332,048 research outputs found
Modelling Extreme Traffic Loading on Bridges Using Kernal Density Estimators
No full textInnovations on Bridges and Soil-Bridge Interaction (IBSBI 2011), Athens, Greece, October 13-15, 2011Kernel density estimators are a non-parametric method of
estimating the probability density function of sample data. In this paper, the
method is applied to find characteristic maximum daily truck weights on
highway bridges. The results are then compared with the conventional
approach.Deposited by bulk impor
Stability of liquid bridges between twisted elliptical disks
No full textThe influence in the stability of long liquid bridges supported between two elliptical-shaped disks of their main axis relative orientation is investigated. A numerical continuation method capable of finding equilibrium shapes, both stable and unstable, is used to calculate a series of equilibrium shapes supported by disks of increasing eccentricity for different relative orientation of the disks axis. The stable or unstable character of each of the shapes is calculated to determine the position of the stability limit and its characte
Comparative structural response of two steel bridges constructed 100 years apart
No full textThis paper presents a comparative numerical analysis of the structural behaviour and seismic performance of two existing steel bridges, the Infiernillo II Bridge and the Pinhao Bridge, one located in Mexico and the other in Portugal. The two bridges have similar general geometrical characteristics, but were constructed 100 years apart. Three-dimensional structural models of both bridges are developed and analysed for various load cases and several seismic conditions. The results of the comparative analysis between the two bridges are presented in terms of natural frequencies and corresponding vibration modes, maximum stresses in the structural elements and maximum displacements. The study is aimed at determining the influence of a 1 century period in material properties, transverse sections and expected behaviour of two quite similar bridges. In addition, the influence of the bearing conditions in the global response of the Pinhao Bridge was evaluated
Maximum dynamic stress on bridges traversed by moving loads
No full textMost current research on dynamic effects due to traffic load on simply supported bridges focuses on the mid-span section of the bridge, since this location corresponds to the worst static bending moment. However, the maximum total moment allowing for dynamics, may differ considerably from the maximum moment at mid-span. This paper shows how the maximum can occur in a section relatively far from mid-span with a significant difference in magnitude.Other funderJournal websitewww.bridgesjournal.comEuropean 6th Framework Programme ARCHES (Assessment and Rehabilitation of Central European Highway Structures)Publisher requires the journal URL to appear on the record: www.bridgesjournal.com. Could use Description web link: Journal website as in http://hdl.handle.net/10197/2437? - AV 1/11/2010 au ke SB. 15/11/'1
Caissons for bridges over water
No full textThe design of foundations for over-water bridges and offshore marine terminals might be a challenging task for the bridge engineer. Whereas the ground conditions at the bridge location may be the dominating factor in the design of foundations for a bridge on land, in the case of over-water bridges they can be of relatively minor importance compared with the design problems posed by the environment. Bridges in the open waters of a wide estuary or bay crossing are generally subjected to environmental factors like wind and wave action which can limit the period of operation of floating construction plant and can cause damage to the partly completed structures.Peer ReviewedPostprint (published version
Caissons for bridges over water
No full textThe design of foundations for over-water bridges and offshore marine terminals might be a challenging task for the bridge engineer. Whereas the ground conditions at the bridge location may be the dominating factor in the design of foundations for a bridge on land, in the case of over-water bridges they can be of relatively minor importance compared with the design problems posed by the environment. Bridges in the open waters of a wide estuary or bay crossing are generally subjected to environmental factors like wind and wave action which can limit the period of operation of floating construction plant and can cause damage to the partly completed structures.Peer ReviewedPostprint (published version
The calculation of noise from railway bridges and viaducts
No full textPandrol Rail Fastenings Limited are a designer and manufacturer of railway rail-fastening systems. As an organisation they have the capability to reduce the noise impact of bridges using resilient track components. They also have a commercial interest in providing such technology. Knowledge of the processes behind bridge noise is important to Pandrol in two ways; to aid the engineers within the organisation in the design of fastening systems and to demonstrate a state-of-the-art understanding of the problem of railway bridge noise to customers, as this will aid in the sale of Pandrol products. The fitting of new rail components to an existing track form, or failure to meet noise regulations with a new track form, can be costly. It is important to be able to predict accurately the effectiveness of noise reduction techniques. Currently, Pandrol’s knowledge of the problem consists almost entirely of experience gained and data gathered while working on existing bridge projects. To expand their knowledge base, Pandrol perform noise and vibration measurements on railway bridges and viaducts and then use the measured data to predict the performance of their systems on other bridges. This completely empirical approach to predicting bridge noise is both costly and situation specific results cannot be provided before the installation of the fastening system. Another approach to predicting bridge noise is through the application of analytical models. Limited analytical modelling in the context of bridge noise is currently conducted within the organisation. For these reasons, Pandrol are sponsoring research into bridge noise in the form of this EngD project. Here an existing rapid calculation approach is identified that relies less on the exact geometry of the bridge and more on its general characteristics. In this approach an analytical model of the track is coupled to a statistical energy analysis (SEA) model of the bridge. This approach forms a suitable basis from which to develop a better model here by concentrating on its weaknesses. A mid-frequency calculation for the power input to the bridge via a resilient track system has been developed by modelling the track-bridge system as two finite Timoshenko beams continuously connected by a resilient layer. This has resulted in a power input calculation which includes the important effects of coupling between the rail and bridge and the resonance effects of the finite length of a bridge. In addition, a detailed study of the frequency characteristics of deep I-section beams has been performed using Finite Element, Boundary Element and Dynamic stiffness models. It is shown that, at high frequencies, the behaviour of the beam is characterised by in-plane motion of the beam web and bending motion in the flange. This knowledge has resulted in an improved calculation for the mobility of a bridge at high frequencies. The above improvements are included in an improved model for use by Pandrol in their general activities. Data from real bridges is compared to predictions from the improved model in order to validate different aspects of the model. The model is then used to study the effect on noise of varying many bridge design parameters. It is shown that the parameter that has most influence on the noise performance of a bridge is the dynamic stiffness of the resilient rail fastening system. Additionally it is demonstrated that for a given bridge and noise receiver location, an optimum fastener stiffness exists where the noise radiated by the bridge and track is at a minimum
Non-Axisymmetric Effects on Long Liquid Bridges
No full textThe stability of long liquid bridges under non-axisymmetric disturbances like a microgravitational force acting perpendicular to the liquid bridge axis or a non-coaxiality of the disks is analyzed through an asymptotic method based on bifurcation techniques. Results obtained indicate that such non-axisymmetric effects are of higher order than those produced by axisymmetric perturbations
Literature review on the images of the nurse and nursing in the media
No full textThis study concentrates on the images of the nurse and nursing seen most commonly in the media and attempts to trace the images back to their origins and to explain their continued use, despite the rapidly changing role of the nurse in today's world. The images have been derived mostly from the historical roots of nursing and sometimes as a reaction to the increasing influence of the feminist movement. The author takes a look at the four main images of the nurse seen in the media, which are the ministering angel, the battleaxe, the naughty nurse and the doctor's handmaiden and then goes on to take a brief look at the other images commonly perpetuated by the media. The author summarizes the probable effects of the media stereotypes on nurses themselves and the service they provide and also takes a look at attempts to dispel these stereotypes
Vibration of railway bridges in the audible frequency range
No full textThe noise level associated with a train travelling on a bridge is normally greater than that for a train travelling on plain track. It is sometimes the bridge noise that causes the highest levels of disturbance to people in the vicinity or triggers action underregulations such as the Environmental Noise Directive. Consequently, there is a need to study means of predicting noise levels from proposed bridges, noise controlmeasures for existing structures and principles of low-noise bridge design.This thesis describes a programme of work in which an existing calculation model for bridge noise and vibration has been tested and alternative calculation methods havebeen developed where required. The existing model is based on analytical models for wheel-rail interaction and the calculation of the power input to the bridge. Theresponse of the various component parts of the bridge for this power input is found using a simplified SEA scheme.In this work, the existing model has been tested against measurements made on railway bridges and the results of an advanced method of structural analysis, theWaveguide Finite Element (WFE) method. This method is well-suited to modelling some important types of railway bridge. Specifically, it allows a numerical modellingapproach to be used up to higher frequency than conventional Finite Element methods. It has been found to offer some significant advantages over the existingbridge noise model, particularly for concrete-steel composite bridges and concretebox-section viaducts.The track support structure has an important influence on bridge noise and vibration, through its role in the transmission of vibration from the rail to the bridge. Laboratory measurements have been made in this work to characterise the vibration transmissionproperties of two important types of track support structure on bridges; ballasted trackand two-stage resilient baseplate track. Improved methods of modelling the dynamic behaviour of these track forms have been developed from the measurements, whichcan be used in calculation models for both bridge noise and also for rolling noise.<br/
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