Bridging the wrong gap?

Delamination propagation in fibrous laminates is often accompanied by development of a damage zone, within which intact fibers bridge the crack faces that constitutes a major toughening mechanism. A direct experimental assessment of the crack closure tractions due to bridging fibers is a challenging task. In addition, when the length of the bridging zone becomes comparable with the laminate linear dimensions, referred to as large scale bridging, the extent of bridging can be influenced by the laminate size and layup. Hence, traction-separation relations used in computational methods to predict fracture do not always rely on solid experimental evidence of large scale bridging and for numerical convenience simple linear traction-€“separation expressions are often considered. In this work, a semi-experimental methodology is employed to identify the contribution of large scale bridging to delamination resistance of unidirectional and cross-ply carbon fiber/epoxy laminates. Double cantilever beam specimens of different thickness are prepared and subjected to monotonic and fatigue mode I loadings. In selected specimens, optical fibers with multiplexed fiber Bragg grating (FBG) sensors are embedded. The strain distribution in the vicinity of the crack plane is monitored by FBG sensors. The strain data are used in an inverse identification procedure to quantify the bridging tractions and the energy release rate (ERR) due to the bridging. Subsequently, the identified tractions are implemented in a cohesive zone model to simulate delamination propagation. Employing the aforementioned approach, specimen thickness dependence of large scale bridging in delamination of unidirectional laminates is investigated. The results indicate that onset of delamination is independent of the specimen geometry. However, the extent of the bridging zone and the plateau level of delamination resistance both significantly increase with increasing the specimen thickness. The maximum traction at the crack tip is independent of the specimen size while the length of the steady state bridging zone scales linearly with the thickness of laminate. Moreover, the nonlinear rate of tractions decay is inversely proportional to the specimen thickness. It is shown that the tractions decay parameter is controlled by the curvature of the specimen arm. Evaluation of bridging effects on fatigue delamination of unidirectional laminates indicates that the stable phase of fatigue crack growth is more extended in the thicker specimens and the critical ERR increases by increasing the specimen thickness. Similar to the trend observed in monotonic delamination, fatigue delamination in the thicker specimens is accompanied by a longer bridging zone in which the bridging tractions decay with a lower rate. The maximum bridging traction at the crack tip is independent of the specimen thickness. It is demonstrated that the traction-separation relation and the ERR due to the large scale bridging depend on the ply orientations at the crack interface whereas ERR values at the onset of delamination are almost the same. As compared to delamination of a unidirectional specimen, crack propagation in cross-ply laminate is accompanied by a smaller bridging zone, but fiber bridging in the cross-ply specimens is more efficient. The adopted methodology in this work provides a robust assessment of large scale bridging and is a step towards a better understanding of delamination in fiber reinforced composites.

As important man-made targets, bridges have been a major focus of Synthetic Aperture Radar (SAR) image interpretation, and many researchers have developed methods for bridge detection. The core frameworks of these methods are analogical, a river is first extracted, and a water bridge is detected based on the positional relationship between the river and bridge. However, existing bridge detection methods relying on river extraction; cannot be utilized detect land bridges. This is because the background environment under a bridge is land, not river, which has different scattering characteristics and shape layouts. As such, the traditional method for extracting rivers is not suitable for extracting land background, and it is impossible to locate a bridge based on prior knowledge of its location of. To resolve this problem, in this study, we propose a land bridge detection method based on polarized Circular SAR (CSAR) images. In our proposed method, the Circular Polarization Entropy (CPE) of an observed scene is introduced to separate possible bridge targets from a land background (In our experiment, the average CPE of the bridge is 0.4018, and that of the land background is 0.7819; thus there is a clear difference between the bridge and background). False targets are removed based on the difference in the polarization entropy variance features of the bridges and other ground objects; and the size characteristics of the bridges. Finally, accurate extractions of land bridges are obtained based on the geometric characteristics of the bridges. Experimental results based on real airborne L-band polarized CSAR data verify the correctness of the theoretical analysis and effectiveness of the proposed method.

The paper draws attention to the interaction between construction method and finished form in bridge design. The influence of constructive features on completed bridge appearance in Japan and the UK is compared against the background of recent aesthetic policy in the two countries. The bridges which are briefly described and discussed are: a) the Itamana Bridge, whose girders were made monolithic with the main piers, and whose piers were introduced at unusual positions in the side spans; b) Ohshima Bridge, 1988, which was the first suspension bridge in Japan to use a box section girder; c) Shorenjigawa Bridge, 1989, a steel box girder bridge; d) Hokawazu Bridge, 1974, which is a two hinged reinforced concrete arch of 170m span. It was the first bridge in the world to be constructed using a full cantilever method with cabling tied back over the abutment spandrel walls; e) Orwell Bridge, 1982, the largest prestressed concrete bridge in the United Kingdom; f) the Severn Bridge, 1966; g) Foyle Bridge, 1984; and h) Kessock Bridge, 1982. The French title of this article is: Esthetique et construction des ponts au Japon et au Royaume-Uni. The German title of this article is: Aesthetik und Konstruktion der Bruecken in Japan und Grossbritannien. For the covering abstract of the conference see IRRD 851274.

Enzymes are the same biomolecules such as proteins, has only a functional difference. Enzymes are bio catalyst that recently applied to many industrial fields. To be applied in the field of industrial enzymes should be enhanced stability against temperature. Analysis of the salt bridge is able to demonstrate the potential of residues mutated to improve thermal stability. Molecular dynamics simulations performed by observing the unfolding process. Variations in temperature used is 400 K, 450 K and 500 K, respectively performed for 2.5 ns. Then analyzed the pair a salt bridge is formed. There are 25 pairs of salt bridges at a temperature of 400 K, 24 pairs of salt bridges at a temperature of 450 K, and there are 30 pairs of the salt bridge is formed at a temperature of 500 K. To determine the salt bridge partner is a key enzyme kesstabilan we then plotted salt bridge between distances (A ) with time (ns) only at a temperature of 500 K, for allegedly at these temperatures has been a process of unfolding. Of the 30 pairs of the salt bridge that had plotted the distance with time, the pair obtained a salt bridge that pattern similar to the pattern chart graph analysis Root-mean-square deviation (RMSD). There are three curves salt bridge that pattern is similar to the pattern of RMSD curve and SASA, namely the salt bridge Glu84-Arg134, Asp104-Arg134 and Asp113-Arg115. The sharp rise in the value of RMSD and the resulting rupture SASA three pairs of the salt bridges. So when carried mutations in-silico candidate mutants that will be transferred is the amino acid residues are thought to play a role in electrostatic interactions and replace it with another amino acid residue on the basis of structural similarities. Keywords : Salt bridge, Electrostatic bond, Mutation, Unfolding

This work reports investigations upon weakly superconducting proximity effect bridges. These bridges, which exhibit the Josephson effects, are produced by bisecting a superconductor with a short (<1µ) region of material whose superconducting transition temperature is below that of the adjacent superconductors. These bridges are fabricated from layered refractory metal thin films whose transition temperature will depend upon the thickness ratio of the materials involved. The thickness ratio is changed in the area of the bridge to lower its transition temperature. This is done through novel photolithographic techniques described in the text, Chapter 2. If two such proximity effect bridges are connected in parallel, they form a quantum interferometer. The maximum zero voltage current through this circuit is periodically modulated by the magnetic flux through the circuit. At a constant bias current, the modulation of the critical current produces a modulation in the dc voltage across the bridge. This change in dc voltage has been found to be the result of a change in the internal dissipation in the device. A simple model using lumped circuit theory and treating the bridges as quantum oscillators of frequency ω = 2eV/h, where V is the time average voltage across the device, has been found to adequately describe the observed voltage modulation. The quantum interferometers have been converted to a galvanometer through the inclusion of an integral thin film current path which couples magnetic flux through the interferometer. Thus a change in signal current produces a change in the voltage across the interferometer at a constant bias current. This work is described in Chapter 3 of the text. The sensitivity of any device incorporating proximity effect bridges will ultimately be determined by the fluctuations in their electrical parameters. He have measured the spectral power density of the voltage fluctuations in proximity effect bridges using a room temperature electronics and a liquid helium temperature transformer to match the very low (~ 0.1 Ω) impedances characteristic of these devices. We find the voltage noise to agree quite well with that predicted by phonon noise in the normal conduction through the bridge plus a contribution from the superconducting pair current through the bridge which is proportional to the ratios of this current to the time average voltage across the bridge. The total voltage fluctuations are given by = 4kTR^2_d I/V where R_d is the dynamic resistance, I the total current, and V the voltage across the bridge . An additional noise source appears with a strong 1/f^(n) dependence , 1.5 < n < 2, if the bridges are fabricated upon a glass substrate. This excess noise, attributed to thermodynamic temperature fluctuations in the volume of the bridge, increases dramatically on a glass substrate due to the greatly diminished thermal diffusivity of the glass as compared to sapphire.

Selecting the Best Design Scenario of the Smart Structure of Bridges for Probably Future Earthquakes

The inspections that are being done on current bridges in our country are made to go through a process of being recorded on the management system and then converted by the computer. This has deteriorated the credibility of manual-analog types of data, inefficient care of information, and produced potential problems of the structures of bridges through subjective evaluations. In order to solve these troubles, this research has aimed at effectiveness, management, and convenience so that the inspector at the actual scene of the bridge structures will be able to achieve the primary purpose of infrastructure safety through precise supervision. To assist this, this study has suggested a state of the art IT intellectual management system that has applied RFID. This system has been designed to decrease the inspecting time on the actual scene, which will provide more time for efficient inspection and by using the converted DB, managing and utilizing high quality data will come naturally and through the objective evaluation, it will be possible to make exact judgments of the structures of the bridge. Also, regardless of the location, it has been found that the work performance was excellent through highly effective management.

This paper describes methods other than computer aided fabrication for the design of prestressed concrete and steel composite bridges. It first describes the attempts carried out between 1982 and 1985 in France to develop a new design for composite cross sections wherein the classical webs of box girder were replaced by steel webs. Examples provided are: a) the La Ferte Saint Aubin bridge, where the concrete webs have been replaced by plane steel webs; b) the Arbois bridge over the River Cuisance in Jura, where two concrete webs have been replaced by 2 plane steel trusses; c) the Cognac Bridge, over the River Charente. Here the two concrete webs have been replaced by two folded steel webs which do not carry any longitudinal compression. Prestressing efficiency is therefore increased; and d) the Val de Maupre viaduct, near Charolles. Two folded steel webs are used in this box girder bridge, and the concrete bottom flange is replaced by a steel tube filled with concrete. New developments in prestressing classical composite structures are also presented briefly, as is the design method which distributes steel and concrete along the entire length in such a way as to take advantage of the differences in weight between the materials. In essence, the main span is built of lightweight concrete which is balanced by shorter side spans built in traditional concrete. Examples are provided of steel isotropic spans supported by concrete cantilevers, (for example the Queen Mathilde Bridge at Rouen), cable stayed bridges with a steel main span (for example the Chevire Bridge). The use of lightweight concrete for constructing the bridge deck of arch bridges is also described, and illustrated by the bridge over the River Rance. The French title of this article is: Les ponts mixtes associant l'acier et le beton precontraint. The German title of this article is: Vereinigung von Spannbeton und Stahl im Brueckenbau. For the covering abstract of the conference see IRRD 851274.

A bridge comprising of two girders, such as a twin steel box-girder bridge, is classified as fracture critical (i.e., nonredundant). In this study, the various bridge components of the twin steel box-girder bridge are investigated to determine if these could be utilized to improve bridge redundancy. Detailed finite-element (FE) models, capable of simulating prominent failure modes observed in a full-scale bridge fracture test, are utilized to evaluate the contributions of the bridge components on the ultimate behavior and redundancy of the bridge sustaining a fracture on one of its girders. The FE models incorporate material nonlinearities of the steel and concrete members, and are capable of capturing the effects of the stud connection failure and railing contact. Analysis results show that the increased tensile strength of the stud connection and (or) concrete strength are effective in improving bridge redundancy. By modulating these factors, redundancy could be significantly enhanced to the extent that the bridge may be excluded from its fracture critical designation.

Highway bridges play a vital link role in surface transportation network, and their failures not only cause disruption of service but also danger people life. Seismic base isolation is an important technique that is used for reduce the seismic vulnerability by decreasing the seismic demand instead of increasing the seismic capacity. Present work deals with study of response of bridge using seismic control systems. For present study, a two-span prestressed concrete box girder highway bridge is considered and analyzed for seismic forces using SAP2000 software. The seismic response and behavior of Box Girder Bridge is studied by linear time history analysis using Newmark’s beta method. For the analysis four different ground motion data selected and scaled for target spectra as per zone IV. The highway bridge is isolated with Lead Rubber Bearing (LRB). The response of bridge system under earthquakes has been compared with the corresponding bridge with and without the isolation system. It is observed that LRB is highly effective for controlling not only the seismic response of the bridge but also include the structural response on the cost of slight increase in the displacement of the deck.

To evaluate the therapeutic effect of autologous transplantation of Schwann cells as "bridge" between the medial forebrain bundle (MFB) and caudate nucleus, into the brain of hemiparkinsonian monkey. Six monkeys were used following 6-OHDA-induced hemiparkinsonism. Three of them were autologous transplanted using Schwann cells as "bridges" between MFB and caudate nucleus. The Schwann cells were pre-treated using Hoechst33342. The other three monkeys received sham operation as controls. All the monkeys received behavioral assessment. The metabolism of dopamine was measured by SPECT using (99)Tcm-TRODAT-1 and PET using 18F-FP-beta-CIT. After a 4-month follow-up, the monkeys' brain were removed from the skull, fixed in 4% paraformaldehyde and cut into serial sections. A fluorescence microscope examination and a tyroxine hydroxylase (TH) immunohistochemistry study were made on the sections. Cell types were determined by double staining. The level of TH protein around the needle track was determined by Western blotting. All three monkeys, which had undergone Schwann cells autologous bridge graft showed a decrease in the disability score and two of them had an increase in motor activity. The apomorphine evoked rotation was also decreased. The symptoms of the monkeys, which received sham operation, had not amelioration. In SPECT examination, the radioactivity count was greatly increased in the grafted monkeys. The dopamine levels were significantly increased in the caudate nucleus from 61% (before graft) to 79% (after graft) while there's no change in control group. In histological examination, autologous Schwann cells could survive and migrate in the brain. Around the Schwann cells "bridge", there were numerous TH positive short fibers in the MFB area. Around the whole length of the "bridge", there were a lot of TH positive reactive astrocytes, especially in thalamus. TH protein around the needle track of the graft group was 243% compared with that of control group. Autologous Schwann cells bridge graft is a feasible technique with therapeutic effects on parkinson disease monkeys. The Schwann cells play an important role in dopaminergic axonal elongation and in inducing the TH positive phenotype of reactive astroglia cell around it.

Sensor is a device which receives a signal and converts it into electrical form. Wireless based sensors technology has been shown the potential to serve as low cost to substitute traditional cable based monitoring and increasing the facility of the real time bridge monitoring. How ever, bridge monitoring systems using the wireless sensor is still malfunctioning due to the lack of the proper sensor placement techniques. In addition, the improper sensor placement on the bridge girder increase the total number of sensors and the overall cost of installation and maintenance of bridge health monitoring system. In this paper, the sensor placement technique was developed based on the priority of the flexure and shear behavior of the girder; to optimize the sensor used on the girder and to minimize the overall cost of the bridge girder monitoring system. GUI system was developed using Matlab toolbox for monitoring the bridge girder continuously. GUI system would be helpful to evaluate the bridge girder condition based on the monitoring data of wireless based sensor technology.

Iran is located in a seismic prone region with several earthquakes occurring annually causing extensive damage to structures and infrastructure. Guilan province is located in the northern part of the country, exhibiting a large population, moderate climate and extensive river system. This region experiences high humidity, several active faults and high seismic hazard potential. This highlights the importance of an active and extensive maintenance and rehabilitation program for the bridges in this region. Structural Health Monitoring (SHM) is an engineering tool used to control changing conditions of infrastructure providing useful information for management, decision making and in certain circumstances code revision. This paper proposes a method for SHM of bridges. In total, 123 concrete bridges were assessed based on this visual inspection; with statistical analysis of results carried out on decks, piles, abutments, restraints and river engineering which effectively addressed the deficiencies in bridges maintenance. Finally some practical solutions are suggested to enhance the performance and lifetime of bridges. Based on the knowledge of the authors, this is the first comprehensive study on a large group of bridges in Iran which can be used as a base for further studies on management and retrofitting of bridges in the region.

Determination of the most meaningful structural modes and gaining insight into how these modes evolve are important issues for long-term structural health monitoring of the long-span bridges. To address this issue, modal parameters identified throughout the life of the bridge need to be compared and linked with each other, which is the process of mode tracking. The modal frequencies for a long-span bridge are typically closely-spaced, sensitive to the environment (e.g., temperature, wind, traffic, etc.), which makes the automated tracking of modal parameters a difficult process, often requiring human intervention. Machine learning methods are well-suited for uncovering complex underlying relationships between processes and thus have the potential to realize accurate and automated modal tracking. In this study, Gaussian mixture model (GMM), a popular unsupervised machine learning method, is employed to automatically determine and update baseline modal properties from the identified unlabeled modal parameters. On this foundation, a new mode tracking method is proposed for automated mode tracking for long-span bridges. Firstly, a numerical example for a three-degree-of-freedom system is employed to validate the feasibility of using GMM to automatically determine the baseline modal properties. Subsequently, the field monitoring data of a long-span bridge are utilized to illustrate the practical usage of GMM for automated determination of the baseline list. Finally, the continuously monitoring bridge acceleration data during strong typhoon events are employed to validate the reliability of proposed method in tracking the changing modal parameters. Results show that the proposed method can automatically track the modal parameters in disastrous scenarios and provide valuable references for condition assessment of the bridge structure.

Recently, U-section decks have been more and more used in metro and light rail bridges as an innovative concept in bridge deck design and a successful alternative to conventional box girders because of their potential advantages. U-section may be viewed as a single vent box girder eliminating the top slab connecting the webs, with the moving vehicles travelling on the lower deck. U-section bridges thus solve many problems like limited vertical clearance underneath the bridge lowest point, besides providing built-in noise barriers. Beam theory in mechanics assumes that plane section remains plane after bending, but it was found that shearing forces produce shear deformations and the plane section does not remain plane. This phenomenon leads to distortion of the cross section. For a box or a U section, this distortion makes the central part of the slab lagging behind those parts closer to the webs and this is known as shear lag effect. A sample real-world double-track U-section metro bridge is modelled in this paper using a commercial finite element analysis program and is analysed under various loading conditions and for different geometric variations. The three-dimensional finite element analysis is used to demonstrate variations in the transverse bending moments in the deck as well as variations in the longitudinal normal stresses induced in the cross section along the U-girder\'s span thus capturing warping and shear lag effects which are then compared to the stresses calculated using conventional beam theory. This comparison is performed not only to locate the distortion, warping and shear lag effects typically induced in U-section bridges but also to assess the main parameters influencing them the most.