TiO2 hierarchical micro/nanostructures with tunable improved bone cell growth and inhibited bacteria adhesion

Two main origins of failure for hard tissue replacements are structural loosening and prosthetic implant infections (PIIs). Bioinspired multifunctional TiO2 hierarchical micro/nanostructures of conical-shaped TiO2 (CTO), regular TiO2 nanotubes (RTO) and irregular TiO2 nanotubes (ITO) with tunable improved cell growth and inhibited bacteria adhesion were synthesized. CTO and ITO samples indicated superhydrophilicity with contact angles of less than 5°. The MTT assay demonstrated excellent biological performance for RTO and CTO sample with 98.1% and 103.1% of cell viability, respectively. The bridging force for osteoblast cell attachment onto the synthesized porous coatings was presented as a possible mechanism. Ultimately, effect of different synthesized surfaces on both Gram-negative, Esherichia coli, and Gram-positive, Staphylococcus aureus, bacteria were estimated. The number of both Gram-negative and Gram-positive bacteria per field (NBPF) for RTO were calculated 31 and 42 respectively which were reduced more than approximately 7 and 6 times compared to the calculated NBPF of 222 and 258 for the untreated RT substrate. The recommended approach for bacteria adhesion inhibition without using antibiotics presents an auspicious solution to counteracting bacterial resistance to antibiotics.

Characterization of interface properties of fluids by evaporation of a capillary bridge.

The surface properties between two non-miscible fluids are key elements to understand mass transfer, chemistry and bio-chemistry at interfaces. In this paper, surface properties are investigated in evaporating and non-evaporating conditions. A capillary bridge between two large plates (similar to a Hele-Shaw cell) is considered. The temporal evolution of surface forces and mass transfers due to evaporation of the liquid are measured. The force depends on surface properties of the substrate. It is adhesive in the wetting case and repulsive in the non-wetting case. The force is also shown to depend linearly on the volume of the capillary bridge F ∝ V0 and inversely to the height of the bridge. Modelling is performed to characterize both surface force and evaporation properties of the capillary bridge. The evaporation is shown to be diffusion driven and is decoupled from the bridge mechanics.

Study on Dust Deposition Mechanics on Solar Mirrors in a Solar Power Plant

Solar energy is considered to be one of most promising renewable energy sources because of its availability and cleanliness. The phenomenon of dust deposition on solar mirrors greatly reduces the power generation of solar power plants. In this work, the motion behaviors and deposition mechanics of dust particles are analyzed by the discrete element method (DEM). The effects of environmental and solar mirror conditions and particle self-factors on dust deposition weight are systematically studied here. The research results show that dust particles, after particle collision, immediately adhere to the mirror or rebound and finally flow away from the mirror, or they otherwise may remain stationary after making some relative motion. Alternatively, they may glide for some distance and finally come to rest on the mirror or leave from the system. Different motion behaviors after particle collision depend on different leading forces. Here, the leading forces are the liquid bridge force (Fc) and the contact force (Fb). When the leading forces are Fc, or Fc, and Fb, the dust particles will be deposited on the solar mirror. Besides, the force Fc cannot be negligible when studying the motion processes of dust particles. The dust deposition weight on solar mirrors can be controlled by altering the environmental and solar mirror conditions, and particle self-factors. In essence, dust deposition weight on solar mirrors decreases when decreasing the leading force Fc or increasing the leading force Fb. The research results give theoretical guidance for the prevention and removal of dust deposition on solar mirrors.

Geldart classification for wet particles

Cohesion may have a significant effect on particle fluidization. Strong cohesive forces may result in a non-fluidized bed of particles. The effect of cohesive forces mainly depends on the magnitude of the forces and the particle weight. Geldart's classification places materials into four groups based on particle diameter and density difference between the particles and the fluid. Each group has different fluidization characteristics caused by the cohesive forces; specifically, in Geldart's experiments, these were Van der Waals forces (VdWFs). This study presents an investigation of the cohesive forces in fluidized beds. Using Geldart's classification, it attempts to predict the classification of moist particulate materials, affected by the liquid bridge forces (LBFs) and fluidized in air. In order to do so, a model which calculates the LBFs was developed. The classification of the wet particles is predicted by calculating an equivalent diameter and using it in the Geldart chart.

Flow and heat mass performances of wet particle drying process based on liquid volume-varying bridge force

Drying treatment of wet particle system is an important industrial process, involving flow and heat mass transfer multiple process. It has been widely used in many industrial processes, such as renewable energy usage and food storage. In this work, we numerically analyzed the heat mass transfer and flow behaviors of a wet particle system. Liquid volume-varying bridge force model was developed, and taking into account water evaporation. The numerical model data were validated, and we found good agreement with respect to hot particles during the cooling period. For a better explanation of the interactions among flow, heat and mass transfer, we calculated the distribution of particle Nusselt (Nup) and Sherwood (Shp) as a function of Reynolds (Rep), and interaction relationships between multiple processes were evaluated. Moreover, near the walls, lower gas velocity and higher particle volume fraction resulted in weak heat transfer characteristics. If this heat transfer coefficient is improved and addressed appropriately, emulsion phase, which accounts for major proportion as potential underlying cause of forming agglomeration structure, will be effectively avoided and kept to accepted level. This is important for the wet particle handling in actual industrial processes.

Finite Element Analysis of Overhead Pipeline Truss Bridge under Thermal Fluid Loads

The subject used in this study is an overhead pipeline truss bridge which sits in a chemical industrial park. The overhead pipeline truss bridge is a part of a pipeline system consisting of 10 sets of columns, 4 layers of pipe racks and 27 pipelines that transports flowing media under various temperature and pressure conditions. An integrated ANSYS finite element model was built considering the factors such as gravity, medium temperature, and flow load, etc. The results of the distributions of displacement, axial force, shear force, bending moment and stress of the overhead pipeline truss bridge were calculated. The primary stress and secondary stress were checked to judge the reliability of the overhead pipeline truss bridge. It concluded that the computation model and calculation used in this study is feasible and effective. The feature in this paper is to explore a practical method and to provide a solid technological foundation for the safety operation and assessment of overhead pipeline truss bridge.

Structural characteristics and form analysis of taxiway bridge in military airport

The scale of modern airport continues to expand, considering the needs of future use of multiple aircraft types and models, in order to improve the relevant design and planning of taxiways in the current military airport, it is necessary to consider the structure of airport taxiways and Bridges. According to the experience of the civil airport taxi road and bridge construction, the paper analyzes the military airfield taxiing bridge structural characteristics and load characteristic, proposed for use in military airfield taxiing bridge structure form, the slide to the width of the bridge, span layout, section forms, high beam and the size, the details for the military airport taxi provides the reference for the simulation modeling and the analysis of internal force of bridge.

The star in VR

ABSTRACTSince the mid-2010s there has been sustained investment in Virtual Reality (VR) media and technology, aiming to target a mass consumer market; however the industry is far from stable and challenges of adoption for the mass consumer entertainment market remain. This article examines how film stardom is being employed as a means of facilitating VR, aiding negotiation and engagement with new technologies, texts, audiences and markets. It considers the potential cultural, textual and economic significance of the film star to this emergent media technology by identifying three independent-but-interrelated ways that stardom operates in VR. Firstly, as a discursive site where film stardom connotes quality and economic viability in the promotion of the VR platform. Secondly, as a textual structure that embodies the immersive nature of the VR text, reflecting VR’s own dichotomies of perception and presence. Thirdly, as a transmedia system, connecting global markets and enabling capital investment in both film and VR forms. Throughout all arenas, film star significance is located in continuing perceptions of their ability to act as bridging forces, and as images of quality and depth. This further reflects the parallels between stardom and VR, whereby both rely on the promise of immersive, expansive, connected experiences.

Accurate identification method and practical formula of suspender tension based on tri-segment suspender dynamic model

Suspenders are main transmission force and load-bearing components of arch bridges and suspension bridges. The identification of suspender tension in service period is significantly to the normal service state and safety evaluation of structures. Based on the dynamic stiffness theory, this study establishes a tri-segment suspender dynamic model considering the effect of suspender anchorage zone. According to this model, an inverse-analysis characteristic function is established. On this basis, an accurate identification method by two optimization models is proposed, which are solved by the particle swarm optimization (PSO) algorithm, thus realizing the identification of suspender tension. Compared with the identification method of suspender tension based on the uniform equal-section dynamic model, the accuracy of the proposed model is higher. By fitting the data pairs of the suspender tension and frequency generated by the tri-segment suspender dynamic model, a practical formula method of suspender tension is also proposed, which is convenient for engineering use. By modifying the conventional cable tension formula, the practical formula method improves the identification accuracy of suspender tension, especially for short cables. Through a 20 m real cable test, it is proved that the two suspender tension identification methods (the accurate identification method and the practical method) proposed in this study have high identification accuracy and stability.

Hazard Detection Method for the Bearing Pressure Area of Steel Structure Bridge across the Sea

Liu, Q. and Li, C., 2019. Hazard detection method for the bearing pressure area of steel structure bridge across the sea. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 969–974. Coconut Creek (Florida), ISSN 0749-0208.In order to improve the bearing capacity of the bridge with cross-sea steel structure, it is necessary to detect the danger in the bearing area. Based on the analysis of elastic modulus and the evaluation of bearing yield response, a dangerous detection method for the bearing area of the bridge with cross-sea steel structure is proposed. According to the material characteristics of cross-sea steel structure bridge, the bearing capacity model of building structure is established. The composite stiffness analysis of negative moment region and the slip detection method of superposition plane are used to test the bearing force of cross-sea steel structure bridge. The dynamic characteristics such as natural vibration frequency, mode shape and damping ratio of cross-sea steel structure bridge are analyzed. According to the elastic modulus of the compression region of the structure, the structural design reinforcement ratio of the cross-sea steel structure bridge is determined. In this paper, the buckling analysis method is used to evaluate the mechanics and the bearing stress of the bridge with cross-sea steel structure, so as to realize the dangerous detection of the bearing area of the bridge with the cross-sea steel structure. The test results show that the method has high accuracy, high strength, high bearing stress level and good strength and ductility in the bearing area of cross-sea steel structure bridge.