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O'Brien, Eugene J.
Preferred name
O'Brien, Eugene J.
Official Name
O'Brien, Eugene J.
Research Output
Now showing 1 - 10 of 218
Publication
Detection of Bridge Dynamic Parameters Using an Instrumented Vehicle
2010, González, Arturo, O'Brien, Eugene J., McGetrick, P.
Highway structures such as bridges are subject to continuous degradation primarily due to ageing and environmental factors. A rational transport policy requires the monitoring of this transport infrastructure to provide adequate maintenance and guarantee the required levels of transport service and safety. In Europe, this is now a legal requirement - a European Directive requires all member states of the European Union to implement a Bridge Management System. However, the process is expensive, requiring the installation of sensing equipment and data acquisition electronics on the bridge. This paper investigates the use of an instrumented vehicle fitted with accelerometers on its axles to monitor the dynamic behaviour of bridges as an indicator of its structural condition. This approach eliminates the need for any on-site installation of measurement equipment. A simplified half-car vehicle-bridge interaction model is used in theoretical simulations to test the possibility of extracting the dynamic parameters of the bridge from the spectra of vehicle accelerations. The effect of vehicle speed, vehicle mass and bridge span length on the detection of the bridge dynamic parameters are investigated. The algorithm is highly sensitive to the condition of the road profile and simulations are carried out for both smooth and rough profiles.
Publication
Dynamic Load Allowance
2021-12-03, Keenahan, Jennifer, O'Brien, Eugene J., Znidaric, Ales, Kalin, Jan
Chapter 4 provides a good explanation of the current state-of-the-art for the influence of dynamics on bridge traffic loading. It starts with an explanation of the concepts and a review of the various definitions used in the field, such as Dynamic Amplification factor and Impact Factor. It looks at how some of the main codes of practice in the world treat dynamics. A considerable portion of the chapter deals with the statistics of dynamic amplification. It is noted that the biggest dynamic amplifications tend to occur for light vehicle loading events. A statistical approach addresses this issue and provides a more appropriate allowance for dynamics which is called Assessment Dynamic Ratio. The influence of road surface roughness is considered and the implications of a local irregularity or pothole, as sometimes happens near the end joints. A number of field measurement campaigns of dynamic amplification are reported from various countries. These largely support the findings of the numerical studies.
Publication
A Regularised Solution to the Bridge Weigh in Motion Equations
2009, O'Brien, Eugene J., Rowley, C., González, Arturo, et al.
The traditional approach to Bridge Weigh-in-Motion (WIM) developed by Moses, gives good accuracy for estimating gross vehicle weights but is less accurate for individual axle weights. In this paper, Tikhonov regularisation is applied to the original Moses’ equations to reduce some of the inaccuracies inherent within the algorithm. The optimal regularisation parameter is calculated using the L-curve criterion. The new regularised solution is numerically tested using simulations of moving vehicles on a bridge. Results show that the regularised solution performs significantly better than the original approach of Moses and is insensitive to road surface roughness.
Publication
Monitoring Bridge Dynamic Behaviour Using an Instrumented Two Axle Vehicle
2010-09-02, McGetrick, P., González, Arturo, O'Brien, Eugene J.
Highway structures such as bridges are subject to continuous degradation primarily
due to ageing, loading and environmental factors. A rational transport policy must
monitor and provide adequate maintenance to this infrastructure to guarantee the
required levels of transport service and safety. Increasingly in recent years, bridges are
being instrumented and monitored on an ongoing basis due to the implementation of
Bridge Management Systems. This is very effective and provides a high level of
protection to the public and early warning if the bridge becomes unsafe. However, the
process can be expensive and time consuming, requiring the installation of sensors
and data acquisition electronics on the bridge. This paper investigates the use of an
instrumented 2-axle vehicle fitted with accelerometers to monitor the dynamic
behaviour of a bridge network in a simple and cost-effective manner. A simplified
half car-beam interaction model is used to simulate the passage of a vehicle over a
bridge. This investigation involves the frequency domain analysis of the axle
accelerations as the vehicle crosses the bridge. The spectrum of the acceleration
record contains noise, vehicle, bridge and road frequency components. Therefore, the
bridge dynamic behaviour is monitored in simulations for both smooth and rough road
surfaces. The vehicle mass and axle spacing are varied in simulations along with
bridge structural damping in order to analyse the sensitivity of the vehicle
accelerations to a change in bridge properties. These vehicle accelerations can be
obtained for different periods of time and serve as a useful tool to monitor the
variation of bridge frequency and damping with time.
Publication
Experimental Investigation of Drive-by Bridge Inspection
2011, Kim, Chul-Woo, Isemoto, R., Toshinami, T., Kawatani, Mitsuo, McGetrick, P., O'Brien, Eugene J.
This study presents a vibration-based health monitoring strategy for short span bridges utilizing an inspection vehicle. How to screen health condition of short span bridges in terms of the drive-by bridge inspection is described. Feasibility of the drive-by bridge inspection is investigated through a scaled laboratory moving vehicle experiment. The feasibility of using an instrumented vehicle to detect the natural frequency and changes in structural damping of a model bridge is observed. Observations also demonstrate the possibility of diagnosis of bridges by comparing patterns of identified dynamic parameters of bridges through periodical monitoring. It is confirmed that the moving vehicle method identifies the damage location and severity well.
Publication
Load effect of single-lane traffic simulations on long-span bridges
2010, Lipari, Alessandro, Caprani, Colin C., O'Brien, Eugene J.
It 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
Publication
A Two-Stage Direct Integration Approach to Find The Railway Track Profile Using In-Service Trains
2020-08-28, Keenahan, Jennifer, Ren, Yifei, O'Brien, Eugene J.
The railway track is an important element in transportation networks. In recent years, drive-by monitoring of railways has become more popular. Using data measured from in-service trains, the railway profile can be found. In previous research, a complex optimiziton method is used to calculate the railway profile. This paper introduces a new two-stage direct integration approach to find the same track profile much more efficiently. The calculated track profile is similar to a ‘true’ profile and can be used to monitor the condition of the track.
Publication
Traffic Load Effect Forecasting for Bridges
2015-09-23, Leahy, Cathal, O'Brien, Eugene J., O'Connor, Alan
Traffic flows, as well as truck weights, increase with time. This must be taken into account in order to accurately assess traffic loading on bridges. The Eurocode Load Model 1 is used for the design of new bridges but a scaled down version of the model can be used for the assessment of existing bridges. This scaling is usually done by applying α–factors to the load model. The effect of traffic growth on these α–factors is assessed in this paper. Weigh-in-motion data from the Netherlands is used as the basis for traffic models which simulate year-on-year growth of both traffic flow and truck weights. A time-varying generalised extreme value distribution is then used to calculate the characteristic load effects and determine the α–factors. The effect of different traffic growth rates on these α–factors is then examined. It is found that an increase in truck weights has the most influence on the α–factors but that increased flow also has a significant effect.
Publication
Comparison of Two Independently Developed Bridge Weigh-In-Motion Systems
1999, O'Brien, Eugene J., Znidaric, Ales, Dempsey, Anthony T.
This paper describes an experiment in which 2 independently developed bridge weigh-in-motion (WIM) systems are tested and compared, both for accuracy and durability. The systems, an Irish prototype still under development and a commercially available American system, were tested on a bridge in Slovenia. 11 statically pre-weighted trucks were each driven over the bridge several times at a range of typical highway speeds. Accuracies for axle and gross vehicle weights are presented within the framework of the draft European WIM specification, and the bias which can be introduced by the selection of a calibration truck is demonstrated. Performance factors relating to durability are also discussed with particular emphasis on axle detectors
Publication
Long life bridges
2014-04-17, O'Brien, Eugene J., Tucker, M., O'Connor, Alan
The single market is at the core of what the European Union (EU) represents and for Europe in particular, the single market depends on an effective transportation system. However, much of the EU's stock of an estimated 1 million bridges are old and have deteriorated over time. Many of these structures will soon need replacement or maintenance/intervention strategies to optimize their remaining service life. The Long Life Bridges project is a European 7th Framework-funded project that is using advanced analysis techniques to extend the lives of bridges, allowing them to be kept in service longer than would otherwise be possible. Research is centred on the specific considerations of bridge loading and dynamics, life cycle evaluation and fatigue evaluation. It is being carried out by a consortium consisting of two small/medium enterprises and two universities that bring together expertise in the fields of structural assessment, probabilistic analysis and risk quantification from both academic and industrial backgrounds.