Short Bridges Research Articles

Scour depth evaluation of highway bridge piers using vibration measurements and finite element model updating

Scour of piers is one of the major causes of the bridge collapse. Most studies related to scoured bridges focus on the mechanics of bridge scour and detecting or monitoring changes in bridge characteristics caused by scour, but less on the quantitative sour evaluation. This paper proposes a novel method using measured vibration responses and finite element model updating technique to address the quantitative evaluation of existing scour depth, including general scour depth and local scour depth for the common pile foundation in short and medium-span highway bridges. The pile-soil interaction is simulated by the rotational and translational spring elements in horizontal directions. Indices including the residual of natural frequencies and frequency response functions are adopted in the objective function that is iteratively minimized. The longitudinal (i.e. the direction along the bridge axis) response excited by impulse force on bridge pier is proved to be more sensitive to the bridge scour than the transverse (i.e. the direction perpendicular to the bridge axis in the horizontal plane) response, so it is adopted in the numerical analysis. A field test was performed on a typical bridge to validate the proposed method. Test result shows the scour depth of piers can be quantitatively evaluated by the proposed method, which avoids the detailed underwater inspection and continuous vibration monitoring of the piers.

Stiffness Contributions of Ballast in the Context of Dynamic Analysis of Short Span Railway Bridges

Stiffness Contributions of Ballast in the Context of Dynamic Analysis of Short Span Railway Bridges

Bis-Rhodamines Bridged with a Diazoketone Linker: Synthesis, Structure, and Photolysis.

Two fluorophores bound with a short photoreactive bridge are fascinating structures and remained unexplored. To investigate the synthesis and photolysis of such dyes, we linked two rhodamine dyes via a diazoketone bridge (−COCN2−) attached to position 5′ or 6′ of the pendant phenyl rings. For that, the mixture of 5′- or 6′-bromo derivatives of the parent dye was prepared, transformed into 1,2-diarylacetylenes, hydrated to 1,2-diarylethanones, and converted to diazoketones Ar1COCN2Ar2. The high performance liquid chromatography (HPLC) separation gave four individual regioisomers of Ar1COCN2Ar2. Photolysis of the model compound—C6H5COCN2C6H5—in aqueous acetonitrile at pH 7.3 and under irradiation with 365 nm light provided diphenylacetic acid amide (Wolff rearrangement). However, under the same conditions, Ar1COCN2Ar2 gave mainly α-diketones Ar1COCOAr2. The migration ability of the very bulky dye residues was low, and the Wolff rearrangement did not occur. We observed only moderate fluorescence increase, which may be explained by the insufficient quenching ability of diazoketone bridge (−COCN2−) and its transformation into another (weaker) quencher, 1,2-diarylethane-1,2-dione.

Dynamic amplification responses of short span bridges considering scour and debris impacts

During extreme flooding events, bridges could experience large lateral displacements or even collapse due to either strong hydraulic forces or the effects of large waterborne debris, such as tree branches. The effects of waterborne debris on the structural behaviors of bridges include temporary accumulated dams and direct debris impacts. The additional lateral hydraulic forces and the acceleration of bridge scouring process due to temporary accumulated dams were investigated by researchers. Several debris impact force models were proposed to determine the loading effects applied on bridges. However, very few studies were conducted on the dynamic responses of bridges during flooding events considering the effects of large wood debris (LWD) as a combination of additional lateral hydraulic forces, foundation scour, and direct debris impacts. Therefore, the present study performed numerical analyses for bridges subjected to foundation scour and LWD impacts corresponding to flooding events. Besides, the effects of foundation scour and LWD impacts on the dynamic responses were simplified for bridge design purposes. Firstly, various short-span bridges with possible foundation scour depths due to debris accumulation were numerically simulated to obtain dynamic characteristics. Then, the hydraulic forces applied on the bridges were updated considering an extra blocking area due to debris accumulation. The collision forces due to floating woody debris were also introduced into the vehicle-bridge coupling system. Finally, the dynamic amplification factors (DAFs) with and without considering the effects of debris impacts were calculated and compared. It was found that the DAFs increase 20% at the maximum due to the effects of debris impacts. A modified factor was proposed to consider the effects. The reaction forces with and without the effects were also calculated to investigate the effects on the risk of deck unseating. Introducing possible debris impacts during flooding events into the dynamic analyses of bridges brings a more realistic estimation for the safety of bridges. The DAFs of bridges can be further taken as a guide for the supplements of design codes. The updated reaction forces would help to guide the risk mitigation of deck unseating.

Conformation Locking of the Pentose Ring in Nucleotide Monophosphate Coordination Polymers via π-π Stacking and Metal-Ion Coordination.

The conformation of the pentose ring in nucleotides is extremely important and a basic problem in biochemistry and pharmaceutical chemistry. In this study, we used a strategy to regulate the conformation of pentose rings of nucleotides via the synergistic effect of metal-ion coordination and π-π stacking. Seven types of coordination complexes were developed and characterized using Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, ultraviolet-visible spectroscopy, 1H nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. On the basis of two conformational parameters obtained from single-crystal structure analysis, i.e., the pseudorotation phase angle and degree of puckering, the exact conformation of the furanose ring in these coordination polymers was unequivocally determined. Crystallographic studies demonstrate that a short bridging ligand (4,4'-bipyridine) is conducive to the formation of a twist form, and long auxiliary ligands [1,2-bis(4-pyridyl)ethene and 4,4'-azopyridine] induce the formation of an envelope conformation. However, the longest auxiliary ligands [1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene] cannot limit the flexibility of a nucleotide. Our results demonstrated that the proposed strategy is universal and controllable. Moreover, the chirality of these coordination polymers was examined by combining the explanation of their crystal structures with solid-state circular dichroism spectroscopy measurements.

Yakemys multiporcata n. g. n. sp., a Large Macrobaenid Turtle from the Basal Cretaceous of Thailand, with a Review of the Turtle Fauna from the Phu Kradung Formation and Its Stratigraphical Implications

Yakemys multiporcata n. g. n. sp. is described on the basis of shell elements from the upper part of the Phu Kradung Formation (basal Cretaceous), Khorat Plateau, NE Thailand and assigned to Macrobaenidae. The new taxon is unusually large for an early macrobaenid (with an estimated carapace length about 70 cm) and is characterized by a large, rounded, low shell, the presence of a midline keel and numerous additional strong ridges on the carapace, the anterolateral margin upturned to form a gutter, posterolateral peripherals mesiolaterally expanded, narrow vertebrals, the vertebral 4 triangular and narrowed posteriorly, a greatly reduced plastron with a short bridge, an oval and elongate entoplastron with reduced ventral exposure, and strip-shaped epiplastra. The discovery of a macrobaenid turtle provides further support for an Early Cretaceous age for the upper part of the Phu Kradung Formation.

Design of River Galeh Bridge Temanggung Regency with Reinforced Concrete T-Beam Structure

The old bridge of Sungai Galeh is a short span bridge with a reinforced concrete beam superstructure and a masonry bottom structure. This bridge is planned to be replaced for renovation. The replacement Sungai Galeh bridge is planned with the upper structure using reinforced concrete T-beams and the lower structure using reinforced concrete cantilever abutments. The purpose of this paper is to re-plan the Sungai Galeh Bridge in order to provide services for traffic users safely and comfortably. From the analysis results, the dimensions of the reinforced concrete T-beam are 40 x 80 and the dimensions of the diaphragm are 25 x 45.

Damage Identification in Warren Truss Bridges by Two Different Time–Frequency Algorithms

Recently, a number of authors have been focusing on drive-by monitoring methods, exploiting sensors mounted on the vehicle rather than on the bridge to be monitored, with clear advantages in terms of cost and flexibility. This work aims at further exploring the feasibility and effectiveness of novel tools for indirect health monitoring of railway structures, by introducing a higher level of accuracy in damage modelling, achieve more close-to-reality results. A numerical study is carried out by means of a FE 3D model of a short span Warren truss bridge, simulating the dynamic interaction of the bridge/track/train structure. Two kinds of defects are simulated, the first one affecting the connection between the lower chord and the side diagonal member, the second one involving the joint between the cross-girder and the lower chord. Accelerations gathered from the train bogie in different working conditions and for different intensities of the damage level are analyzed through two time-frequency algorithms, namely Continuous Wavelet and Huang-Hilbert transforms, to evaluate their robustness to disturbing factors. Compared to previous studies, a complete 3D model of the rail vehicle, together with a 3D structural scheme of the bridge in place of the 2D equivalent scheme widely adopted in the literature, allow a more detailed and realistic representation of the effects of the bridge damage on the vehicle dynamics. Good numerical results are obtained from both the two algorithms in the case of the time-invariant track profile, whereas the Continuous Wavelet Transform is found to be more robust when a deterioration of track irregularity is simulated.

Monitoring the Dynamic Behavior of PCI Bridges Using Short Period Seismograph and CSI Bridge Modeling

Bridges are a critical part of transport infrastructure networks for social activities and economics of human life. Dynamic analysis of bridge is very important to perform in order to ensure the ability of the bridge to withstand loads and maintain the sustainability of transport infrastructure. This paper presents a methodological framework for monitoring dynamic behavior of the bridge (e.g., natural frequencies, displacement time history) by using civil engineering micro-tremor technique and numerical modeling. The study was conducted at the Alue Raya Bridge located in Lhokseumawe City, Aceh Province, Indonesia. To capture the dynamic behavior of the bridge under traffic loading, the micro-tremor techniques, e.g., Short Period Seismograph (SPS) sensor was placed underneath the bridge at the mid span of the bridge girder. The obtained vibration data were processed using Geopsy software. A three dimensional (3D) model of the bridge was then developed by using CSI Bridge software. The modal analysis was conducted to obtain the modal natural frequencies of the bridge due to traffic loads. The natural frequency measurements using SPS were compared with the simulation results. Through analyzing the measured results, it was found that the natural frequency of the bridge is around 4,3275 Hz which is very close to those obtained from numerical modeling using CSI bridge software. The measured maximum vertical displacement of the bridge girders is below 5mm under normal traffic condition which is under the allowable serviceability limit state requirements of the bridge. The outcomes of this study could have the potential to enable maintenance and capital works decisions which are an important component of the sustainability of transport infrastructure.

Investigation of Indian standard plans issued by Ministry of Surface Transport for T-beam bridges

Bridges are the essential parts of the transportation facilities and are subjected to various forces depending on the onsite conditions and specific location of the bridge. T-beam bridges are pivotal in commuting from one place to other especially in shorter spans. The major forces acting on the T-beam bridges are static load, moving load and seismic load. Design of the T-beam bridges is conventional and versatile, as the main components are beams and slabs.There are various methods for the design of RC bridges, depending on the safety and serviceability. The earlier bridges were designed based on the working stress method as safety was the only criteria. Nowadays, the design is based on safety and serviceability. Most of the short span bridges in India are constructed as per the design details of standard plans by Ministry of Surface transport, Govt. of India. The complete design details for RCC slab and T-beam bridges (volume II) are available for the span ranging from 10 m to 24 m. The design details are established on the basis of working stress method as per code IRC 21: 1987. Provisions of IRC-6:1985 for seismic loading has also been incorporated in the design details. At present, working stress method of design of RC Road bridges has been outdated and IRC 112: 2011 code is in use.The study is about, to check the suitability of standard design drawings for spans varying from 10 m to 24 m based on limit state guidelines. design details are checked for the suitability at all seismic zones. MIDAS Civil (2019) software has been adopted to conduct this study. Comparative study has been made for the suitability of the design details of all spans in all seismic zones as per the new code.

Resonances of railway bridges analysed in frequency domain by the modal-force-excitation, bridge-transfer and axle-sequence spectra

In this article, the passage of different trains over different bridges will be studied for resonant excitation. The intensity of the resonance will be estimated in frequency domain by using three separated spectra. At first, the excitation spectrum of the modal forces is built by the mode shape and the passage time of the train over the bridge. The second spectrum is the frequency response function of the bridge which include the modal frequency, damping and mass. The third part is the spectrum of the axle sequence of the train. The influences of train speed, bridge length, bridge support, track irregularities, and train type on the resonance amplitudes will be analysed for each of these spectra separately for getting a better insight. A variety of axle-sequence spectra and corresponding rules will be presented for different vehicles and trains. As examples, the passage of a slow freight train over a long-span bridge, a normal passenger train over a medium-span bridge, and a high-speed train over a short bridge will be analysed. Corresponding measurements show the amplification, but also the cancellation of the subsequent axle responses. Namely in one of the measurement examples, the first mode of the bridge was amplified and the second mode was cancelled at a low speed of the train and vice versa at a higher speed.

Determination of the structural efficiency of short bridges according to their physical and economic characteristics

Bridges are structures designed and built to overcome natural and artificial obstacles. The analysis and design of bridges is carried out following principles of physics applied to engineering. The aim is to estimate the structural efficiency of short bridges according to their physical and economic characteristics through equations that measure the cost tendency, identifying which ones have the highest structural efficiency for a given length between supports. The design of short bridges was carried out by means of a mathematical modeling in a software based on finite elements. A comparative cost analysis was carried out for various types of short vehicular bridges designed with reinforced concrete decks supported by reinforced concrete beams; post-tensioned concrete beams; and structural steel beams. It was determined that the bridge with a reinforced concrete deck is the alternative with the best structural efficiency according to its physical and economic characteristics with spans of 12 meters and 18 meters. According to the estimated cost equations, it is concluded that, from 18.49 meters post-tensioned concrete bridges are the most efficient physically and economically. Structural steel bridges are the least structurally efficient for short bridges. Therefore, the construction of short vehicular bridges with structural steel is not feasible.

Synthesis and characterization of tracers and development of a fluorescence polarization immunoassay for amantadine with high sensitivity in chicken.

Fluorescence polarization immunoassay (FPIA) is a homogeneous and rapid analytical method that is suitable for high-throughput screening of large numbers of samples. However, FPIA typically suffers from lower sensitivity than the well-established enzyme-linked immunosorbent assay (ELISA), limiting its wide application as an analytical tool that can be run with trace levels of an analyte. Herein, a highly sensitive FPIA for detecting amantadine (AMD) in chicken is described. To achieve high sensitivity, nine chemical tracers of AMD that employ different fluoresceins, fluorescein derivatives, and haptens were synthesized and paired with four previously produced monoclonal antibodies (mAbs). The effect of the tracer structure on the sensitivity of FPIA was investigated and discussed. We found that the tracers with a linear and shorter bridge between adamantane and fluorescein generally provided higher sensitivity. After optimization, N'-(1-adamantyl) ethylenediamine (AEDA), an AMD structural analogue labeled with fluorescein isothiocyanate (FITC), achieved the lowest IC50 value (1.0ng/ml) in the FPIA, which was comparable to that of the heterologous ELISA format that used the same mAb7G2. We also investigated the possible recognition mechanism of mAbs in terms of conformational and electronic aspects. The developed FPIA was applied to chicken to detect AMD residue, demonstrating a limit of detection (LOD) of 0.9µg/kg with recoveries of 76.5-89.3% and coefficients of variation (CVs) below 14.5%. These results show that the proposed FPIA is an efficient, accurate, and convenient method for the rapid screening of AMD residues in chicken. PRACTICAL APPLICATION: The fluorescence polarization immunoassay (FPIA) was developed to determine and quantify amantadine (AMD) in chicken samples with high sensitivity. This homogeneous method avoids coating and washing steps and may provide high-throughput AMD screening in chicken in 10min with high accuracy and precision. FPIA can be used as a monitoring tool and contribute significantly to the rapid detection of AMD in chicken.

FEM Analysis of Bridges with Encased Continuous Shear Connectors

AbstractComposite steel‐concrete constructions with encased I‐beams were initially used as composite floors. Nowadays, they can be usually seen as short railway bridges with span up to 20m. Their main advantages include simplicity of their construction, their low construction height and their effectiveness. To make them more effective, the steel I‐beams were replaced with perforated steel strips. At Technical University of Košice, Faculty of Civil Engineering, several continuous shear connectors with new design were proposed. In order to prove their effectiveness, numerous experiments – push‐out tests, four point flexural tests – were performed at Laboratory of Excellent Research. The purpose was to determine the shear and bending resistance of the connectors. Afterwards, the finite element models were created and analyzed using ABAQUS/CAE software. This paper deals with numerical program of four‐point flexural tests of two strips. The most clue modules ‐ properties, load, step, interaction and mesh are described.

Fusion rate of 89% after knee arthrodesis using an intramedullary nail: a mono-centric retrospective review of 48 cases

PurposeKnee arthrodesis is an established procedure for limb salvage in cases of recurrent infection, total knee arthroplasty soft tissue defect, poor bone stock or a deficient extensor mechanism. Surgical options include compression plate, external fixator and arthrodesis nail. Different types of nail exist: long fusion nail, short modular nail and bridging nail. This study presents the results on knee arthrodesis using different types of intramedullary nails. The aim is to assess if a specific type of nail has a better fusion rate, clinical outcome and lower complication rate.MethodsA mono-centric retrospective study of 48 knees arthrodesis was performed between 2000 and 2018. 15 T2™ Arthrodesis Nail, 6 OsteoBridge® Knee Arthrodesis and 27 Wichita® fusion nail were used. The mean clinic and radiological follow-up was 9.8 ± 3.8 years (2.6–18 years).ResultsFusion rate was 89.6%. Time to fusion was 6.9 months. Mean Parker score was 6.9/9 points. Visual Analogic Scale was 1.9. The Wichita® fusion nail showed better results in terms of fusion, time to fusion and clinical outcome measured by Parker score and VAS but without statistical significance. The early revision rate was 10.4% and 20.8% presented a late complication requiring a surgery, due to nonunion or infection. 93.3% of infection was cured. Two patients live with a fistula (4.2%) and 1 was amputated (2.1%).ConclusionAlthough burdened by a big complication rate, knee arthrodesis with an intramedullary nail provides satisfactory results and is a good alternative to above-knee-amputation. The Wichita® fusion nail shows a tendency to better results compared to the two other nails.Level of evidenceCase series, level IV

Selective Anisotropy of Mechanical Properties in Inconel718 Alloy.

Mechanical anisotropy behaviors are investigated in slightly rolled Inconel718 alloy with string-like δ phase and carbides produced during various solid-solution and aging treatments. A weak anisotropy in the strengths and rupture properties at 650 °C is visible, whereas ductility, i.e., reduction in area (RA) and impact toughness (CVN), presents a sound anisotropy behavior. MC carbides promote the operation of slip systems and thus are conducive to weakening the strength anisotropy. The RA anisotropy mainly stems from high-density δ phase particles that provide more crack nucleation sites and stimulate rapid propagation because of the shorter bridge distance between micro-cracks at the rolling direction. In contrast, CVN anisotropy arises from both δ phase and carbides at a lower solid-solution temperature of 940 °C but only depends on carbides at 980 °C where the δ phase fully dissolves. Apart from dislocation motions operated at room temperature, the activated grain boundary processes are responsible for the weak anisotropy of rupture properties at the elevated temperature. This work provides a guideline for technological applications in the hot working processes for Inconel718 alloys.

Trueness of extra-oral scanner in relation to two span lengths. An in-vitro study

Statement of the problem: Extraoral scanners have been used widely nowadays however there are certain conditions that could affect their accuracy which will subsequently affect the success of the final restoration. Objective: The aim of this study was to determine the accuracy of extraoral scanner in relation to two span lengths. Materials and methods: A typodont (Nissin Dental, Kyoto Japan) was used and two bridges with different span lengths were prepared, the first one with missing upper left second premolar (short straight span (GS)) and the other with missing upper left first and second premolars (long curved span (GL)). Indentations were made on each abutment to be taken as a reference for measurements. For both groups reference scan was taken by inEos X5 extra-oral scanner. Then five physical impression was taken for each group using vinylpolysiloxane impression material (Honigum, Germany) and then poured into type IV dental stone. Casts of each group were scanned using DOF extraoral scanner (DOF Company, Korea). Measurements were made from the indentations on the reference scan and the sample scans, compared with each-other and root mean square value (RMS) was obtained to evaluate the trueness. Results: Comparison between short and long span bridges revealed that there was no statistically significant difference between trueness values of short and long span bridges. Where RMS mean for the short span was 0.0727 mm and that for the long span was 0.1069 mm. Conclusions: Different span lengths do not seem to affect the trueness of the extra-oral scanner tested.

Effect of span length on the trueness of an intraoral scanner. (An in-vitro study)

Abstract Statement of the problem: Digital scanning has been widely used nowadays, however its accuracy in relation to the bridge span length needs further investigations. Objective: The aim of this study was to determine the effect of span length on the trueness of an intra-oral scanner. Materials and methods: On a typodont (Nissin Dental Model, Japan) preparations for two bridge span lengths were made. One resembling missing upper second premolar representing short straight span length (SS) while the second resembling missing upper first and second premolars representing long curved span (LS). Then typodont was scanned by a laboratory scanner (InEos X5 scanner) (Sirona Dental System, Bensheim, Germany) to act as a reference model scan to compare measurements for trueness. Then for each group five scans were taken for the typodont by Medit intraoral scanner (iScan version 1.2.0.1; Medit, Seoul, Korea) to be compared with the reference scan. Then data set from the scans were transferred to STL format and then exported to exocad (exocad version 2.3 Matera exocad GmbH,Darmstadt, Germany) software to get the measurements to determine the trueness. Results: Results of this study showed that in the comparison between short and long span bridges, the long span bridge scans showed statistically significant higher root mean square (RMS) mean value (0.23±0.10 mm), lower trueness than short span bridge scans (0.06±0.04 mm). Conclusions: Long span fixed bridge had an adverse effect on the scanning accuracy. Trueness of intraoral scanner may be affected by the complexity and length of the scanning area.

Torsional fracture of viscoelastic liquid bridges

Short liquid bridges are stable under the action of surface tension. In applications like electronic packaging, food engineering, and additive manufacturing, this poses challenges to the clean and fast dispensing of viscoelastic fluids. Here, we investigate how viscoelastic liquid bridges can be destabilized by torsion. By combining high-speed imaging and numerical simulation, we show that concave surfaces of liquid bridges can localize shear, in turn localizing normal stresses and making the surface more concave. Such positive feedback creates an indent, which propagates toward the center and leads to breakup of the liquid bridge. The indent formation mechanism closely resembles edge fracture, an often undesired viscoelastic flow instability characterized by the sudden indentation of the fluid's free surface when the fluid is subjected to shear. By applying torsion, even short, capillary stable liquid bridges can be broken in the order of 1 s. This may lead to the development of dispensing protocols that reduce substrate contamination by the satellite droplets and long capillary tails formed by capillary retraction, which is the current mainstream industrial method for destabilizing viscoelastic liquid bridges.

Modal frequencies of bridges from GNSS (GPS) monitoring data: Experimental, statistical evidence

GNSS technology (known especially for GPS satellites) for measurement of deflections has proved very efficient and useful in bridge structural monitoring, even for short stiff bridges, especially after the advent of 100 Hz GNSS sensors. Mode computation from dynamic deflections has been proposed as one of the applications of this technology. Apart from formal modal analyses with GNSS input, and from spectral analysis of controlled free attenuating oscillations, it has been argued that simple spectra of deflections can define more than one modal frequencies. To test this scenario, we analyzed 21 controlled excitation events from a certain bridge monitoring survey, focusing on lateral and vertical deflections, recorded both by GNSS and an accelerometer. These events contain a transient and a following oscillation, and they are preceded and followed by intervals of quiescence and ambient vibrations. Spectra for each event, for the lateral and the vertical axis of the bridge, and for and each instrument (GNSS, accelerometer) were computed, normalized to their maximum value, and printed one over the other, in order to produce a single composite spectrum for each of the four sets. In these four sets, there was also marked the true value of modal frequency, derived from free attenuating oscillations. It was found that for high SNR (signal-to-noise ratio) deflections, spectral peaks in both acceleration and displacement spectra differ by up to 0.3 Hz from the true value. For low SNR, defections spectra do not match the true frequency, but acceleration spectra provide a low-precision estimate of the true frequency. This is because various excitation effects (traffic, wind etc.) contribute with numerous peaks in a wide range of frequencies. Reliable estimates of modal frequencies can hence be derived from deflections spectra only if excitation frequencies (mostly traffic and wind) can be filtered along with most measurement noise, on the basis of additional data.