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Full-Text Articles in Engineering
A Review Of Probabilistic Methods Of Assessment Of Load Effects In Bridges, Eugene J. Obrien, F Schmidt, Donya Hajializadeh, X-Y Zhou, Bernard Enright, Colin C. Caprani, Simon Wilson, Emma Sheils
A Review Of Probabilistic Methods Of Assessment Of Load Effects In Bridges, Eugene J. Obrien, F Schmidt, Donya Hajializadeh, X-Y Zhou, Bernard Enright, Colin C. Caprani, Simon Wilson, Emma Sheils
Articles
This paper reviews a range of statistical approaches to illustrate the influence of data quality and quantity on the probabilistic modelling of traffic load effects. It also aims to demonstrate the importance of long-run simulations in calculating characteristic traffic load effects. The popular methods of Peaks Over Threshold and Generalized Extreme Value are considered but also other methods including the Box-Cox approach, fitting to a Normal distribution and the Rice formula. For these five methods, curves are fitted to the tails of the daily maximum data. Bayesian Updating and Predictive Likelihood are also assessed, which require the entire data for …
Nonlinear Analysis Of Isotropic Slab Bridges Under Extreme Traffic Loading, Donya Hajializadeh, A. Salam Al-Sabah, Eugene J. Obrien, Debra F. Laefer, Bernard Enright
Nonlinear Analysis Of Isotropic Slab Bridges Under Extreme Traffic Loading, Donya Hajializadeh, A. Salam Al-Sabah, Eugene J. Obrien, Debra F. Laefer, Bernard Enright
Articles
Probabilistic analysis of traffic loading on a bridge traditionally involves an extrapolation from measured or simulated load effects to a characteristic maximum value. In recent years, Long Run Simulation, whereby thousands of years of traffic are simulated, has allowed researchers to gain new insights into the nature of the traffic scenarios that govern at the limit state. For example, mobile cranes and low-loaders, sometimes accompanied by a common articulated truck, have been shown to govern in most cases. In this paper, the extreme loading scenarios identified in the Long Run Simulation are applied to a non-linear, two-dimensional (2D) plate finite …
Spatial Time-Dependent Reliability Analysis Of Reinforced Concrete Slab Bridges Subject To Realistic Traffic Loading, Donya Hajializadeh, Mark Stewart, Bernard Enright, Eugene J. Obrien
Spatial Time-Dependent Reliability Analysis Of Reinforced Concrete Slab Bridges Subject To Realistic Traffic Loading, Donya Hajializadeh, Mark Stewart, Bernard Enright, Eugene J. Obrien
Articles
Resistance and loads are often correlated in time and space. The paper assesses the influence of these correlations on structural reliability/probability of failure for a typical two-lane RC slab bridge under realistic traffic loading. Spatial variables for structural resistance are cover and concrete compressive strength, which in turn affect the strength and chloride-induced corrosion of RC elements. Random variables include pit depth and model error. Correlation of weights between trucks in adjacent lanes and inter-vehicle gaps are also included and are calibrated against Weigh-In-Motion (WIM) data. Reliability analysis of deteriorating bridges needs to incorporate uncertainties associated with parameters governing the …
Monte Carlo Simulation Of Extreme Traffic Loading On Short And Medium Span Bridges, Bernard Enright, Eugene J. Obrien
Monte Carlo Simulation Of Extreme Traffic Loading On Short And Medium Span Bridges, Bernard Enright, Eugene J. Obrien
Articles
The accurate estimation of site-specific lifetime extreme traffic load effects is an important element in the cost-effective assessment of bridges. A common approach is to use statistical distributions derived from weigh-in-motion measurements as the basis for Monte Carlo simulation of traffic loading. However, results are highly sensitive to the assumptions made, not just with regard to vehicle weights but also to axle configurations and gaps between vehicles. This paper presents a comprehensive model for Monte Carlo simulation of bridge loading for free-flowing traffic, and shows how the model matches results from measurements on five European highways. The model has been …
The Effect Of Clusters Within Crowds Of Pedestrians On The Vertical Response Of A Flexible Footbridge, Joe Keogh, Colin C. Caprani, Paul Archbold, Paul Fanning
The Effect Of Clusters Within Crowds Of Pedestrians On The Vertical Response Of A Flexible Footbridge, Joe Keogh, Colin C. Caprani, Paul Archbold, Paul Fanning
Conference papers
The issue of excessive vibrations of footbridges due to the passage of pedestrians has been well documented in the past decade. Despite this there still remains great uncertainty as to how to predict the acceleration response of a footbridge due to crowd loading. This paper investigates the vibration response of a flexible footbridge subjected to crowd loading. Using a statistical model which caters for the variability of pedestrians, the vibration response of the footbridge is obtained. In this work, the effect of social groups or clusters of pedestrians in a crowd is investigated. Herein a cluster is defined as two …
The Response Of A Footbridge To Pedestrians Carrying Additional Mass, Darragh O'Sullivan, Colin Caprani, Joe Keogh
The Response Of A Footbridge To Pedestrians Carrying Additional Mass, Darragh O'Sullivan, Colin Caprani, Joe Keogh
Conference papers
Footbridges with low natural frequency are susceptible to excessive vibration serviceability problems if the pedestrian pacing frequency matches the bridge natural frequency. Much research has been done into describing the response of a footbridge to single pedestrian loading. However, many pedestrians carry additional mass such as shopping bags and backpacks, and this has generally not been accounted for in previous research. This work examines this problem using an experimental bridge excited with many single pedestrian events, both with and without additional mass. The vertical acceleration response is measured and compared to moving force, moving mass, and moving spring-mass-damper models. The …
Estimating Characteristic Bridge Loads On A Non-Primary Road Network, Eugene J. Obrien, Bernard Enright, Brendan Williams, Cathal Leahy
Estimating Characteristic Bridge Loads On A Non-Primary Road Network, Eugene J. Obrien, Bernard Enright, Brendan Williams, Cathal Leahy
Conference papers
When collecting truck loading data on a primary road network a common approach is to install a large network of permanent pavement-based Weigh-In-Motion systems. An alternative to this approach would be to use one or more portable Bridge Weigh-In-Motion systems which could be moved between bridges at regular intervals to determine the traffic loading throughout the network. A data collection strategy is needed to put such a system to best use. This paper details the data collection strategies which were examined for the National Roads Authority in Ireland. The use of urban economic concepts including Central Place Theory are discussed …
Portable Bridge Wim Data Collection Strategy For Secondary Roads, Bernard Enright, Cathal Leahy, Eugene J. Obrien, Jennifer Keenahan
Portable Bridge Wim Data Collection Strategy For Secondary Roads, Bernard Enright, Cathal Leahy, Eugene J. Obrien, Jennifer Keenahan
Conference papers
A common method of collecting traffic loading data across a large road network is to use a network of permanent pavement-based WIM systems. An alternative is to use one or more portable Bridge Weigh-In-Motion systems which are moved periodically between bridges on the network. To make optimum use of such a system, a suitable data collection strategy is needed to choose locations for the system. This paper describes a number of possible strategies which the authors have investigated for the National Roads Authority in Ireland. The different strategies are examined and their advantages and disadvantages compared. Their effectiveness at detecting …
Modeling Same-Direction Two-Lane Traffic For Bridge Loading, Eugene J. Obrien, Bernard Enright
Modeling Same-Direction Two-Lane Traffic For Bridge Loading, Eugene J. Obrien, Bernard Enright
Articles
Many highway bridges carry traffic in two same-direction lanes, and modeling the traffic loading on such bridges has been the subject of numerous studies. Different assumptions have been used to model multiple-presence loading events, particularly those featuring one truck in each lane. Using a database of weigh-in-motion measurements collected at two European sites for over 1 million trucks, this paper examines the relationships between adjacent vehicles in both lanes in terms of vehicle weights, speeds and inter-vehicle gaps. It is shown that there are various patterns of correlation, some of which are significant for bridge loading. A novel approach to …
Modeling Extreme Traffic Loading On Bridges Using Kernel Density Estimators, Cathal Leahy, Eugene J. Obrien, Bernard Enright
Modeling Extreme Traffic Loading On Bridges Using Kernel Density Estimators, Cathal Leahy, Eugene J. Obrien, Bernard Enright
Conference papers
Kernel 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
Simulation Of Traffic Loading On Highway Bridges, Bernard Enright
Simulation Of Traffic Loading On Highway Bridges, Bernard Enright
Other resources
This work is based on weigh-in-motion measurements for approximately three million trucks obtained from sites in five European countries. Techniques have been developed, supported by photographic evidence, for filtering the measurements to identify and remove unreliable values, and for the classification of extremely heavy vehicles. The collected measurements have been used as the basis for building and calibrating a Monte Carlo simulation model for bridge loading. Two-lane traffic is simulated – either two lanes in the same direction or one lane in each direction. The model allows for vehicles that are both heavier and have more axles than in the …
Characteristic Dynamic Increment For Extreme Traffic Loading Events On Short And Medium Span Highway Bridges, Eugene J. Obrien, Daniel Cantero, Bernard Enright, Arturo González
Characteristic Dynamic Increment For Extreme Traffic Loading Events On Short And Medium Span Highway Bridges, Eugene J. Obrien, Daniel Cantero, Bernard Enright, Arturo González
Articles
More accurate assessment of safety can prevent unnecessary repair or replacement of existing bridges which in turn can result in great cost savings at network level. The allowance for dynamics is a significant component of traffic loading in many bridges and is often unnecessarily conservative. Critical traffic loading scenarios are considered in this paper with a model that allows for vehicle-bridge interaction and takes into account the road surface condition. Characteristic dynamic allowance values are presented for the assessment of mid-span bending moment in a wide range of short to medium span bridges for bi-directional traffic.
A New Congested Traffic Load Model For Highway Bridges, Colin C. Caprani, Colm Carey, Bernard Enright
A New Congested Traffic Load Model For Highway Bridges, Colin C. Caprani, Colm Carey, Bernard Enright
Conference papers
Long span highway bridges are critical components of any nation’s infrastructure. Therefore accurate assessment of highway bridge loading is essential, and it is well known that congested traffic governs load effect for such bridges. Current congestion models use conservative assumptions about traffic and inter-vehicle gaps. This research investigates congested traffic flow through the use of traffic microsimulation which has the ability to reproduce complex traffic phenomena based on driver interactions. A time series model has been developed to produce a speed time-series similar to the results of the microsimulation. The speed time-series from the new model, combined with the established …
Management Strategies For Special Permit Vehicles For Bridge Loading, Bernard Enright, Eugene J. Obrien
Management Strategies For Special Permit Vehicles For Bridge Loading, Bernard Enright, Eugene J. Obrien
Conference papers
An examination of weigh-in-motion data collected recently at sites in five European countries has shown that vehicles with weights well in excess of the normal legal limits are found on a daily basis. These vehicles would be expected to have permits issued by the responsible authorities. It can be seen from the measurements that most of them are travelling at normal speeds. Photographic evidence indicates that, while many are accompanied by an escort vehicle, normal traffic is flowing alongside in other lanes. As European freight volume grows, the frequency of these special vehicles can be expected to increase. Hence, the …
Site Specific Modelling Of Traffic Loading On Highway Bridges, Bernard Enright, Eugene J. Obrien
Site Specific Modelling Of Traffic Loading On Highway Bridges, Bernard Enright, Eugene J. Obrien
Conference papers
Accurate traffic loading models based on measured weigh-in-motion (WIM) data are essential for the accurate assessment of existing bridges. Much work has been published on the Monte Carlo simulation of single lanes of heavy vehicle traffic, and this can easily be extended to model the loading on bridges with two streams of traffic in opposing directions. However, a typical highway bridge will have multiple lanes in the same direction, and various types of correlation are evident in measured traffic, such as groups of very heavy vehicles travelling together and heavy vehicles being overtaken by lighter ones. These traffic patterns affect …
The Influence Of Correlation On The Extreme Traffic Loading Of Bridges, Eugene J. Obrien, Bernard Enright, A. T. Dempsey
The Influence Of Correlation On The Extreme Traffic Loading Of Bridges, Eugene J. Obrien, Bernard Enright, A. T. Dempsey
Conference papers
Accurate traffic loading models based on measured data are essential for the accurate assessment of existing bridges. There are well-established methods for the Monte Carlo simulation of single lanes of traffic, and this can easily be extended to model the loading on bridges with two independent streams of traffic in opposing directions. However, a typical highway bridge will have multiple lanes in the same direction, and various types of correlation are evident in measured traffic. This paper analyses traffic patterns using multi-lane WIM data collected at two European sites. It describes an approach to the Monte Carlo simulation of this …
Importance Of The Tail In Truck Weight Modeling For Bridge Assessment, Eugene J. Obrien, Bernard Enright, Abraham Getachew
Importance Of The Tail In Truck Weight Modeling For Bridge Assessment, Eugene J. Obrien, Bernard Enright, Abraham Getachew
Articles
To predict characteristic extreme traffic load effects, simulations are sometimes performed of bridge loading events. To generalize the truck weight data, statistical distributions are fitted to histograms of weight measurements. This paper is based on extensive WIM measurements from two European sites and shows the sensitivity of the characteristic traffic load effects to the fitting process. A semi-parametric fitting procedure is proposed: direct use of the measured histogram where there are sufficient data for this to be reliable and parametric fitting to a statistical distribution in the tail region where there are less data. Calculated characteristic load effects are shown …
The Structural Reliability Of Bridges Subject To Time-Dependent Deterioration, Colin C. Caprani, C. Mcnally, E. J. O'Brien, A. Bordallo-Ruiz
The Structural Reliability Of Bridges Subject To Time-Dependent Deterioration, Colin C. Caprani, C. Mcnally, E. J. O'Brien, A. Bordallo-Ruiz
Conference papers
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 strategy.
Finding The Distribution Of Bridge Lifetime Load Effect By Predictive Likelihood, Colin C. Caprani, E. J. O'Brien
Finding The Distribution Of Bridge Lifetime Load Effect By Predictive Likelihood, Colin C. Caprani, E. J. O'Brien
Conference papers
To 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. …
Determination Of Characteristic Bridge Daf Using Dynamic Finite Element Analysis Of Critical Static Loading Scenarios, Colin C. Caprani, Paraic Rattigan, Arturo Gonzalez, E. J. O'Brien
Determination Of Characteristic Bridge Daf Using Dynamic Finite Element Analysis Of Critical Static Loading Scenarios, Colin C. Caprani, Paraic Rattigan, Arturo Gonzalez, E. J. O'Brien
Conference papers
The development of accurate codes for the design of bridges and the evaluation of existing structures requires adequate assessment of site-specific heavy traffic loading and also the dynamic interaction that may occur as this traffic traverses the structure. Shortcomings in current design codes occur due to the relatively independent manner in which critical static loading values and the corresponding allowance for dynamic amplification factor (DAF) are obtained. It is important that an approach is adopted that allows for the reduced probability of both high static loading and high dynamic amplification occurring simultaneously. Consideration of only relevant critical loading events will …
Statistical Computation For Extreme Bridge Traffic Load Effects, Colin C. Caprani, E. J. O'Brien
Statistical Computation For Extreme Bridge Traffic Load Effects, Colin C. Caprani, E. J. O'Brien
Conference papers
The 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 …
Bridge Dynamics And Loading, Colin C. Caprani, Eugene O'Brien, Arturo Gonzalez, Yingyan Li, Paraic Rattigan, Niall Harris
Bridge Dynamics And Loading, Colin C. Caprani, Eugene O'Brien, Arturo Gonzalez, Yingyan Li, Paraic Rattigan, Niall Harris
Conference papers
Recent UCD research on dynamic bridge-truck interaction and bridge traffic loading in general is reported. The accuracy of bridge traffic load assessment has been significantly improved by identifying the differences in the sources of traffic loading on short- to medium-span bridges and treating them separately. It is shown that results can be significantly improved by treating 1-,2-,3- and 4-truck loading events separately. Gaps between trucks are also identified as a critical issue that strongly influences the frequency of key3-and 4-truck events. Trends in the dynamics of traffic loading are identified using simple force models on simply supported beams. It is …
Estimating Risk Of Failure Of Engineering Structures Using Predictive Likelihood, Colin C. Caprani, A. Bordallo-Ruiz, E. J. O'Brien
Estimating Risk Of Failure Of Engineering Structures Using Predictive Likelihood, Colin C. Caprani, A. Bordallo-Ruiz, E. J. O'Brien
Conference papers
It has been common engineering practice to define characteristic values for loading and capacity of structures in order to assess the structural capacity of existing structures. This approach, yet practical and intuitive, lead to the comparison of deterministic values (characteristic values) that had to represent all the variability of the problem and is considered to be conservative, as usually loading is overestimated and capacity underestimated, yielding to calculations with high safety margins for the extreme events. Probabilistics methods have tried to overcom e this limitation by computing the overall probability of failure (Pf) for the lifetime of the structure, taking …
Study Of Same-Lane And Inter-Lane Gvw Correlation, Bernard Enright, Eugene J. O'Brien, Colin C. Caprani
Study Of Same-Lane And Inter-Lane Gvw Correlation, Bernard Enright, Eugene J. O'Brien, Colin C. Caprani
Conference papers
The methodology used is to generate a number of years of simulated traffic and to use extreme value statistics to predict more accurately the characteristic loading for a given bridge. The parameters and probability distributions used in the Monte Carlo simulation must be based on observed sample traffic data. Some previous studies have made unsubstantiated assumptions regarding correlation between the Gross Vehicle Weights (GVW) of trucks in the same lane, or between trucks in adjacent, same-direction lanes. For this paper, an extensive database of Dutch Weigh-in-Motion data is analysed. Data are collected from two same-direction lanes and are time-stamped to …
Probalistic Analysis Of Highway Bridge Traffic Loading, Colin C. Caprani
Probalistic Analysis Of Highway Bridge Traffic Loading, Colin C. Caprani
Other resources
Many bridges of the world’s highway networks have been in service for decades and are subject to escalating volumes of traffic. Consequently, there is a growing need for the rehabilitation or replacement of bridges due to deterioration and increased loading. The assessment of the strength of the existing bridge is relatively well understood, whereas the traffic loading it is subject to, is not as well understood. Accurate assessment of the loading to which bridges may be subject, can result in significant savings for the highway maintenance budgets internationally. In recent years, a general approach has emerged in the research literature: …
Site-Specific Probabilistic Load Modelling For Bridge Reliability Analysis, Colin C. Caprani, A. Belay, A. J. O'Connor
Site-Specific Probabilistic Load Modelling For Bridge Reliability Analysis, Colin C. Caprani, A. Belay, A. J. O'Connor
Conference papers
Reliability assessment of a short span beam-slab reinforced concrete bridge in Vienna is proposed using site-specific traffic data recorded using the Slovenian Weigh in Motion (SiWIM) system. An initial evaluation of the bridge using a determinintic approach shows that the critical limit state is bending. This paper describes the statistical analysis of the SiWIM data and the traffic flow simulations performed to predict the characteristic extreme load effects to which the bridge may be subjected during its remaining lifetime. These values are compared to the magnitude obtained from a deterministic approach. The influence lines used in the simulations are the …