Stability Of Bridge Research Articles

Wind-Induced Stability of a Cable-Stayed Bridge with Double Main Spans of 1,500 m and a Twin-Box Section

AbstractBoth aerostatic torsional divergence and flutter are challenging for the wind-resistant performance of long-span cable-stayed bridges. Aiming at a cable-stayed bridge with double main spans...

Modeling of capillary pressure in horizontal rough-walled fractures in the presence of liquid bridges

Capillary continuity between adjacent matrix blocks through formation of liquid bridge controls the recovery factor of gravity drainage process in fractured reservoirs. However, stability of liquid bridges as well as related capillary pressure in horizontal rough fractures is not well discussed in the available literature. In this work, new models of rough-walled fracture are developed and the role of roughness size and frequency on formation of liquid bridge and fracture capillary pressure are investigated. The Young-Laplace equation is numerically solved to characterize the liquid bridge formed in the proposed models of rough fractures. Critical fracture aperture for a range of liquid saturations, various roughness models and wettability conditions, is computed. Moreover, an expression is proposed to predict critical fracture aperture as a function of liquid saturation and contact angle for different models of rough fracture. Thereafter, as an interesting result, variation of fracture capillary pressure with liquid saturation, fracture aperture and wettability is evaluated for different models of rough fractures. It has been found that the trend of obtained fracture capillary pressure is similar to a typical matrix capillary pressure curve. The results also revealed that fracture capillary pressures as high as 1 psi (6.9 KPa) are viable when liquid saturation in the fracture is low (<5%) and fracture is sufficiently thin. Increasing wettability to liquid phase decreases the critical fracture aperture and enhances the fracture capillary pressure. At last, a semi-empirical model for capillary pressure as a function of effective fracture aperture, fracture roughness, contact angle and liquid saturation is proposed. The findings of this work help to better understand how liquid bridge stability and fracture capillary pressure may change in rough-walled horizontal fractures.

IABSE Task Group 3.1 Benchmark Results. Part 2: Numerical Analysis of a Three-Degree-of-Freedom Bridge Deck Section Based on Experimental Aerodynamics

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. To this end, the working group set up a benchmark procedure consisting of several steps with increasing complexity to define reference results useful for this validation. The simplest step (1.1a) was presented in Part 1. In this paper (Part 2), the contributions and reference results of the second sub-step (1.1c) are discussed. It consists of the simulation of the aeroelastic response of a three-degree-of-freedom bridge deck section forced by turbulent wind, using experimental aerodynamic coefficients measured in a wind tunnel. The increase in complexity, compared to the previous step, involves the experimental definition of unsteady force coefficients that are defined in a limited range of reduced velocities, and inclusion of the lateral motion and horizontal turbulent wind velocity components. Comparison of the different outputs, obtained by Task Group 3.1 participants with the same input data, is presented, revealing differences that are not always negligible. Moreover, the increase in complexity of the test case results in larger spreads of the results compared to the fully analytical case, analysed in Part 1.

IABSE Task Group 3.1 Benchmark Results. Part 1: Numerical Analysis of a Two-Degree-of-Freedom Bridge Deck Section Based on Analytical Aerodynamics

IABSE Task Group 3.1 has the mandate to define reference results for the validation of methodologies and programs used to study both stability and buffeting responses of long-span bridges. These tools for the simulation of the aeroelastic behaviour are fundamental in the safe design of bridges and they should be validated. The working group decided to set up a benchmark procedure consisting of several steps to define reference results for this validation. For each step, contributors use their own methodology to simulate the bridge behaviour using the same input data. All the results are then compared, and reference values are defined through statistical analysis. The benchmark procedure is considered as a three-step problem with substeps of increasing difficulty: Step 1 compares numerical results only, Step 2 is validation against wind tunnel experiments, and Step 3 is validation against full-scale data. In this paper, the contributions and the reference results of the simplest initial substep (1.1a) are presented. It consists of the simulation of the aeroelastic response of a two-degree-of-freedom bridge deck section, with analytical aerodynamic coefficients, forced by turbulent wind. Despite the problem’s simplicity, differences in some contributions are significant, confirming the necessity of having solid references to validate software programs.

Determination of weathered degree and mechanical properties of stone relics with ultrasonic CT: A case study of an ancient stone bridge in China

A lot of cultural heritages in the world made up of or supported by stones are damaged seriously because of long-term weathering. It is necessary to assess the weathered degrees and stabilities of these heritages. In this paper, a procedure to assess the weathered degrees and stabilities of stone relics was put forward on the base of ultrasonic CT techniques. The procedure was applied to an ancient stone bridge in eastern China, Guyue Bridge constructed about 820 years ago. Firstly, P-wave velocity distribution profiles of stone ashlars of the bridge were obtained with ultrasonic CT techniques. Secondly, according to velocity ratio of the in situ P-wave velocities of the stone ashlars to the P-wave velocity of the fresh rock specimens of the same lithology with those of the stone ashlars, the weathered degrees of the stone ashlars were determined. Finally, the same rock specimens with different weathered degree, which were collected from a quarry near the historic bridge, were tested to get their P-wave velocities, UCS and elastic moduli, and the relations between the P-wave velocity and these mechanical properties were put forward. On the base of these relations, the mechanical property distributions of the detected stones could be obtained. In this study, two vertical sections of an ashlar in the historic stone bridge were detected by the assessment procedure. According to the assessment results, the two cross sections have different weathered degrees because of different stress states: higher weathered degree and lower compressive strength present to the section near the joint connecting two stone ashlars, where pressive stress is much stronger than that of the section far away from the joint. Correspondingly, the higher weathered section had worse physical and mechanical properties, which would be the key location for the stability of the old bridge.

Calculated research of aeroelastic stability of a bridge over the river Ob in Salekhard at the stage of assembling and operation

Recently, long span bridge construction has been demanded for development of the regions of the Russian Federation. In terms of economy, it’s useful to build a combined road-railway bridge. Such bridges, generally, constitute a metal cross-cutting girder with carriageways on lower, upper or both zones of the girder. The major advantages of combined bridges are high strength and load capacity, plus cross-cutting to wind load. Focus of this research is a combined road-railway bridge over the Ob river at the stage of assembling and operation. The purpose of the study was to determine the limits of aeroelastic stability of combined road-railway bridge at the stage of assembling and operation using numerical simulation. To better understand the bridges behaviour in air flow, flow around a section model has been researched with CFD simulation in the ANSYS FLUENT. Then based on the given results of the calculations the dependence of the bridge vibrations on wind speed within a specified range is obtained, and also values of drag coefficient Сх, lift coefficient Су and torque coefficient Мz are received. These studies were carried out in the range of angles of attack α = ±3°. The possibility of divergence and galloping was also estimated. The results of the study made it possible to estimate the influence of air flow on combined bridge cross-cutting girder. Overall, the conducted research seems promising for further investigation and development in the field of bridge aeroelasticity.

Optimization for vertical stabilizers on flutter stability of streamlined box girders with mountainous environment

Wind environment in mountainous areas is very different from that in coastal and plain areas. Strong winds always show large angles of attack, affecting the flutter stability of long-span bridges which is one of the most important design factors. The central vertical stabilizer has been demonstrated to be an effective aerodynamic measure to improve the flutter stability, and this article optimizes the stabilizer to improve its applicability in mountainous areas. Computational fluid dynamics simulations are first performed to analyze the effects of stabilizers with different positions and forms on the flutter stability of an ideal box girder, and the aerodynamic mechanism is discussed based on the static and the dynamic flow fields, respectively. Wind tunnel tests are then carried out to test the critical flutter wind speed of a real box girder equipped with different stabilizers, and the change in its flutter stability is further analyzed. The results show that the vertical stabilizer with appropriate positions and heights can improve the participation level of structural heaving vibration, and thereby increases the flutter stability. At large angles of attack, the big vortex on the leading edge which may drive the bridge to flutter instability is gradually weakened with the increase in stabilizer’s height. Compared with a single stabilizer, double vertical stabilizers, in the midst of which exists a negative pressure region, could achieve better effects.

Small-sized platinum nanoparticles in soil organic matter: Influence on water holding capacity, evaporation and structural rigidity

Engineered and anthropogenic nanoparticles represent a new type of pollutants. Up until now, many studies have reported its adverse effect on biota, but the potential influence on the properties and functions of environmental compartments has largely been ignored. In this work, the effect of Pt nanoparticles on the functions and properties of model soil organic matter has been studied. Using differential scanning calorimetry and molecular modeling, the effect of a wide range of 3 nm Pt nanoparticles concentrations on water holding capacity, the strength of water binding, the stability of water molecule bridges and the content of aliphatic crystallites was studied. It was found that strong hydration of the nanoparticles influences the 3D water structural network and acts as kosmotropic agents (structure-forming) in water bridges and as chaotropic agents (i.e. water destructuring) in larger water volumes. Contrarily, the interaction with soil organic matter moieties partially eliminates these effects. As a result, the 3 nm Pt nanoparticles decreased the evaporation enthalpy of water in soil organic matter and supported soil desiccation. They also increased the strength of water molecule bridges and increased the soil structural rigidity even at low concentrations. Additionally, at high concentrations, they decreased the water content in soil organic matter and induced the aliphatic moieties' crystallization. It is concluded that the small-sized Pt nanoparticles, and perhaps other types as well, may affect the local physicochemical processes in soils and may consequently contribute to enhanced evapotranspiration and deterioration of soil functions.

Geotechnical stability assessment of a railway arch bridge more than 100-year old: a case study

In the present investigation, the geotechnical stability of the substructure of 100-year-old brick masonry rail bridges has been analysed numerically in the presence of nearby newly proposed concrete box bridges. Two different arch bridges (1273/1 and 1274/1) of Indian Railways (IR) have been considered in this analysis. Both bridges are made of brick masonry with different numbers of barrels. The numerical analysis has been performed using the finite-element (FE) method. The existing railway track between Kanpur and Jhansi, India, runs on these bridges, which were basically constructed by the British between 1888 and 1900. Therefore, the assessment of geotechnical safety and stability of such heritage bridges was of paramount importance from the IR point of view since the modern rail loading and other associated factors were changed significantly. A detailed geotechnical investigation along with the plate load test was carried out at the respective bridge locations, and the results are reported in this paper. The distribution of the vertical stress and the settlement developed below the foundation of the bridges have been acquired from the FE investigation to judge the foundation safety against the strength and the serviceability perspective.

Building bridges between chromosomes: novel insights into the abscission checkpoint.

In the presence of chromatin bridges, mammalian cells delay completion of cytokinesis (abscission) to prevent chromatin breakage or tetraploidization by regression of the cleavage furrow. This abscission delay is called "the abscission checkpoint" and is dependent on Aurora B kinase. Furthermore, cells stabilize the narrow cytoplasmic canal between the two daughter cells until the DNA bridges are resolved. Impaired abscission checkpoint signaling or unstable intercellular canals can lead to accumulation of DNA damage, aneuploidy, or generation of polyploid cells which are associated with tumourigenesis. However, the molecular mechanisms involved have only recently started to emerge. In this review, we focus on the molecular pathways of the abscission checkpoint and describe newly identified triggers, Aurora B-regulators and effector proteins in abscission checkpoint signaling. We also describe mechanisms that control intercellular bridge stabilization, DNA bridge resolution, or abscission checkpoint silencing upon satisfaction, and discuss how abscission checkpoint proteins can be targeted to potentially improve cancer therapy.

Reinterpretation of a Phoenician dental appliance.

Background Since its discovery in 1862, the Gaillardot Phoenician gold wire dental bridge (Louvre artefact no. 5,777) has been the subject of conflicting interpretations as to its correct situation in the jaws, the origin of replaced teeth, and the possibility of teeth having been rearranged within the appliance.Methods This paper offers an analysis based on examination and digital macrophotography of the appliance at the Louvre. Resultant images aided never-before considered points of evidence such as aspects of individual tooth anatomy, occlusion, and the need of the fabricating artisan to allow for crowding of the original dentition.Results Pontic and abutment teeth bear a labial horizontal developmental groove and are the same colour. Canines and incisors conform to mandibular teeth anatomy and canines are in their correct positions. Canine incisal cusp wear and a flat labial arch indicates the dentition had been an Angle Class III anterior relationship. The incisor pontic teeth had originally been crowded out of the arch and were trimmed to reduce their width to fit the bridge within the arch.Conclusions This extra evidence confirms the interpretation of a mandibular setting and correct positioning of teeth within the appliance. To create a favourable dental arrangement to address bridge stability and longevity, the fabricating artisan had to modify the dentition.

Stability analysis of double x-shape arch bridge during construction

The main bridge of Zhanhe River, which is located in Pingdingshan city, China, is a double X-shape reinforced concrete arch bridge. With the aid of the Midas/civil finite element software, the three-dimensional finite element model of the Zhanhe Bridge is established according to the actual construction stages and the design construction stages. The stability safety coefficients for different construction stages, such as arch-rib completion, tie bar beam tensioning and suspender tensioning are calculated. The calculation results indicate that the minimum stability coefficient for this arch bridge during construction is 7.28, which meets the requirement of arch bridge stability. The main results are useful for the design, construction and m aintenance of the same bridges.

An extracellular matrix protein promotes anillin-dependent processes in the Caenorhabditis elegans germline.

Cell division requires constriction of an actomyosin ring to segregate the genetic material equally into two daughter cells. The spatial and temporal regulation of the contractile ring at the division plane primarily depends on intracellular signals mediated by the centralspindlin complex and astral microtubules. Although much investigative work has elucidated intracellular factors and mechanisms controlling this process, the extracellular regulation of cytokinesis remains unclear. Thus far, the extracellular matrix protein Hemicentin (HIM-4) has been proposed to be required for cleavage furrow stabilization. The underlying molecular mechanism, however, has remained largely unknown. Here, we show that HIM-4 and anillin (ANI-1) genetically act in the same pathway to maintain the rachis bridge stability in the germline. Our FRAP experiments further reveal that HIM-4 restricts the motility of ANI-1. In addition, we demonstrate that HIM-4 is recruited to the cleavage site in dividing germ cells and promotes the proper ingression of the cleavage membrane. Collectively, we propose that HIM-4 is an extracellular factor that regulates ANI-1 for germ cell membrane stabilization and contractile ring formation in Caenorhabditis elegans germline cells.

A novel method for the analysis of particle coating behaviour via contact spreading in a tumbling drum: Effect of coating liquid viscosity

Spray coating is a common method of distributing liquids over powders, especially in the pharmaceutical, detergent and food industries. During this process, liquid drops are deposited on the surface of particles. Liquid is then transferred between particles via particle collisions, in a process called liquid contact spreading. This contact spreading process facilitates inter-particle coating, in which wetting, de-wetting, mixing and drying are occurring simultaneously. This work presents the first experimental study of the mechanism of liquid contact spreading. In this work, a novel experimental method has been developed to investigate the mechanism of contact spreading, incorporating a newly developed image analysis technique, based on colourimetric measurements, to quantitatively determine coating behaviour via contact spreading.Here, experiments designed to isolate the contact spreading coating mechanism were performed in a tumbling drum using a model material system; alumina particles and dyed polyethylene glycol solutions of varying viscosities. The coating uniformity was quantified by the variation in inter-particle coating; the coefficient of variation (CoV). For all systems, the uniformity of the coating increased with time until the CoV decreased to an asymptotic value. The rate of the decrease in the CoV was successfully fitted using an exponential decay function.The viscosity of the coating solution had a significant effect on the rate of liquid transfer; the lower the viscosity the faster the contact spreading process. This effect is attributed to differences in the formation and stability of liquid bridges between the particles, influencing the extent of liquid transfer. The results also show that in most cases examined here, viscous forces play a main role in the contact spreading process, and the contribution of capillary forces are minimal. This understanding could assist with the design and scale up of wet coating processes.

Circular time-domain reflectometry system for monitoring bridge scour depth

Sediment has a severe effect on bridge stability, and time-domain reflectometry (TDR) is a suitable method for assessing scour depth. This paper presents a fundamental study to demonstrate the suitability of a circular TDR system to enhance the resolution when monitoring scour depth with consideration of detailed local changes over a wide area around piers. A total of 32 electrodes are vertically installed on a cylinder pier around the circumference at ∼7.36 mm intervals. Scour depth is investigated through small-scale laboratory experiments, where a measured waveform reflects the artificially constructed scour depth with high resolution (≈5 mm). Different scour types including circular, mushroom, elliptical, and irregular shapes are developed to verify the application of circular TDR, and shapes are predicted through the detailed local distribution. The influences of the reflected waveform according to water level change, temperature variation, and salinity effect are investigated as additional considerations, and the relative deviation of scour depth is analyzed. This study demonstrates that the proposed circular TDR system achieves better resolution than existing single TDR systems and may provide a better alternative technique for monitoring scour depth.

A new method for estimation of aerostatic stability safety factors of cable-stayed bridges

An inverse reliability-based approach is proposed to estimate the aerostatic stability safety factors of long-span cable-stayed bridges in order that their reliability against the failure mode of aerostatic stability meets a desired level of safety. For the purpose of estimation, uncertainties associated with the basic wind speed at the bridge deck location, critical aerostatic stability velocity, the wind conversion factor from a scaled model to the prototype structure and the gust speed factor are taken into account. The proposed approach combines concepts from the inverse reliability method and the calculation method of the critical aerostatic stability velocity of long-span cable-stayed bridges. A procedure of the proposed approach for the estimation of aerostatic stability safety factor, which at the same time achieves a target reliability, is outlined. This proposed approach is illustrated using three existing long-span cable-stayed bridges. The results indicate that the proposed approach provides validity information concerning the improved accuracy of the estimation of aerostatic stability of long-span cable-stayed bridges over the traditional method. Additionally, the effects of various parameters on the aerostatic stability safety factor of long-span cable-stayed bridges are analysed and discussed.

Analysis of co-contraction of the trunk muscles in the side bridge stabilization exercise with different unstable surfaces

Analysis of co-contraction of the trunk muscles in the side bridge stabilization exercise with different unstable surfaces

Affinity Improvement of a Cancer-Targeted Antibody through Alanine-Induced Adjustment of Antigen-Antibody Interface

To investigate favorable single amino acid substitutions that improve antigen-antibody interactions, alanine (Ala) mutagenesis scanning of the interfacial residues of a cancer-targeted antibody, B5209B, was performed based on X-ray crystallography analysis. Two substitutions were shown to significantly enhance the binding affinity for the antigen, by up to 30-fold. One substitution improved the affinity by a gain of binding enthalpy, whereas the other substitution improved the affinity by a gain of binding entropy. Molecular dynamics simulations showed that the enthalpic improvement could be attributed to the stabilization of distant salt bridges located at the periphery of the antigen-antibody interface. The entropic improvement was due to the release of water molecules that were stably trapped in the antigen-antibody interface of the wild-type antibody. Importantly, these effects of the Ala substitutions were caused by subtle adjustments of the binding interface. These results will be helpful to design high-affinity antibodies with avoiding entropy-enthalpy compensation.

Evaporation and instability of an unbounded-axisymmetric liquid bridge between chemically similar and different substrates

HypothesisIn this manuscript we examine the stability of an evaporating-unbounded axisymmetric liquid bridge confined between parallel-planar similar or chemically different substrates using both theory and experiments. With a quasistatic assumption we use hydrostatics to estimate the minimum stable volume Vmin via the Young-Laplace equation for Bond numbers 0⩽Bo⩽1, and top/bottom wall contact angles 5°<θ<175° although the primary focus is on wetting and partial wetting fluids. Solving the Young-Laplace equation requires knowledge of appropriate capillary pressure values, which appear as a constant, and may not provide unique solution. To examine uniqueness of numerical solutions and volume minima determined from the Young-Laplace equation for unbounded-axisymmetric liquid bridges we analyzed capillary pressure for large and small liquid volume-asymptotic limits at zero Bond number. ExperimentsExperiments were performed to compare with the volume minima calculations for Bond numbers 0.04⩽Bo⩽0.65. Three substrates of varying surface energy were used, with purified water as the primary liquid. Volume estimates and contact angle data were extracted via image analysis and evaporation rates measured from this data are reported. FindingsVolume minima were in the range 0.1<Vmin<20 μl depending on Bond number. There was good agreement when comparing predicted volume minima and those determined from experiments for the range of parameters studied.

The effect of different alcohols on the Asp23-Lys28 and Asp23-Ala42 salt bridges of the most effective peptide in Alzheimer's disease: Molecular dynamics viewpoints

The beta-amyloid peptide Aβ1-42 is the most effective peptide in the process of forming plaque and creating Alzheimer's. After the separation of Aβ1-42 from APP membrane protein, the membrane surface is transmitted to the extracellular environment, which is a crowded environment. On the other hand, stability of salt bridges Asp23-Lys28 and Lys28-Ala42 is important for monomer toxicity and fibrillation formation. In this work, the effects of ethanol, propanol, butanol, pentanol, hexanol, heptanol and octanol on the Asp23-Lys28 and Lys28-Ala42 salt bridges of the Aβ1-42 have been investigated by molecular dynamics simulation. The radial distribution function of the oxygen atoms of the water around the atoms Cγ-Asp23, Nξ-Lys28 and O-Ala42 was calculated in the presence of the alcohols. The results show that the peak height of the radial distribution function around the Cγ-Asp23 atom is larger than the other two atoms. Also, the numbering of water molecules in the interval corresponding to the first peak in the radial distribution function for all atoms involved in the two salt bridges Asp23-Lys28 and Lys28-Ala42 was calculated. The results show that the obtained coordinate numbers are within the range of experimental numbers reported for water. The results also show that the order of water molecules around the O-Ala42 is lower. The results of solvent accessible surface area of Aβ1-42 show that the Lys28-Ala42 Salt bridge stability is more important for toxicity of monomer.