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Caprani, Colin C.
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Caprani, Colin C.
Official Name
Caprani, Colin C.
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Now showing 1 - 10 of 12
- PublicationLoad effect of single-lane traffic simulations on long-span bridgesIt is well acknowledged that long-span road bridges (about 50 m long and more) are governed by congestion traffic rather than free-flow conditions. A conventional model for the design of new long-span bridges is to place over the bridge a load model representing a platoon of heavy vehicle with the gaps between them reduced to a minimum. This assumption is too conservative for existing bridges, given the large disruption costs faced by their closure for rehabilitation. In order to model the close gaps between vehicles, characteristic of congested traffic, microsimulation is needed to accurately capture drivers’ behaviour. In this work, a microsimulation model is studied and found to replicate many different known forms of congestion. As a first approach to the topic, single-lane simulations of identical vehicles have been carried out in order to obtain load effect on a sample bridge. This load effect is studied with reference to the form of traffic causing the load effect. It is found that the most extreme load effect may not be caused by purely congested traffic but also by non-stationary congested conditions
276 - PublicationStatistical computation for extreme bridge traffic load effectsThe maintenance of highway infrastructure constitutes a major expenditure in many countries. This cost can be reduced significantly by minimizing the repair or replacement of highway bridges. In the assessment of existing bridges, the strength estimate tends to be more accurate than that of traffic loading, due to the more variable nature of loading. Recent advances in the statistical analysis of highway bridge traffic loading have resulted in more accurate forecasts of the actual loading to which a bridge is subject. While these advances require extensive numerical computation, they can significantly improve the accuracy of the calculation. This paper outlines the recent advances and describes the associated computational aspects in detail
499 - PublicationHeadway modelling for traffic load assessment of short to medium span bridgesSite-specific assessment of the loading to which existing bridges are subject has considerable potential for saving on rehabilitation and replacement costs of the bridge stock. Monte Carlo simulations, with traffic measurements from site, are used to estimate the characteristic values for load effects. In this paper, it is shown that the critical loading events from which the characteristic effects are derived, are strongly dependent on the assumptions used for the headways of successive trucks. A new approach which uses measured headway statistical distributions is developed and is shown to be a reasonable balance between conservative assumptions and less realistic scenarios. The sensitivity of characteristic load effects to conventional headway assumptions is shown to be significant.
2356 - PublicationDetermination of Minimum Gap in Congested Traffic(2012-09-07)
; ; ; Accurate evaluation of site-specific loading can lead to cost and material savings in rehabilitation and replacement of bridges. Currently, bridge traffic load assessment is carried out using long run traffic simulations based on weigh-in-motion (WIM) data obtained at the site. Congestion is the governing load condition for long-span bridges. To correctly model congestion, a minimum gap between vehicles is usually assumed. Where the gap is overestimated, the calculated characteristic load is smaller than the actual characteristic load leading to an unsafe assessment. If the gap is underestimated, the safety assessment is too conservative, which is both costly and wasteful of finite resources. This paper outlines the development of an optical method to measure parameters required to model driver behaviour in congestion. Images are obtained using a camera with a wide angle, aspherical lens. Edge detection and Hough transforms are used to location wheels and bumpers. The resulting data can increase the accuracy of traffic microsimulation and hence, the assessment of long span bridge traffic loading.180 - PublicationEffect of Single-Lane Congestions on Long-Span Bridge Traffic Loading(2012-09-07)
; ; It is well known that traffic loading of long-span bridges is governed by congestion. In spite of the fact that field observations in the past decades have shown that congestion can take up different forms, most previous studies on bridge traffic loading consider only a queue of standstill vehicles. In this paper, a micro-simulation tool is used for generating congested traffic on a single-lane roadway. The underlying micro-simulation model has been found capable of successfully replicating observed congestion patterns on motorways by simulating single-lane traffic with identical vehicles. Here trucks are introduced into the model, in an investigation of the total load for a 200m span bridge. Different congestion patterns are found and studied in relation to their effect on loading. It is found that the bumper-to-bumper queue is not necessarily the most critical situation for the sample long-span bridge, since it does not allow the flowing of vehicles and therefore decreases the probability of observing critical loading events. Slow-moving traffic, corresponding to heavy congestion, can be more critical, depending on the truck proportion.138 - PublicationCharacteristic traffic load effects from a mixture of loading events on short to medium span bridgesIn recent years highway bridge load assessment has been recognised as an area through which savings can be made by avoiding unnecessary bridge refurbishment and replacement. Load effects in bridges result from single truck crossings or multiple-truck presence events which are, statistically, not identically distributed. Conventional approaches fit statistical distributions to mixtures of non-identically distributed load effects. Inaccuracies in the conventional approach are identified and an alternative approach is developed to find the characteristic load effects. Theoretical and field data is used to show the potential implications of conventional techniques and to demonstrate the application of the new approach.
1077Scopus© Citations 77 - PublicationAssessment dynamic ratio for traffic loading on highway bridges(Taylor & Francis, 2011-11-28)
; ; ; The determination of characteristic bridge load effect is a complex problem. Usually, statistical extrapolation of simulated static load effects is used to derive a lifetime characteristic static load effect. However, when a vehicle crosses a bridge, dynamic interaction occurs which often causes a greater total load effect. This total load effect is related to the static load effect through a dynamic amplification factor (DAF). Specifications often recommend a conservative level for DAF, based on bridge length, number of lanes, and type of load effect only. Therefore significant improvements in the accuracy of this calculation are possible if a DAF, specific to the considered bridge, is applied. In this paper, the authors develop a novel method that considers site-specific bridge and traffic load conditions and allows for the reduced probability of both high static loading and high dynamic interaction occurring simultaneously. This approach utilises multivariate extreme value theory, in conjunction with static simulations and finite element vehicle-bridge dynamic interaction models. It is found that the dynamic allowance for the sample bridge and traffic considered, is significantly less than recommended by bridge codes. This finding can have significant implications for the assessment of existing bridge stock.726Scopus© Citations 29 - PublicationDetermination of bridge lifetime dynamic amplification factor using finite element analysis of critical loading scenariosThe development of accurate codes for the design of bridges and the evaluation of existing structures requires adequate assessment of heavy traffic loading and also the dynamic interaction that may occur as this traffic traverses the structure. Current approaches generally first calculate characteristic static load effect and then apply an amplification factor to allow for dynamics. This neglects the significantly-reduced probability of both high static loading and high dynamic amplification occurring simultaneously. This paper presents an assessment procedure whereby only critical loading events are considered to allow for an efficient and accurate determination of independent values for characteristic (lifetime-maximum) static and total (including dynamic interaction) load effects. Initially the critical static loading scenarios for a chosen bridge are determined from Monte Carlo simulation using weigh-in-motion data. The development of a database of 3-dimensional finite element bridge and truck models allows for the analysis of these various combinations of vehicular loading patterns. The identified critical loading scenarios are modelled and analysed individually to obtain the critical total load effect. It is then possible to obtain a correlation between critical static load effect and corresponding total load effect and to extrapolate to find a site-specific dynamic amplification factor.
1949Scopus© Citations 45 - PublicationThe use of predictive likelihood to estimate the distribution of extreme bridge traffic load effectTo assess the safety of an existing bridge, the loads to which it may be subject in its lifetime are required. Statistical analysis is used to extrapolate a sample of load effect values from the simulation period to the required design period. Complex statistical methods are often used and the end result is usually a single value of characteristic load effect. Such a deterministic result is at odds with the underlying stochastic nature of the problem. In this paper, predictive likelihood is shown to be a method by which the distribution of the lifetime extreme load effect may be determined. An estimate of the distributions of lifetime maximum load effect facilitates the reliability approach to bridge assessment. Results are presented for some cases of bridge loading, compared to a return period approach and significant differences identified. The implications for the assessment of existing bridges are discussed.
1039Scopus© Citations 34 - PublicationThe structural reliability of bridges subject to time-dependent deterioration(Civil-Comp Press, 2007-09)
; ; ; The reliability of the structural performance of any given structure is affected by both in-service loading and material deterioration due to environmental attack. They must be evaluated at any given time in order to compute lifetime probability of failure. This paper presents an innovative methodology to derive the structure lifetime load effect due to existing traffic using a statistical tool known as Predictive Likelihood. Loss of resistance due to corrosion originated by chloride ingression is also taken into account. Finally the lifetime probability of failure is evaluated via the application of a time-discretization strategy2124