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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 79
- PublicationFleet Monitoring - Using Sensors in a Fleet of Passing Vehicles to Monitor the Health of Bridges(2021-09-17)
; ; ; ; This paper proposes the use of a fleet of instrumented vehicles to monitor the condition of infrastructure and bridges. It is anticipated that data from privately owned vehicles with low-cost accelerometer and GPS data, will be available for this purpose in the future. An inverse version of the well known Newmark-Beta method is proposed to determine road/rail surface profile from measured accelerations. Some results are reported from an instrumented train that made repeat runs on railway track over a period of a month. For bridge health monitoring, the concept of a moving reference influence line is proposed as a damage indicator. It is shown in simulation to give good indications of bearing damage in a simply supported bridge.153 - PublicationSensitivity of SHM Sensors to Bridge StiffnessBridges play an important role in transport infrastructure and it is necessary to frequently monitor them. Current vibration-based bridge monitoring methods in which bridges are instrumented using several sensors are sometimes not sensitive enough. For this reason, an assessment of sensitivity of sensors to damage is necessary. In this paper a sensitivity analysis to bridge flexural stiffness (EI) is performed. A discussion between the use of strain or deflections is provided. A relation between deflection and stiffness can be set by theorem of virtual work, expressing the problem as a matrix product. Sensitivity is obtained by deriving the deflection respect to the reciprocal of the stiffness at every analysed location of the bridge. It is found that a good match between the deflection and the bridge stiffness profile can be obtained using noise-free measurements. The accuracy of sensors is evaluated numerically in presence of damage and measurement noise. Field measurements in the United States are also described to identify the potential issues in real conditions.
181 - PublicationThe Impact of a Bump on the Response of a Bridge to TrafficThere are numerous studies on the dynamic amplification factors caused by traffic flow on a bridge. For short- and medium-span bridges, the road profile appears as a dominant parameter on the bridge dynamic response. In theoretical investigations, the road profile is usually modelled as a stochastic random process. However, this approach does not take into account the high irregularities that are prone to develop in the connection of the bridge to its approach, as result of a damaged expansion joint and/or differential settlement. Most of research on dynamic amplification due to traffic has focused in bending moment effects. This paper uses planar vehiclebridge interaction models to assess the increase in shear effects at the supports that a bump prior to the bridge may cause. Results for a range of bumps, bridge lengths, traffic configurations and road conditions are discussed.
490 - PublicationProcedures for Calibration of Eurocode Traffic Load Model 1 for National Conditions(2012-09-07)
; ; Since April 2010 Eurocode Load Model 1 (LM1) is the prescribed traffic load model to be employed in the design of highway bridges in the European Union (EU). Uniquely, the code permits member states to calibrate the load model, through the application of 'α-factors' to allow for national or regional conditions. Some countries with high volumes of very heavy traffic may find that they require α-factors in excess of unity whilst other less heavily trafficked road networks may require much lesser values. The importance of accurate calibration of the α-factors is clear from a safety and economic point of view. This paper describes procedures for calibration of α-factors using Weigh in Motion (WIM) data. WIM data allows classification of the traffic loads in individual countries, enabling the specific Gross Vehicle Weights (GVWs), axle loads and frequencies of heavy trucks to be taken into account. Simulations calibrated using this data, for a wide range of structural forms (i.e., influence lines, spans and numbers of lanes) and scenario types (i.e., free flowing, congested and mixed traffic conditions); allow comparison of the load effects generated by the site-specific traffic to those obtained when employing LM1. Statistical Extreme Value Distributions (EVDs) are fitted to simulated results to determine characteristic load effect values using the same methodology as was employed in the calibration of LM1 itself. Appropriate α adjustment factors are then determined to cater for variation in predicted characteristic extreme load effects on a network by network basis. Where α<1.0, the prescribed approach delivers significant savings by preventing unnecessary overdesign of bridges. On the other hand, for cases where α>1.0 it allows bridge designers to design bridges with adequate levels of safety.416 - PublicationA New Damage Indicator for Drive-by Monitoring using Instantaneous Curvature(Austroads, 2017-04-06)
; ; ; Drive-by monitoring has enhanced the possibilities for bridge damage detection, with the potential to deliver a bridge rating in the time it takes an instrumented vehicle to pass overhead. This paper outlines the importance of Instantaneous Curvature (IC) as an indicator of local damage. For the IC calculation, bridge deflections are measured from the vehicle before and after the occurrence of damage, so that a comparison between the two situations can be made. Differences in curvature are clearly visible in numerical simulations, especially at the damage location. A Finite Element model of a simply supported bridge subject to a crossing vehicle is modelled dynamically. In this paper, the Curvature Ratio (CR) is proposed as the damage indicator, defined as the ratio of IC in the current bridge to IC in the corresponding healthy bridge. Road profile and random noise in the simulated measurements are considered to represent realistic conditions. Simulations in MATLAB demonstrate that CR is an effective indicator in most of the analysis cases.292 - PublicationMaximum total load effects in vehicle-bridge dynamic interaction problems for simply supported structures(European Association for Structural Dynamics, 2014-07-02)
; ; This paper quantifies the underestimation of bending moment that results from exclusively considering the mid-span section of bridges when calculating vehicle-bridge dynamic interaction. A numerical model of a simply supported Euler-Bernoulli beam, traversed by a 1-DOF vehicle, is used to evaluate the differences. The simplicity of the model is justified by the additional insight that the results provide on the complex vehicle-bridge interaction problem. The results are presented using three dimensionless parameters that uniquely define the solution, taking into account the coupled system (vehicle and beam) frequencies and masses as well as the velocity of the passing vehicle. The results show that the overall maximum load effect occurs in the vicinity of the mid-span section and can be of significantly higher magnitude when compared to the maximum at mid-span.188 - PublicationComparison of Two Independently Developed Bridge Weigh-In-Motion SystemsThis 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
1035 - PublicationSpatially Variable Assessment of Lifetime Maximum Load Effect Distribution in Bridges(2012-09-07)
; ; ; Bridge structures are key components of highway infrastructure and their safety is clearly of great importance. Safety assessment of highway bridges requires accurate prediction of the extreme load effects, taking account of spatial variability through the bridge width and length. This concept of spatial variability i s also known as random field analysis. Reliability - based bridge assessment permits the inclusion of uncertainty in all parameters and models associated with the deterioration process. Random field analysis takes account of the probability that two points n ear each other on a bridge will have correlated properties. This method incorporates spatial variability which results in a more accurate reliability assessm ent. This paper presents an integrated model for spatial reliability analysis of reinforced concre te bridges that considers both the bridge capacity and traffic load. A sophisticated simulation model of two - directional traffic is used to determine accurate annual maximum distributions of load effect. To generate the bridge loading scenarios, an extensi ve Weigh-in-Motion (WIM) database, from five European countries, is used. For this, statistical distributions for vehicle weights, inter - vehicle gaps and other characteristics are derived from the measurements, and are used as the basis for a Monte Carlo simulation of traffic. Results are presented for bidirectional traffic, with one lane in each direction, with a total flow of approximately 2000 trucks per day.187 - PublicationCalculating an Influence Line from Direct MeasurementsThe response of a bridge to a pre-weighed truck can be measured on site. This paper describes a mathematical method for converting the measured response of a load effect into an influence line for that effect. One influence ordinate is calculated for each scan of the data acquisition system. The vector of ordinates is found by solving a large set of simultaneous equations expressed in matrix form. The general form of the matrices is described, and the particular matrices for a three-axle truck are given. The technique is demonstrated using measured strain on two bridges using pre-weighed trucks with different numbers of axles.
1581 - PublicationCamera-based Bridge Safety Monitoring(2016-01-08)
; ; ; This paper describes a research project focused on the safety assessment of bridges using camera-based technologies. It is a collaboration with partners in three countries: Ireland, the United Kingdom and the United States. A major challenge of the project is the development of algorithms and methods that transform the measured sensor signals and video images into a form that is highly damage-sensitive/ change-sensitive for bridge safety assessment. The study will exploit the unique attributes of computer vision systems, where the signal is "continuous in space". This research will significantly advance current sensor-based structural health monitoring with computer-vision techniques, leading to practical applications for damage detection of complex structures with a novel approach. In the long term, monitoring with cameras is expected to be more broadly utilized for structural engineering purposes because of its potential for inexpensive deployment in real life bridges. While advancing the knowledge by integrating multidisciplinary concepts from theory to application, this research will have direct benefits as civil infrastructure (and particularly aged bridges) has become a critical societal concern from safety and cost perspectives. The paper will describe the bridge monitoring system that will be developed. It will include a weigh-in-motion (WIM) system to weigh vehicles, with cameras to monitor both the traffic and the bridge. The WIM system and the 1st camera will track the traffic and will extract its properties. The 2nd camera with some supplementary sensors will monitor the response of the bridge to the traffic. Structural identification algorithms will transform all of this data into damage indicators that indicate when the bridge has deteriorated or changed. The system will be tested using numerical simulation, scale models in the laboratory and trials using full scale bridges in the field.312